***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: A popular method to attempt to enhance performance is for athletes to sleep at natural or simulated moderate altitude ( SMA ) when training daily near sea level . Based on our previous observation of periodic breathing in athletes sleeping at SMA , we hypothesised that athletes ' sleep quality would also suffer with hypoxia . Using two typical protocol s of nocturnal SMA ( 2650 m ) , we examined the effect on the sleep physiology of 14 male endurance-trained athletes . The selected protocol s were Consecutive ( 15 successive exposure nights ) and Intermittent ( 3x 5 successive exposure nights , interspersed with 2 normoxic nights ) and athletes were r and omly assigned to follow either one . We monitored sleep for two successive nights under baseline conditions ( B ; normoxia , 600 m ) and then at weekly intervals ( nights 1 , 8 and 15 ( N1 , N8 and N15 , respectively ) ) of the protocol s. Since there was no significant difference in response between the protocol s being followed ( based on n=7 , for each group ) we are unable to support a preference for either one , although the likelihood of a Type II error must be acknowledged . For all athletes ( n=14 ) , respiratory disturbance and arousal responses between B and N1 , although large in magnitude , were highly individual and not statistically significant . However , SpO2 decreased at N1 versus B ( p<0.001 ) and remained lower on N8 ( p<0.001 ) and N15 ( p<0.001 ) , not returning to baseline level . Compared to B , arousals were more frequent on N8 ( p=0.02 ) and N15 ( p=0.01 ) . The percent of rapid eye movement sleep ( REM ) increased from N1 to N8 ( p=0.03 ) and N15 ( p=0.01 ) . Overall , sleeping at 2650 m causes sleep disturbance in susceptible athletes , yet there was some improvement in REM sleep over the study duration OBJECTIVES To assess sleep patterns and associations between sleep and match performance in elite Australian female basketball players . DESIGN Prospect i ve cohort study . METHODS Seventeen elite female basketball players were monitored across two consecutive in-season competitions ( 30 weeks ) . Total sleep time and sleep efficiency were determined using triaxial accelerometers for Baseline , Pre-match , Match-day and Post-match timings . Match performance was determined using the basketball efficiency statistic ( EFF ) . The effects of match schedule ( Regular versus Double-Header ; Home versus Away ) and sleep on EFF were assessed . RESULTS The Double-Header condition changed the pattern of sleep when compared with the Regular condition ( F(3,48)=3.763 , P=0.017 ) , where total sleep time Post-match was 11 % less for Double-Header ( mean±SD ; 7.2±1.4h ) compared with Regular ( 8.0±1.3h ; P=0.007 ) . Total sleep time for Double-Header was greater Pre-match ( 8.2±1.7h ) compared with Baseline ( 7.1±1.6h ; P=0.022 ) and Match-day ( 7.3±1.5h ; P=0.007 ) . Small correlations existed between sleep metrics at Pre-match and EFF for pooled data ( r=-0.39 to -0.22 ; P≥0.238 ) . Relationships between total sleep time and EFF ranged from moderate negative to large positive correlations for individual players ( r=-0.37 to 0.62 ) and reached significance for one player ( r=0.60 ; P=0.025 ) . CONCLUSIONS Match schedule can affect the sleep patterns of elite female basketball players . A large degree of inter-individual variability existed in the relationship between sleep and match performance ; nevertheless , sleep monitoring might assist in the optimisation of performance for some athletes To determine whether exercise duration effects the recovery sleep following exercise , eight fit male endurance athletes , ages 23 - 42 yr , had their sleep electrophysiologically studied . This was done on four separate occasions : after a day on which no specific exercise was performed ; after a day of a 15-km run ; after a 42.2-km run day ; after a day in which the athletes participated in a strenuous ultra-triathlon .  