Sprint profile of professional female soccer players

Journal of Sports Sciences, August 2012; 30(12): 1259–1265

Sprint profile of professional female soccer players during competitive matches: Female Athletes in Motion (FAiM) study

JASON D. VESCOVI Kinesiology and Health Science, York University, Toronto, Ontario, Canada

Downloaded by [UGR-BTCA Gral Universitaria] at 01:14 20 August 2012

(Accepted 30 May 2012)

Abstract The aim of this study was to determine sprint profiles of professional female soccer players and evaluate how various speed thresholds impact those outcomes. Seventy-one professional players competing in full matches were assessed repeatedly during 12 regular season matches using a Global Positioning System (GPS). Locomotion !18 km " h71 was defined as sprinting and each event was classified into: Zone 1: 18.0–20.9 km" h71; Zone 2: 21.0–22.9 km " h71; Zone 3: 23.0– 24.9 km " h71 and Zone 4: 425 km " h71. Outcomes included: duration (s), distance (m), maximum speed (km " h71), duration since previous sprint (min) and proportion of total sprint distance. In total 5,019 events were analysed from 139 player-matches. Mean sprint duration, distance, maximum speed and time between sprints were 2.3 + 1.5 s, 15.1 + 9.4 m, 21.8 + 2.3 km" h71, and 2.5 + 2.5 min, respectively. Mean sprint distances were 657 + 157, 447 + 185, and 545 + 217 m for forwards, midfielders and defenders, respectively (P # 0.046). Midfielders had shorter sprint duration (P ¼ 0.023), distance (P # 0.003) and maximum speed (P 5 0.001), whereas forwards performed more sprints per match (43 + 10) than midfielders (31 + 11) and defenders (36 + 12) (P # 0.016). Forty-five percent, 29%, 15%, and 11% of sprints occurred in sprint Zones 1, 2, 3 and 4, respectively. This group of professional female soccer players covered 5.3 + 2.0% of total distance !18 km " h71 with positional differences and percent decrements distinct from other previously identified elite players. These data should guide the development of high intensity and sprint thresholds for elitestandard female soccer players.

Keywords: women’s soccer, sprint, speed thresholds, non-differential GPS

Introduction Distance covered at high speed during soccer matches has been identified as an important indicator of match performance (Mohr, Krustrup, & Bangsbo, 2003), with sprinting being the highestintensity effort performed. Quantification of this measure requires consistent implementation of speed thresholds that accurately reflect the ability of players. Few studies have described the physical demands of women’s soccer (Andersson, Randers, Neiner-Moller, Krustrup, & Mohr, 2010; Krustrup, Mohr, Ellingsgaard, & Bangsbo, 2005; Mohr, Krustrup, Andersson, Kirkendal, & Bangsbo, 2008) and have used speed thresholds originally derived from men’s data (Bangsbo, Norregaard, & Thorso, 1991) with no regard for sex differences in sprint speed (Mujika, Santisteban, Impellizzeri, & Castagna, 2009). Sprint ability varies across a wide age range for female soccer players (Vescovi, Rupf, Brown, & Marques, 2011) so the speed zones used

to classify sprints for different standards have implications for motion-analysis studies. The speeds for motion analysis reported by Bangsbo et al. (1991) were means for various locomotor activities, not thresholds, yet they have been routinely used to define various boundaries in previous studies for the men’s and women’s match. To the author’s knowledge no one has clearly explained whether the sprint speed, 25 km " h71, is used to define the upper or lower threshold for classifying sprints in the women’s match (Andersson et al., 2010; Krustrup et al., 2005; Mohr et al., 2008). This is of particular importance because if it is the lower threshold and sprints must exceed this value, then there is a strong likelihood that many sprint activities have been missed since the speed over 20–35 metres for players selected during the inaugural Women’s Professional Soccer draft ranged between 21.6–23.9 km " h71 (Vescovi, 2012) i.e. substantially lower than 25 km " h71. Conversely, 25 km " h71 could be the upper limit with

Correspondence: J. D. Vescovi, York University, Kinesiology and Health Science, 4700 Keele Street, Toronto, Ontario, M3J 1P3 Canada. E-mail: [email protected] ISSN 0264-0414 print/ISSN 1466-447X online ! 2012 Taylor & Francis http://dx.doi.org/10.1080/02640414.2012.701760


