Effects of Domestic Air Travel on Technical and Tactical Performance ...

International Journal of Sports Physiology and Performance, 2014, 9, 378  -386 http://dx.doi.org/10.1123/IJSPP.2013-0484 © 2014 Human Kinetics, Inc.

www.IJSPP-Journal.com ORIGINAL INVESTIGATION

Effects of Domestic Air Travel on Technical and Tactical Performance and Recovery in Soccer Peter Fowler, Rob Duffield, and Joanna Vaile The current study examined the effects of short-haul air travel on competition performance and subsequent recovery. Six male professional Australian football (soccer) players were recruited to participate in the study. Data were collected from 12 matches, which included 6 home and away matches against the same 4 teams. Together with the outcome of each match, data were obtained for team technical and tactical performance indicators and individual player-movement patterns. Furthermore, sleep quantity and quality, hydration, and perceptual fatigue were measured 2 days before, the day of, and 2 days after each match. More competition points were accumulated (P > .05, d = 1.10) and fewer goals were conceded (P > .05, d = 0.93) in home than in away matches. Furthermore, more shots on goal (P > .05, d = 1.17) and corners (P > .05, d = 1.45) and fewer opposition shots on goal (P > .05, d = 1.18) and corners (P < .05, d = 2.32) occurred, alongside reduced total distance covered (P > .05, d = 1.19) and low-intensity activity (P < .05, d = 2.25) during home than during away matches. However, while oxygen saturation was significantly lower during than before and after outbound and return travel (P < .01), equivocal differences in sleep quantity and quality, hydration, and perceptual fatigue were observed before and after competition away compared with home. These results suggest that, compared with short-haul air travel, factors including situational variables, territoriality, tactics, and athlete psychological state are more important in determining match outcome. Furthermore, despite the potential for disrupted recovery patterns, return travel did not impede player recovery or perceived readiness to train. Keywords: football, travel fatigue, sleep, psychology, home advantage Short-haul air travel is one of a myriad of factors purported to affect match outcome in football (soccer)1,2 and, in particular, the tendency for teams to perform better at home than away, referred to as the home advantage.1,2 Hence, it is frequently highlighted by the media, coaching staff, and players as an explanation for poor away-match performances.3 However, limited data exist to support this perception, with few studies, particularly in football, reporting the acute effects of short-haul air travel on physical performance, physiological and perceptual responses, and ensuing match outcome or technical and tactical performance indicators.4,5 Of further concern is the potential impact of travel on postmatch recovery, considering that many domestic football competition schedules require short-haul air travel the day after an away match. However, the effects of postcompetition travel on recovery are yet to be determined.

Fowler is with the School of Human Movement Studies, Charles Sturt University, Bathurst, NSW, Australia. Duffield is with the Sport & Exercise Discipline Group, University of Technology Sydney, Sydney, NSW, Australia. Vaile is with Performance Recovery, Australian Institute of Sport, Canberra, ACT, Australia. Correspondence concerning this article should be addressed to Peter Fowler. E-mail: [email protected]

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After short-haul air travel, symptoms of travel fatigue may include lethargy, confusion, and headaches6 resulting from the conditions encountered during travel. This includes exposure to mild hypoxia,7 cramped conditions with restricted activity,6,8 and disruption of routines such as eating and sleeping patterns.9,10 However, to date, only 2 studies have reported acute effects of short-haul air travel on integrated physical performance, physiological and perceptual responses, and ensuing match outcome and technical and tactical performance indicators.4,5 Although adverse effects on psychological state and perceived sleep quality were identified the day before competition in professional rugby league and Australian Football League players, respectively, subsequent effects on physical, technical, and tactical performance during competition were equivocal.4,5 Therefore, further research is required to establish whether short-haul air travel per se affects match outcome, as opposed to other factors including, situational variables such as match location, match status and opposition quality,11 territoriality,12 tactics, and the expectancy to perform worse away from home.13 Competitive football matches involve a large number of physically demanding activities and thus induce acute fatigue and physical-performance decrements.14 A progressive return to prematch state occurs during the recovery process, but this may take more than 72 hours.14