Sleep patterns following the no exercise day and the 15-km and the 42.2-km run days were similar . The sleep pattern of the ultra-triathlon day when compared with the other three days showed significantly increased wakefulness and delayed and decreased rapid eye movement ( REM ) sleep . The duration of slow wave sleep ( SWS ) in the first 6 h after lights out , however , was no different . The increased wakefulness and decreased REM clearly indicate increased stress after the ultra-triathlon . REM sleep appears to be a more sensitive index of exercise induced stress than SWS PURPOSE This study aim ed to examine whether ( i ) objective markers of sleep quantity and quality are altered in endurance athletes experiencing overreaching in response to an overload training program and ( ii ) potential reduced sleep quality would be accompanied with a higher prevalence of upper respiratory tract infections in this population . METHODS Twenty-seven trained male triathletes were r and omly assigned to either overload ( n = 18 ) or normal ( CTL , n = 9 ) training groups . Respective training programs included a 1-wk moderate training phase followed by a 3-wk period of overload or normal training , respectively , and then a subsequent 2-wk taper .  Maximal aerobic power and oxygen uptake ( VO2max ) from incremental cycle ergometry were measured after each phase , whereas mood states and incidences of illness were determined from question naires . Sleep was monitored every night of the 6 wk using wristwatch actigraphy . RESULTS Of the 18 overload training group subjects , 9 were diagnosed as functionally overreached ( F-OR ) after the overload period , as based on declines in performance and VO2max with concomitant high perceived fatigue ( P < 0.05 ) , whereas the other 9 overload subjects showed no decline in performance ( AF , P > 0.05 ) . There was a significant time-group interaction for sleep duration ( SD ) , sleep efficiency ( SE ) , and immobile time ( IT ) . Only the F-OR group demonstrated a decrease in these three parameters ( -7.9 % ± 6.7 % , -1.6 % ± 0.7 % , and -7.6 % ± 6.6 % for SD , SE , and IT , respectively , P < 0.05 ) , which was reversed during the subsequent taper phase . Higher prevalence of upper respiratory tract infections were also reported in F-OR ( 67 % , 22 % , and 11 % incidence rate for F-OR , AF , and CTL , respectively ) . CONCLUSION This study confirms sleep disturbances and increased illness in endurance athletes who present with symptoms of F-OR during periods of high volume training Background Tart Montmorency cherries have been reported to contain high levels of phytochemicals including melatonin , a molecule critical in regulating the sleep-wake cycle in humans . Purpose The aim of our investigation was to ascertain whether ingestion of a tart cherry juice concentrate would increase the urinary melatonin levels in healthy adults and improve sleep quality . Methods In a r and omised , double-blind , placebo-controlled , crossover design , 20 volunteers consumed either a placebo or tart cherry juice concentrate for 7 days . Measures of sleep quality recorded by actigraphy and subjective sleep question naires were completed . Sequential urine sample s over 48 h were collected and urinary 6-sulfatoxymelatonin ( major metabolite of melatonin ) determined ; cosinor analysis was used to determine melatonin circadian rhythm ( mesor , acrophase and amplitude ) . In addition , total urinary melatonin content was determined over the sample d period . Trial differences were determined using a repeated measures ANOVA . Results Total melatonin content was significantly elevated ( P < 0.05 ) in the cherry juice group , whilst no differences were shown between baseline and placebo trials . There were significant increases in time in bed , total sleep time and sleep efficiency total ( P < 0.05 ) with cherry juice supplementation . Although there was no difference in timing of the melatonin circardian rhythm , there was a trend to a higher mesor and amplitude . Conclusions These data suggest that consumption of a tart cherry juice concentrate provides an increase in exogenous melatonin that is beneficial in improving sleep duration and quality in healthy men and women and might be of benefit in managing disturbed sleep Purpose In athletes , caffeine use is common although its effects on sleep have not been widely studied . This r and omised , double-blind , placebo-controlled crossover trial investigated the effects of late-afternoon caffeine and carbohydrate-electrolyte ( CEB ) co-ingestion on cycling performance and nocturnal sleep . Methods Six male cyclists/triathletes ( age 27.5 ± 6.9 years ) completed an afternoon training session ( TS ; cycling 80 min ; 65 % VO2max ) followed by a 5 kJ kg−1 cycling time trial ( TT ) . Caffeine ( split dose 2 × 3 mg kg−1 ) or placebo was administered 1 h prior and 40 min into the TS . A 7.4 % CEB ( 3 ml kg−1 every 15 min ) was administered during the TS , followed 30 min after by a st and ardised evening meal . Participants retired at their usual bedtime and indices of sleep duration and quality were monitored via polysomnography . Data : mean ± SD . Results All participants performed better in the caffeine TT ( caffeine 19.7 ± 3.3 ; placebo 20.5 ± 3.5 min ; p = 0.006 ) , while ratings of perceived exertion ( caffeine 12.0 ± 0.6 ; placebo 12.9 ± 0.7 ; p = 0.004 ) and heart rate ( caffeine 175 ± 6 ; placebo 167 ± 11 bpm ; p = 0.085 ) were lower in the caffeine TS . Caffeine intake induced significant disruptions to a number of sleep indices including increased sleep onset latency ( caffeine 51.1 ± 34.7 ; placebo 10.2 ± 4.2 min ; p = 0.028 ) and decreased sleep efficiency ( caffeine 76.1 ± 19.6 ; placebo 91.5 ± 4.2 % ; p = 0.028 ) , rapid eye movement sleep ( caffeine 62.1 ± 19.6 ; placebo 85.8 ± 24.7 min ; p = 0.028 ) and total sleep time ( caffeine 391 ± 97 ; placebo 464 ± 49 min ; p = 0.028 ) . Conclusions This study supports a performance-enhancing effect of caffeine , although athletes ( especially those using caffeine for late-afternoon/evening training and competition ) should consider its deleterious effects on sleep OBJECTIVES To evaluate sleep in professional football players and describe clinical features of players at risk for sleep for sleep-disordered breathing ( SDB ) . METHODS The Multivariable Apnea Prediction ( MAP ) index was used to stratify players into high ( MAP > or = 0.5 ) and low ( MAP<0.5 ) risk for SDB . Players from both risk groups were r and omly selected for overnight polysomnography , with over-sampling from the High-risk group . Of 302 players from eight professional football teams ; 52 underwent attended polysomnography .  Anthropometrics including neck circumference , airway size ( Mallampati score , maxillary overjet ) and sleepiness measured by Epworth scores ( ESS ) were recorded . The primary outcome measures were ESS and an apnea-hypopnea index ( AHI ) > or = 10 . RESULTS Ninety-two percent of players were < 30 years old ( mean ( SD ) age : 25.5+/-2.7 years ) with large necks ( 45.2+/-3.6 cm ) and elevated BMI ( 31.5+/-4.6 ) . More than 20 % of players had an ESS>10 with ESS highest in habitual snorers . An AHI of > or = 10 was found in 13 ( 34 % , 95 % confidence interval ( CI ) 21 - 50 % ) high-risk players but only one ( 7 % , 95 % CI 1 - 31 % ) of 14 low-risk players . Offensive ( 9 ) or defensive ( 3 ) linemen accounted for the majority of the positive cases . Based on our sample , we estimate the prevalence of SDB to be 14 % ( 2 - 25 % ) . CONCLUSIONS Excessive daytime sleepiness ( EDS ) is present in a large fraction of professional football players . Some but not all of this may be due to an increased prevalence of SDB . Further study is required to underst and all of the factors responsible for EDS and to determine which of the biggest players will have SDB , which may impact not only performance and productivity but also future health INTRODUCTION Elite athletes frequently undergo periods of intensified training ( IT ) within their normal training program . These periods can lead athletes into functional overreaching , characterized by high perceived fatigue , impaired sleep , and performance . Because whole-body cryostimulation ( WBC ) has been proven to be an effective recovery method in the short term ( < 76 h ) , we investigated whether daily WBC sessions during IT could prevent exercise and sleep-related signs of overreaching . METHODS After a normal training week ( BASE ) , 
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Reduced SE was attributed to high wake after sleep onset rather than sleep onset latency .
Athletes ' sleep duration was found to be short with low SE , in comparison to the general consensus for non-athlete healthy adults .
Notable sleep issues were revealed in young athletes .
Sleep quality and architecture tend to change across different training periods