heart rate monitoring in soccer

13 downloads 0 Views 188KB Size Report
... been used for evaluating the physiological demands of elite soccer players in competitive ... Owing to the continuous competitive characteristics of soccer, it is ...
BRIEF REVIEW

HEART RATE MONITORING IN SOCCER: INTEREST AND LIMITS DURING COMPETITIVE MATCH PLAY AND TRAINING, PRACTICAL APPLICATION DELLAL ALEXANDRE,1,2,3 CRISTIANO DINIZ DA SILVA,4 STEPHEN HILL-HAAS,5 DEL P. WONG,6 ANTONIO J. NATALI,4 JORGE R. P. DE LIMA,7 MAURICIO G.B. BARA FILHO,7 JOAO J.C.B. MARINS,4 EMERSON SILAMI GARCIA,8 AND CHAMARI KARIM3,9 1

Olympic Lyon FC (Soccer), Department of Fitness Training and Research, Lyon, France; 2Sport Science and Research Department, Orthopedic Health Clinic, Lyon, France; 3Tunisian Research Laboratory ‘‘Sport Performance Optimization’’ National Center of Medicine and Science in Sport (CNMSS), El Menzah, Tunisia; 4Department of Physical Education, Center of Biological and Health Sciences, Federal University of Vicxosa, Vicxosa, Brazil; 5High Performance Sport New Zealand, Auckland, New Zealand; 6Department of Health and Physical Education, The Hong Kong Institute of Education, Hong Kong; 7 Faculty of Physical Education and Sports, Federal university of Juiz de Fora, Juiz de Fora, Brazil; 8School of Physical Education, Physiotherapy and Occupational Therapy of the Federal University of Minas Gerais, Cruzeiro Sport Club, Belo Horizonte, Brazil; and 9ISSEP Ksar-Said, Manouba University, Manouba, Tunisia

ABSTRACT Alexandre, D, Da Silva, C, Hill-Haas, S, Wong, DP, Natali, AJ, De Lima, JRP, Filho, MGB, Marins, JCB, Garcia, ES, and Chamari, K. Heart rate monitoring in soccer: Interest and limits during competitive match play and training–Practical application. J Strength Cond Res 26(10): 2890–2906, 2012—The identification of physiological loads imposed by soccer training or match play reveals essential information, which may help improve training and recovery strategies. Until today, the use of heart rate (HR) monitoring is not standardized in soccer. Thus, the aim of this review was to analyze, determine and compare the exercise intensity (EI) monitored by HR in professional, youth, and recreational soccer players during matches and training sessions using a meta-analysis. Heart rate is one of the most common physiological variables used to determine exercise internal training load. The mean EI recorded during competitive matches was described as 70–80% of V_ O2max or 80–90% of maximal heart rate (HRmax), independent of the playing level. With respect to HR training zones, approximately 65% of the total match duration is spent at intensity of 70–90% HRmax and rarely below 65% HRmax. However, although HRmax is mostly employed in the literature, monitoring EI should be expressed in relation to reserve heart rate, as it was described as a more reliable indicator of HR, allowing interindividual comparisons. The HR response according to the playing position indicates Address correspondence to Alexandre Dellal, alexandredellal@gmail. com. 26(10)/2890–2906 Journal of Strength and Conditioning Research Ó 2012 National Strength and Conditioning Association

2890

the

that midfielders are characterized by the highest EI, followed by forwards and fullbacks. Moreover, in the second half of the match, the EI is lower than that observed during the first half; this reduction could be correlated with the level of the player’s physical conditioning. Consequently, coaches may favor the use of interval training or small-sided training games because these are shown to improve both aerobic capacity and the ability to repeat high-intensity actions. Small-sided games allow reaching similar HR responses to those found during interval training and match play but with greater heterogeneity values. Future investigations should include a larger sample of players with special reference to playing position and the expression of EI in percentage of the reserve heart rate, analyzing the possible intergender differences in HR response.

KEY WORDS fitness training, heart rate reserve, workload, physical performance, aerobic system, endurance INTRODUCTION

S

occer is the most popular sport in the world with nearly 200 million practitioners (58). Match analyses of the physical demand have revealed that the game is characterized by the mix of short-duration sprints, high-intensity running (HIR), jumps, duels, tackles, directional changes, backwards, and walking and standing episodes with an average game intensity ranging from 80 to 90% of maximal heart rate (HRmax) (18,20,40,46–48,116,117). For instance, top-level players require developing specific physical capacities such as an elevated aerobic power and the ability to perform repeated HIR (including sprinting) with limited rest period, to be able to cope with the game demands. Moreover, physical, technical, and tactical

TM

Journal of Strength and Conditioning Research

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

the

TM

Journal of Strength and Conditioning Research conditioning needs to be matched to each positional role (1,11,15,19,40,106,116). In this context, the exercise intensity (EI) differs according to the playing position during matches, and therefore, accurate determination of the physical demands during a match play is required. Measurement of the total distance covered during matches has been extensively reported, with time-motion analysis revealing the distribution of the efforts into categories according to speed thresholds. The most common method employed for this type of analysis involves semiautomated, computerized, player tracking technologies, which are widely used in elite soccer (19,20,26,40,46–48). These systems allow a quicker and more accurate data collection than the traditional visual estimation techniques (26,104). In addition, they provide a simultaneous analysis of physical efforts, movement patterns, and technical actions of players while allowing a comparison of performance (26). One of the major limitations of this technique is that it only measures the external load and it is not combined with the analysis of the physiological variables and therefore does not supply reliable estimations of the internal energetic expenses. In this context, several methods have been used for evaluating the physiological demands of elite soccer players in competitive situations. The physiological responses during a match play have been previously examined with the analysis of the blood lactate (4,11,54,92,94) core and muscle temperatures (5,11,51,109), depletion of muscle glycogen stores (16,70,79), and heart rate (HR) (11,24,54,55,63,96,116,117). Evaluations have also been performed by direct measurements of oxygen uptake (V_ O2) using portable analyzers in simulated games and in circuits reproducing game actions (62,96) and in small-sided games (SSGs) (66). Although data obtained through direct measurements of V_ O2 can represent objective information as to the energy expenditure of a game, this method is only applicable in training situations. Indeed, despite technological advances in portable oxygen analyzers, making them lighter and smaller, their use during official games is prohibited and incompatible with competitive situations (3,23,50). Furthermore, these apparatuses are believed to interfere with the players’ movements during soccer training sessions and or matches, which further decrease its validity. The difficulty of determining V_ O2 during actual soccer matches makes it necessary to use other physiological variables for the determination or estimation of the physical workload. Consequently, the measurement of blood lactate concentration has been extensively used. Methodological aspects such as the number of measures and the time point at which blood is collected have been questioned. However, Pyne et al. (99) validated blood sampling at the third minute post exercise using a portable analyzer (Lactate Pro; Arkray, Kyoto, Japan). Owing to the continuous competitive characteristics of soccer, it is impossible to collect blood samples during matches. Furthermore, the values of blood lactate observed are unlikely to reflect the overall physical demands before the collection because it is not collected directly from the muscle

| www.nsca.com

and it has been revealed that the correlation between blood and muscular lactate concentration is not high (13,14,79). Because of the limitations of the methods previously presented, HR appears to be more suitable for an indirect estimation of the aerobic energy production in soccer (13,55,56,106) but no for an anaerobic energy production, speed exercises, and power exercise (1–4,13,84,86,113). Esposito et al. (56) and Eniseler (55) validated the use of HR as an indicator of aerobic demand during soccer activities and in testing amateur soccer players, but not to determine or detect the overtraining in players, whereas it constitutes a good tool to examine the overuse during consecutive games. It also represents a noninvasive method that is universally used for monitoring the physiological response in team sports. The methodological advantage of most commercially available HR monitors allows to measure and store the HR values with a high reliability (1,84). Physiologically, HR measurements present a high relationship with physiological variables such as V_ O2 in intermittent activities (as soccer), among professional players (11,66), amateur players (49,56), youth and female players (27,28,35,36,63). Current systems of radio telemetry allow monitoring HR during short time intervals simultaneously on all the players of a team, improving the planning and control of training (50,106). However, it is important to acknowledge that purchasing monitors for an entire soccer squad can be expensive, and such data still require expert analysis and somewhat time-consuming interpretation. Considering the advantages presented by HR monitoring, such as the correlation with V_ O2 and the ease of data collection, several studies have analyzed the HR responses in soccer, both during training and match play. Heart rate monitoring has been extensively implemented during professional soccer training sessions, comprising SSGs (37,39,41,42,44,45,59,67,77,97,101,112) and during unofficial match play (56,80,119), but it has been also widely used in amateur and youth soccer physiological load of soccer training and matches. In these last decades, the interest of heart rate variability (HRV) has grew up especially in sport, but this special area will be not discussed in detail in this article because it needs a large literature exploration. The objectives of the present review were to present a historical overview of the use of HR in soccer and to examine and compare the EI in male professional, youth, female, and recreational soccer players both in match play and training situations using a meta-analysis. By providing a review of the use of HR monitoring in soccer, it is hoped that this might (a) help coaches and scientists to determine the physiological load across different playing levels in soccer, (b) present the more reliable methods of HR monitoring (HRmax vs. reserve heart rate [HRres]), (c) differentiate the HR responses according to different playing positions, and (d) provide valuable information for monitoring players during training and matches at the same time of facilitating a more efficient planning and manipulation of the player’s internal training load. VOLUME 26 | NUMBER 10 | OCTOBER 2012 |

2891

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

HR in Soccer: A Practical Review OVERVIEW According to the different aims of the present review, the following parts compose the structure of this article: (a) a descriptive presentation of the historical aspects of using HR monitoring in soccer until nowadays (I); (b) an analysis of the interest of HR in soccer training and match play (II) with an examination of the relationship between HR and the exercises intensity (II.1) and the metabolic thresholds (II.2), the determination of the EI using the %HRmax (II.3), the HR responses during match play with a comparison between the first and second halves (II.4) and in differentiating the different playing positions (II.5), and the HR responses in soccer training with special reference to the SSGs and highintensity intermittent exercises (II.6); and (c) a discussion of the limitation of HR monitoring in soccer (III). I. Historical Aspects of Using Heart Rate Monitoring in Soccer