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18 km " h71 serving as the lower threshold (defined as high-speed running); however in this circumstance some sprint distance might be inadvertently discarded because flying sprint speeds of 10–30 metres often exceeded 25 km " h71 and sometimes reached 30 km "h71 in the same group of drafted female players (Vescovi, 2012). These observations have clear implications for match analysis, especially when reporting on sprint activities of elite-standard women. For example, the mean sprint distance reported for high-standard Swedish and Danish female soccer players ranged from 160 to 460 metres per match with the distance per sprint ranging from approximately 6 m to 15 m (Andersson et al., 2010; Krustrup et al., 2005; Mohr et al., 2008). Gregson, Drust, Atkinson, & Salvo (2010) reported high match-tomatch variability for high-speed and sprint distances for men’s matches played in the English Premier League (coefficient of variation (CV) ¼ 25– 30%), which is similar to the variability of distance covered above 18 km " h71 for female professional soccer (typical error ¼ 135 m; CV ¼ 28%, unpublished data). Nonetheless, the large disparity among previously published reports (Andersson et al., 2010; Krustrup et al., 2005; Mohr et al., 2008) exceeds what would be expected, and is curious because identical methods (i.e., video recording, computerised coding and speed thresholds) were reported in each paper and highlights an issue for sport scientists: irregular assessment of high-speed running distances in women’s soccer. The discrepancy between studies suggests sprintmotion profiles have not been reported accurately for elite-standard female soccer players. The primary aim of this study was to determine sprint characteristics of professional female soccer players during competitive matches. Specifically, the aim was to describe the distances covered, duration, maximum speeds and recovery periods as well as the proportion of sprint distance to total distance. A secondary objective was to assess how various speed thresholds (!18 km " h71) impact sprint characteristic outcomes. Methods This was a prospective observational study designed to evaluate sprint profiles of female soccer players competing in a professional league in the United States. Study procedures were approved by the Office of Research Ethics at York University. All athletes were verbally informed of the experimental procedures and written informed consent was obtained from the participants prior to volunteering in the study. The investigation was conducted in accordance with the Declaration of Helsinki.

Participants Seventy-nine professional female soccer players were recruited and volunteered to participate in this study. All played in a professional league in the United States. Player position was generically described as forwards, midfielders and defenders according to each head coach on match-day. Thirty of the players also represented their respective national teams (from seven countries) that were ranked in the top 15 in the world according to the most recent official list from the International Federation of Association Football (FIFA). Players typically participated in approximately 2 hours of training per day, 5 days per week and one match per week. All of the participants had a minimum of 10 years experience playing soccer. Match analysis Data from participants completing an entire match were included in the final analysis; eight players did not compete in a full match. Therefore a total of 139 player-matches were assessed from 71 athletes (forwards, n ¼ 16; midfielders, n ¼ 26; and defenders, n ¼ 29) monitored one to five times during 12 matches over the entire regular season (four months). Before each match the starting outfield players were fitted with a non-differential Global Positioning System (GPS) unit (SPI Pro, GPSports, Canberra, Australia), which operated at a sampling frequency of 5 Hz. Units were worn between the shoulder-blades in a specially made vest. Other investigators have reported on the reliability and validity of non-differential GPS (Gray, Jenkins, Andrews, Taaffe, & Glover, 2010; Macleod, Morris, Nevill, & Sunderland, 2009) with improved reliability and validity demonstrated at greater collection frequency (Jennings, Cormack, Coutts, Boyd, & Aughey, 2010). During all matches 7–12 satellites were available for signal transmission (GPSport, Team AMS R1 2011.1), which is optimal for assessment of human movement (Jennings et al., 2010). The horizontal dilution of precision (DHOP) is not available from the Team AMS software, however any value in excess of four results in an automatic rejection of the data (personal communications). This threshold is well below the maximum value (50) reported to result in inaccurate outcomes (Witte & Wilson, 2004). A digital watch that received satellite time identified the start and end of each half, as signalled by the referee’s whistle. These times were used to delineate the raw GPS data file so that only time on the pitch during the matches was included for analysis. After each match the data were extracted using proprietary software (GPSport, Team AMS R1

Sprint profiles of professional women’s soccer 2011.1) with all locomotor activities exceeding 18 km " h71 and lasting more than one second defined as a sprint and used for subsequent analysis. Each identified event was also classified into one of the following four operationally defined Zones: Zone 1: 18.0–20.9 km " h71; Zone 2: 21.0–22.9 km " h71; Zone 3: 23.0–24.9 km "h71 and Zone 4: 425.0 km " h71. The primary outcome measures were the number of sprints performed, sprint duration, sprint distance, maximum speed, duration between sprints and the proportion of sprint distance to total distance.


