Sleep is known to be an important component of recovery from training, yet little is known about the quality and quantity of sleep achieved by elite athletes. The aim of the present study was to quantify sleep in elite athletes using wristwatch actigraphy. Individual nights of sleep from a cohort of Olympic athletes (n = 47) from various sports were analysed and compared to non-athletic controls (n = 20). There were significant differences between athletes and controls in all measures apart from 'time asleep' (p = 0.27), suggesting poorer characteristics of sleep in the athlete group. There was a significant effect of gender on 'time awake' (mean difference: 12 minutes higher in males; 95% likely range: 3 to 21 minutes) and 'sleep efficiency' (mean difference: 2.4 lower in males; 95% likely range: 0.1 to 4.8). Athletes showed poorer markers of sleep quality than an age and sex matched non-athletic control group (Sleep efficiency: 80.6 ± 6.4% and 88.7 ± 3.6%, respectively. Fragmentation Index: 36.0 ± 12.4 and 29.8 ± 9.0, respectively) but remained within the range for healthy sleep. This descriptive study provides novel data for the purpose of characterising sleep in elite athletes.

The purpose of this investigation was to analyse the concurrent validity and reliability of an iPhone app (called: My Jump) for measuring vertical jump performance. Twenty recreationally active healthy men (age: 22.1 ± 3.6 years) completed five maximal countermovement jumps, which were evaluated using a force platform (time in the air method) and a specially designed iPhone app. My jump was developed to calculate the jump height from flight time using the high-speed video recording facility on the iPhone 5 s. Jump heights of the 100 jumps measured, for both devices, were compared using the intraclass correlation coefficient, Pearson product moment correlation coefficient (r), Cronbach's alpha (α), coefficient of variation and Bland-Altman plots. There was almost perfect agreement between the force platform and My Jump for the countermovement jump height (intraclass correlation coefficient = 0.997, P < 0.001; Bland-Altman bias = 1.1 ± 0.5 cm, P < 0.001). In comparison with the force platform, My Jump showed good validity for the CMJ height (r = 0.995, P < 0.001). The results of the present study showed that CMJ height can be easily, accurately and reliably evaluated using a specially developed iPhone 5 s app.

The ability to repeatedly produce a high-power output or sprint speed is a key fitness component of most field and court sports. The aim of this study was to evaluate the validity and reliability of eight different approaches to quantify this parameter in tests of multiple-sprint performance. Ten physically active men completed two trials of each of two multiple-sprint running protocols with contrasting recovery periods. Protocol 1 consisted of 12 x 30-m sprints repeated every 35 seconds; protocol 2 consisted of 12 x 30-m sprints repeated every 65 seconds. All testing was performed in an indoor sports facility, and sprint times were recorded using twin-beam photocells. All but one of the formulae showed good construct validity, as evidenced by similar within-protocol fatigue scores. However, the assumptions on which many of the formulae were based, combined with poor or inconsistent test-retest reliability (coefficient of variation range: 0.8-145.7%; intraclass correlation coefficient range: 0.09-0.75), suggested many problems regarding logical validity. In line with previous research, the results support the percentage decrement calculation as the most valid and reliable method of quantifying fatigue in tests of multiple-sprint performance.

Ischemic preconditioning improved peak and mean power output during the early stages of repeated sprint cycling and may be beneficial for sprint sports.

The activity patterns of many sports (e.g. badminton, basketball, soccer and squash) are intermittent in nature, consisting of repeated bouts of brief (

Although the effect of recovery duration on caffeine-induced responses to multiple sprint work requires further investigation, the results of the present study show that caffeine has ergogenic properties with the potential to benefit performance in both single and multiple sprint sports.

The aim of this study was to examine the acute supplementation effects of dietary nitrate, caffeine, and their combination on 20 km cycling time-trial performance. Using a randomized, counterbalanced, double-blind, Latin-square design, 14 competitive, female cyclists (age: 31  7 years; height: 1.69  0.07 m; body mass: 61.6  6.0 kg) completed four 20 km time-trials on a racing bicycle fitted to a turbo-trainer. 2.5 hours before each trial, subjects consumed a 70 ml dose of concentrated beetroot juice containing either 0.45 g of dietary nitrate, or with the nitrate content removed (placebo). 1 hour before each trial, subjects consumed a capsule containing either 5 mgkg There were no effects (p ≥ 0.05) of supplementation on cycling cadence, ratings of perceived exertion, V O 2 , or integrated electromyographic activity. The results of this study support the well-established beneficial effects of caffeine supplementation on endurance performance. In contrast, acute supplementation with dietary nitrate appears to have no effect on endurance performance and adds nothing to the benefits afforded by caffeine supplementation.

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