Since the end of the 1960s, HR monitoring has been used to examine and quantify the physiological load during match play and training in soccer (91,113,127). Heart rate response during various sporting activities was traditionally measured by continuous electrocardiogram (ECG) recording, which were transmitted by short-range radio telemetry. However, the nature of soccer activities (including jumps, tackles, contact with opponents, etc.) and the sweat production during exercise compromised the connection of the electrodes to the skin surface (3). In the early 1980s, wireless cardio monitoring technology was developed, which facilitated the electronic transfer of HR data from a transmitter belt worn on the chest to a receiver worn as a ‘‘wristwatch.’’ This allowed HR monitoring during actual playing situations (friendly games), without the limitations of the previous ECG monitoring (124). By the end of the 1980s, further technological advancements allowed the introduction of more reliable and less bulky monitoring systems. The memory/data storage capacity was also improved, which helped establishing the scientific validity of this technology (1,3,84). In this context, this type of HR monitoring was used during official match play both in the Danish professional first league and in the Scottish semiprofessional league or in other professional team (109,123,124). Nevertheless, there were still some limitations, particularly because of the interference of the electromagnetic waves of the equipment between players, which amplified the difficulty of simultaneously monitoring the HR response of several players in proximity (3). Consequently, the determination of the EI according to individual playing position in a collective situation was still not possible. In the early 1990s, a new system was implemented, which included the integration of the HR monitor with a microcomputer, the codification of the signal transmissions, and a specific data analysis software. Currently, this system allows simultaneous monitoring of all the players, storing the HR data in the receiver belt, and allowing a subsequent transfer to the microcomputer. Moreover, the most recent step-Polar

2892

the

Team2 HR system allows real-time HR monitoring with the possibility to express the HR responses as a percentage of the reserve heart rate (%HRres), which induced a massive step forward in sport science. The old Polar Team 1 system only allowing a retrospective analysis of the HR recordings, as the data needed to be downloaded at the end of training/matches and subsequently analyzed with the specific software (1). This new technology also allows the monitoring of the rate to rate intervals (R-R), similar to the Omega Wave Sport System, but it seems to be more practical (98). The HR response can be analyzed in several ways to estimate the EI. Some studies have reported the playing intensity after analyzing an average of observed HR values or a percentage distribution of HR in absolute values (3,9,11,54,96,124). These approaches do not allow for intersubject comparison of players’ EI because of the differences between HRmax and resting heart rate (HRrest) among players (1). Consequently, high intersubject variability was evident in relation to the intermittent nature of the technical training, the age range of the players, and the cardiovascular effects of fitness training, which is associated with a decrease in HRmax because of autonomic nervous system changes (103). The expression of HR data in relation to HRmax values has been habitually employed in different studies during official and friendly match play (e.g., (119)). However, the HR response expressed in %HRres appears to be more reliable (1,39,43,97,129). Percentage of the reserve heart rate has been calculated using the formulae [%HRres = [(mean exercise HR 2 resting HR)/(HRmax 2 resting HR)] 3 100]. This equation considers the biorhythm variations and consequently allows a comparison of interindividual HR responses in different types of soccer training. In sport mean, the HR rest value correspond to the minimal HR observed during either a 10-minute period in which players are laid on a bed in a calm environment with the eyes closed or immediately at wakeup using similar procedures (1,39,41,43,97,129). Complementary, the HRV is considered by scientists as an essential research item in the last decades but, to the best of our knowledge, no studies have success in showing the interest of HRV analysis in sports men and soccer players. Furthermore, HR has also been related to the anaerobic blood lactate threshold of 4 mmolL21 in friendly and competitive match play (11) and in diverse training situations (102). Thus, the HR estimation of the internal training load could be improved and should reach a similar reliability level as the ratings of perceived exertion (RPE, global load) method, which constitutes not a physiological tool but provide general information of the exercise difficulty felt by players (2,33,68). Heart rate could provide stronger information about the players’ overuse because of the repetition of matches in short period duration, but it is still considered a weak tool to detect the overtraining in soccer, which not really exists in elite soccer (1,84,103). It is probably

TM

Journal of Strength and Conditioning Research

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

the

TM

Journal of Strength and Conditioning Research because of the limitation of the number of training and their duration compared with another activity (rugby, athletic, and swimming), and almost other physiological variables (hormonal, omega wave, and stress) appear to bring greater precise information (1,84). In the following sections, the EI of soccer from several competitive playing levels will be outlined in accordance with different strategies of HR analysis. Comparisons between first and second half recordings and between different positional roles will also be outlined. II. Heart Rate in Soccer

The mean HR recorded during match play ranges between 165 and 175 bmin21, both in competitive (Table 1) and friendly match play (Table 2). In relation to age, some peculiarities have been observed both in youth and older soccer players. Capranica et al. (24) reported that youth soccer players’ mean HR exceeded 170 bmin21 for 84% of total match duration during official matches with regular field dimensions (100 3 65 m). In contrast, Tessitore et al. (119) reported absolute HR values ranging between 120 and 140 bmin21 for older amateur players (62.8 6 5.9 years old) during a match play. However, these analyses of HR only considered the absolute values (bmin21) and consequently may result in

| www.nsca.com

misinterpretation because the analysis of HR responses should be related to the age, gender, and fitness level of the players (2,13,36,65,69,114,116). Previous studies have suggested that female players tax similarly the aerobic and anaerobic energy systems compared with male players (2,6,35,36,63,78,116,122). Moreover, despite international female players presented a greater total distance covered and a higher number of high-intensity actions than domestic female players during match play, no differences in HR data were observed (6,78,82). In the same context, elite female soccer players presented similar HR responses (87% HRmax) than elite male players during match play (6,116). However, the percentage of HRres obtained from either laboratory- or field-based maximal exercise tests and corresponding to the individual metabolic thresholds should be favored instead of HRmax to allow better comparisons and extrapolation of results (37,39,43,72,97,121,129). II.1. Exercise Intensity and the Heart Rate-V_ O2 Relationship. Based on the linear HR-V_ O2 relationship established in laboratory treadmill tests, it was found that the average intensity of elite adult players ranged from 70 to 80% V_ O2max during a match play (14,54,96,110,116). Strøyer et al. (117) reported similar values using Danish youth players

TABLE 1. Male soccer players’ HR responses in competitive match play expressed as average in absolute values (bmin21) and in %HRmax. Source

Level

n

Rhode and Espersen (110) Klimt et al. (76) Florida-James and Reilly (60) Rico-Sanz et al. (107) Helgerud et al. (63) Capranica et al. (24) Thatcher and Batterham (120) Strøyer et al. (117)

First division/Denmark

6

U-11/U12/Germany University/United Kingdom Elite junior/Porto Rico Junior elite/Norwegian U12/Italy U-20 professional/ United Kingdom Elite beginning the puberty/Denmark Academy/ United Kingdom U-17/Brazil Junior/Brazil U-17/Brazil Junior/Brazil Junior of professional eams/Italy Elite U-17/Brazil

15 12

Billows et al. (16) Coelho (31) Mortimer et al. (95) Impellizzeri et al. (67) Rodrigues et al. (109)

HR (bmin21) ;170

%HRmax

No. of match play (min)

;84

Four (90)

160–180 161

Two in competitive (90) One (90)

8 8 6 6

171 ;180 ;166

;83

One (90) Two (90) One (90)* One in formation 4 3 4 3 2 (90)

9

174

;87

One in formation 4 3 4 3 2 (90)

20

;86

Series of matches (70)

26 18 13 12 29

;85 ;85 ;84 ;84 ;83

Fourteen (90) Fifteen (90) Fourteen (90) Eight (90) Two of preseason (90)

;84

Six (90)

8

168 169 166

;83 ;84

VOLUME 26 | NUMBER 10 | OCTOBER 2012 |

2893

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

HR in Soccer: A Practical Review

TABLE 2. Male soccer players’ HR responses in friendly match play expressed as average in absolute values (bmin21) and in %HRmax. Source Seliger (113) Van Gool et al. (124) Van Gool et al. (123) Ali and Farrally (3) Ogushi et al. (96) Fernandes (57) Mohr et al. (94) Bachev et al. (9) Tessitore et al. (119) Eniseler (55) Krustrup et al. (79) Edwards and Clark (53) Krustrup et al. (80) Condessa (32)

Level

n

Not informed/Czechoslovakia University/Belgium University/Belgium Semiprofessional/United Kingdom University/United Kingdom Recreational/United Kingdom Professional/Japan First division/Brazil Fourth division/Denmark

16 5 7 9 9 9 2 19 9 16 16 12 10 31 8 7 12 22

Junior national/Bulgaria Amateurs ; 62 years old/Italy First division/Turkey Four division/Denmark University/United Kingdom First division/United Kingdom Recreational adults/no informed First division/Brazil

(12–14 years), with the application of linear regression equations based on the individual HR-V_ O2 relationship calculated from submaximal and maximal treadmill tests. In terms of energy expenditure, a value of 1.360 kcal has been reported during match play for a player weighing 75 kg and having mean oxygen consumption (V_ O2max) of 60 mlkg21min21 (11). However, these intensities appear to be somewhat inflated because both elite adult and youth players are often stationary or walking during soccer training and/or matches (14,40,46,93,100,108). Both standing still and walking constitute approximately 15 and 40%, respectively, of the total playing time during a 90-minute match (100). However, high-intensity activities, (sprinting, directional changes, and tackles/duels) and short/insufficient recovery intervals between these actions, elevate the EI close to maximal values (20,40,46,100). Because the majority of soccer activities are performed at low to moderate intensities, it is described as an ‘‘intermittent aerobic sport’’ with approximately 90% of total energy expenditure provided by aerobic energy sources/ pathways (11,37,116). However, 150–250 (approximately 15%) soccer actions are performed at a high intensity (93), which are sufficient to increase the blood lactate concentration to submaximal values (3–8 mmolL21) (5,14,24,54,60,79,93). Therefore, it could be argued that blood lactate values underestimate the actual intensity because of the process of lactate removal/clearance at the moment of blood sampling. There is a difference between lactate production and lactate removal in the muscle and in the blood. The blood lactate

2894

the

HR (bmin21) 165 166 167 ;171 ;167 ;168 161 166 160 162 165

%HRmax 80 ;85

82 86 85 86 ;85

157 156 156 161 157 171

80 84 84 ;86

No. of friendly match play (min) Simuled (10) One (90) One (90) One (90) One (90) One (90) One (90) Two (90) One (90) One (90) One (90) One (70) One (20) Three (90) One (90) One (90) Two (90) One (45)

values derived from field-based sampling do not necessarily represent or reflect actual muscle lactate concentration (11,21,96). However, caution should be taken as to interpretations based on the linear HR-V_ O2 relationship. This relationship is based on a continuous treadmill running test, and this linearity does not necessarily apply during match play because of the intermittent nature of soccer (66,96,125). This finding emphasizes that the relationship between HR and EI may be best described by a sigmoid equation where the tendency of HR to plateau at the highest exercise intensities is clearly illustrated (e.g., considering the presence of limitations such as overestimation) (86). This method could be adopted to estimate EI if the activities, such as sprints that elevate HR values in a nonlinear way, do not exceed 1 minute (12,66,93). Previous studies did not succeed to demonstrate significant differences between the HR-V_ O2 relation obtained either by intermittent testing on the treadmill with specific soccer play speeds or by continuous testing using the same average speeds (e.g., (23)). In addition, no differences were detected between field tests (circuits) simulating game actions and intermittent and continuous treadmill tests to exhaustion in either amateur or professional soccer players (30,66,75). II.2. Relationship Between Heart Rate and Metabolic Thresholds. Some studies have estimated the EI based on the relationship between match and the anaerobic HR threshold obtained in a continuous laboratory treadmill test (32,49,57,75,96,123).