Travel, Performance, and Recovery in Soccer   379

Given the limited time between matches and subsequent training and competition, various recovery procedures are commonly used to regain optimal performance more quickly.14 However, due to domestic football competition schedules, short-haul air travel is often a necessity the day after an away match, particularly in North and South America and Australia, where large distances are traveled by away teams.2 As conditions during air travel may induce acute physiological and perceptual stress,6,7 and the disruption of routines can inhibit the use of recovery interventions, the recovery process after away matches could be impeded. However, as yet, no data exist on the effects of postcompetition travel on recovery. Therefore, the purpose of the current study was to investigate the acute effects of short-haul air travel on physiological and perceptual measures before and after competition and technical and tactical performance indicators during competition in elite Australian football players. We hypothesized that short-haul air travel would have an acute negative impact on physiological and perceptual responses, which would result in worse technical and tactical performance during competition, match outcome, and ensuing recovery.

Methods Participants Six male professional Australian football players were recruited to participate in the current study, mean (95% confidence intervals [CI]) age 23.4 (19.9–25.9) years, body mass 78.0 (72.3–83.7) kg, height 182.8 (178.4–187.2) cm. The players were representatives of a professional team located in North Queensland, Australia, and competed in the highest Australian national soccer competition (A-League). Due to the team’s location, players were required to undertake short-haul air travel for all away matches. The players volunteered to participate, were informed of any associated risks before the commencement of the study, and provided verbal and written informed consent. The study was approved by the institutional human research ethics committee.

Experimental Design After familiarization with all experimental measures and procedures, due to selection in the team and the competition structure and schedule, data were collected from the players for 12 matches during the 2010–11 A-League season, which included 6 home and away matches against the same 4 teams. Measures were obtained 2 days before (Pre 1 and Pre 2), the day of (match day), and 2 days after (Post 1 and Post 2) each match. Accordingly, to account for the effect of opposition quality on match outcome, the current study was a within-subject, crossover design, which allowed the comparison of measures against the same opposition for both home and away matches. Mean (95% CI) air-travel time and distance for the 6 away matches were 5.3 (3.1–7.5) hours and 3759 (2453–5065)

km, respectively. Direction of outbound and return travel was south and north to Melbourne, VIC; west and east across 2 time zones to Perth, WA; and east and west across 2 time zones to Wellington, New Zealand.

Experimental Procedures Key Performance Indicators.  For the 12 matches inc­ luded in analyses, match outcome and technical and tactical performance indicators were obtained postmatch from a freely accessible game-statistics Web site (www. footballaustralia.com.au/aleague/matchcentre). All Web site data are provided by OPTA Sportsdata (OPTA Client System, OPTA Australia, Sydney, NSW), which has been reported to have a high level of interoperator reliability (kappa value = 0.94).15 Specifically, standardized typical errors and intraclass correlation coefficients varied from .00 to .37 and .88 to 1.00, respectively for shots on goal, corners, opposition corners, and fouls.15 During each match, total distance covered (m), mean speed (m/min), and the distance covered (m) in 3 predefined categories16—low-intensity activity (14.5 km/h), and very-high intensity running (>20 km/h)—were determined via 1-Hz global positioning satellite (GPS) devices (SPI elite, GPSports, Canberra, Australia). For each match, players wore the same individually assigned device between the scapulae in a customized harness, and data were subsequently analyzed using device-specific software (Team AMS, GPSports, Canberra, Australia). Match physical load (arbitrary units [AU]) was calculated for each player by multiplying his respective playing duration (min) and rating of perceived exertion on a scale from 0 (nothing at all) to 10 (maximal) approximately 30 minutes after each match.17 At the same time, players rated their physical feeling during each match on a scale of –5 (very bad) to 5 (very good),18 and the morning after each match, player performance was subjectively assessed by the same member of coaching staff on a scale from 1 (very poor) to 10 (excellent). Physiological Measures.  Sleep patterns were assessed

using ActiGraphy watches (ReadiBand, Fatigue Science, Honolulu, HI) worn on players’ nondominant wrist 2 days before, the day of, and 2 days after each match. ActiGraph records were subsequently analyzed using customized manufacturer software (Sleep Analyzer, Fatigue Science, Honolulu, HI) for quantity and quality of sleep. Hydration status was also assessed at the same time points. Specifically, participants provided a midstream urine sample on awakening, which was subsequently analyzed for urine specific gravity using a visual-scale urine refractometer (Refractometer 503, Nippon Optical Works, Co, Tokyo, Japan). For each away match, oxygen saturation was recorded while seated with a pulse oximeter (Nonin 4000 Avant Bluetooth Pulse Oximeter, Nonin, North Plymouth, MN) immediately before, halfway through, and immediately after outbound and return travel. Values were recorded after stabilization of the reading.