Statistical analysis After verification of underlying assumptions, a between-groups one-way analysis of variance (ANOVA) compared sprint duration, distance, maximum speed and duration between sprints among the three positions as well as among the four speed zones, followed by Scheffe’s post-hoc analysis when appropriate. After arcsine transformation of the proportional data, a mixed-design factorial ANOVA compared measures-by-position for each half. The effect size (Cohen’s d) estimated from the ratio of the mean difference to the pooled standard deviation was also calculated (Cohen, 1988). Effect size values of 0–0.19, 0.20–0.49, 0.50–0.79 and !0.8 were considered weak, small, moderate and large, respectively (Vincent, 1999). Statistical significance

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was accepted at P 5 0.05. Data are presented as mean + s. All statistical procedures were performed using SPSS version 11.0.1 (SPSS Inc., Chicago, IL, USA). Results In total 5,019 events met the criteria to be considered a sprint. The mean duration, distance, maximum speed and duration between sprints are presented in Table I. Differences occurred for each outcome (P # 0.007) with midfielders having shorter mean sprint duration (P ¼ 0.023; Cohen’s d ¼ 0.07), lower sprint distance (P # 0.003; Cohen’s d ¼ 0.11–0.13) and lower maximum speed (P 5 0.001; Cohen’s d ¼ 0.22–0.31) than forwards and defenders. All three positions differed for mean duration between sprints (P # 0.001; Cohen’s d ¼ 0.11–0.27). The number of sprints differed (P 5 0.001) with forwards performing more sprints per match (43 + 10) than midfielders (31 + 11) and defenders (36 + 12) (P # 0.016; Cohen’s d ¼ 0.61–1.13), with no difference between midfielders and defenders (P ¼ 0.12). Table II displays the characteristics of the sprints using various speed thresholds. The proportion of sprints that occurred in sprint Zones 1, 2, 3 and 4 were 45%, 29%, 15%, and 11%, respectively. Differences occurred for mean sprint duration, distance covered and maximum speed achieved

Table I. Duration and distance of sprints during regular season matches.

Forward (n ¼ 1209) Midfielders (n ¼ 1504) Defenders (n ¼ 2306) All (n ¼ 5019)

Sprint Duration (s)*

Sprint Distance (m)*

Maximum Speed (km " h71)*

2.3 + 1.5 2.2 + 1.4** 2.3 + 1.5 2.3 + 1.5

15.5 + 9.6 14.3 + 9.1** 15.3 + 9.4 15.1 + 9.4

22.1 + 2.4 21.4 + 2.1** 21.9 + 2.3 21.8 + 2.3

Time since previous sprint (min)* { 2.1 2.8 2.5 2.5

+ + + +

2.0 3.0 2.4 2.5

n ¼ number of sprints for each position. * Difference between positions (P # 0.007). ** Midfielders less than forwards and defenders (P # 0.023). { All paired tests different from one another (P # 0.001).

Table II. Sprint profile for various speed thresholds.

18.0–20.9 km " h71 (n ¼ 2252) 21.0–22.9 km " h71 (n ¼ 1465) 23.0–24.9 km " h71 (n ¼ 754) 425.0 km " h71 (n ¼ 548)

Sprint Duration (s)*{

Sprint Distance (m)*{

+ + + +

9.2 + 4.4 15.3 + 6.8 22.0 + 8.6 29.0 + 9.8

1.4 2.3 3.3 4.1

0.8 1.2 1.5 1.5

n ¼ number of sprints within each sprint speed zone. * Difference between speed zone classifications (P 5 0.001). { All paired tests different from one another (P 5 0.001).

Maximum Speed (km " h71)*{ 19.9 21.9 23.8 26.5

+ + + +

0.7 0.6 0.6 1.2

Time since previous sprint (min) 2.5 2.4 2.5 2.4

+ + + +

2.7 2.4 2.4 2.2


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(P 5 0.001). The mean sprint duration (Cohen’s d range 0.53–2.76), distance covered (Cohen’s d range 0.77–3.38) and maximum speeds achieved (Cohen’s d 4 3.0) became progressively greater across the increasing speed zones (P 5 0.001). Duration between sprints was similar among the four speed zones (P 4 0.7). The distance covered in each speed zone for the first half, second half and entire match is shown for forwards, midfielders and defenders in Figure 1. There was a main effect (P # 0.001) for total mean distance covered in a match above 18 km " h71 with forwards, midfielders and defenders covering 657 + 157, 447 + 185, and 545 + 217 m, respectively. Pairwise comparisons revealed differences between each position (P # 0.046; Cohen’s d range