TM

Journal of Strength and Conditioning Research

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

the

TM

Journal of Strength and Conditioning Research Fernandes (57) examined Brazilian professional first division players during 2 friendly matches and concluded that the HR stayed below the anaerobic threshold for 56.7 6 21.9% of total match duration. Physiological load with increased anaerobic characteristics was reported by Coelho (31) in Brazilian youth elite players during competitive matches, using linear interpolation in the field tests to determine the percentage of HR corresponding to 4 mmolL21 of blood lactate, showing that players remained above 85% of the HRmax for more than half the match, which corresponded to the anaerobic threshold. Using the same procedure, Eniseler (55) confirmed these results as 49.6 6 21.1% of the total duration of a match play was spent by elite Turkish players above the anaerobic threshold. These studies used the anaerobic threshold as a reference point to correspond to the complexity of the physiological stimuli of soccer. The metabolic interaction above the anaerobic threshold highlights the importance of developing aerobic capacity, expressed by V_ O2max, which allows an elevated level of recovery, the removal of the produced lactate, and the capacity to perform repeated high-intensity actions (115). It is thus suggested that coaches should structure HR zone-based training sessions based on the results of laboratory and/or field test to individualize and optimize the physical training of the players. II.3. Exercise Intensity and Maximum Heart Rate Percentage. The intensity of elite competitive match play ranges between 80 and 90% of HRmax (14,110,116). The method of studying the game intensity based on HRmax has been adopted by the majority of studies for interindividual comparison purposes. The same zone of EI has been observed in lower level, professional (3,56,79,94), older players in recreational matches (119) and elite U-12 (24,76), U-13 (117), U-15 (16), U-17 (16,31,95), and U-20 players (63,67,95,120) in competitive matches (Tables 1 and 2). Despite the similarities in EI between several age categories and competitive levels, the anaerobic pathways of energy supply are underdeveloped in adolescents and may therefore not be appropriate for expressing HR values as a percentage of time below and above 85% of HRmax, which is a wellestablished threshold between aerobic and anaerobic supply of energy in adults (16). Billows et al. (16) observed, in adolescent players, that HRs were below 85% of HRmax for 37% of match duration with the remaining limit of metabolic transition (relationship of 1:3) being different from those observed for adult players (relationship of 2:1). However, it is expected that the demands of high-level match play presents a greater percentage of high-intensity actions (34) compared with the results presented by Billows et al. (16) in young players. This difference could also be explained by the fact that the professional players have higher fitness levels and a greater level of position specialization, which raises the absolute motor and physiological demands during the match (83). On the other hand, the overall shorter duration of the

| www.nsca.com

youth and older players’ games could induce an increase of the intensity of the cardiac response in %HRmax similarly than those observed in elite players. Helgerud et al. (63) calculated the time spent in the following intensity categories: ,70%, 70–85%, 85–90%, 90–95% and .95% of the HRmax, concluding that HR remained at the zone intensity of 85–90% and 70–85% of the HRmax during approximately 37% of the total duration of the match for these two zones. Additional observations showed in elite Brazilian players confirmed that the greatest time was spent within the 70–85% HRmax zone (31). Rohde and Espersen (110) found that second division professional Danish players spent 63% of the match in the HR zone between 73 and 92% HRmax, whereas Fernandes (57) reported that HR was above 77% HRmax during 66% of the total time in the fourth division Brazilian footballers. However, Tessitore et al. (119) showed that older players spent a shorter time in the high-intensity zones, with results indicating that the HR responses of the older players were above 85% HRmax for approximately 50% of the total match duration. The HR distribution of these older players showed a tendency toward higher standard deviations and higher coefficient of variations. Furthermore, it was noticed that more time was spent at intensities below 70% HRmax in the second half of the match, differing from the other age groups (119). This fact could explain the lower recovery capacity after high-intensity stimuli, resulting in walking a higher percentage of time during the second half (approximately 69%) in comparison to the values found (approximately 40%) in previous studies both in youth (117) and elite adult players (14,63,108,116). It remains that the precise analysis of the HR responses should be interpreted according to the different halves during a match play. In conclusion of this topic, it appears that the use of HRmax is not the best indicator to evaluate the EI in soccer as this method does not take into account the magnitude of the HR responses (HRmax 2 HRrest). Indeed, although 2 players can have a similar HRmax, they might possess different resting HR, which could induce a difference of HR responses during training or match play. In this context, it is suggested that the HR responses need to be analyzed after considering the resting HR as proposed by Karvonen et al. (73): %HRres = (mean exercise HR 2 resting HR)/ (HRmax 2 resting HR) 3 100. II.4. Exercise Intensity During the First and Second Halves of Match Play. The precise analysis of HR responses during match play according to the different halves reveals that the mean EI, measured by HR, decreases in the second half with respect to the first half in elite adult (11,53,94,96,110), junior (63,95,120), university (31,123), recreational (3), and youth players (24,116). When the EI was considered as a function of time in relation to the HRmax intensity zones, Helgerud et al. (63) found a redistribution of the zones in the second half. They observed a reduction in the time spent within 85–90% VOLUME 26 | NUMBER 10 | OCTOBER 2012 |

2895

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

HR in Soccer: A Practical Review HRmax and an increase of the time spent in the lower intensity zone (75–80% HRmax). The same tendency was presented by Coelho (31) reporting a drastic change in the time spent between 70 and 85% HRmax from the first half (34.5 6 2.4%) to the second half (43.9 6 1.1%) of the match, but it could not justify the detection of overtraining and overuse or a detraining (103). During the second half of the match, professional players covered 5–10% less distance than during the first half, especially in the moderate (11.1–19.0 kmh21) and high-intensity (18.0–30.0 kmh21) speed categories (5,14,15,47,89,103). In the same context, blood lactate concentration, distance covered at high intensity, and number of sprints confirmed the decrease of high-intensity actions during the second half, which was described as independent of the playing level (79,116). These fitness performance reductions occurring at the end of the match induce the coach to plan specific fitness training in order to try to reduce this decrease. The team in which players present the lowest reduction of high-intensity actions (such as the total distance covered in sprint) during a match should be the winning team in the majority of the cases (20,48,83). These reductions were also described as greater in amateurs than in elite soccer players (37,47), illustrating the higher capacity to perform high-intensity actions. Therefore, professional players do have higher performances in maximum aerobic power, muscular force, and capacity to perform short-duration intermittent exercise at high intensity (41,116). In this context, the reduction of the HR responses in the second half of the match cannot be only linked to the reduction of physical performance, as was previously stated (15). A possible reason to explain these findings is that the player’s HR response during a match rarely reaches values less than 65% HRmax, even in youth (3,80) and older players (119). So, with the brusque and constant changes of intensity during the play, it seems that the V_ O2 is limited by local factors, such as the oxidative capacity of the active muscles (12,13). Some local physiological mechanisms could explain the lower physical activity of the players at the end of the second half. During the match play, a progressive degradation of muscle glycogen (from 40 to 90%) in muscle fibers has been observed, especially in the IIb fiber type (12,79). There is also a reduction in the levels of creatine phosphate, muscular pH, an increase of muscle monophosphate ionosine, an accumulation of the potassium stocks (79), and a temporary decrease in the temperature of the quadriceps (94) and the body (53), in addition to dehydration (12,107). Despite these suggestive factors, the reason that might cause fatigue or overuse in soccer players during a match are multifactorial and still not clear and are not always associated with a reduction in the performance of sprints (12,79). The physiological load of soccer and the hydration difficulties during competitive situations provoke a mean loss

2896

the

of 1.4 L of sweat (79), a reduction of 1.5–4% in body mass, and a decrease of 7–12% in the blood plasma volume (51,94). These aspects have to be linked to the thermogenesis’ regulation that would induce an increase of the players’ HR responses in the second half of play for cardiovascular compensation. However, a lack of increase of the HR responses was observed in the second half probably because of a lower physical demand of the match (20,47,94). It has been also suggested that these reductions of physical performance in the second half of the match could be caused by other factors such as the tactical, technical, and psychological aspects. For example, Ali and Farrally (3) related that depending on the match score and the importance of the game, the players could perform a different effort, tending to decrease the physical performance when the results are favorable and the spread on the scoreboard is comfortable. Indeed, Lago-Penas et al. (83) showed that the team that lead during a match spent more time in its defensive zone and presented lower total distance covered in high-intensity conditions. Keeping in mind that the intensity in the second half of the match is lower, 2 practical recommendations could be suggested. The first refers to the return of injured athletes after the rehabilitation period; it is recommended that they could be introduced during the second half of the match, when the rhythm tends to be less intense. The second refers to the necessity that the team is well prepared physically and that nutritional strategies should be established to minimize the decrease of muscle glycogen reserves, enhancing the chance of better performances. Moreover, Mohr et al. (94) demonstrated that the decline in physical performance and muscle temperature during halftime was associated with the reduction of sprint capacity (approximately 2.4%) at the beginning of the second half. Nevertheless, this capacity was maintained when low-intensity activities (approximately 70%) of the peak HR reached during the game were performed during half-time to preserve the temperature of the quadriceps muscles. Therefore, body temperature maintenance strategies should be adopted during half-time of the match. However, it could be interesting to examine specifically the relationship between HR and overuse in soccer, but it appears that too much variables should be considered concomitantly (hormonal variation, omega wave, stress, etc.), and therefore, HR could not be isolated and constituted a limited interest, especially in soccer. II.5. Exercise Intensity and Heart Rate Responses According to the Playing Position. In professional (37,47,48,123), junior, youth (31,117), and university players (124), it has been shown that HR responses differed according to the playing positions, with the greatest values for the midfielders and lowest values for the central defenders. Ali and Farrally (3) were in agreement with this observation by showing greater HR responses (176 6 9 bmin21) for midfielders, in comparison

