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The effect of interstate travel on sleep patterns of elite Australian Rules footballers
The effect of interstate travel on sleep patterns of elite Australian Rules footballers / Richmond 1, B Dawson 1, DR Hillman 2 & PR Eastwood 1,2 1School of Human Movement and Exercise Science, University of Western Australia, Crawley, Western Australia, Austalia. 2WestAustralian Sleep Disorders Research Institute, Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.
The purpose of the current study was to examine the effect of interstate air travel on the quality and quantity of sleep in elite Australian Rules football players. Ten elite male athletes, who were members of a Western Australian-based Australian Football League (AFL) team, participated in the study. Sleep pattern was assessed by measuring sleep duration (SLD), sleep efficiency (SE}, number of wakings (NW) and total wake time after sleep onset (WT) using a wrist-worn actigraph. Subjective sleep quality (SQ) was assessed using a scale of sleep rating. Throughout the 2002 AFL season, measurements were obtained on the night before (N1), the night of (N2) and the night after {N3) home and away games. Baseline measurements were obtained from five consecutive non-game nights. Compared to baseline, SLD on N1 was increased when home and away (by 51 and 105 mins respectively, p<0.05), while all other measures of sleep pattern were unchanged. On N2, SLD was decreased to a similar degree whether home or away (by 68 and 64 mins respectively, p<0.05), while all other measures of sleep pattern were unchanged. By N3 all measures of sleep pattern had returned to baseline values. Relative to baseline, perception of SQ was worst on N2 of a home game. This study has shown that interstate travel by elite AFL players has no adverse effects on sleep pattern on the night before a game. (J Sci Med Sport 2004;7:2:186-196
Introduction Recent research has indicated that athletic team and individual performance is o f t e n i m p a i r e d following i n t e r s t a t e a i r travel, p a r t i c u l a r l y w h e n t r a v e l is in a n e a s t w a r d d i r e c t i o n 1-5. F o r e x a m p l e , R o w b o t t o m a n d P i c k e r i n g 3 h a v e r e c e n t l y r e p o r t e d t h a t i n t e r s t a t e ( a c r o s s 1-2 t i m e zones) t r a v e l l i n g A u s t r a l i a n R u l e s f o o t b a l l t e a m s h a d s i g n i f i c a n t l y l o w e r t a l l i e s in k i c k s , m a r k s a n d h a n d b a l l s w h e n p l a y i n g a w a y (following travel) t h e n w h e n p l a y i n g a t h o m e . N o r t h A m e r i c a n - b a s e d s t u d i e s h a v e s h o w n s i m i l a r effects of t r a v e l o n p e r f o r m a n c e : m a j o r l e a g u e b a s e b a l l t e a m s s c o r e fewer r u n s t h a n u s u a l w h e n t h e v i s i t o r h a s j u s t c o m p l e t e d e a s t w a r d travel2; e a s t w a r d - t r a v e l l i n g college football t e a m s c r o s s i n g a t l e a s t o n e t i m e z o n e s c o r e fewer p o i n t s , a l l o w m o r e p o i n t s a n d s u f f e r a g r e a t e r m a r g i n of d e f e a t t h a n w e s t w a r d - t r a v e l i n g t e a m s S ; a n d w e s t c o a s t based professional football teams travelling eastward show a significant d e c r e a s e in p e r f o r m a n c e w h e n c o m p a r e d to g a m e s p l a y e d a w a y f r o m h o m e b u t w i t h i n t h e s a m e t i m e z o n e 1. The mechanisms underlying this performance impairment are unclear, but o n e p o s s i b l e c o n t r i b u t o r is t h e effect of a i r t r a v e l o n t h e q u a l i t y a n d q u a n t i t y of sleep. S l e e p l o s s h a s b e e n i d e n t i f i e d a s a p o t e n t i a l c a u s e of p o o r p e r f o r m a n c e 6. Effects of s l e e p l o s s i n c l u d e i m p a i r e d j u d g m e n t , a n i n a b i l i t y to c o n c e n t r a t e , s l o w e d r e a c t i o n t i m e s , r e d u c e d d a y t i m e a l e r t n e s s a n d d i s t u r b e d m o o d 7-9, all ()f w h i c h c a n i n f l u e n c e a t h l e t i c P e r f o r m a n c e . To d a t e , it r e m a i n s u n k n o w n to
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w h a t degree interstate travel affects sleep p a t t e r n s in healthy young athletes. The aim of the p r e s e n t s t u d y w a s to determine the effect of interstate travel on the sleep p a t t e r n s of elite Australian Football players. We hypothesised that the quality and quantity of sleep would be impaired following interstate travel on the night before, the night of and the night after a n a w a y game when c o m p a r e d to the night before, the night of and the night after a home game.
Methods Subjects Ten professional athletes who were currently playing for a Western Australianb a s e d Australian Football League (AFL) t e a m were recruited for the s t u d y (Table 1). Inclusion was b a s e d on (a} their probable t e a m selection each week in the 2002 season, (b) perceived individual reliability and (c) willingness to participate in the study. The s t u d y was approved b y the H u m a n Ethics Committee of the University of Western Australia. Informed written consent was obtained from each volunteer prior to participation. Subject Number
Age (yr)
Height (m)
1 2 3 4 5
22 22 23 26 24 28 21 23 21 21 23 (2)
187 187 185 181 174 183 192 178 204 196 187 (9)
6 7 8 9 10 Mean (±SD)
Weight VO2max (kg) (ml.kg'l.min"1) 84.4 77.2 84.4 81.4 76.6 88.0 89.8 81.2 101,0 94,2 85.8 (7.6)
66.7 68.0 62.7 62.7 65.1 61.7 59,3 61,7 61.7 58.7 62.8 (3.0)
Maximum oxygen consumption (VO2max) was estimated from 20 metre multistage shuttle run tests (27) performed in the pre-season.
Table 1: Subject characteristics,
Study design For each subject, m e a s u r e m e n t s of sleep quality and quantity were obtained t h r o u g h o u t the 2002 AFL s e a s o n using actigraphy and sleep logs. Measurem e n t s were u n d e r t a k e n on the night before (N1), the night of (N2) and the night after (N3) a h o m e a n d away game. Where possible, multiple m e a s u r e m e n t s (more t h a n one night) were obtained for each night u n d e r each condition. During away g a m e s only N 1 was s p e n t interstate, as participants flew b a c k to Western Australia immediately following a game. Baseline m e a s u r e m e n t s were obtained from five consecutive nights while in Western Australia. None of these
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b a s e l i n e n i g h t s preceded or followed participation in a game. Data were collected only when games were played during the day (ie, night games were excluded from the study). Home games were played in Western Australia (starting at 11:40 or 13:40 Western Standard Time (WST)), while away games included games played in South Australia (starting at 13:40 WST), Victoria (starting at 12:10 WST), or the Australian Capital Territory (starting at 11:10 WST). At the time of the study, Victoria and the Australian Capital Territory were two h o u r s ahead of Western Australia, while South Australia was 1.5 h o u r s ahead.