0.48–1.2). There was no interaction but there was a main effect for sprinting distance in each half 425 km " h71, with a 21% reduction (62 + 55 vs. 49 + 51 m, P ¼ 0.004; Cohen’s d ¼ 0.25). There was an interaction for sprint Zone 2 (P ¼ 0.005) with a 32% reduction in the mean distance covered by forwards (Cohen’s d ¼ 0.71) with a small reduction (mean change 5 5 m) for defenders and a small increase (mean change 55 m) for midfielders. There was no interaction or main effect for distance covered in sprint Zones 1 (P ! 0.059) and 3 (P ! 0.181). There was an interaction for the total distance of sprinting (P ¼ 0.017) highlighted by a 21% reduction for forwards (Cohen’s d ¼ 0.74) and a much smaller 5–9% reduction for midfielders (Cohen’s d ¼ 0.20) and defenders (Cohen’s d ¼ 0.11). The proportion of distance covered in each individual and combined sprint Zones i.e. relative to the total distance, is displayed in Table III. There was an interaction for the percent distance in sprint Zone 2 (P ¼ 0.032) with a reduction for forwards but no change for the other two positions. There was a main effect for the percent distance covered above 18.0 km " h71 (P ¼ 0.003; Cohen’s d ¼ 0.10), 21.0 km " h71 (P ¼ 0.007; Cohen’s d ¼ 0.17), 23.0 km " h71 (P ¼ 0.014; Cohen’s d ¼ 0.18) and 25.0 km " h71 (P ¼ 0.014; Cohen’s d ¼ 0.20) indicating a decrease in the proportion of sprint distance in the second half. Discussion

Figure 1. Sprint distances in various speed zones in each half for forwards, midfielders, and defenders. *The interaction (P # 0.017) indicates a larger reduction in distance covered between the first and second half in Zone 2 (Cohen’s d ¼ 0.71) and Total (Cohen’s d ¼ 0.74) by forwards than between each half for defenders (Cohen’s d # 0.13) and midfielders (Cohen’s d # 0.20).

To the author’s knowledge this is the first study to describe the sprint profile of professional female soccer players during matches. The data supports and expands previous findings indicating that the mean duration and distance of individual sprints is similar between elite-standard men’s and women’s matches (Mohr et al., 2003; Mohr et al., 2008). Unique to this study was the evaluation of various speed zones (!18 km " h71) in the assessment of sprint performance, highlighted by identifying that 11% of all sprints exceeded 25 km " h71 which accounted for 1.1% (111 + 93 m) of the total distance covered. Another distinct observation was that forwards had larger reductions in the number of sprints and total sprint distance from the first half to the second half than midfielders and defenders. Finally, the proportion of total distance covered at !18 km " h71 was 5.3 + 2.0%, having similar total distances (9,997 + 928 m) to previous reports about women’s soccer (Andersson et al., 2010; Krustrup et al., 2005; Mohr et al., 2008). The mean sprint distance for the entire match ranged from 477 + 185 m (midfielders) to

Sprint profiles of professional women’s soccer

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Table III. Percent distance in each sprint speed zone relative to total distance. Forward 1st half 418.0 km " h71 ** 421.0 km " h71 ** 423.0 km " h71 ** 425.0 km " h71 ** 18.0–20.9 km " h71 21.0–22.9 km " h71* 23.0–24.9 km " h71

7.1 5.5 3.3 1.8 1.6 2.2 1.6

+ + + + + + +

1.7 1.7 1.5 1.2 0.6 1.1 0.7

Midfielder

2nd half 5.8 4.5 3.0 1.5 1.4 1.5 1.4

+ + + + + + +

2.2 2.1 1.8 1.2 0.4 0.7 1.1

1st half 4.3 2.9 1.7 0.8 1.5 1.2 1.0

+ + + + + + +

1.7 1.6 1.3 0.9 0.5 0.6 0.8

Defender

2nd half 4.2 2.7 1.3 0.5 1.5 1.3 0.8

+ + + + + + +

2.0 1.6 1.2 0.8 0.7 0.8 0.7

1st half 5.7 4.3 2.5 1.4 1.5 1.7 1.1

+ + + + + + +

2.1 1.9 1.5 1.1 0.7 0.9 0.9

All

2nd half 5.6 4.2 2.5 1.2 1.4 1.7 1.3

+ + + + + + +

2.5 2.2 1.7 1.0 0.7 1.0 0.9

1st half 5.5 4.0 2.4 1.2 1.5 1.6 1.2

+ + + + + + +

2.1 2.0 1.5 1.1 0.6 0.9 0.8

2nd half 5.2 3.7 2.2 1.0 1.4 1.5 1.2

+ + + + + + +

2.4 2.1 1.7 1.1 0.7 0.9 0.9


*Interaction (P ¼ 0.032) indicating a larger reduction between the first and second half for forwards than for midfielders and defenders. **Main effect indicating a reduction in the relative proportion of sprint distance (P 5 0.05).