TM

Journal of Strength and Conditioning Research

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

the

TM

Journal of Strength and Conditioning Research with forwards (173 6 12 bmin21) and central defenders (166 6 15 bmin21). The midfielders’ cardiovascular overload could be explained by the tactical functions of these players in the modern soccer tactical systems of play. These players presented a greater total distance covered in sprint, higher number of ball possession, and greater number of duels (40,46). Moreover, from a technical and tactical point of view, they are included both in offensive and defensive play. Midfielders usually present the best highest aerobic capacity, which allow them greater possibilities of active participation during games (10,116,128). An interesting strategy for future studies is the adoption of HR responses to determine the precise EI according to the playing position. Coelho (31) have studied Brazilian junior players, finding that midfielders spent more time at 85–90% and 90–95% HRmax than the other positions. However, the fullback presented the highest total duration spent at 95–100% HRmax intensity zone, and in contrast, they were also players remaining more time in the smallest EI at 70% of HRmax. Fullback’s role is characterized by a high number of very high intensity actions (20,40,46,47), which could explain why they require a greater period of recovery than other playing positions. This strategy of analysis would facilitate the differentiation of physical loads between the playing positions. Traditional studies have reported that forwards and fullbacks had a greater number of anaerobic actions (sprints) than other positions (18–20,40,46–48). Complementarily, defenders covered greater total distance in running backward, and midfielders spent more time in jogging and in running at a high intensity (18,108). Despite these differences in timemotion characteristics, style of play, and tactical obligations, the use of the EI as a means of the total duration spent in a precise intensity zone could better represent the physiological load according to the playing position. The interaction of several positions in a determined tactical system and the combination with different tactical systems could bring important information to establish goals and strategic projections for the physical preparation, match, and recovery. Another interrogation to consider is the style of play between the countries (17,19,40). Few studies have undertaken this, but it is suggested that the style and the culture could be an important factor in the differentiation of physiological game load. Indeed, Dellal et al. (40) have shown that the physical and technical demands according to the playing positions during an elite match play differed between 2 very high level European Leagues: the Spanish Liga (Spain first division) and the English Premier League. Silva et al. (114) pointed out that the Brazilian players presented certain different physical performances according to the positional roles, with a special distinction of the fullbacks who presented the greatest V_ O2max values contrasting with some values presented in European fullback players.

| www.nsca.com

II.6. Use of Heart Rate Monitoring During Soccer Training. Use

of heart rate monitoring during high-intensity intermittent exercises. Training prescription should be based on the players’ positional physical match demands. The different HR zones could be used as an indicator of the EI. Because of several continuous aerobic tests (22,29,81,85), coaches use these performances to apply intermittent exercises. Different studies ((39,43,51,52); Table 3) have showed that short intermittent exercises in-line induce a high percentage of HR responses with, for example, about 91 to 92% of HRmax for a 15-15-second at 120% of maximal aerobic speed (MAS) (15 seconds of work at 120% of MAS and 15 seconds of recovery). A 5-20-second, a 10-10-second, a 15-15-second, and a 30-30-second allow reaching values ranging from 76.8 to 85.8% of HRres (39). The intensity of the work period increases the impact on HR responses both for 30-30-second, 15-15-second, and 10-10-second (43), showing the effect of speed increase on the central component (HR). Additionally, the type of recovery (active vs. passive) could modify the HR responses. Indeed, the passive recovery during a 30-30-second at 100% of MAS induces a significantly lower HR response than an active recovery (with %HRres: 77.2 vs. 85.7%) (39), whereas it was not the case for a 15-15-second at 120% of MAS (with %HRmax: 92.0 vs. 91.3%) (52). It could be explained by the fact that the HR kinetics was too short during the recovery period of the 15-15-second and 10-10-second, but 30 seconds of recovery period appears to be enough to reduce significantly the HR values during a 30-30-second. Moreover, the type of effort during short-duration intermittent exercises should also alter the HR responses. Dellal et al. (43) revealed that specific interval training with directional changes altered consistently the HR responses compared with a traditional in-line interval training for a 30-30-second both at 100% (76.3 vs. 82.1% of HRres), 105% (80.1% vs. 86.5% of HRres), and 110% (85.0 vs. 90.0% of HRres), but no difference were found concerning a 10-10-second (at 110, 115, and 120%) and a 15-15-second (at 105, 110, and 115%). Deceleration, directional changes, and reacceleration during this specific exercise have a very high effect on HR responses but almost on the anaerobic metabolism solicitation. Use of heart rate monitoring during smallsided soccer games. Furthermore, several exercises including the presence of the ball are more often used in modern soccer. Technical training with the ball can be an intense stimulus as shown by Dellal et al. (39). In this context, SSGs were demonstrated allowing similar or even higher HR responses to those found during short-duration intermittent exercise and match play (39,97,105). Small-sided games are considered as a multifactorial training because of the integration of simultaneous physical, technical, and tactical elements. The 6 vs. 6, 4 vs. 4, and 3 vs. 3 situations appears to be the best choice to recreate the physical and technical demands of match play (Table 4), at the same time allowing VOLUME 26 | NUMBER 10 | OCTOBER 2012 |

2897

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

HR in Soccer: A Practical Review

TABLE 3. Male soccer players’ HR responses in different high-intensity intermittent exercises expressed as average in absolute values (bmin21), in %HRmax, and in %HRres.*

Source

Interval training

Dupont et al. (51)

15-15

Dupont et al. (52)

15-15

Dellal et al. (37,39) 5-20 10-10 15-15 30-30† 30-30† Dellal et al. (43,46) 10-10

Work intensity (percentage of MAS) 110 120 130 120 120 110 100 100 100 110 115 120

15-15

105 110 120

30-30†

100 105 110

%HR maximal or maximal bmin21 Type of recovery Block duration reached %HRres

Type of exercise In-line run In-line run In-line run In-line run In-line run In-line run In-line run In-line run In-line run In-line run In-line run With directional changes In-line run With directional changes In-line run With directional changes In-line run With directional changes In-line run With directional changes In-line run With directional changes In-line run With directional changes In-line run With directional changes In-line run With directional changes

Passive Passive Passive Passive Active Passive Passive Passive Passive Active Passive

Until exhaustion Until exhaustion Until exhaustion Until exhaustion Until exhaustion 1 3 7 min 2 3 7 min 2 3 10 min 2 3 10 min 2 3 10 min 1 3 6 min, 50 seconds

189.0 189.0 191.0 92.0% 91.3% 80.2 85.8 76.8 77.2 85.7 86.6 88.1 88.3 89.3 90.0 91.3

Passive

1 3 9 min, 45 seconds

83.8 86.0 86.7 88.2 89.5 90.2

Active

1 3 11 min, 30 seconds

76.3 82.1 80.1 86.5 85.0 90.0

*%HRres = percentage of heart rate reserve. †30-30: alternance of 30 seconds of work and 30 seconds of recovery period.

an improvement of the V_ O2max and a high demand of cardiovascular system (39,77,111). The determination of the type, format, and rules of SSG during training depends on the period of the season (preseason, midseason, or competition) and the training objectives (38,39,42,44,101,118). An interesting aspect in the adoption of SSG strategies is that the motivational factor, through incentives and commands given by the coach, may strongly influence the intensity of training (101). Another type of manipulation that can increase the EI in this type of training is the quick ball replacement and emphasis in pressuring the opponent.

2898

the

Dellal et al. (39) observed that the presence of goalkeepers increased the tax of %HRres in SSG in French professional players, whereas Mallo and Navarro (90) showed the opposite tendency. Moreover, a number of prescriptive variables influence the intensity and HR responses during the SSG training, especially the HR responses. These variables include the pitch size (74), presence of the goalkeepers (39), goal size (87), number of players (39,64,126), total duration and number of bouts period (71), availability of replacement soccer balls (101), and balance of the opposition (64). In the same context, the number of ball touches authorized by

TM

Journal of Strength and Conditioning Research

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

TABLE 4. Male soccer players’ HR responses in different training situations (especially SSGs) expressed as average in absolute values (bmin21), in %HRmax, and in %HRres.*

Elite/Norwegian Junior elite/Australia

6 13

Sixth division/Italy Not informed/Italy

7 15

Elite/Champions League

9

Eniseler (55)

First division/Turkey

10

Tessitore et al. (118)

Regional level/Italy

9

Little and Williams (87)

Division I/England

23

Rampinini et al. (101) Williams and Owen (126) Rodrigues et al. (109)

Amateurs/Italy Premier League/United Kingdom U-17 of high level/Brazil

20 9 8

Kelly and Drust (74) Mallo and Navarro (90)

Second division/United Kingdom Elite U-19/not informed

8 10

Dellal et al. (37,39)

First division/France

10

Hill-Haas et al. (64)

Domestic League/Australia

16

First division/Scotland

15

Esposito et al. (56) Rampinini et al. (102) Sassi et al. (112)

VOLUME 26 | NUMBER 10 | OCTOBER 2012 |

Owen et al. (97)

184 135–155 155–178 155–178 156

;178 ;170 ;167 ;140 135 126 118 .160 .160 173

163 150 157 ;173 ;173

%HRmax

%HRres

;91 ;59 ;78 ;78 ;88 ;78 ;85 ;91 ;91 ;85 ;72

;90 ;87 ;90 80–90 ;75 ;79 ;90 ;91 ;91 ;88 77 80 77 80 71 75 89 85 83 ;90 ;81

Training situations (min) 5 vs. 5 + GK (50 3 40 m) Kick direct to the goal (15 min) Physical of zig-zag (10 min) 6 vs. 7 SSG (2/3 of the field, 20 min) Modified circuit of Ekblom (1998) 4 vs. 4 SSG (4 3 4 min) 4 vs. 2 SSG (2 3 4 min) 10 vs. 10 SSG (10 min) 4 vs. 4 SSG 8 vs. 8 SSG 4 3 1,000 m technical and tactical training Simuled game (20 min) Tactical (20 min) Technical (20 min) 6 vs. 6 SSG (30 3 40 m) 6 vs. 6 SSG (50 3 40 m) 2 vs. 2; 3 vs. 3; 4 vs. 4; 5 vs. 5 6 vs. 6; 8 vs. 8 SSG 5 vs. 5 and 6 vs. 6 SSG 3 vs. 3; 4 vs. 4; 5 vs. 5; 6 vs. 6 SSG 2 vs. 2; 3 vs. 3; 4 vs. 4; 5 vs. 5 SSG Simuled game 8 vs. 8 SSG 4 vs. 4 SSG 3 vs. 3 SSG 3 vs. 3 SSG + 2 out players 3 vs. 3 SSG + GK 1 vs. 1 SSG 2 vs. 2 SSG 4 vs. 4 SSG + GK 8 vs. 8 SSG + GK 8 vs. 8 SSG 10 vs. 10 SSG +GK 2 vs. 2 SSG 4 vs. 4 SSG 6 vs. 6 SSG 3 vs. 3 + GK 9 vs. 9 + GK