Actigraphy Measurements of sleep pattern were obtained using a wrist-worn actigraph (Micro Mini-Motion Logger, Ambulatory Monitoring Inc., Ardsley, NY). The device was set to 'zero crossing mode', which represents a m e a s u r e of frequency of movement. On each occasion, participants were instructed to place the actigraph on their n o n - d o m i n a n t wrist at least 30-minutes before 'lights off and to continue to wear it for at least 30-minutes after waking up each morning. Actigraph records were later downloaded to a personal computer and the recordings analysed using device-specific software (ACT Millennium and Action 4, Ambulatory Monitoring Inc., Ardsley, NY). For each night, m e a s u r e m e n t s were derived for (i) sleep duration, (ii) wake time after sleep onset, (iii) sleep efficiency (= (sleep duration - wake time)/sleep duration) x 100), and (iv) the n u m b e r of wakings.
Sleep logs On each s t u d y night participants completed a sleep log detailing perceived rating of sleep quality. Participants recorded how well they thought they had slept on a scale of one to five, time of 'lights on' and 'lights off, sleeping arrangements (ie, p a r t n e r / n o partner) and sleeping location (ie, own h o m e / partners home/hotel). Participants were also encouraged to note any other relevant c o m m e n t s such as reasons for waking up during the night a n d / o r reasons for experiencing trouble falling asleep.
Analysis During the five baseline nights, night-to-night variability of sleep variables was compared using a one-way repeated m e a s u r e s ANOVA. Each variable was t h e n averaged over the five nights to provide a single baseline measurement. Where m e a s u r e m e n t s were obtained on multiple nights before, during or after home or away games, the data were averaged to obtain a single m e a s u r e m e n t for that condition for t h a t individual. The m e a n baseline data were compared to home and away m e a s u r e m e n t s using a one-way repeated m e a s u r e s ANOVA. Post hoc analyses were performed using a Dunnett's test. A two-way repeated m e a s u r e s ANOVA was used to compare data obtained from different nights (N1, N2, N3) and between the two conditions (home and away). Post hoc analyses were performed using a Tukey's test. Pearson's correlation coefficients were used to examine the strength of associations between (i) the rating of sleep quality (sleep logs) and each actigraphy-based m e a s u r e m e n t , (ii) eastward flight time and actigraphy
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m e a s u r e m e n t s from N 1, and (iii) westward (return) flight time and actigraphy m e a s u r e m e n t s from N2. For all statistical comparisons, p<0.05 was considered significant.
ReSults During the 2002 AFL season, sleep d a t a were collected from a total of 188 nights in the 10 subjects. Each subject w a s studied on 19-+3 separate nights, including the five baseline nights. In one subject (subject 4), technical difficulties resulted in data being obtained from only four baseline nights. In nine subjects at least two s e p a r a t e m e a s u r e m e n t s were obtained for each night u n d e r each condition (home and away). In subject 7, during the away-game condition, d a t a were u n a b l e to be obtained on N2 and only a single night of data were obtained on N 1 a n d N3. Baseline m e a s u r e m e n t s From the time of sleep onset to waking, on average, subjects slept for 8.4 hours, woke 12 times during this period for a total of 57 minutes, with a sleep efficiency of 88% (Table 2). Group analyses showed no significant differences between baseline nights for sleep duration (p=0.8}, wake time (p=0.2), sleep efficiency (p=0.3), n u m b e r of wakings (p=0.2) or rating of sleep quality (p=0.3). Flight times E a s t w a r d flight time was 186+18 m i n s (range, 140 to 195 mins} and westward (return) flight time was 222_+24 m i n s (range 170 to 240 mins). There were no significant correlations between eastward or westward flight times a n d any actigraphy-based sleep variable for NI or N2, respectively.
BaselineStudy Night Night I Sleep duration (min) Wake time (min) Sleep efficiency (%) Number of wakings Sleep quality
522 (41) 45 (29) 91,2 (5.6) 12 (7) 3.5 (0.9)
Night2 Night 3 497 (65) 41 (40) 92.0 (7.6) 9 (5) 4.1 (0.5)
495 (56) 59 (46) 87.9 (9.9) 13 (8) 3.7 (1.0)
Night4 522 (54) 86 (63) 82.6 (14.7) 13 (4) 3.7 (0.5)
Night5 488 (138) 55 (37) 86.2 (11.6) 11 (6) 3.9 (0.4)
Mean 505 (16) 57 (18) 88.0 (3.8) 12 (2) 3.8 (0.2)
CV 10 (4) 65 (26) 7 (4) 39 (18) 33 (15)
CV, within-subject coefficient of variation (= SD/mean x 100%)
Table 2: Group (+_SD)baseline sleep measurements (n=10).
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The effect of interstate travel on sleep patterns of... Comparisons between conditions Sleep (h~ration
Relative to mem~ baseline data (Fig. ]) during both home and away games, sleep duration increased on NI (by 51 a n d 105 minutes, respectively, p<0.05), decreased on N2 (by 68 and 64 minutes, respectively, p<0.05) and was not significantly different on N3. Between-night c o m p a r i s o n s showed that, w h e t h e r h o m e or away, sleep duration w a s significantly greater on N1 t h a n b o t h N2 (119 a n d 169 m i n u t e s less, respectively, p<0.001) a n d N3 (51 a n d 55 m i n u t e s less, respectively, p< 0.05). Within-night c o m p a r i s o n s showed t h a t sleep duration w a s significantly less on N2 w h e n away from h o m e (p<0.005), b u t t h a t N1 a n d N3 were not significantly different between the conditions.
Wake time after sleep onset While there was a tendency for wake time to be greater during N ] a n d N3 w h e n away t h a n home, the differences were not statistically significant (Fig. 2). Overall, wake time was not significantly different between baseline m e a s u r e m e n t s a n d h o m e (p= 0.2) or away nights (p= 0.4), or between nights u n d e r the s a m e condition (p= 0.9) or between the s a m e night u n d e r each of the two conditions (p= 0.5).
Sleep efficiency For b o t h h o m e a n d away conditions, sleep efficiency tended to be less on N2 (Fig. 3). Similarly, sleep efficiency tended to fall on all nights away v e r s u s home. A significant overall difference was found between baseline and 'home' night sleep efficiency (p= 0.03). However post hoc analyses (Dunnett's Method) produced no significant differences. Overall, sleep efficiency was not significantly different between nights u n d e r the s a m e condition (p= 0.3) or between the s a m e night u n d e r each of the two conditions (p= 0.8).
1 I r
Lk
600
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500
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400
300 BL
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N2
.Study night 190
N3
Figure 1: Sleep duration measured on the baseline night (open bar), and the night before (N1), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +SD. * p<0.05, n=lO.
The effect of interstate travel on sleep patterns of...
180 160 A
140 120
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80 60 40
20 0 BL
N1
N2
N3
Study night
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90
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N1
N2
Study night
N3
Figure2: Wake time after sleep onset measured on the baseline night (open bar), and the night before (NI), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +_SD,n=lO.
