Search

The 2019 International Amateur Athletics Federation Track-and-Field World Championships will take place in Qatar in the Middle East. The 2020 Summer Olympics will take place in Tokyo, Japan. It is quite likely that these events may set the record for hottest competitions in the recorded history of both the Track-and-Field World Championships and Olympic Games. Given the extreme heat in which track-and-field athletes will need to train and compete for these games, the importance of hydration is amplified more than in previous years. The diverse nature of track-and-field events, training programs, and individuality of athletes taking part inevitably means that fluid needs will be highly variable. Track-and-field events can be classified as low, moderate, or high risk for dehydration based on typical training and competition scenarios, fluid availability, and anticipated sweat losses. This paper reviews the risks of dehydration and potential consequences to performance in track-and-field events. The authors also discuss strategies for mitigating the risk of dehydration.

The aim of the current study was to assess the effects of dehydration on cricket specific motor skill performance among fast-bowlers, fielders, and batsmen playing in a hot and humid environment. 10 fast-bowlers, 12 fielders and 8 batsmen participated in two field trials conducted 7 days apart: a fluid provision trial (FP) and a fluid restriction trial (FR). Each trial consisted of a 2-hr standardized training session and pretraining and posttraining skill performance assessments. Bowling speed and accuracy (line and length), throwing speed and accuracy (overarm, sidearm and underarm) and timed running between wickets (1, 2, and 3 runs) was assessed pre to posttraining in each trial. Mass loss was 0.6 ± 0.3 kg (0.9 ± 0.5%) in FP, and 2.6 ± 0.5kg (3.7 ± 0.8%) in FR trials. Maintaining mass within 1% of initial values did not cause any significant skill performance decline. However, the dehydration on the FR trial induced a significant time and trial effect for bowling speed by 1.0 ± 0.8% reduction (0.3 ± 0.8% reduction in FP trial; p < .01) and 19.8 ± 17.3% reduction in bowling accuracy for line (3.6 ± 14.2% reduction in FP trial; p < .01), but no effect on bowling length. A significant decline was noted in the FR trial for throwing speed for overarm (6.6 ± 4.1%; p < .01; 1.6 ± 3.4% reduction in FP trial) and sidearm (4.1 ± 2.3%; p < .01; 0.6 ± 4.7% increase in FP trial) techniques, and for throwing accuracy for overarm (14.2 ± 16.3%; p < .01; 0.8 ± 24.2% increase in FP trial) and sidearm (22.3 ± 13.3%; p < .05; 3.2 ± 34.9% reduction in FP trial) techniques. Batsmen demonstrated significant performance drop in making three runs (0.8 ± 1.2% increase in time in FP trial and 2.2 ± 1.7% increase in time in FR trial; p < .01). Moderate-severe dehydration of 3.7% body mass loss significantly impairs motor skill performance among cricketers, particularly bowlers and fielders, playing in hot and humid conditions. Fluid ingestion strategies maintaining mass loss within 1% prevented a decline in skill performance.

Dual energy x-ray absorptiometry (DXA) is a popular tool to determine body composition (BC) in athletes, and is used for analysis of fat-free soft tissue mass (FFST) or fat mass (FM) gain/loss in response to exercise or nutritional interventions. The aim of the current study was to assess the effect of exercise-heat stress induced hypohydration (HYP, >2% of body mass (BM) loss) vs. maintenance of euhydration (EUH) on DXA estimates of BC, sum of skinfolds (SF), and impedance (IMP) measurements in athletes. Competitive athletes (23 males and 15 females) recorded morning nude BM for 7 days before the first main trial. Measurements on the first trial day were conducted in a EUH condition, and again after exercise-heat stress induced HYP. On the second trial day, fluid and electrolyte losses were replaced during exercise using a sports drink. A reduction in total BM (1.6 ± 0.4 kg; 2.3 ± 0.4% HYP) and total FFST (1.3 ± 0.4 kg), mainly from trunk (1.1 ± 0.5 kg), was observed using DXA when participants were HYP, reflecting the sweat loss. Estimated fat percent increased (0.3 ± 0.3%), however, total FM did not change (0.1 ± 0.2 kg). SF and IMP declined with HYP (losses of 1.5 ± 2.9% and 1.6 ± 3% respectively) suggesting FM loss. When EUH was maintained there were no significant changes in BM, DXA estimates, or SF values pre to post exercise, but IMP still declined. We conclude that use of DXA for FFST assessment in athletes must ensure a EUH state, particularly when considering changes associated with nutritional or exercise interventions.