380  Fowler, Duffield, and Vaile

Perceptual Measures.  Perceived sleep quality, stress, fatigue, and muscle soreness were assessed on a scale19 of 1 (very, very good/very very low) to 7 (very, very bad/very very high), and perceived sleepiness was assessed on a scale20 of 1 (feeling active/alert/wide awake) to 8 (asleep) 2 days before, the day of, and 2 days after each match. To assess players’ stress-recovery balance, the RecoveryStress Questionnaire for Athletes (RESTQ-19 Sport)21 was completed at the same time points. In addition, fatigue and sleepiness were recorded immediately before and immediately after outbound and return travel.

where a significant effect was observed (P < .05), a Tukey honestly significant difference post hoc test was used to determine differences between means. Analyses were performed using JMP statistical software (JMP Pro v 10.0, SAS, Cary, NC). Furthermore, standardized effect size (Cohen d) analysis was used to interpret the magnitude of differences between home and away matches. Due to the substantial amount of statistical analyses performed, only large effect sizes (ES; d > 0.90) are reported.

Statistical Analysis

Key Performance Indicators

Data for each player were only included in analyses if playing duration was ≥60 minutes in both the home and away match against the same opposition. Data are presented as mean (95% CI). One-way analysis of variance (ANOVA) was used to determine differences between home and away matches for all key performance indicators, as well as differences between before and after outbound and return travel in perceived fatigue and sleepiness. A 1-way ANOVA with repeated measures was used to identify differences between before, during, and after outbound and return travel in oxygen saturation. A linear mixed model was used for analyses of all other physiological and perceptual measures. Specifically, time and location (home vs away) and their interaction were fitted as fixed effects to determine whether there was a difference in the effect of location over time. In addition, player and location (within player) were fitted as random effects to account for the possible correlation within players and within location within players. For all analyses,

No significant differences were identified between home and away for match outcome (P > .05). However, large ESs indicated more points accrued (1.0 vs 0.3; P = .21; d = 1.10) and fewer goals conceded (1.5 vs 2.2; P = .47; d = 0.93) at home than away. While number of opposition corners was significantly greater in away than in home matches (P = .02; Table 1), no significant differences were evident for any other technical and tactical performance indicators (P > .05). Large ESs suggested more shots off target (d = 1.18), shots on goal (d = 1.17), and corners (d = 1.45), with fewer opposition shots on goal (d = 1.18) or corners (d = 2.32) occurring at home than away. No significant differences in coach subjective ratings of player performance were observed between home (7.2 [6.9–7.5]) and away (7.6 [7.1–8.0]) matches (P > .05). Low-intensity activity and total distance covered were significantly (P = .001, d = 2.25) and almost significantly (P = .06; d = 1.19) greater, respectively, in away than in home matches (Table 2). No significant

Results

Table 1  Mean (95% CI) Technical and Tactical Performance Indicators From 6 Home and 6 Away Matches Possession (%)

Shots on target

Shots off target (6–12)a

Home

49 (45–52)

5 (2–8)

9

Away

48 (45–51)

5 (2–7)

7 (4–10)

Shots on goal 14

(11–17)a

11 (8–14)

Opposition shots on goal 11

(7–15)a

16 (8–24)

Corners 7

(3–11)a

4 (2–6)

Opposition corners 4

Fouls

(0–7)*a

12 (8–16)

8 (5–11)

12 (9–14)

*Significantly different from away matches (P < .05). a Large ES for difference from away matches (d > 0.90).