Figure 3. Sleep efficiency (= (sleep duration - wake time)/ sleep duration) x 100) measured on the baseline night (open bar), and the night before (N1), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +SD, n=10.
Number of wakings The n u m b e r of wakings tended to be less on N 1 a n d N2 w h e n away relative to b o t h baseline a n d to the s a m e nights u n d e r the h o m e condition (Fig. 4). However, these differences were not statistically significant. Overall, the n u m ber of wakings was not significantly different between baseline a n d h o m e (p= 0.7) or away nights (p= 0.06), between nights u n d e r the s a m e condition (p=0.3) or between the s a m e night u n d e r each of the two conditions (p= 0.5).
Rating of sleep quality Relative to baseline, subjects perceived their sleep quality to be reduced on N2 w h e n h o m e (p= 0.006) (Fig. 5). Although sleep quality tended to be less t h a n baseline w h e n away on b o t h N1 and N2, the decrease did not reach statistical significance. Between-night c o m p a r i s o n s showed reduced sleep quality on N2 w h e n h o m e t h a n for b o t h N1 (p= 0.043) and N3 (p= 0.022}. When away, sleep quality was also reduced on N2 relative to N3 (p= 0.047). There were no
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2O u~ 01 c
18 16
E
8
Z
6 4
BL
N1
N2
N3
Study night
Figure 4: Number of wakings measured on the baseline night (open bar), and the night before (N1), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +_SD,n=lO.
7
4.5
W
A
o
4.0
3.5 o" 3.0 o0 2.5
_I BL
N1
N2
Study night
N3
Figure 5: Perceived quality of sleep measured on the baseline night (open bar), and the night before (N1), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +-SD. * p
significant differences in sleep quality between the same night u n d e r each condition (p=0.9). Pearson's correlations were also performed between perceived sleep quality and each of the actigraphy-based sleep variables. Significant, b u t extremely weak relationships were found between sleep quality and sleep efficiency (r= 0.19, p= 0.01), the n u m b e r of wakings (r= -0.20, p= 0.007) and wake time (r= 0.20, p= 0.008). No significant association was noted between sleep quality and sleep duration (r= 0.043, p= 0.6).
Discussion This study utilised the technique of actigraphy to evaluate the effect of air travel on the sleep p a t t e r n s of 10 elite Australian Rules football players during the 2002 season. Actigraphy allowed an objective a s s e s s m e n t of sleep quality and quantity. It is based on a n acceleration sensor that senses physical
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The effect of interstate travel on sleep patterns of...
motion. Because the actigraph c a n be attached to an individual's wrist, the technique is non-intrusive a n d is convenient for the subject. The technique requires minimal supervision as multiple nights of sleep data can be stored for downloading at a later date. Actigraphy h a s b e e n validated against laboratoryb a s e d p o l y s o m n o g r a p h y as being a n a c c u r a t e m e a s u r e of sleep duration, sleep efficiency, n u m b e r of wakings and wake time after sleep onset 1°-12. The algorithms applied to the stored information have b e e n d e m o n s t r a t e d to correlate highly with the traditional p o l y s o m n o g r a p h y for nocturnal sleep periods 11. Baseline m e a s u r e m e n t s were obtained for each athlete via actigraphic monitoring for five consecutive nights, none of which preceded or followed participation in a football game. M e a s u r e m e n t s obtained over five nights have been shown to e n s u r e good reliability of actigraphic m e a s u r e s of sleep 13. The subjects in this s t u d y showed n o r m a l sleep p a t t e r n s at baseline, sleeping for 8.4 h o u r s and waking 12 times during this period for a total of 57 minutes. The r e s u l t a n t sleep efficiency of 88% was within n o r m a l ranges for y o u n g healthy individuals 14. During the season, actigraphic m e a s u r e s of sleep were c o m p a r e d to subjective ratings of sleep quality. It was notable t h a t all actigraphy-based m e a s u r e s were poorly COlTelated to perceived quality of sleep. Such a finding is consistent with previous studies showing discrepancies in night sleep measu r e d b y subjective (questionnaire) and objective (actigraphy a n d / o r polysomnography) m e t h o d s 15,16 a n d is consistent with evidence suggesting t h a t people have difficulties a s s e s s i n g their own sleeping p a t t e r n s 15. These findings highlight the i m p o r t a n c e of using objective m e a n s to identify the effect of interventions on sleep. On the night before a game, relative to baseline, subjects slept longer whether at h o m e or away. This is likely to reflect voluntary behaviour, as p a r t of the athletes' p r e p a r a t i o n for competition is a belief t h a t 'a good night's sleep' will maximise g a m e p e r f o r m a n c e the next day. While subjects slept longer, they tended to perceive t h a t the quality of sleep on the night before a game was less t h a n usual. It was interesting to note t h a t this perception was not supported by other actigraphy-based sleep variables, as time s p e n t awake, sleep efficiency a n d n u m b e r of wakings were not different from baseline. Our original hypothesis w a s t h a t sleep would be m o s t impaired on the night prior to a n away game, as a consequence of the effects of air travel. In support of this hypothesis are the findings that, w h e n c o m p a r e d to the night prior to a h o m e game, subjects tended to have increased wake time, decreased sleep efficiency a n d a perception of impaired sleep quality. However, these trends were small a n d non-significant. Conversely, the d a t a provide a more compelling case for a lack of effect of travel on sleep or sleep duration, which was similar for b o t h h o m e and away, and which was associated with fewer awakenings w h e n sleeping away from home. In general, the findings of similar duration of sleep and only small and nonsignificant changes in other sleep variables on the night before a n away game, suggest t h a t eastward interstate air travel a n d the associated 1.5- to two-hour advance of the body clock b a d minimal effect on sleep p a t t e r n s of the subjects in this study. It m a y be t h a t s u c h a finding is unique to young healthy 193
The effect of interstate travel on sleep patterns of...