2899

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

| www.nsca.com

Hoff et al. (66) Flanagan and Merrick (59)

HR (bmin21)

TM

n

the

Level

Journal of Strength and Conditioning Research

Source

the

Journal of Strength and Conditioning Research

International players

20

TM

Dellal et al. (38,40–42,44)

Ko¨klu¨ et al. (77)

Amateur players (fourth French division)

Elite youth/Turkey

20

16

;169 ;172 ;182 ;179

90.0 90.1 90.0 90.0 89.4 89.6 87.6 85.6 84.7 92.3 91.5 91.6 91.2 90.0 89.5 87.4 86.6 85.1 ;86 ;88 ;93 ;91.5

87.2 86.9 86.8 86.7 86.0 86.3 83.6 80.8 79.7 89.6 88.6 88.6 88.2 86.5 85.8 83.0 82.0 79.9

2 2 2 3 3 3 4 4 4 2 2 2 3 3 3 4 4 4 1 2 3 4

vs. 2 vs. 2 vs. 2 vs. 3 vs. 3 vs. 3 vs. 4 vs. 4 vs. 4 vs. 2 vs. 2 vs. 2 vs. 3 vs. 3 vs. 3 vs. 4 vs. 4 vs. 4 vs. 1 vs. 2 vs. 3 vs. 4

with 1 ball contact with 2 ball contact with free play with 1 ball contact with 2 ball contact with free play with 1 ball contact with 2 ball contact with free play with 1 ball contact with 2 ball contact with free play with 1 ball contact with 2 ball contact with free play with 1 ball contact with 2 ball contact with free play

authorized authorized authorized authorized authorized authorized authorized authorized authorized authorized authorized authorized

*GK = goalkeepers; HR = heart rate; SSG = small-sided games; %HRres = percentage of heart rate reserve.

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

HR in Soccer: A Practical Review

2900 Dellal et al. (38,40–42,44)

the

TM

Journal of Strength and Conditioning Research possession directly affected the total distance covered in sprint or in high intensity both in amateurs and elite soccer players (41). However, despite greater HR responses for amateur players during a 3 vs. 3 played in 1 ball contact authorized, no difference was found between elite and amateur players for the 3 vs. 3 played in 2 ball contact authorized or free play and for the 2 vs. 2 and 4 vs. 4 whatever the number of ball contact authorized (41). Dellal et al. (45) have also demonstrated that the proportion of total distance covered in sprint and in high intensity was significantly greater during SSG than during a match play. Indeed, during a match, the maximal percentage of the total distance covered in sprint and in high intensity corresponds to 5.3% of the total activity (40,46) according to the playing positions, whereas the values found during SSG were 37.3% during a 4 vs. 4, 41.1% during a 3 vs. 3, and 42.5% during a 2 vs. 2 (40,45,46). Consequently, the use of SSG becomes an interesting alternative combining the technical and tactical actions in more realistic match situations, whereas the physical demand is increased with a special solicitation of cardiovascular system and therefore the HR response. Furthermore, although the SSG is considered as an excellent training strategy with a quite strong reproducibility (64), it is necessary to point out that the workload is not highly controlled, with a larger intersubject variability (8,102) than in separated fitness conditioning (generic training). Castagna et al. (27) suggested that it is necessary to have an idea of the EI and HR responses of a determined SSG to use it because of the fact that the intensity of the stimulus is related to the technical and tactical quality of the players. However, the traditional use of short generic intermittent exercise should not be discarded, providing greater control over the EI and allowing a larger reproducibility of the proposed stimulus. High loads of training (e.g., 90–95% HRmax) are more easily maintained with interval running compared with the SSG (39). III. Limitations of Heart Rate Monitoring

Although the use of the HR is practical, its responses might be influenced during training by several aspects besides the physical conditioning of the player. Among these factors, the environmental conditions could be cited. Indeed, the external temperature, the relative humidity, the atmospheric pressure, the altitude, the air resistance, the hormonal variation during match play (i.e., adrenaline), and the medications’ use could alter the HR responses of the players during soccer training (1,84), and thus, the use of HR as a reliable detection method of overuse in soccer is discussed. Specifically, it is suitable to note that the conditions of the field, such as a wet state or short grass and the type of pitch (grass or synthetic turf ), could also interfere in the EI of the players. These factors may lead to an overestimation or underestimation of the V_ O2 because they alter the behavior of the HR without affecting the V_ O2 in the same proportion (50,66,110). It is necessary for the studies to specify the environmental conditions of the

| www.nsca.com

training location and the place where the tests are applied, to improve the analysis of the physiologic and internal training load. Although the environmental conditions influence the HR-V_ O2 relation, it is suggested that the reproduction of external temperature, the relative humidity, and the type of pitch should be strictly controlled. This strategy was examined in the study of Esposito et al. (56). These authors observed a very strong correlation (0.991; p , 0.001) between HR-V_ O2 obtained in the laboratory and in the field for amateur players executing characteristic activities of soccer in circuit training, measured in both situations with a portable gas analysis system. It is suggested that the EI, as a function of the HRmax or the HRres, should be performed based on the greatest value of HR observed in several situations, such as laboratory and field tests. There is a strong tendency to observe the value of HR in competitive soccer situations, but it has been shown that the use of the equation ‘‘220-age’’ leads to a poor estimation of the HRmax of the players, compromising the analysis of EI during the match and the training, and limiting the prescription of the physical sessions based on HRmax percentage (7). In children and adolescents, Mahon et al. (89) have also revealed that the ‘‘208 2 0.7 age’’ equation allows similar results of HRmax prediction as ‘‘220 2 age,’’ but the 2 methods do not take in consideration the rest HR chronological and maturational age and need further studies for this population (88). Some alternatives to evaluate the HRmax, which have been suggested, are increments in maximum aerobic potential tests on the treadmill as adopted by Wisløff et al. (128) or a field test for an indirect continuous aerobic evaluation of players by an incremental running speed such as the VamEval test derived from the Le´ger-Boucher test, validated to determine the HRmax and estimate the V_ O2max (29,85). The HRmax and V_ O2max were calculated according to the velocity attained in the last 1-minute stage completed by the players. Furthermore, the 1,000 m maximum running test (109) or the 3 3 600 m with a running incremental intensity (61) has been used to estimate the HRmax of soccer players; however, these procedures have not been yet validated. Intermittent tests as the Yo-Yo intermittent recovery tests, which have been validated as a highly valid test for soccer (81), were created to provide HRmax in similar condition than those found in soccer, an intermittent activity. In the same context, the 30-15 Intermittent Fitness Test (30-15IFT), proposed by Buchheit (22), suggested to provide accurate assessment of the V_ O2peak and therefore HRmax. However, each test provides their own HRmax values with small differences between tests, but it could be hypothesized that an intermittent aerobic test (30-15IFT or Yo-Yo test) results in a better estimation of HRmax than continuous aerobic tests because of the nature of the game (intermittent). Players should be more performant in this type of test, knowing that each test induces a specific training (continuous or intermittent). When the objective is to estimate the energy expenditure of the players through HR, some considerations should be VOLUME 26 | NUMBER 10 | OCTOBER 2012 |

2901

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

HR in Soccer: A Practical Review respected. First of all, although this estimation is valid, it is necessary to obtain the individual relation between HR and V_ O2 (1,23). It is still considered that, in this case, the energy estimate should be performed only with aerobic metabolism, without clearly indicating the energy induced from the anaerobic metabolism (12,13). To appreciate the anaerobic participation in the energetic supply during match play, it is necessary to consider the high-intensity and technical actions, complementary to the HR responses. Studies have demonstrated that the total duration of high-intensity actions is approximately 7 minutes long, which represent approximately 57 high running speed activity and 19 sprints with an average duration of 2 seconds (14). Moreover, it has been observed that the players have a number of ball possessions ranging from 43 to 58 (40,46) and that 1.5–3% of the total distance traveled is carried out with the ball (34,47,48). Carling (25) added that players performed 191 6 38 m with the individual ball possession with especially 34.3% on speed superior to 19 kmh21. As suggested by Drust et al. (50), the integration of simultaneous HR monitoring and the use of multiple camera systems can provide a precise profile of each player according to their playing positions. This combination could improve the understanding of the specific physiologic load and internal training load in soccer, especially the link between technical, physical, and tactical activities with HR responses (26). Moreover, advancement in monitoring equipment such as global positional system (GPS) should be able to monitor and examine concomitantly the HR and the physical runs, allowing a precise analysis of the physical demand and HR response in soccer during specific training and match (45). Another important factor concerns the hormonal activity, which could change the distribution of participation of the energetic sources without directly reflecting the HR (1,84). Hormonal changes, like the decrease of insulin plasma rates and the increase of catecholamine and adrenaline during match play, could increase the use and the concentration of free fatty acids progressively and, therefore, induce a modification of the HR response (13,79). However, HRmax, which is the most common HR reference value used in the scientific literature, is not the best indicator to estimate the HR responses in soccer players. Indeed, 2 players presenting similar HRmax might not often have similar HR responses during a specific training both in a continuous and intermittent form (37,43). Although these players have a similar HRmax, they might have different resting HR, which could explain this difference of HR responses in soccer when scientist or coach uses the HRmax as an indicator. For instance, it is suggested that the HR responses need to be analyzed considering the resting HR such as the HRres formula proposed by Karvonen et al. (73): %HRres = (mean exercise HR 2 resting HR)/(HRmax 2 resting HR) 3 100. Resting HR is the minimal value of HR obtained for 3 consecutive interval times after 10 minutes when players were in a quiet room, on a mat in the supine

2902

the

position, with their eyes closed and without having performed any prior exercise as reported by Dellal et al. (39,43). This calculation of the %HRres allows an interindividual comparison, and the coach and scientists should only use the HRres values as the indicator of HR responses in soccer.