657 + 157 m (forwards), that is similar to distances reported by Mohr et al. (2008) but greater than Krustrup et al. (2005) and Andersson et al. (2010) for female soccer players. Andersson and colleagues (2010) reported that top-class women players covered approximately 220–260 m of sprints during domestic and international matches, whereas elitestandard Danish players sprinted approximately 160 m per match (Krustrup et al., 2005). The mean number of sprints performed in these latter two studies indicates that female soccer players cover about 6–11 m per sprint. This is in contrast to the findings of Mohr et al. (2008) and of the current study: the combined results indicate a mean distance of about 14–15 m per sprint. The differences between these studies are surprising because identical methods, processing, coding and speed thresholds were used and suggest that there was a discrepancy in the application of speeds zones even in the same group of investigators. Detailed analysis of sprint performance for elitestandard male soccer players has been reported (Di Salvo, Gregson, Atkinson, Tordoff, & Drust, 2009; Di Salvo et al., 2010) with approximately 4–6% of the total distance covered represented by sprinting in excess of 30 km " h71 (Mohr et al., 2003) and 2.4% in excess of 25 km " h71 (Bradley et al., 2009). Data reported on female soccer players are slightly lower than those of male players and indicate that approximately 1.6–4.5% of the total distance is covered by sprinting (Andersson et al., 2010; Krustrup et al., 2005; Mohr et al., 2008), although it is unclear if the same speed thresholds were used among studies considering the low proportion of sprint distance to total distance (*1.6%) reported by Krustrup et al. (2005) in a group of elite-standard players from a Danish league. The current findings demonstrate the relative distance covered over 18 km " h71 and 25 km " h71 was 5.3 + 2.0% and 1.1 + 1.0%, respectively; however a direct comparison with previous reports is difficult. Nevertheless, the

difference between studies could reflect the standard of player with nearly half of the current participants competing for their respective national teams highlighting their elite-standard ability. It is also possible that some of the variability between studies is a result of tactics used by the coach, which could modify (up or down) the amount of sprinting that is performed during any given match. However for players to cover longer or shorter sprint distances consistently, similar tactics would have had to be used for the majority of matches monitored in each study. Regardless of the differences in player ability or the tactics used, compared with previous studies, what is considered sprinting varies despite researchers having reported use of the same speed thresholds. To examine the impact of speed thresholds on sprint performance characteristics several speed zones were operationally defined in the current study. As anticipated, the cumulative percent of sprint distance decreased from 5.3 + 2.0% (418.0 km " h71) to 3.9 + 1.8% (421.0 km " h71), 2.3 + 1.5% 71 (423.0 km " h ) and 1.1 + 1.0% (425.0 km "h71) with increasing speed thresholds. When using 18–25 km " h71 as the lower and upper boundaries for sprint performance 11% of the sprint distance was eliminated. Use of 25 km " h71 as the lower threshold is probably too high since many players might not exceed this speed even though they are indeed sprinting. This higher threshold results in an erroneous observation of little or, in some circumstances, no sprinting during a match. To date, researchers have used speed classifications from the men’s match (Bangsbo et al., 1991) and simply transposed them to studies with women’s soccer. However, there is now a growing body of knowledge that describes the physical performance (Vescovi, 2012; Vescovi et al., 2011) and time-motion characteristics (Dwyer & Gabbett, 2012) of women’s soccer that should be used to improve the classification of physical demands for this sport. For example, previous work from the author’s lab has