individuals as both age 17 and the level of fitness 18 influence the degree to which the internal biological clock can readjust with rapid travel across time zones. It m a y also be that travel across a greater n u m b e r of time zones is required before sleep p a t t e r n is affected 19,2°. While recognising t h a t elite team performance is a multifaceted entity, it was notable that of those games analysed in this study, all eight home games were won, b u t only one of eight away games was won. Taken together, these findings argue against the need for more t h a n one night of acclimatisation prior to an away game after crossing only one or two time zones. They also argue against a major influence of sleep disruption as a consequence of s u c h travel on s u b s e q u e n t game performance. While we did not specifically m e a s u r e performance during a game, others have reported a detrimental effect of interstate travel on team performance. Rowbottom and Pickering 3 have recently reported that e a s t / w e s t (across 1-2 time-zones) travelling AFL teams h a d significantly lower tallies in kicks, m a r k s and handballs when playing away (following travel) then when playing at home. Such an effect h a s also been reported in sports other t h a n Australian Rules football. A s t u d y of North American major league baseball teams showed that, while the overall winning percentages of eastern and western teams were similar, the home team could expect to score 1.24 more r u n s t h a n u s u a l when the visitor h a d j u s t completed e a s t w a r d travel 2. The a u t h o r s postulated that one major c o m p o n e n t affecting the outcome of baseball games is previous transcontinental travel, b u t only if the direction of travel was eastward. Similarly, in a n examination of the 1996 American National Collegiate Athletic Association (NCAA) football season, Worthen and Wade 5 found that eastwardtravelling t e a m s crossing at least one time zone scored fewer points, allowed more points and suffered a greater margin of defeat t h a n westward-traveling teams. J e h u e et all studied the effect of time zone changes on team performance in the American National Football League (NFL) and showed that west coast-based teams travelling to Central America or to the East Coast (twoor three- h o u r advance respectively) showed a significant decrease in performance when compared to games played away from home b u t within the same time zone. Thus, there is a body of evidence suggesting that interstate travel, and in particular eastward interstate travel, h a s a detrimental effect on performance. While this m a y be the case, the data from our s t u d y suggest that any effect on performance is a result of air travel itself a n d / o r to disruption of the internal body clock (circadian rhythm) due to a conflict between clock time at the new location versus clock time at home 1, rather t h a n to a n effect of travel on quality of sleep. Consistent with this conclusion is the observation by Rowbottom and Pickering 3 that both e a s t / w e s t (across 1-2 time-zones) and n o r t h / s o u t h (across no time zones) travelling AFL teams had significantly lower tallies in kicks, m a r k s and handballs when playing away (following travel) then when playing at home. Dry air in aircraft cabins can lead to dehydration and associated symptoms, while reduced partial pressure of oxygen can be associated with headaches, light-headedness and reduced feelings of wellbeing 21. These factors, together with the effect of athletes having to spend a prolonged period in cramped and uncomfortable positions, m a y influence s u b s e q u e n t performance independently of sleep-related factors. 194
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In this s t u d y the m o s t m a r k e d differences in sleep duration were observed on the night o f a g a m e when, regardless of w h e t h e r following a h o m e or away game,
athletes slept for a shorter time. In the case of a h o m e g a m e it was observed t h a t time of 'lights out' was several h o u r s later t h a n t h a t indicated for the night before or after a h o m e g a m e or w h e n c o m p a r e d to baseline conditions. It is unlikely t h a t flight time influenced sleep duration, as eastward flight time was not correlated with a n y actigraphy-based sleep variable. Because the majority of g a m e s played at h o m e were won, it is probable t h a t late night celebrations contributed to the decreased sleep duration. Alcohol consumption, which is widely recognised as being a c a u s e of sleep disruption 22,2a, m a y also have contributed to the decreased sleep duration. The decrease in sleep duration was m o s t m a r k e d on the night of a n away game (N2), w h e n subjects slept for nearly two h o u r s less t h a n baseline. On this night sleep efficiency was decreased as was an individual's perceived sleep quality. It is likely t h a t these changes reflect the fact t h a t on all occasions players flew h o m e immediately following the game. Very few of the players reported n a p p i n g on the plane on the way home. Thus, the observed i m p a i r m e n t s in sleep m o s t likely reflect the combined effects of participating in strenuous, prolonged exercise, flying interstate and arriving h o m e late. It is possible t h a t the combined effects of prolonged confinement due to travel immediately following a game, together with impaired sleep, could affect postgame recovery b y potentially exacerbating m u s c l e soreness and fatigue. While sleep duration was shortest and sleep efficiency and perceived sleep quality worst on the night of a game, these m e a s u r e s h a d all r e t u r n e d to normal baseline values on the night following a game. Thus, it a p p e a r s t h a t a c o m p e n s a t o r y increase in sleep duration to m a k e u p for the reduced quality and quantity of sleep experienced on the night of a g a m e (N2) did not occur. Such c o m p e n s a t i o n h a s b e e n well documented, although it is likely t h a t a greater degree of sleep d i s t u r b a n c e is required to elicit s u c h changes in recovery sleep 24. Alternatively, it m a y be t h a t fit y o u n g athletes recover quickly from m i n o r sleep deprivation. Several studies have shown t h a t athletes are more efficient sleepers t h a n non-athletes 25,26. The r e a s o n s for these differences r e m a i n speculative. However, greater fitness levels (due to more physical activity) and more optimal body composition (increased percentage of lean body m a s s resulting in a faster metabolic rate) in athletes m a y be contributing factors 26.
Acknowledgements The a u t h o r s would like to t h a n k Glenn Stewart, Sports Science Manager with the West Coast Eagles, for his a s s i s t a n c e with this r e s e a r c h study. We would also like to t h a n k Ms Kelly Shepherd, West Australian Sleep Disorders Research Institute, for help with the actigraph recordings and analyses.
References (1) Jehue R, Street D and Huizenga R. Effect of time zone and game time changes on team performance: National Football League. Med Sci Sports Exerc 1993; 25:127-131. (2) Recht LD, Lew RA and Schwartz WJ. Baseball teams beaten by jet lag. Nature 1995; 377:583. (3) Rowbottom DG and Pickering DM. The effects of travel on team performance in the Australian Football League. 2000 Pre-Olympic Congress. International Congress on Sport 195