Table 2  Mean (95% CI) Physical Demands From 6 Home and 6 Away Matches Distance (m)

Mean speed (m/min)

LIA (m)

HIR (m)

VHIR (m)

sRPE

Physical load (AU)

Home

10,620 (10,208–11,033)a

111 (107–115)

8340 (8114–8566)*a

2280 (2008–2552)

519 (425–614)

7.6 (7.1–8.2)

688 (640–736)

Away

11,128 (10,730–11,527)

115 (110–121)

8953 (8665–9241)

2175 (1947–2403)

461 (325–597)

8.1 (7.4–8.7)

720 (664–776)

Abbreviations: LIA, low-intensity activity; HIR, high-intensity running; VHIR, very-high-intensity running; sRPE, session rating of perceived exertion; AU, arbitrary unit. *Significantly different from away matches (P < .01). a Large ES for difference from away matches (d > 0.90).

Travel, Performance, and Recovery in Soccer   381

differences were evident between home and away matches for high-intensity running, very-high-intensity running, match physical load, or physical feeling (0.1 [–1.1 to 1.2] vs 0.6 [–0.3 to 1.4]; P > .05).

Physiological Measures There were no significant differences between home and away matches for any sleep measure (P > .05; Figure 1). However, large ESs indicated that sleep latency was greater (d = 0.99) and variance from mean bed time was earlier (d = 2.46) away than home on Pre 2 and Pre 1, respectively. Moreover, variance from mean bed time was earlier (d = 0.90) and sleep latency (d = 1.34) and duration (d = 1.95) were greater on Post 1 away than home. On Post 2, variance from mean bed time was earlier (d = 1.51) and sleep duration (d = 1.40) and both number and duration (d > 1.20) of wake bouts were greater at home than away. Furthermore, variance from mean bed time was significantly later on match day than on Pre 1 for away matches (P = .02; Figure 1[A]). Sleep duration was significantly reduced on match day compared with Pre 1 (P = .001) and Post 1 (P = .005) for away matches and compared with Pre 1 (P = .001) and Post 2 (P = .04) for home matches (Figure 1[B]). No significant effects of time were identified for sleep latency, sleep efficiency, and number or duration of awakenings (P > .05; Figure 1[C–F]). No significant differences between home and away matches were evident for urine specific gravity (Figure 2; P > .05, d < 0.90). Oxygen saturation was significantly lower during than before and after outbound and return travel (P < .01, d > 0.90; Table 3); however, no significant differences were identified during outbound compared with during return travel (P > .05, d < 0.90).

Perceptual Measures There were no significant differences between home and away matches for any perceptual measure (P > .05; Figure 3). However, large ESs indicated that fatigue was greater away than at home on Pre 1 (d = 1.26), and stress (d = 0.97) and muscle soreness (d = 1.11) were greater at home than away on Post 1. Sleep quality and stress-recovery balance were significantly lower on match day compared with Pre 1 for home and away matches (P < .01) and compared with Pre 2 for home matches (P < .05). Stress and sleepiness were significantly higher at Post 1 than on match day (P < .01) and Pre 1 (P < .05) for home matches. Furthermore, sleepiness was almost significantly greater after than before outbound travel (P = .09, d = 1.32; Table 3). A significantly greater level of fatigue was observed at Post 1 than at all other time points for home matches (P < .05) and than match day (P = .0007) and Pre 2 (P = .007) for away matches. Fatigue was also significantly greater at Post 2 than match day for away matches (P = .03). Muscle soreness was significantly greater at Post 1 than at all other time points for home matches (P < .001) and than at all other time points except Post 2 for away

matches (P < .001). Furthermore, muscle soreness was significantly greater at Post 2 than Pre 2 (P = .02), Pre 1 (P = .003), and match day (P = .0006) for away matches and than Pre 1 (P = .001) and match day (P = .0002) for home matches.