The present study aimed to investigate the influence of timing of preexercise carbohydrate feeding (Part A) and carbohydrate concentration (Part B) on short-duration high-intensity exercise capacity. In Part A, 17 males, and in Part B 10 males, performed a peak power output (PPO) test, two familiarization trials at 90% of PPO, and 4 (for Part A) or 3 (for Part B) experimental trials involving exercise capacity tests at 90% PPO. In Part A, the 4 trials were conducted following ingestion of a 6.4% carbohydrate/electrolyte sports drink ingested 30 (C30) or 120 (C120) minutes before exercise, or a flavor-matched placebo administered either 30 (P30) or 120 (P120) minutes before exercise. In Part B, the 3 trials were performed 30 min after ingestion of 0%, 2% or 12% carbohydrate solutions. All trials were performed in a double-blind cross-over design following and overnight fast. Dietary intake and activity in the 2 days before trials was recorded and replicated on each visit. Glucose, lactate, heart rate, and mood/arousal were recorded at intervals during the trials. In Part A, C30 produced the greatest exercise capacity (mean ± SD; 9.0 ± 1.9 min, p < .01) compared with all other trials (7.7 ± 1.5 min P30, 8.0 ± 1.7 min P120, 7.9 ± 1.9 min C120). In Part B, exercise capacity (min) following ingestion of the 2% solution (9.2 ± 2.1) compared with 0% (8.2 ± 0.7) and 12% (8.0 ± 1.3) solutions approached significance (p = .09). This study provides new evidence to suggest that timing of carbohydrate intake is important in short duration high-intensity exercise tasks, but a concentration effect requires further exploration.

Twenty-two tennis players were individually studied on 2 occasions. They performed a prematch skill test, a 2-hr tennis match against an equally ranked opponent, and a postmatch skill test. A carbohydrate-electrolyte (CHO-E; Lucozade Sport) or flavor-matched placebo-electrolyte (PL) beverage was administered in a double-blind fashion. During the trials, heart-rate and movement intensity were monitored, and the match was recorded for performance analysis. There were no differences in skill-test scores pre- to postmatch or between trials (154±38 pre- and 160±35 postmatch on PL, 155±36 pre- and 165±33 postmatch on CHO-E). CHO-E ingestion elevated blood glucose concentration throughout the match, and participants reported feeling more energetic (general activation) and more tense (high activation) 1 hr into the match than at baseline (p<.05). Participants in the CHO-E trial spent more time in moderate-intensity activity and less time in low-intensity activity than on PL. Performance analysis revealed that CHO-E ingestion increased overall serve success (M±SD, 68%±7% for CHO-E vs. 66%±7% for PL; p<.05) and success of first serves (65%±9% for CHO-E, 61%±7% for PL; p<.01) and serves to the advantage side (70%±9% for CHO-E, 66%±7% for PL; p<.05). Return success was greater during the second set of the match (p<.05) in the CHO-E trial. Differences in serve and return success were not associated with blood glucose response to CHO or player ability.