The effect of interstate travel on sleep patterns of... Science, Sports Medicine and Physical Education. Brisbane, Australia. 7-12 September, 2000. (4) Steenland K a n d Deddens JA. Effect of travel a n d rest on performance of professional basketball players. Sleep 1997; 20:366-369. (5) Worthen J B a n d Wade CE. Direction of travel a n d visiting team athletic performance: support for a circadian dysrhythmia hypothesis. J Sport Behav 1999; 22:279-287. (6) Youngstedt SD a n d O'Connor PJ. The influence of air travel on athletic performance. Sports Med 1999; 28:197-207. (7) Jean-Louis G, Kripke DF a n d Ancoli-Israel S. Sleep a n d Quality of Well-Being. Sleep 2000; 23:1115-1121. (8) Pickett GF a n d Morris AF. Effects of acute sleep a n d food deprivation on total body response time a n d cardiovascular performance. J Sports Med Phys Fitness 1975; •5:49-56. (9) Waiters PH. Sleep, the athlete, a n d performance. Nat Strength Cond Assoc 2002; 24:17-24. (10) Cole RJ, Kripke DF, G r u e n W, et al. Automatic sleep/wake identification from wrist activity. Sleep 1992; 15:461-469. (11) S a d e h A, Sharkey KM a n d Carskadon MA. Activity-based sleep-wake identification: a n empirical test of methodological issues. Sleep 1994; 17:201-207. (12) Thorpy M, Chesson A, Derderian S, et al. Practice parameters for the use of actigraphy in the clinical a s s e s s m e n t of sleep disorders. Sleep 1995; •8:285-287. (13) Acebo C, Sadeh A, Seifer R, et al. Estimating sleep p a t t e r n s with activity monitoring in children a n d adolescents: how m a n y nights are necessary for reliable m e a s u r e s ? Sleep 1999; 22:95-103. {14} Carskadon MA a n d Dement WC. Normal h u m a n sleep: a n overview. In: Principles and practice of sleep medcine. M. H. Kryger, T. Roth a n d W. C. Dements: M. H. Kryger, T. Roth a n d W. C. Dement. Philadelphia. W.B. S a u n d e r s Co. 2000. (15) C a r s k a d o n MA, Dement WC, Mitler MM, et al. Self-reports versus sleep laboratory findings in 122 drug-free subjects with complaints of chronic insomnia. Am J Psych 1976; 133:1382-1388. (16) Sadeh A, Hauri PJ, Kripke DF, et al. The role of actigraphy in the evaluation of sleep disorders. Sleep 1995; •8:288-302. (17) Moline ML, Pollack CP, Monk TH, et al. Age-related differences in recovery from simulated jet-lag. Sleep 1992; 15:28-40. (18) Atkinson G, Coldwells A a n d Reilly T. A comparison of circadian r h y t h m s in work performance between physically active a n d inactive subjects. Ergonomics 1993; 36:273-281. (19) Desir D, Van Cauter E, Fang VS, et al. Effects of "jet lag" on h o r m o n a l patterns. I. Procedures, variations in total p l a s m a proteins, a n d disruption of adrenocorticotropin-cortisol periodicity. J Clin Endocrinol Metab 1981; 52:628-641. (20) Manfredini R, Manfredini F, Fersini C et al. Circadian rhythms, athletic performance, and jet lag. Br J Sports Med 1998; 32:101-106. (21) Reilly T, Atkinson G a n d Waterhouse J. Travel fatigue a n d jet-lag. J Sports Sci 1997; •5:365-369. (22} Brower KJ. Alcohol's effect on sleep in alcoholics. Alcohol Res Health 2001; 25:110-125. (23) Roehrs T a n d Roth T. Sleep, sleepiness a n d alcohol use. Alc Res Hlth: J Nat Inst Alc Abuse Alc 2001; 25:101-109. (24) Borbely AA, B a u m a n n F, Brandeis D, et al. Sleep deprivation: effect on sleep stages a n d EEG power density in man. Electroencephalogr Clin 1981; 51:483-493. (25) Porter J M and Horne JA. Exercise a n d sleep behaviour - a questionnaire approach. Ergonomics 1981; 24:511-521. (26) Shapiro CM, Catterall J, Warren P, Oswald I, Trinder J, Paxton S a n d East BW. Lean body m a s s a n d non-rapid eye movement sleep. Brit Med J 1986; 294:22. (27) Leger LA, Mercier D, Gadoury C et al. The multistage 20 metre shuttle r u n test for aerobic fitness. J Sports Sci 1988; 6:93-101.
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The purpose of the current study was to examine the effect of interstate air travel on the quality and quantity of sleep in elite Australian Rules football players. Ten elite male athletes, who were members of a Western Australian-based Australian Football League (AFL) team, participated in the study. Sleep pattern was assessed by measuring sleep duration (SLD), sleep efficiency (SE}, number of wakings (NW) and total wake time after sleep onset (WT) using a wrist-worn actigraph. Subjective sleep quality (SQ) was assessed using a scale of sleep rating. Throughout the 2002 AFL season, measurements were obtained on the night before (N1), the night of (N2) and the night after {N3) home and away games. Baseline measurements were obtained from five consecutive non-game nights. Compared to baseline, SLD on N1 was increased when home and away (by 51 and 105 mins respectively, p<0.05), while all other measures of sleep pattern were unchanged. On N2, SLD was decreased to a similar degree whether home or away (by 68 and 64 mins respectively, p<0.05), while all other measures of sleep pattern were unchanged. By N3 all measures of sleep pattern had returned to baseline values. Relative to baseline, perception of SQ was worst on N2 of a home game. This study has shown that interstate travel by elite AFL players has no adverse effects on sleep pattern on the night before a game. (J Sci Med Sport 2004;7:2:186-196
Introduction Recent research has indicated that athletic team and individual performance is o f t e n i m p a i r e d following i n t e r s t a t e a i r travel, p a r t i c u l a r l y w h e n t r a v e l is in a n e a s t w a r d d i r e c t i o n 1-5. F o r e x a m p l e , R o w b o t t o m a n d P i c k e r i n g 3 h a v e r e c e n t l y r e p o r t e d t h a t i n t e r s t a t e ( a c r o s s 1-2 t i m e zones) t r a v e l l i n g A u s t r a l i a n R u l e s f o o t b a l l t e a m s h a d s i g n i f i c a n t l y l o w e r t a l l i e s in k i c k s , m a r k s a n d h a n d b a l l s w h e n p l a y i n g a w a y (following travel) t h e n w h e n p l a y i n g a t h o m e . N o r t h A m e r i c a n - b a s e d s t u d i e s h a v e s h o w n s i m i l a r effects of t r a v e l o n p e r f o r m a n c e : m a j o r l e a g u e b a s e b a l l t e a m s s c o r e fewer r u n s t h a n u s u a l w h e n t h e v i s i t o r h a s j u s t c o m p l e t e d e a s t w a r d travel2; e a s t w a r d - t r a v e l l i n g college football t e a m s c r o s s i n g a t l e a s t o n e t i m e z o n e s c o r e fewer p o i n t s , a l l o w m o r e p o i n t s a n d s u f f e r a g r e a t e r m a r g i n of d e f e a t t h a n w e s t w a r d - t r a v e l i n g t e a m s S ; a n d w e s t c o a s t based professional football teams travelling eastward show a significant d e c r e a s e in p e r f o r m a n c e w h e n c o m p a r e d to g a m e s p l a y e d a w a y f r o m h o m e b u t w i t h i n t h e s a m e t i m e z o n e 1. The mechanisms underlying this performance impairment are unclear, but o n e p o s s i b l e c o n t r i b u t o r is t h e effect of a i r t r a v e l o n t h e q u a l i t y a n d q u a n t i t y of sleep. S l e e p l o s s h a s b e e n i d e n t i f i e d a s a p o t e n t i a l c a u s e of p o o r p e r f o r m a n c e 6. Effects of s l e e p l o s s i n c l u d e i m p a i r e d j u d g m e n t , a n i n a b i l i t y to c o n c e n t r a t e , s l o w e d r e a c t i o n t i m e s , r e d u c e d d a y t i m e a l e r t n e s s a n d d i s t u r b e d m o o d 7-9, all ()f w h i c h c a n i n f l u e n c e a t h l e t i c P e r f o r m a n c e . To d a t e , it r e m a i n s u n k n o w n to
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w h a t degree interstate travel affects sleep p a t t e r n s in healthy young athletes. The aim of the p r e s e n t s t u d y w a s to determine the effect of interstate travel on the sleep p a t t e r n s of elite Australian Football players. We hypothesised that the quality and quantity of sleep would be impaired following interstate travel on the night before, the night of and the night after a n a w a y game when c o m p a r e d to the night before, the night of and the night after a home game.