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demonstrated that sprint ability in female soccer players tended to plateau between 14–17 years as there were no observable increases in mean speed over 9.1–36.6 m for a group of players 18–21 years (Vescovi et al., 2011). Similarly Mujika et al. (2009) reported no difference on 15-m sprint scores between senior (mean age 23 years) and junior (mean age 17 years) female soccer players. Considering the mean maximal speed achieved for sprinting in matches (21.8 + 2.3 km " h71), the current findings suggest that the threshold used to define sprinting in women’s soccer should be reconsidered and consistently implemented for motion-analysis studies with players 16–17 years and older and adjusted for younger athletes to reflect the lower physical abilities of those individuals. Several studies have reported fatigue in matches defined as a reduction in high-intensity and sprint distances in the second half compared with the first (Andersson et al., 2010; Carling & Dupont, 2011; Mohr et al., 2003). There was little change in the sprint distance for the current group of midfielders and defenders between the first and second half (*20 m or 6–9%), however forwards had a substantially larger decrement in total sprint distance in the second half (79 m or 21%). This is consistent with previous reports on top-class men’s (Mohr et al., 2003) and women’s (Andersson et al., 2010) matches where 12–14% reductions in sprinting distance occurred. This outcome is also reflected in the reduced number of sprints for forwards (24 + 7 vs. 20 + 6 sprints) a finding that is similar to topclass male players (Mohr et al., 2003). Thus it appears that the fewer sprints performed is primarily responsible for the overall reduction in sprint distance rather than a reduction in the mean distance per sprint. There are several limitations to this study that should be considered. First, while every attempt was made for players to wear the same unit for the duration of the study, it was impossible to accomplish this objective. For example, units 1 to 10 could be worn by players on Team A and Team B when playing in separate matches but when these two teams competed against each other, it was not feasible. Second, matches were monitored at various times throughout the day although Petersen, Pyne, Portus, & Dawson (2009) reported that validity and reliability of distance measured by GPS was not affected by time of day. Conclusions Based on the current sprint analysis of professional female soccer players, of which 42% had international-standard experience for their national teams, these athletes covered between 447 + 185 m and

657 + 157 m (or 5.3 + 2.0%) 418 km " h71. There is uncertainty about definitions of speed thresholds and whether 18 km " h71 or 25 km "h71 is the lower limit to consider an event as a sprint. The novel finding that approximately 11% of sprints are performed in excess of 25 km " h71 highlights the capability of these elite-standard players but also suggests that investigators using this threshold as a ceiling for women’s soccer will mistakenly omit a proportion of sprint distance. There is likely a need to develop a strategy using linear sprint speed, or other testing outcome measures, to individualise speed thresholds used in future motion analysis studies (Harley et al., 2010) that are specific to female soccer players. In the meantime reconsideration of high intensity and sprint thresholds for elitestandard athletes is necessary and should reflect the ability of female soccer players (Vescovi, 2012; Dwyer & Gabbett, 2012). Acknowledgements Thanks are extended to all of the players for their participation in this study as well as to Women’s Professional Soccer and all of the coaches for their support. This study was supported in part by grants from the National Strength and Conditioning Association and the Research Program in Applied Sport Science from the Ministry of Health Promotion (Canada). References Andersson, H.A., Randers, M.B., Heiner-Moller, A., Krustrup, P., & Mohr, M. (2010). Elite female soccer players perform more high-intensity running when playing in international games compared with domestic league games. Journal of Strength and Conditioning Research, 24, 912–919. Bangsbo, J., Norregaard, L., & Thorso, F. (1991). Activity profile of competition soccer. Canadian Journal of Sport Science, 16, 110–116. Bradley, P.S., Sheldon, W., Wooster, B., Olsen, P., Boanas, P., & Krustrup, P. (2009). High-intensity running in English FA Premier League soccer matches. Journal of Sports Sciences, 27, 159–168. Carling, C., & Dupont, G. (2011). Are declines in physical performance associated with a reduction in skill-related performance during professional soccer match-play? Journal of Sports Sciences, 29, 63–71. Cohen, J. (1988). Statistical power analysis for the behavioral sciences. Hillsdale, NJ: Erlbaum. Di Salvo, V., Baron, R., Gonzalez-Haro, C., Gormasz, C., Pigozzi, F., & Bachl, N. (2010). Sprinting analysis of elite soccer players during European Champions League and UEFA Cup matches. Journal of Sports Sciences, 28, 1489–1494. Di Salvo, V., Gregson, W., Atkinson, G., Tordoff, P., & Drust, B. (2009). Analysis of high intensity activity in Premier League soccer. International Journal of Sports Medicine, 30, 205–212. Dwyer, D.B., & Gabbett, T.J. (2012). Global positioning system data analysis: Velocity ranges and a new definition of sprinting for field sport athletes. Journal of Strength and Conditioning Research, 26, 818–824.


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