CONCLUSIONS In conclusion, some points appear to be well documented in the literature and are highlighted: (a) HR can be used to monitor the physiologic load and internal training load in soccer players with good validity, especially when the analysis is considered as a function of HRres or at least with HRmax; (b) competitive match intensity is described as 70–80% of V_ O2max and 80–90% of HRmax, independently of the playing level including elite, recreational, female, and youth soccer players; (c) when intensity zones are considered, approximately 65% of the total duration of a match play is spent at an intensity between 70 and 90% of HRmax and rarely below 65% HRmax; (d) HR response varies according to playing positions, and midfielders presented greater EI, followed by forwards and fullbacks; (e) in the second half of the match, the EI is lower than in the first half, and this reduction could be correlated with the physical conditioning of the player; and (f ) SSGs allows similar HR responses to those found during short-duration intermittent exercise and those described during match play, but with greater interindividual coefficient of variation. In this context, the control of EI through HR in training and in match play should always express as the HRres because it is considered as the most reliable HR indicator, allowing a more accurate interindividual comparison. The most recent system equipments and their associated software (i.e., Polar Team2; Polar Electro, Kempele, Finland) allow to follow in real time the player’s HRres during the training. Future perspective of time-motion analysis of soccer players is to suggest the concomitant use of GPS or semiautomatic multiple camera system with HR monitor to determine the precise variation of HR according to the technical, physical, and technical nature of a match play or a specific training exercise. Moreover, further studies should examine in detail the post-exercise heart rate recovery (HRR) after different type of exercises (SSGs, repeated sprint ability, high-intensity intermittent exercises, continuous runs, etc). Another review about the interest of the HRV use in soccer will be also recommended.

PRACTICAL APPLICATIONS Previous studies have demonstrated that the HR monitoring is an interesting tool to evaluate the internal load both during training and soccer games. This review presents to the coaches the different methods to estimate the HRmax, the rest HR, and how it should be used and interpreted during the training and match play. One of the conclusions is that HRres should be favored because it is considered as the most reliable HR indicator, allowing a more accurate interindividual comparison. HRres is the only one method taking into

TM

Journal of Strength and Conditioning Research

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

the

TM

Journal of Strength and Conditioning Research consideration the HR magnitude (HRmax-HRrest) and the circadian biorhythm variation, allowing a better comprehension of the coaches. Furthermore, the major finding showed that HR monitoring provides valuable information of players during aerobic exercises (continuous or long interval training) with a possible variation according to the environmental conditions (temperature, humidity, wind speed, and type of pitch) and the time of the day (hormonal circadian biorhythm). Coaches have to keep in mind that these factors could alter the HR responses and the stress or psychologic aspect. However, HR monitoring is not considered as the most reliable indicator during all exercises including combined or isolated directional changes, SSGs, high-intensity intermittent exercises, anaerobic solicitation, specific technical or tactical exercises, power training, repeated sprint ability, and so on. In these cases and during matches, coaches need to analyze the HR response combined with other tools as, for example, blood lactate samples, metabolic thresholds, timemotion characteristics, or RPE values. Soccer is a multifactorial activity, and HR monitoring is only one of the different tools to examine the physiologic and internal load. Future perspective of time-motion analysis of soccer players is to suggest the concomitant use of GPS or semiautomatic multiple camera system with HR monitor to determine the precise variation of HR according to the technical, physical, and technical nature of a match play or a specific training exercise. Moreover, further studies should examine in detail the postexercise HRR after different type of exercises (SSGs, repeated sprint ability, high-intensity intermittent exercises, continuous runs, etc.). Finally, HR monitoring is an essential indicator during aerobic exercises, but coaches have to combine it with other methods when they use other types of training.

ACKNOWLEDGMENTS The authors thank CAPES for providing the necessary funding and resources to make this review possible. The authors also thank David Behm for his valuable assistance in this project.

REFERENCES 1. Achten, J and Jeukendrup, AE. Heart rate monitoring: Applications and limitations. Sports Med 33: 517–538, 2003. 2. Alexiou, H and Coutts, AJ. A comparison of methods used for quantifying internal training load in women soccer players. Int J Sports Physiol Perform 3: 320–339, 2008. 3. Ali, A and Farrally, M. Recording soccer players’ heart rates during matches. J Sport Sci 9: 183–189, 1991. ´ lvarez, JCB and Castagna, C. Heart-rate and activity-speed of 4. A professional soccer players in match. In: VIth World Congress on Science and Football. Antalya, Turkey: Book of Abstracts, 2007. pp. 209. 5. Ananias, GEO, Kokubun, E, Molina, R, Silva, PRS, and Cordeiro, JR. Functional capacity and metabolic solicitation in professional soccer players during real situation of match-play. Rev Bras Med Esporte 4: 87–95, 1998.

| www.nsca.com

6. Andersson, HA, Randers, MB, Heiner-Møller, A, Krustrup, P, and Mohr, M. Elite female soccer players perform more high-intensity running when playing in international games compared with domestic league games. J Strength Cond Res 24: 912–919, 2010. 7. Antonacci, L, Mortimer, LF, Rodrigues, VM, Coelho, DB, Soares, DD, and Silami-Garcia, E. Competition, estimated, and test maximum heart rate. J Sports Med Phys Fitness 47: 418–421, 2007. 8. Aroso, J, Rebelo, N, and Gomez-Pereira, J. Physiological impact of selected game-related exercises. J Sports Sci 22: 522, 2004. 9. Bachev, V, Marcov, P, Georgiev, P, and Iliev, M. Analyses of intensity of physical load during a soccer match. In: Science and Football V (1st ed.). T. Reilly, J. Cabri, and A. Duarte, eds. London, United Kingdom: Routledge, 2005. pp. 231–236. Book of Abstracts. 10. Balikian, P, Lourencxa˜o, A, Ribeiro, L, Festuccia, W, and Neiva, C. Maximal oxygen uptake and anaerobic threshold in professional soccer players : comparison between different positions. Rev Bras Med Esporte 8: 32–36, 2002. 11. Bangsbo, J. The physiology of soccer: With special reference to intense intermittent exercise. Acta Physiol Scand 151(Suppl. 619): 1–155, 1994. 12. Bangsbo, J, Iaia, FM, and Krustrup, P. Metabolic response and fatigue in soccer. Int J Sports Physiol Perform 2: 111–127, 2007. 13. Bangsbo, J, Mohr, M, and Krustrup, P. Physical and metabolic demands of training and match-play in the elite football player. J Sports Sci 24: 665–674, 2006. 14. Bangsbo, J, Norregaard, L, and Thorso, F. Activity profile of competition soccer. Can J Sport Sci 12: 110–116, 1991. 15. Barros, RML, Misuta, MS, Menezes, RP, Figueroa, PJ, Moura, FA, Cunha, SA, Anido, R, and Leite, NJ. Analysis of the distances covered by first division Brazilian soccer players obtained with an automatic tracking method. J Sports Sci Med 6: 233–242, 2007. 16. Billows, D, Reilly, T, and George, K. Physiological demands of match-play on elite adolescent footballers. In: Science and Football V (1st ed.). T. Reilly, J. Cabri, and A. Duarte, eds. London, United Kingdom: Routledge, 2005. pp. 453–461. Book of Abstracts. 17. Bloomfield, J, Polman, R, Butterly, R, and O’Donoghue, P. Analysis of age, stature, body mass, BMI and quality of elite soccer players from 4 European Leagues. J Sports Med Phys Fitness 45: 58–67, 2005. 18. Bloomfield, J, Polman, RCJ, and O’Donoghue, PG. Physical demands of different positions in FA Premier League soccer. J Sports Sci Med 6: 63–70, 2007. 19. Bradley, PS, Carling, C, Archer, D, Roberts, J, Dodds, A, Di Mascio, M, Paul, D, Diaz, AG, Peart, D, and Krustrup, P. The effect of playing formation on high-intensity running and technical profiles in English FA Premier League soccer matches. J Sports Sci 29: 821–830, 2011. 20. Bradley, PS, Sheldon, W, Wooster, B, Olsen, P, Boanas, P, and Krustrup, P. High-intensity running in English FA Premier League soccer matches. J Sports Sci 27: 159–168, 2009. 21. Brooks, GA. Cell-cell and intracellular lactate shuttles. J Physiol 1: 5591–5600, 2009. 22. Buchheit, M. The 30-15 intermittent fitness test: Accuracy for individualizing interval training of young intermittent sport players. J Strength Cond Res 22: 365–374, 2008. 23. Burnley, M and Jones, AM. Oxygen uptake kinetics as a determinant of sports performance. Eur J Sport Sci 7: 63–79, 2007. 24. Capranica, L, Tessitore, A, Guidetti, L, and Figura, F. Heart rate and match analysis in pre-pubescent soccer players. J Sports Sci 19: 379–384, 2001. 25. Carling, C. Analysis of physical activity profiles when running with the ball in a professional soccer team. J Sports Sci 38: 319–326, 2010. 26. Carling, C, Bloomfield, J, Nelsen, L, and Reilly, T. The role of motion analysis in elite soccer: Contemporary performance measurement techniques and work rate data. Sports Med 38: 839–862, 2008. VOLUME 26 | NUMBER 10 | OCTOBER 2012 |

2903

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

HR in Soccer: A Practical Review 27. Castagna, C, Belardinelli, R, and Abt, G. The VO2 and HR response to training with a ball in youth soccer players. In: Science and Football V (1st ed.). T. Reilly, J. Cabri, and A. Duarte, eds. London, United Kingdom: Routledge, 2005. pp. 462–464. Books of Abstracts.

45. Dellal, A, Owen, A, Wong, DP, Krustrup, P, Van Exsel, M, and Mallo, J. Technical and physical demands of small vs. large sided games in relation to playing position in elite soccer. Hum Mov Sci. In press.

28. Castagna, C, Belardinelli, R, Impellizzeri, FM, Abt, GA, Coutts, AJ, and D’Ottavio, S. Cardiovascular responses during recreational 5-a-side indoor-soccer. J Sports Sci Med 10: 89–95, 2007.

46. Dellal, A, Wong, DP, Moalla, W, and Chamari, K. Physical and technical activity of soccer players in the French first division—With special reference to the playing position. Int Sport Med J 11: 278– 290, 2010.

29. Cazorla, G and Le´ger, L, eds. How to test and improve your aerobic capacity. Shuttle run and Vameval test. Bordeaux, France: AREAPS, 1993.