Methods Subjects Ten professional athletes who were currently playing for a Western Australianb a s e d Australian Football League (AFL) t e a m were recruited for the s t u d y (Table 1). Inclusion was b a s e d on (a} their probable t e a m selection each week in the 2002 season, (b) perceived individual reliability and (c) willingness to participate in the study. The s t u d y was approved b y the H u m a n Ethics Committee of the University of Western Australia. Informed written consent was obtained from each volunteer prior to participation. Subject Number
Age (yr)
Height (m)
1 2 3 4 5
22 22 23 26 24 28 21 23 21 21 23 (2)
187 187 185 181 174 183 192 178 204 196 187 (9)
6 7 8 9 10 Mean (±SD)
Weight VO2max (kg) (ml.kg'l.min"1) 84.4 77.2 84.4 81.4 76.6 88.0 89.8 81.2 101,0 94,2 85.8 (7.6)
66.7 68.0 62.7 62.7 65.1 61.7 59,3 61,7 61.7 58.7 62.8 (3.0)
Maximum oxygen consumption (VO2max) was estimated from 20 metre multistage shuttle run tests (27) performed in the pre-season.
Table 1: Subject characteristics,
Study design For each subject, m e a s u r e m e n t s of sleep quality and quantity were obtained t h r o u g h o u t the 2002 AFL s e a s o n using actigraphy and sleep logs. Measurem e n t s were u n d e r t a k e n on the night before (N1), the night of (N2) and the night after (N3) a h o m e a n d away game. Where possible, multiple m e a s u r e m e n t s (more t h a n one night) were obtained for each night u n d e r each condition. During away g a m e s only N 1 was s p e n t interstate, as participants flew b a c k to Western Australia immediately following a game. Baseline m e a s u r e m e n t s were obtained from five consecutive nights while in Western Australia. None of these
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b a s e l i n e n i g h t s preceded or followed participation in a game. Data were collected only when games were played during the day (ie, night games were excluded from the study). Home games were played in Western Australia (starting at 11:40 or 13:40 Western Standard Time (WST)), while away games included games played in South Australia (starting at 13:40 WST), Victoria (starting at 12:10 WST), or the Australian Capital Territory (starting at 11:10 WST). At the time of the study, Victoria and the Australian Capital Territory were two h o u r s ahead of Western Australia, while South Australia was 1.5 h o u r s ahead.
Actigraphy Measurements of sleep pattern were obtained using a wrist-worn actigraph (Micro Mini-Motion Logger, Ambulatory Monitoring Inc., Ardsley, NY). The device was set to 'zero crossing mode', which represents a m e a s u r e of frequency of movement. On each occasion, participants were instructed to place the actigraph on their n o n - d o m i n a n t wrist at least 30-minutes before 'lights off and to continue to wear it for at least 30-minutes after waking up each morning. Actigraph records were later downloaded to a personal computer and the recordings analysed using device-specific software (ACT Millennium and Action 4, Ambulatory Monitoring Inc., Ardsley, NY). For each night, m e a s u r e m e n t s were derived for (i) sleep duration, (ii) wake time after sleep onset, (iii) sleep efficiency (= (sleep duration - wake time)/sleep duration) x 100), and (iv) the n u m b e r of wakings.
Sleep logs On each s t u d y night participants completed a sleep log detailing perceived rating of sleep quality. Participants recorded how well they thought they had slept on a scale of one to five, time of 'lights on' and 'lights off, sleeping arrangements (ie, p a r t n e r / n o partner) and sleeping location (ie, own h o m e / partners home/hotel). Participants were also encouraged to note any other relevant c o m m e n t s such as reasons for waking up during the night a n d / o r reasons for experiencing trouble falling asleep.
Analysis During the five baseline nights, night-to-night variability of sleep variables was compared using a one-way repeated m e a s u r e s ANOVA. Each variable was t h e n averaged over the five nights to provide a single baseline measurement. Where m e a s u r e m e n t s were obtained on multiple nights before, during or after home or away games, the data were averaged to obtain a single m e a s u r e m e n t for that condition for t h a t individual. The m e a n baseline data were compared to home and away m e a s u r e m e n t s using a one-way repeated m e a s u r e s ANOVA. Post hoc analyses were performed using a Dunnett's test. A two-way repeated m e a s u r e s ANOVA was used to compare data obtained from different nights (N1, N2, N3) and between the two conditions (home and away). Post hoc analyses were performed using a Tukey's test. Pearson's correlation coefficients were used to examine the strength of associations between (i) the rating of sleep quality (sleep logs) and each actigraphy-based m e a s u r e m e n t , (ii) eastward flight time and actigraphy
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m e a s u r e m e n t s from N 1, and (iii) westward (return) flight time and actigraphy m e a s u r e m e n t s from N2. For all statistical comparisons, p<0.05 was considered significant.
ReSults During the 2002 AFL season, sleep d a t a were collected from a total of 188 nights in the 10 subjects. Each subject w a s studied on 19-+3 separate nights, including the five baseline nights. In one subject (subject 4), technical difficulties resulted in data being obtained from only four baseline nights. In nine subjects at least two s e p a r a t e m e a s u r e m e n t s were obtained for each night u n d e r each condition (home and away). In subject 7, during the away-game condition, d a t a were u n a b l e to be obtained on N2 and only a single night of data were obtained on N 1 a n d N3. Baseline m e a s u r e m e n t s From the time of sleep onset to waking, on average, subjects slept for 8.4 hours, woke 12 times during this period for a total of 57 minutes, with a sleep efficiency of 88% (Table 2). Group analyses showed no significant differences between baseline nights for sleep duration (p=0.8}, wake time (p=0.2), sleep efficiency (p=0.3), n u m b e r of wakings (p=0.2) or rating of sleep quality (p=0.3). Flight times E a s t w a r d flight time was 186+18 m i n s (range, 140 to 195 mins} and westward (return) flight time was 222_+24 m i n s (range 170 to 240 mins). There were no significant correlations between eastward or westward flight times a n d any actigraphy-based sleep variable for NI or N2, respectively.
BaselineStudy Night Night I Sleep duration (min) Wake time (min) Sleep efficiency (%) Number of wakings Sleep quality
522 (41) 45 (29) 91,2 (5.6) 12 (7) 3.5 (0.9)
Night2 Night 3 497 (65) 41 (40) 92.0 (7.6) 9 (5) 4.1 (0.5)
495 (56) 59 (46) 87.9 (9.9) 13 (8) 3.7 (1.0)
Night4 522 (54) 86 (63) 82.6 (14.7) 13 (4) 3.7 (0.5)
Night5 488 (138) 55 (37) 86.2 (11.6) 11 (6) 3.9 (0.4)
Mean 505 (16) 57 (18) 88.0 (3.8) 12 (2) 3.8 (0.2)
CV 10 (4) 65 (26) 7 (4) 39 (18) 33 (15)
CV, within-subject coefficient of variation (= SD/mean x 100%)
Table 2: Group (+_SD)baseline sleep measurements (n=10).
