Skill execution and sleep deprivation: effects of acute caffeine or creatine supplementation - a randomized placebo-controlled trial

<p>Abstract</p> <p>Background</p> <p>We investigated the effects of sleep deprivation with or without acute supplementation of caffeine or creatine on the execution of a repeated rugby passing skill.</p> <p>Method</p> <p>Ten elite rugby players completed 10 trials on a simple rugby passing skill test (20 repeats per trial), following a period of familiarisation. The players had between 7-9 h sleep on 5 of these trials and between 3-5 h sleep (deprivation) on the other 5. At a time of 1.5 h before each trial, they undertook administration of either: placebo tablets, 50 or 100 mg/kg creatine, 1 or 5 mg/kg caffeine. Saliva was collected before each trial and assayed for salivary free cortisol and testosterone.</p> <p>Results</p> <p>Sleep deprivation with placebo application resulted in a significant fall in skill performance accuracy on both the dominant and non-dominant passing sides (p < 0.001). No fall in skill performance was seen with caffeine doses of 1 or 5 mg/kg, and the two doses were not significantly different in effect. Similarly, no deficit was seen with creatine administration at 50 or 100 mg/kg and the performance effects were not significantly different. Salivary testosterone was not affected by sleep deprivation, but trended higher with the 100 mg/kg creatine dose, compared to the placebo treatment (p = 0.067). Salivary cortisol was elevated (p = 0.001) with the 5 mg/kg dose of caffeine (vs. placebo).</p> <p>Conclusion</p> <p>Acute sleep deprivation affects performance of a simple repeat skill in elite athletes and this was ameliorated by a single dose of either caffeine or creatine. Acute creatine use may help to alleviate decrements in skill performance in situations of sleep deprivation, such as transmeridian travel, and caffeine at low doses appears as efficacious as higher doses, at alleviating sleep deprivation deficits in athletes with a history of low caffeine use. Both options are without the side effects of higher dose caffeine use.</p

Baseline strength can influence the ability of salivary free testosterone to predict squat and sprinting performance

The objective of this study was to determine if salivary free testosterone can predict an athlete’s performance during back squats and sprints over time and the influence baseline strength on this relationship. Ten weight-trained male athletes were divided into 2 groups based on their 1 repetition maximum (1RM) squats, good squatters (1RM . 2.0 3 body weight, n = 5) and average squatters (1RM , 1.9 3 body weight, n = 5). The good squatters were stronger than the average squatters (p , 0.05). Each subject was assessed for squat 1RM and 10-m sprint times on 10 separate occasions over a 40-day period. A saliva sample was collected before testing and assayed for free testosterone and cortisol. The pooled testosterone correlations were strong and significant in the good squatters (r = 0.92 for squats, r = 20.87 for sprints, p , 0.01), but not significant for the average squatters (r = 0.35 for squats, r = 20.18 for sprints). Cortisol showed no significant correlations with 1RM squat and 10-m sprint performance, and no differences were identified between the 2 squatting groups. In summary, these results suggest that free testosterone is a strong individual predictor of squat and sprinting performance in individuals with relatively high strength levels but a poor predictor in less strong individuals. This information can assist coaches, trainers, and performance scientists working with stronger weight-trained athletes, for example, the preworkout measurement of free testosterone could indicate likely training outcomes or a readiness to train at a certain intensity level, especially if real-time measurements are made. Our results also highlight the need to separate group and individual hormonal data during the repeated testing of athletes with variable strength levels

The workout responses of salivary-free testosterone and cortisol concentrations and their association with the subsequent competition outcomes in professional rugby league

This study assessed the responses of salivary-free testosterone (T) and cortisol (C) concentrations across selected training workouts and their association with the subsequent competition outcomes in professional rugby league. Thirteen rugby league players were assessed for salivary-free T and C concentrations across 5 training workouts performed 3-4 days before a competitive game. The game outcomes included wins and losses and game-ranked performance (1-5) based on the number of points scored, the points differential, and a coach rating. Data were pooled across the winning (n = 3) and losing (n = 2) outcomes. Pooled free T concentrations (absolute and relative changes) were significantly (p < 0.01) elevated across those workouts that preceded winning games, but not the losses, and the relative (percent) T changes were significantly (p < 0.05) higher before winning (30.9%) than before losing (3.4%). Both outcomes were associated with workout decreases in pooled free C concentrations and the relative C changes were not significantly different between wins (222.9%) and losses (225.6%). In conclusion, the free T responses to selected training workouts showed some association with subsequent winning (being elevated) and losing (no change) during a limited number of competitive games in professional rugby league. Speculatively, the free T responses to a midweek workout might provide an early sign of team readiness to compete or to recovery state, thereby providing a novel format for implementing training or management strategies to improve the competition outcomes