47. Di Salvo, V, Baron, R, Tschan, H, Calderon Montero, FJ, Bachl, N, and Pigozzi, F. Performance characteristics according to playing position in elite soccer. Int J Sports Med 28: 222–227, 2007.

30. Chamari, K, Hachana, Y, Kaouech, F, Jeddi, R, Moussa-Chamari, I, and Wisløff, U. Endurance training and testing with the ball in young elite soccer players. Br J Sports Med 39: 24–28, 2005.

48. Di Salvo, V, Gregson, W, Atkinson, G, Tordoff, P, and Drust, B. Analysis of high intensity activity in Premier League soccer. Int J Sports Med 30: 205–212, 2009.

31. Coelho, DB. Determination of the activity’s intensity of soccer players during official match play according to the heart rate monitoring. Doctoral thesis, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil, 2005.

49. Drust, B, Reilly, T, and Cable, NT. Physiological responses to laboratory-based soccer-specific intermittent and continuous exercise. J Sports Sci 18: 885–892, 2000.

32. Condessa, LA. Analise da intensidade de trainamentos especificos de futebol. Master’s thesis, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil, 2007. 33. Coutts, AJ, Rampinini, E, Marcora, SM, Castagna, C, and Impellizzeri, FM. Heart rate and blood lactate correlates of perceived exertion during small-sided soccer games. J Sci Med Sport 12: 79–84, 2009. 34. Da Silva, NP, Kirkendall, DT, and De Barros Neto, TL. Movement patterns in elite Brazilian youth soccer. J Sports Med Phys Fitness 47: 270–275, 2007. 35. Davis, JA and Brewer, J. Applied physiology of female soccer players. Sports Med 16: 180–189, 1993. 36. Davis, JA, Brewer, J, and Atkin, D. Pre-season physiological characteristics of English first and second division soccer players. J Sports Sci 10: 541–547, 1992. 37. Dellal, A. Analyze of the soccer player physical activity and of its consequences in the training: Special reference to the high intensities intermittent exercises and the small sided-games. Doctoral thesis, University of Sport Sciences, Strasbourg, France, 2008. 38. Dellal, A, Chamari, K, Owen, A, Wong, DP, Lago-Penas, C, and Hill-Haas, S. Influence of the technical instructions on the physiological and physical demands within small-sided soccer games. Eur J Sport Sci 11: 353–359, 2011. 39. Dellal, A, Chamari, K, Pintus, A, Girard, O, Cotte, T, and Keller, D. Heart rate responses during small-sided games and short intermittent running training in elite soccer players: A comparative study. J Strength Cond Res 22: 1449–1457, 2008. 40. Dellal, A, Chamari, C, Wong, DP, Ahmaidi, S, Keller, D, Barros, MLR, Bisciotti, GN, and Carling, C. Comparison of physical and technical performance in European professional soccer matchplay: The FA Premier League and La LIGA. Eur J Sport Sci 11: 51–59, 2011. 41. Dellal, A, Hill-Haas, S, Lago-Penas, C, and Chamari, K. Small sidedgames in soccer: Amateur vs. professional players’ physiological responses, physical and technical activities. J Strength Cond Res 25: 2371–2381, 2011. 42. Dellal, A, Jannault, R, and Pialoux, V. Influence of the players numbers in the heart rate responses of youth soccer players within 2 vs. 2, 3 vs. 3 and 4 vs. 4 small-sided games. J Hum Kinet 28: 107–114, 2011.

50. Drust, B, Atkinson, G, and Reilly, T. Future perspectives in the evaluation of the physiological demands of soccer. Sports Med 37: 783–805, 2007. 51. Dupont, G, Blondel, N, Lensel, G, and Berthoin, S. Critical velocity and time spent at a high level of VO2 for short intermittent runs at supramaximal velocities. Can J Appl Physiol 27: 103–115, 2002. 52. Dupont, G, Blondel, N, and Berthoin, S. Performance for short intermittent runs: Active versus passive recovery. Eur J Appl Physiol 89: 548–554, 2003. 53. Edwards, AM and Clark, NA. Thermoregulatory observations in soccer match play: Professional and recreational level applications using an intestinal pill system to measure core temperature. Br J Sports Med 40: 133–138, 2006. 54. Ekblom, B. Applied physiology of soccer. Sports Med 3: 50–60, 1986. 55. Eniseler, N. Heart rate and blood lactate concentrations as predictors of physiological load on elite soccer players during various soccer training activities. J Strength Cond Res 19: 799–804, 2005. 56. Esposito, F, Impellizzeri, FM, Margonato, V, Vanni, R, Pizzini, G, and Veicsteinas, A. Validity of heart rate as an indicator of aerobic demand during soccer activities in amateur soccer players. Eur J Appl Physiol 93: 167–172, 2004. 57. Fernandes, SR. Heart rate during soccer match play. Doctoral thesis, Universidade Federal de Sa˜o Paulo, Sa˜o Paulo, Brazil, 2002. 58. FIFA. Fe´de´ration Internationale de Football Association [online]. Available at: http://www.fifa.com/. Accessed January 14, 2008. 59. Flanagan, T and Merrick, E. Quantifying the work-load of soccer players. In: Science and Football IV (1st ed.). W. spinks, T. Reilly, and A. Murphy, eds. London, United Kingdom: Routledge, 2002. pp. 341–349. 60. Florida-James, G and Reilly, T. The physiological demands of Gaelic football. Br J Sports Med 29: 41–45, 1995. 61. Fontes, M, Mortimer, L, Condessa, L, Garcia, A, Szmuchrowski, L, and Garcia, E. Intensity of four types of elite soccer training sessions. In: VIth World Congress on Science and Football. Antalya, Turkey: J Sports Sci Med 6, supplementum 10 2007. pp. 82. Book of Abstracts. 62. Gatterer, H. Oxygen uptake during soccer. In: VIth World Congress on Science and Football. Antalya, Turkey: J Sports Sci Med 6, supplementum 10 2007. pp. 111–112. Book of Abstracts. 63. Helgerud, J, Engen, LC, Wisloff, U, and Hoff, J. Aerobic endurance training improves soccer performance. Med Sci Sports Exerc 33: 1925–1931, 2001.

43. Dellal, A, Keller, D, Carling, C, Chaouachi, A, Wong, PL, and Chamari, K. Physiological effects of directional changes in intermittent exercise in soccer players. J Strength Cond Res 24: 3219–3322, 2010.

64. Hill-Haas, SV, Dawson, BT, Coutts, AJ, Rowsell, GJ. Physiological responses and time-motion characteristics of various small-sided soccer games in youth players. J Sports Sci 27: 1–8, 2009.

44. Dellal, A, Lago-Penas, C, Wong, DP, and Chamari, K. Effect of the number of ball touch within bouts of 4 vs. 4 small-sided soccer games. Int J Sports Physiol Perform 6: 322–333, 2011.

65. Hoff, J and Helgerud, J. Endurance and strength training for soccer players: Physiological considerations. Sports Med 34: 165–180, 2004.

2904

the

TM

Journal of Strength and Conditioning Research

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

the

TM

Journal of Strength and Conditioning Research 66. Hoff, J, Wisløff, U, Engen, LC, Kemi, OJ, and Helgerud, J. Soccer specific aerobic endurance training. Br J Sports Med 36: 218–221, 2002. 67. Impellizzeri, FM, Marcora, SM, Castagna, C, Reilly, T, Sassi, A, Iaia, FM, and Rampinini, E. Physiological and performance effects of generic versus specific aerobic training in soccer players. Int J Sports Med 27: 483–492, 2006.

| www.nsca.com

86. Lima, JPR. Heart Rate in progressive workload: sigmoid adjustment, inflexion point and analysis of heart rate variability. Doctoral thesis, Universidade de Sa˜o Paulo, Sa˜o Paulo, Brazil, 1997. 87. Little, T and Williams, AG. Suitability of soccer training drills for endurance training. J Strength Cond Res 20: 316–319, 2006.

68. Impellizzeri, FM, Rampinini, E, Coutts, AJ, Sassi, A, and Marcora, SM. Use of RPE-based training load in soccer. Med Sci Sports Exerc 36: 1042–1047, 2004.

88. Machado, FA and Denadai, BS. Validity of maximum heart rate prediction equations for children and adolescents. Arq Bras Cardiol 97: 136–140, 2011.

69. Impellizzerri, FM, Rampinini, E, and Marcora, SM. Physiological assessment of aerobic training in soccer. J Sports Sci 23: 583–592, 2005.

89. Mahon, AD, Marjerrison, AD, Lee, JD, Woodruff, ME, and Hanna, LE. Evaluating the prediction of maximal heart rate in children and adolescents. Res Q Exerc Sport 81: 466–471, 2010.

70. Jacobs, I, Westlin, N, Karlsson, J, Rasmusson, M, and Houghton, B. Muscle glycogen and diet in elite soccer players. Eur J Appl Physiol Occup Physiol 48: 297–302, 1982.

90. Mallo, J and Navarro, E. Physical load imposed on soccer players during small-sided training games. J Sports Med Phys Fitness 48: 166–171, 2008.

71. Jones, S and Drust, B. Physiological and technical demands of 4 vs. 4 and 8 vs.8 in elite youth soccer players. Kinesiology 39: 150–156, 2007.

91. Mathews, DK, Fox, EL, and Tanzi, D. Physiological responses during exercise and recovery in a football uniform. J Appl Physiol 26: 611–615, 1996.

72. Karvonen, J and Vuoriamaa, T. Heart rate and exercises intensity during sports activities. Sports Med 8: 303–312, 1988.

92. McMillan, K, Helgerud, J, Grant, SJ, Newell, J, Wilson, J, Macdonald, R, and Hoff, J. Lactate threshold responses to a season of professional British youth soccer. Br J Sports Med 39: 432–436, 2005.