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The effect of interstate travel on sleep patterns of... Comparisons between conditions Sleep (h~ration
Relative to mem~ baseline data (Fig. ]) during both home and away games, sleep duration increased on NI (by 51 a n d 105 minutes, respectively, p<0.05), decreased on N2 (by 68 and 64 minutes, respectively, p<0.05) and was not significantly different on N3. Between-night c o m p a r i s o n s showed that, w h e t h e r h o m e or away, sleep duration w a s significantly greater on N1 t h a n b o t h N2 (119 a n d 169 m i n u t e s less, respectively, p<0.001) a n d N3 (51 a n d 55 m i n u t e s less, respectively, p< 0.05). Within-night c o m p a r i s o n s showed t h a t sleep duration w a s significantly less on N2 w h e n away from h o m e (p<0.005), b u t t h a t N1 a n d N3 were not significantly different between the conditions.
Wake time after sleep onset While there was a tendency for wake time to be greater during N ] a n d N3 w h e n away t h a n home, the differences were not statistically significant (Fig. 2). Overall, wake time was not significantly different between baseline m e a s u r e m e n t s a n d h o m e (p= 0.2) or away nights (p= 0.4), or between nights u n d e r the s a m e condition (p= 0.9) or between the s a m e night u n d e r each of the two conditions (p= 0.5).
Sleep efficiency For b o t h h o m e a n d away conditions, sleep efficiency tended to be less on N2 (Fig. 3). Similarly, sleep efficiency tended to fall on all nights away v e r s u s home. A significant overall difference was found between baseline and 'home' night sleep efficiency (p= 0.03). However post hoc analyses (Dunnett's Method) produced no significant differences. Overall, sleep efficiency was not significantly different between nights u n d e r the s a m e condition (p= 0.3) or between the s a m e night u n d e r each of the two conditions (p= 0.8).
1 I r
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N3
Figure 1: Sleep duration measured on the baseline night (open bar), and the night before (N1), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +SD. * p<0.05, n=lO.
The effect of interstate travel on sleep patterns of...
180 160 A
140 120
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80 60 40
20 0 BL
N1
N2
N3
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'i
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,~
90
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N2
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N3
Figure2: Wake time after sleep onset measured on the baseline night (open bar), and the night before (NI), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +_SD,n=lO.
Figure 3. Sleep efficiency (= (sleep duration - wake time)/ sleep duration) x 100) measured on the baseline night (open bar), and the night before (N1), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +SD, n=10.
Number of wakings The n u m b e r of wakings tended to be less on N 1 a n d N2 w h e n away relative to b o t h baseline a n d to the s a m e nights u n d e r the h o m e condition (Fig. 4). However, these differences were not statistically significant. Overall, the n u m ber of wakings was not significantly different between baseline a n d h o m e (p= 0.7) or away nights (p= 0.06), between nights u n d e r the s a m e condition (p=0.3) or between the s a m e night u n d e r each of the two conditions (p= 0.5).
Rating of sleep quality Relative to baseline, subjects perceived their sleep quality to be reduced on N2 w h e n h o m e (p= 0.006) (Fig. 5). Although sleep quality tended to be less t h a n baseline w h e n away on b o t h N1 and N2, the decrease did not reach statistical significance. Between-night c o m p a r i s o n s showed reduced sleep quality on N2 w h e n h o m e t h a n for b o t h N1 (p= 0.043) and N3 (p= 0.022}. When away, sleep quality was also reduced on N2 relative to N3 (p= 0.047). There were no
191
The effect of interstate travel on sleep patterns of...
2O u~ 01 c
18 16
E
8
Z
6 4
BL
N1
N2
N3
Study night
Figure 4: Number of wakings measured on the baseline night (open bar), and the night before (N1), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +_SD,n=lO.
7
4.5
W
A
o
4.0
3.5 o" 3.0 o0 2.5
_I BL
N1
N2
Study night
N3
Figure 5: Perceived quality of sleep measured on the baseline night (open bar), and the night before (N1), the night of (N2) and the night after (N3) home (shaded bar) and away (solid bar) games. Error bars +-SD. * p
significant differences in sleep quality between the same night u n d e r each condition (p=0.9). Pearson's correlations were also performed between perceived sleep quality and each of the actigraphy-based sleep variables. Significant, b u t extremely weak relationships were found between sleep quality and sleep efficiency (r= 0.19, p= 0.01), the n u m b e r of wakings (r= -0.20, p= 0.007) and wake time (r= 0.20, p= 0.008). No significant association was noted between sleep quality and sleep duration (r= 0.043, p= 0.6).
Discussion This study utilised the technique of actigraphy to evaluate the effect of air travel on the sleep p a t t e r n s of 10 elite Australian Rules football players during the 2002 season. Actigraphy allowed an objective a s s e s s m e n t of sleep quality and quantity. It is based on a n acceleration sensor that senses physical
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The effect of interstate travel on sleep patterns of...
motion. Because the actigraph c a n be attached to an individual's wrist, the technique is non-intrusive a n d is convenient for the subject. The technique requires minimal supervision as multiple nights of sleep data can be stored for downloading at a later date. Actigraphy h a s b e e n validated against laboratoryb a s e d p o l y s o m n o g r a p h y as being a n a c c u r a t e m e a s u r e of sleep duration, sleep efficiency, n u m b e r of wakings and wake time after sleep onset 1°-12. The algorithms applied to the stored information have b e e n d e m o n s t r a t e d to correlate highly with the traditional p o l y s o m n o g r a p h y for nocturnal sleep periods 11. Baseline m e a s u r e m e n t s were obtained for each athlete via actigraphic monitoring for five consecutive nights, none of which preceded or followed participation in a football game. M e a s u r e m e n t s obtained over five nights have been shown to e n s u r e good reliability of actigraphic m e a s u r e s of sleep 13. The subjects in this s t u d y showed n o r m a l sleep p a t t e r n s at baseline, sleeping for 8.4 h o u r s and waking 12 times during this period for a total of 57 minutes. The r e s u l t a n t sleep efficiency of 88% was within n o r m a l ranges for y o u n g healthy individuals 14. During the season, actigraphic m e a s u r e s of sleep were c o m p a r e d to subjective ratings of sleep quality. It was notable t h a t all actigraphy-based m e a s u r e s were poorly COlTelated to perceived quality of sleep. Such a finding is consistent with previous studies showing discrepancies in night sleep measu r e d b y subjective (questionnaire) and objective (actigraphy a n d / o r polysomnography) m e t h o d s 15,16 a n d is consistent with evidence suggesting t h a t people have difficulties a s s e s s i n g their own sleeping p a t t e r n s 15. These findings highlight the i m p o r t a n c e of using objective m e a n s to identify the effect of interventions on sleep. On the night before a game, relative to baseline, subjects slept longer whether at h o m e or away. This is likely to reflect voluntary behaviour, as p a r t of the athletes' p r e p a r a t i o n for competition is a belief t h a t 'a good night's sleep' will maximise g a m e p e r f o r m a n c e the next day. While subjects slept longer, they tended to perceive t h a t the quality of sleep on the night before a game was less t h a n usual. It was interesting to note t h a t this perception was not supported by other actigraphy-based sleep variables, as time s p e n t awake, sleep efficiency a n d n u m b e r of wakings were not different from baseline. Our original hypothesis w a s t h a t sleep would be m o s t impaired on the night prior to a n away game, as a consequence of the effects of air travel. In support of this hypothesis are the findings that, w h e n c o m p a r e d to the night prior to a h o m e game, subjects tended to have increased wake time, decreased sleep efficiency a n d a perception of impaired sleep quality. However, these trends were small a n d non-significant. Conversely, the d a t a provide a more compelling case for a lack of effect of travel on sleep or sleep duration, which was similar for b o t h h o m e and away, and which was associated with fewer awakenings w h e n sleeping away from home. In general, the findings of similar duration of sleep and only small and nonsignificant changes in other sleep variables on the night before a n away game, suggest t h a t eastward interstate air travel a n d the associated 1.5- to two-hour advance of the body clock b a d minimal effect on sleep p a t t e r n s of the subjects in this study. It m a y be t h a t s u c h a finding is unique to young healthy 193
The effect of interstate travel on sleep patterns of...
