Effects of sports drinks on the maintenance of physical performance during 3 tennis matches: a randomized controlled study.

BACKGROUND: Tennis tournaments often involve playing several consecutive matches interspersed with short periods of recovery. OBJECTIVE: The objective of this study was firstly to assess the impact of several successive tennis matches on the physical performance of competitive players and secondly to evaluate the potential of sports drinks to minimize the fatigue induced by repeated matches. METHODS: This was a crossover, randomized controlled study. Eight male regionally-ranked tennis players participated in this study. Players underwent a series of physical tests to assess their strength, speed, power and endurance following the completion of three tennis matches each of two hours duration played over three consecutive half-days (1.5 day period for each condition). In the first condition the players consumed a sports drink before, during and after each match; in the second, they drank an identical volume of placebo water. The results obtained were compared with the third 'rest' condition in which the subjects did not play any tennis. Main outcomes measured were maximal isometric strength and fatigability of knee and elbow extensors, 20-m sprint speed, jumping height, specific repeated sprint ability test and hand grip strength. RESULTS: The physical test results for the lower limbs showed no significant differences between the three conditions. Conversely, on the upper limbs the EMG data showed greater fatigue of the triceps brachii in the placebo condition compared to the rest condition, while the ingestion of sports drinks attenuated this fatigue. CONCLUSIONS: This study has demonstrated for the first time that, when tennis players are adequately hydrated and ingest balanced meals between matches, then no large drop in physical performance is observed even during consecutive competitive matches. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01353872.

Energy turnover during 24 hours and 6 days of adventure racing.

Energy turnover was assessed in two conditions of mixed ultra-endurance exercise. In Study 1, energy expenditure and intake were measured in nine males in a laboratory over 24 h. In Study 2, energy expenditure was assessed in six males during an 800-km Adventure race (mean race time 152.5 h). Individual correlations between heart rate and oxygen uptake (VO(2)) were established during pre-tests when kayaking, cycling, and running. During exercise, energy expenditure was estimated from continuous heart rate recordings. Heart rate and VO(2) were measured regularly during fixed cycling work rates to correct energy expenditure for drift in oxygen pulse. Mean energy expenditure was 18,050 +/- 2,390 kcal (750 +/- 100 kcal h(-1)) and 80,000 +/- 18,000 kcal (500 +/- 100 kcal h(-1)) in Study 1 and Study 2 respectively, which is higher than previously reported. Energy intake in Study 1 was 8,450 +/- 1,160 kcal, resulting in an energy deficit of 9,590 +/- 770 kcal. Body mass decreased in Study 1 (-2.3 +/- 0.8 kg) but was unchanged in Study 2. Fat mass decreased in Study 2 (-2.3 +/- 1.5 kg). In Study 1, muscle glycogen content decreased by only 60%. Adventure racing requires a high energy expenditure, with large inter-individual variation. A large energy deficit is caused by inadequate energy intake, possibly due to suppressed appetite and gastrointestinal problems. The oxygen pulse, comparing start to 12 h of exercise and beyond, increased by 10% and 5% in Study 1 and Study 2 respectively. Hence, estimations of energy expenditure from heart rate recordings should be corrected according to this drift.

Repeated resistance exercise training induces different changes in mRNA expression of MAFbx and MuRF-1 in human skeletal muscle.

The gain in muscle mass as a result of resistance training is dependent on changes in both anabolic and catabolic reactions. A frequency of two to three exercise sessions per week is considered optimal for muscle gain in untrained individuals. Our hypothesis was that a second exercise session would enlarge the anabolic response and/or decrease the catabolic response. Eight male subjects performed resistance exercise on two occasions separated by 2 days. Muscle biopsies were taken from the vastus lateralis before and 15 min, 1 h, and 2 h after exercise. Exercise led to severalfold increases in phosphorylation of mTOR at Ser2448, p70 S6 kinase (p70S6k) at Ser424/Thr421 and Thr389, and ribosomal protein S6, which persisted for up to 2 h of recovery on both occasions. There was a tendency toward a larger effect of the second exercise on p70S6k and S6, but the difference did not reach statistical significance. The mRNA expression of MuRF-1, which increased after exercise, was 30% lower after the second exercise session than after the first one. MAFbx expression was not altered after exercise but downregulated 30% 48 h later, whereas myostatin expression was reduced by 45% after the first exercise and remained low until after the second exercise session. The results indicate that 1) changes in expression of genes involved in protein degradation are attenuated as a response to repetitive resistance training with minor additional increases in enzymes regulating protein synthesis and 2) the two ubiquitin ligases, MuRF-1 and MAFbx, are differently affected by the exercise as well as by repeated exercise.

Neuromuscular and circulatory adaptation during combined arm and leg exercise with different maximal work loads.

Cardiopulmonary kinetics and electromyographic activity (EMG) during exhausting exercise were measured in 8 males performing three maximal combined arm+leg exercises (cA+L). These exercises were performed at different rates of work (mean+/-SD; 373+/-48, 429+/-55 and 521+/-102 W) leading to different average exercise work times in all tests and subjects. VO2 reached a plateau versus work rate in every maximal cA+L exercise (range 6 min 33 s to 3 min 13 s). The three different exercise protocols gave a maximal oxygen consumption (VO2MAX) of 4.67+/-0.57, 4.58+/-0.52 and 4.66+/-0.53 l min(-1) (P=0.081), and a maximal heart rate (HRmax) of 190+/-6, 189+/-4 and 189+/-6 beats min(-1) (P=0.673), respectively. Root mean square EMG (EMGRMS) of the vastus lateralis and the triceps brachii muscles increased with increasing rate of work and time in all three cA+L protocols. The study demonstrates that despite different maximal rates of work, leading to different times to exhaustion, the circulatory adaptation to maximal exercise was almost identical in all three protocols that led to a VO2 plateau. The EMG(RMS) data showed increased muscle recruitment with increasing work rate, even though the HRmax and VO2MAX was the same in all three cA+L protocols. In conclusion, these findings do not support the theory of the existence of a central governor (CG) that regulates circulation and neuronal output of skeletal muscles during maximal exercise.