Discussion The current study examined effects of short-haul air travel, with minimal or no change in time zones, on match outcome, technical and tactical performance during competition, and sleep, hydration, and perceptual fatigue before and after competition in elite Australian football players. Although a reduction in oxygen saturation was identified during short-haul air travel, it appeared to have negligible effects on ensuing competition performance and postmatch recovery, as equivocal differences in sleep quantity and quality, hydration, and perceptual measures were observed at home compared with away. However, in contrast, more points were accrued, fewer goals were conceded, and technical and tactical performance was superior, resulting in reduced physical demands at home compared with away. Therefore, compared with short-haul air travel, other factors including situational variables such as match location, match status, and opposition quality11; territoriality12; and tactics and the expectancy to perform worse away from home13 may be of greater importance in determining match outcome. However, we recognize that the small sample size and number of games from which data were collected is a limitation of the current study, restricting the generalizability of the results to other teams or travel demands. Due to the myriad of factors influencing match outcome, isolating the effects of travel is complex and requires control of numerous confounding variables.1 A recent study confirmed a home advantage in the highest Australian national football competition (A-League) and reported a strong positive association with the number of time zones crossed during travel.2 However, given the logistical issues, there are limited data available detailing the travel effects on integrated physical performance, physiological and perceptual responses, and ensuing competition performance. Indeed, only 2 studies have attempted to isolate effects of short-haul air travel on key performance indicators during competition.4,5 While professional rugby league players performed more tackles and covered less distance,5 no differences in game statistics, including time between possessions and team assists, were evident in professional Australian Football League players during away compared with home matches.4 In the current study, more points were accrued and fewer goals were conceded, in addition to more shots on goal and corners and fewer opposition shots on goal and corners, in home than away matches. This not only supports the finding that teams tend to perform better at home than away in the A-League2 but also could explain the greater distance covered, particularly in low-intensity activity, during away than home matches. Specifically,

382

Figure 1 — Effect of time and location on sleep volume and quality. Mean (95% CI) variance from mean (A) bed time, (B) sleep duration, (C) sleep latency, (D) sleep efficiency, (E) number of awakenings, and (F) duration of awakenings for home and away matches. *Significantly different from Pre 1 (away) (P < .05). a Large effect size for difference between home and away (d > .90).

Travel, Performance, and Recovery in Soccer   383

with greater tactical dominance by the opposition during away matches, greater movement tracking the ball and/or opposition players is required.11,22 Furthermore, evidence suggests that an expectancy to perform worse away from home may result in a change in tactics that in turn can alter physical-performance demands compared with home matches.11 However, despite greater distance covered, no difference in match physical load was evident, possibly resulting from the similar high-intensity-running and very-high-intensity-running distance observed in away and home matches. The conflicting results between studies for the aforementioned key performance indicators could be due to the different sports analyzed and/or the plethora of factors that influence match outcome, including the ability and tactics of the team analyzed and the opposition, which have an interactive effect.5,13 While the current study attempted to control for some of these factors by analyzing “pairs” of matches against the same teams at home and away, previous research has compared performance

Figure 2 — Effect of time and location on hydration status. Mean (95% CI) urine specific gravity for home and away matches.

in consecutive home and away matches against different opposition,5 where opposition quality could affect the results. Consequently, further research is required with larger data sets and across multiple sports, teams, and seasons to conclusively determine the effects of travel on specific match outcomes. Physiological consequences of air travel may include reduced oxygen saturation23 and sleep quality,24 as observed during and after prolonged exposure to mild hypoxia. Oxygen saturation was reduced during both outbound and return travel in the current study, similar to previously reported values.23,25 In addition, disruption of routine on arrival, for example, residing in an unfamiliar environment rather than at home, may affect sleep.10 In contrast, results from the current study suggest that players tended to be in bed earlier on both the day before and the day after and also slept for longer the day after away compared with home matches. This could be due to monitoring of players’ sleeping patterns while away, when players and coaching staff reside together in a hotel, compared with at home, where players are left to their own practices. Regardless, sleep-quality measures were similar at home and away. Previously, no differences in ActiGraphy-derived sleep measures were observed in Australian Football League players the night before competition, although players perceived their sleep quality to be better at home than away.4 Consequently, these results suggest that short-haul air travel has equivocal effects on sleep patterns. Furthermore, anecdotal evidence suggests that athletes who compete at night, as is often the case in football, have difficulties with sleep after competition.26 Thus, a novel finding of the current study was the reduction in sleep quantity and perceived sleep quality observed in elite football players after both home and away matches. Given the physically demanding nature of competitive football matches14 and the recent emphasis placed on the importance of sleep,26 further research is warranted for recovery purposes.27 Conditions during air travel, particularly prolonged exposure to mild hypoxia, cramped conditions, and

Table 3  Mean (95% CI) Physiological and Perceptual Measures Collected Before, During, and After Outbound and Return Travel for 6 Away Matches Measure

Time

Oxygen saturation (%)

Before

97.9 (97.5–98.3)