individuals as both age 17 and the level of fitness 18 influence the degree to which the internal biological clock can readjust with rapid travel across time zones. It m a y also be that travel across a greater n u m b e r of time zones is required before sleep p a t t e r n is affected 19,2°. While recognising t h a t elite team performance is a multifaceted entity, it was notable that of those games analysed in this study, all eight home games were won, b u t only one of eight away games was won. Taken together, these findings argue against the need for more t h a n one night of acclimatisation prior to an away game after crossing only one or two time zones. They also argue against a major influence of sleep disruption as a consequence of s u c h travel on s u b s e q u e n t game performance. While we did not specifically m e a s u r e performance during a game, others have reported a detrimental effect of interstate travel on team performance. Rowbottom and Pickering 3 have recently reported that e a s t / w e s t (across 1-2 time-zones) travelling AFL teams h a d significantly lower tallies in kicks, m a r k s and handballs when playing away (following travel) then when playing at home. Such an effect h a s also been reported in sports other t h a n Australian Rules football. A s t u d y of North American major league baseball teams showed that, while the overall winning percentages of eastern and western teams were similar, the home team could expect to score 1.24 more r u n s t h a n u s u a l when the visitor h a d j u s t completed e a s t w a r d travel 2. The a u t h o r s postulated that one major c o m p o n e n t affecting the outcome of baseball games is previous transcontinental travel, b u t only if the direction of travel was eastward. Similarly, in a n examination of the 1996 American National Collegiate Athletic Association (NCAA) football season, Worthen and Wade 5 found that eastwardtravelling t e a m s crossing at least one time zone scored fewer points, allowed more points and suffered a greater margin of defeat t h a n westward-traveling teams. J e h u e et all studied the effect of time zone changes on team performance in the American National Football League (NFL) and showed that west coast-based teams travelling to Central America or to the East Coast (twoor three- h o u r advance respectively) showed a significant decrease in performance when compared to games played away from home b u t within the same time zone. Thus, there is a body of evidence suggesting that interstate travel, and in particular eastward interstate travel, h a s a detrimental effect on performance. While this m a y be the case, the data from our s t u d y suggest that any effect on performance is a result of air travel itself a n d / o r to disruption of the internal body clock (circadian rhythm) due to a conflict between clock time at the new location versus clock time at home 1, rather t h a n to a n effect of travel on quality of sleep. Consistent with this conclusion is the observation by Rowbottom and Pickering 3 that both e a s t / w e s t (across 1-2 time-zones) and n o r t h / s o u t h (across no time zones) travelling AFL teams had significantly lower tallies in kicks, m a r k s and handballs when playing away (following travel) then when playing at home. Dry air in aircraft cabins can lead to dehydration and associated symptoms, while reduced partial pressure of oxygen can be associated with headaches, light-headedness and reduced feelings of wellbeing 21. These factors, together with the effect of athletes having to spend a prolonged period in cramped and uncomfortable positions, m a y influence s u b s e q u e n t performance independently of sleep-related factors. 194
The effect of interstate travel on sleep patterns of...
In this s t u d y the m o s t m a r k e d differences in sleep duration were observed on the night o f a g a m e when, regardless of w h e t h e r following a h o m e or away game,
athletes slept for a shorter time. In the case of a h o m e g a m e it was observed t h a t time of 'lights out' was several h o u r s later t h a n t h a t indicated for the night before or after a h o m e g a m e or w h e n c o m p a r e d to baseline conditions. It is unlikely t h a t flight time influenced sleep duration, as eastward flight time was not correlated with a n y actigraphy-based sleep variable. Because the majority of g a m e s played at h o m e were won, it is probable t h a t late night celebrations contributed to the decreased sleep duration. Alcohol consumption, which is widely recognised as being a c a u s e of sleep disruption 22,2a, m a y also have contributed to the decreased sleep duration. The decrease in sleep duration was m o s t m a r k e d on the night of a n away game (N2), w h e n subjects slept for nearly two h o u r s less t h a n baseline. On this night sleep efficiency was decreased as was an individual's perceived sleep quality. It is likely t h a t these changes reflect the fact t h a t on all occasions players flew h o m e immediately following the game. Very few of the players reported n a p p i n g on the plane on the way home. Thus, the observed i m p a i r m e n t s in sleep m o s t likely reflect the combined effects of participating in strenuous, prolonged exercise, flying interstate and arriving h o m e late. It is possible t h a t the combined effects of prolonged confinement due to travel immediately following a game, together with impaired sleep, could affect postgame recovery b y potentially exacerbating m u s c l e soreness and fatigue. While sleep duration was shortest and sleep efficiency and perceived sleep quality worst on the night of a game, these m e a s u r e s h a d all r e t u r n e d to normal baseline values on the night following a game. Thus, it a p p e a r s t h a t a c o m p e n s a t o r y increase in sleep duration to m a k e u p for the reduced quality and quantity of sleep experienced on the night of a g a m e (N2) did not occur. Such c o m p e n s a t i o n h a s b e e n well documented, although it is likely t h a t a greater degree of sleep d i s t u r b a n c e is required to elicit s u c h changes in recovery sleep 24. Alternatively, it m a y be t h a t fit y o u n g athletes recover quickly from m i n o r sleep deprivation. Several studies have shown t h a t athletes are more efficient sleepers t h a n non-athletes 25,26. The r e a s o n s for these differences r e m a i n speculative. However, greater fitness levels (due to more physical activity) and more optimal body composition (increased percentage of lean body m a s s resulting in a faster metabolic rate) in athletes m a y be contributing factors 26.
Acknowledgements The a u t h o r s would like to t h a n k Glenn Stewart, Sports Science Manager with the West Coast Eagles, for his a s s i s t a n c e with this r e s e a r c h study. We would also like to t h a n k Ms Kelly Shepherd, West Australian Sleep Disorders Research Institute, for help with the actigraph recordings and analyses.
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