73. Karvonen, MJ, Kentala, E, and Mustala, O. The effects of training on heart rate; a longitudinal study. Ann Med Exp Biol Fenn 35: 307–315, 1957. 74. Kelly, DM and Drust, B. The effect of pitch dimensions on heart rate responses and technical demands of small-sided soccer games in elite players. J Sports Sci Med 12: 475–479, 2008. 75. Kemi, OJ, Hoff, J, Engen, LC, Helgerud, J, and Wisløff, U. Soccer specific testing of maximal oxygen uptake. J Sports Med Phys Fitness 43: 139–144, 2003. 76. Klimt, F, Betz, M, and Seitz, U. Metabolism and circulation system of children playing soccer. In: Children and Exercise XVI: Paediatric Work Physiology (1st ed.). J. Coubert and E. Van Praagh, eds. Paris, France: Masson, 1992. pp. 127–129. 77. Ko¨klu¨, Y, Asxxci, A, Koc xak, FU, Alemdarog˘lu, U, and Du¨ndar, U. Comparison of the physiological responses to different small-sided games in elite young soccer players. J Strength Cond Res 25: 1522–1528, 2011. 78. Krustrup, P, Mohr, M, Ellingsgaard, H, and Bangsbo, J. Physical demands during an elite female soccer game: Importance of training status. Med Sci Sports Exerc 37: 1242–1248, 2005. 79. Krustrup, P, Mohr, M, Steensberg, A, Bencke, J, Kjaer, M, and Bangsbo, J. Muscle and blood metabolites during a soccer game: Implications for sprint performance. Med Sci Sports Exerc 38: 1165–1174, 2006. 80. Krustrup, BR, Rollo, I, Nielsen, JJ, and Krustrup, P. Effects on training status and health profile of prolonged participation in recreational football: Heart rate response to recreational football training and match-play. In: VIth World Congress on Science and Football. Antalya, Turkey: J Sports Sci Med 6, supplementum 10 2007. pp. 116–117. Book of Abstracts. 81. Krustrup, P, Mohr, M, Amstrup, T, Rysgaard, T, Johansen, J, Steensberg, A, Pedersen, PK, and Bangsbo, J. The yo-yo intermittent recovery test: Physiological response, reliability, and validity. Med Sci Sports Exerc 35: 697–705, 2003. 82. Krutsrup, P, Zebis, M, Jensen, JM, and Mohr, M. Game-induced fatigue patterns in elite female soccer. J Strength Cond Res 24: 437–441, 2010. 83. Lago-Penas, C, Lago-Ballesteros, J, and Dellal, A. Game-related statistics that discriminated winning, drawing and losing teams from the Spanish soccer league. J Sports Sci Med 9: 288–293, 2010.

93. Mohr, M, Krustrup, P, and Bangsbo, J. Match performance of highstandard soccer players with special reference to development of fatigue. J Sports Sci 21: 519–528, 2003. 94. Mohr, M, Krustrup, P, Nybo, L, Nielsen, JJ, and Bangsbo, J. Muscle temperature and sprint performance during soccer matches: Beneficial effect of re-warm-up at half-time. Scand J Med Sci Sports 14: 156–162, 2004. 95. Mortimer, L, Condessa, L, Rodrigues, V, Coelho, D, Soares, D, and Silame-Garcia, E. Comparison between the effort intensity of young soccer players in the first and second halves of the soccer game. Rev Port Cien Desp 6: 154–159, 2006. 96. Ogushi, T, Ohani, J, Nagahama, H, Isokawa, S, and Suzuki, S. Work intensity during soccer match-play (a case study). In: Science and Football II (2nd ed.). T. Reilly, J. Clarys, and A. Stibbe, eds. London, United Kingdom: E and FN Spon, 1993. pp. 121–123. 97. Owen, AL, Wong, DP, McKenna, M, and Dellal, A. Heart rate responses and technical comparison between small-vs. large-sided games in elite professional soccer. J Strength Cond Res 25: 2104–2110, 2011. 98. Parrado, E, Garcia, MA, Ramos, J, Cervantes, JC, Rodas, G, and Capdevilla, L. Comparison of Omega Wave System and Polar S810i to detect R-R intervals at rest. Int J Sports Med 31: 336–341, 2010. 99. Pyne, DB, Boston, T, Martin, DT, and Logan, A. Evaluation of the Lactate Pro blood lactate analyser. Eur J Appl Physiol 82: 112–116, 2000. 100. Rampinini, E, Impellizzeri, FM, Castagna, C, Azzalin, A, Ferrari Bravo, D, and Wisløff, U. Effect of match-related fatigue on shortpassing ability in young soccer players. Med Sci Sports Exerc 40: 934–942, 2008. 101. Rampinini, E, Impellizzeri, FM, Castagna, C, Abt, G, Chamari, K, Sassi, A, and Marcora, SM. Factors influencing physiological responses to small-sided soccer games. J Sports Sci 25: 659–666, 2007. 102. Rampinini, E, Sassi, A, and Impellizzeri, FM. Reliability of heart rate recorded during soccer training. In: Science and Football V (1st ed.). T. Reilly, J. Cabri, and A. Duarte, eds. London, United Kingdom: Routledge, 2005. pp. 348–352.

84. Laukkanen, RMT and Virtanen, PK. Heart rate monitors: State of the art. J Sports Sci 16: 112, 1998.

103. Rebelo, AN, Costa, O, Rocha, AP, Soares, JM, and Lago, P. Is autonomic control of the heart rate at rest altered by detraining? A study of heart rate variability in professional soccer players after the pretraining period and after the preparatory period for competitions. Rev Port Cardiol 16: 535–541, 508, 1997.

85. Le´ger, L and Boucher, R. An indirect continuous running multistage field test. The University of Montre´al track test. Can J Appl Sport Sci 15: 77–84, 1980.

104. Reilly, Tand Thomas, V. A motion analysis of work-rate in different positional roles in professional football match play. J Hum Mov Stud 2: 87–97, 1976. VOLUME 26 | NUMBER 10 | OCTOBER 2012 |

2905

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

HR in Soccer: A Practical Review 105. Reilly, T and White, C. Small-sided games as an alternative to interval-training for soccer players. J Sports Sci 22: 558–559, 2004. 106. Reilly, T. An ergonomics model of the soccer training process. J Sports Sci 23: 561–572, 2005. 107. Rico-Sanz, J, Frontera, WR, Rivera, MA, Rivera-Brown, A, Mole, PA, and Meredith, CN. Effects of hyperhydration on total body water, temperature regulation and performance of elite young soccer players in a warm climate. Int J Sports Med 17: 85–91, 1996. 108. Rienzi, E, Drust, B, Reilly, T, Carter, JE, and Martin, A. Investigation of anthropometric and work-rate profiles of elite South American international soccer players. J Sports Med Phys Fitness 40: 162–169, 2000. 109. Rodrigues, V, Mortimer, L, Condessa, L, Coelho, D, Soares, D, and Garcia, E. Exercise intensity in training sessions and official games in soccer. In: VIth World Congress on Science and Football. Antalya: J Sports Sci Med 6, supplementum 10 2007. pp. 58. Book of Abstracts. 110. Rohde, H and Espersen, T. Work intensity during soccer training and match-play. In: Science and Football (1st ed.). T. Reilly, A. Lees, K. Davids, and W.J. Murphy, eds. London, United Kingdom: E and FN Spon, 1988. pp. 68–75. _ ´ n˜ez, SJ, Abrantes, C, and 111. Sampaio, J, Garcia, G, Mac xa˜s, V, Iba Caixinha, P. Heart rate and perceptual responses to 2x2 and 3x3 small-sided youth soccer games. In: VIth World Congress on Science and Football. Antalya: J Sports Sci Med 6, supplementum 10 2007. pp. 121–112. Book of Abstracts. 112. Sassi, R, Reilly, T, and Impellizzeri, F. A comparison of smallsided games and interval training in e´lite professional soccer players. In: Science and Football V (1st ed.). T. Reilly, J. Cabri, and A. Duarte, eds. London, United Kingdom: Routledge, 2005. pp. 341–343. 113. Seliger, V. Heart rate as in index of physical load in exercise. Scripta Medica 41: 231–240, 1968. 114. Silva, CD, Bloomfield, J, and Marins, JCB. A review of stature, body mass and Vo2max profiles of U17, U20 and first division players in Brazilian soccer. J Sports Sci Med 7: 309–319, 2008. 115. Spencer, M, Bishop, D, Dawson, B, and Goodman, C. Physiology and metabolic responses of repeated-sprint activities: Specific to field-based team sports. Sports Med 35: 1025–1044, 2005. 116. Stølen, T, Chamari, K, Castagna, C, and Wisløff, U. Physiology of soccer: An update. Sports Med 35: 501–536, 2005.

2906

the

117. Strøyer, J, Hansen, L, and Klausen, K. Physiological profile and activity pattern of young soccer players during match play. Med Sci Sports Exerc 36: 168–174, 2004. 118. Tessitore, A, Meeusen, R, Piacentini, MF, Demarie, S, and Capranica, L. Physiological and technical aspects of ‘‘6-a-side’’ soccer drills. J Sports Med Phys Fitness 46: 36–43, 2006. 119. Tessitore, A, Meeusen, R, Tiberi, M, Cortis, C, Pagano, R, and Capranica, L. Aerobic and anaerobic profiles, heart rate and match analysis in older soccer players. Ergonomics 48: 1365–1177, 2005. 120. Thatcher, R and Batterham, AM. Development and validation of a sport-specific exercise protocol for elite youth soccer players. J Sports Med Phys Fitness 44: 15–22, 2004. 121. Thomas, V and Reilly, T. Fitness assessment of English league soccer players through the competitive season. Br J Sports Med 13: 103–109, 1976. 122. Tumilty, D. Physiological characteristics of elite soccer players. Sports Med 16: 80–96, 1992. 123. Van Gool, D, Van Gervan, D, and Boutmans, J. The physiological load imposed on soccer players during real match-play. In: Science and Football (1st ed.). T. Reilly, A. Lees, K. Davids, and W.J. Murphy, eds. London, United Kingdom: E and FN Spon, 1988. pp. 51–59. 124. Van Gool, D, Van Gerven, D, and Boutmans, J. Heart rate telemetry during a soccer game: A new methodology. J Sports Sci 1: 154, 1983. 125. Wicks, JR, Olridge, NB, Nielsen, LK, and Vickers, CE. Heart rate index—A simple method for pre´diction of oxygen uptake. Med Sci Sports Exerc 43: 2005–2012, 2011. 126. Williams, K and Owen, A. The impact of player numbers on the physiological responses of small-sided games. J Sports Sci Med 6(Suppl. 10): 100, 2007. 127. Wilmore, JH and Haskell, WL. Body composition and endurance capacity of professional football players. J Appl Physiol 33: 564–567, 1972. 128. Wisløff, U, Helgerud, J, and Hoff, J. Strength and endurance of elite soccer players. Med Sci Sports Exerc 30: 462–467, 1998. 129. Wong, DP, Carling, C, Chaouachi, A, Dellal, A, Castagna, C, Chamari, K, and Behm, DG. Estimation of oxygen uptake from heart rate and ratings of perceived exertion in young soccer players. J Strength Cond Res 25: 1983–1988, 2011.

TM

Journal of Strength and Conditioning Research

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited. Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.