97.8 (97.4–98.2)

During

95.0 (94.4–95.6)*

94.4 (93.9–95.0)*

After Fatigue Sleepiness

Outbound travel

Return travel

98.2 (97.7–98.6)

97.7 (97.3–98.1)

Before

3.8 (3.3–4.2)

4.3 (3.7–5.0)

After

4.2 (3.5–4.8)

4.2 (3.4–5.0)

Before

3.1 (2.3–3.9)

4.1 (3.2–5.0)

(3.8–4.9)a

4.2 (3.4–5.0)

After

4.3

*Significantly different from before and after travel (P < .01). a Large ES for difference from before (d > 0.90).

384

Figure 3 — Effect of time and location on perceptual responses. Mean (95% CI) (A) perceived sleep quality, (B) stress, (C) fatigue, (D) muscle soreness, (E) stress recovery, and (F) sleepiness for home and away matches. *Significantly different from Pre 1 (away) (P < .05). #Significantly different from Pre 1 (home) (P < .05). †Significantly different from Pre 2 (home) (P < .05). ¶Significantly different from Pre 1 and match day (home) (P < .05). ‡Significantly different from all other time points (home) (P < .05). α Significantly different from Pre 2 and match day (away) (P < .05). **Significantly different from match day (away) (P < .05). ##Significantly different to Pre 2, Pre 1 and match day (away) (P < .05). a Large effect size for difference between home and away (d > .90).

Travel, Performance, and Recovery in Soccer   385

activity restrictions, can induce acute increases in perceptual fatigue and muscle discomfort.6,7,23 Indeed, worse psychological states and greater perceived sleepiness have previously been reported immediately posttravel in Australian rugby league players traveling routes similar to those in the current study.5 Yet since these perceptual effects subsided before competition the following day, it is unlikely they were present during competition and, therefore, affected performance. In the current study, greater perceived sleepiness was evident immediately after than before outbound travel, and perceptual fatigue was increased 1 day before competition away compared with home. However, no differences were evident between home and away matches for perceived stress, fatigue, and muscle soreness on match day. These findings confirm those of the aforementioned research and suggest that while short-haul air travel may acutely increase perceptual fatigue, it is unlikely to affect competition performance. Considering these effects on fatigue and the fact that short-haul air travel is often a necessity the day after an away match (commonly the largest physical load of the training week), postcompetition recovery may be impeded. However, results from the current study suggest that on the day after competition, perceived stress and muscle soreness were greater at home than away. This is surprising considering that less distance was covered during home than away matches, although the crowd, tactics, and environment may also be factors. Given the importance of recovery for subsequent performance and the limited preparation time until ensuing training and competition, further investigation is required to confirm these findings. In conclusion, more points were accrued, fewer goals were conceded, and technical and tactical performance was superior, resulting in reduced physical demands during competition, at home than away. Furthermore, while short-haul air travel may acutely increase perceptual fatigue, equivocal effects on sleep quantity and quality and perceptual responses were observed. These results indicate that compared with short-haul air travel, other situational variables11 could have a greater impact on match outcome, and that return travel did not impede player recovery. However, it should be noted that travel fatigue could be cumulative and may accrue over the course of a season. As such, research into the longitudinal effects of short-haul air travel is warranted.

Practical Implications • Despite further evidence that teams tend to perform better at home than away in the A-League, short-haul air travel does not appear to influence match outcome in football. • Short-haul air travel after competition appears to have a limited effect on recovery. However, postmatch sleep restriction is an issue regardless of match location.

• Research into the effects of travel on performance recovery when more than 1 game is played per week is justified. Acknowledgments The authors gratefully acknowledge the funding provided by Football Federation Australia to conduct this study and assistance from Dr Jeff Steinweg. The authors would like to thank the players and the club for their time and enthusiasm and gratefully acknowledge the allocation of resources provided by North Queensland Football Club in support of this project. The authors would also like to thank Alan McCall (Université Lille Nord de France, Lille, France, and LOSC Lille Métropole Football Club, Camphin-en-Pévèle, France) for facilitating the project and Dr Emma Knight (Performance Research Centre, Australian Institute of Sport, Canberra, ACT, Australia) for her assistance with the statistical analysis. The authors report no conflict of interest.

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