This study assessed fluid balance, sodium losses, and effort intensity during indoor tennis match play (17 ± 2 °C, 42% ± 9% relative humidity) over a mean match duration of 68.1 ± 12.8 min in 16 male tennis players. Ad libitum fluid intake was recorded throughout the match. Sweat loss from change in nude body mass; sweat electrolyte content from patches applied to the forearm, calf, and thigh, and back of each player; and electrolyte balance derived from sweat, urine, and daily food-intake analysis were measured. Effort intensity was assessed from on-court heart rate compared with data obtained during a maximal treadmill test. Sweat rate (M ± SD) was 1.1 ± 0.4 L/hr, and fluid-ingestion rate was 1.0 ± 0.6 L/hr (replacing 93% ± 47% of fluid lost), resulting in only a small mean loss in body mass of 0.15% ± 0.74%. Large interindividual variabilities in sweat rate (range 0.3-2.0 L/hr) and fluid intake (range 0.31-2.52 L/hr) were noted. Whole-body sweat sodium concentration was 38 ± 12 mmol/L, and total sodium losses during match play were 1.1 ± 0.4 g (range 0.5-1.8 g). Daily sodium intake was 2.8 ± 1.1 g. Indoor match play largely consisted of low-intensity exercise below ventilatory threshold (mean match heart rate was 138 ± 24 beats/min). This study shows that in moderate indoor temperature conditions players ingest sufficient fluid to replace sweat losses. However, the wide range in data obtained highlights the need for individualized fluid-replacement guidance.

Twenty nonvegetarian active males were pair-matched and randomly assigned to receive 2 g of L-carnitine L-tartrate (LC) or placebo per day for 2 wk. Participants exercised for 90 min at 70% VO2max after 2 days of a prescribed diet (M +/- SD: 13.6 +/- 1.6 MJ, 57% carbohydrate, 15% protein, 26% fat, 2% alcohol) before and after supplementation. Results indicated no change in carbohydrate oxidation, nitrogen excretion, branched-chain amino acid oxidation, or plasma urea during exercise between the beginning and end of supplementation in either group. After 2 wk of LC supplementation the plasma ammonia response to exercise tended to be suppressed (0 vs. 2 wk at 60 min exercise, 97 +/- 26 vs. 80 +/- 9, and 90 min exercise, 116 +/- 47 vs. 87 +/- 25 micromol/L), with no change in the placebo group. The data indicate that 2 wk of LC supplementation does not affect fat, carbohydrate, and protein contribution to metabolism during prolonged moderate-intensity cycling exercise. The tendency toward suppressed ammonia accumulation, however, indicates that oral LC supplementation might have the potential to reduce the metabolic stress of exercise or alter ammonia production or removal, which warrants further investigation.

In a randomized, placebo-controlled, double-blind crossover design, 15 trained males undertook exercise trials during two 4 wk supplementation periods, with either 3 g L-Carnitine L-tartrate (LCLT) or 3 g placebo (P) daily. Total carbohydrate and fat oxidation during 90 min steady state cycling were not different between 0 or 4 wk within LCLT or P trials (mean +/- standard deviation: carbohydrate oxidation P0 99 +/- 36, P4W 111 +/- 27, LCLT0 107 +/- 33, LCLT4W 112 +/- 32 g, respectively; fat oxidation P0 99 +/- 28, P4W 92 +/- 21, LCLT0 94 +/- 18, LCLT4W 90 +/- 22 g, respectively). Subsequent 20 km time trial duration was shorter after P (P0 31:29 +/- 3:50, P4W 29:55 +/- 2:58 min:s, P < 0.01), with no significant change over LCLT (LCLT0 31:46 +/- 4:06, LCLT4W 31.19 +/- 4.08 min:s). Four weeks LCLT supplementation had no effect on substrate utilization or endurance performance.

Twelve healthy active subjects (6 male, 6 female) performed 60 min of exercise (60% VO(2max)) on 3 occasions after supplementing with L-Carnitine L-tartrate (LCLT) or placebo. Each subject received a chronic dose, an acute dose, and placebo in a randomized, double-blind crossover design. Dietary intake and exercise were replicated for 2 d prior to each trial. In males there was a significant difference in rate of carbohydrate (CHO) oxidation between placebo and chronic trials (P = 0.02) but not placebo and acute trials (P = 0.70), and total CHO oxidation was greater following chronic supplementation vs. placebo )mean +/- standard deviation) of 93.8 (17.3) g/hr and 78.2 (23.3) g/h, respectively). In females, no difference in rate of, or total, CHO oxidation was observed between trials. No effects on fat oxidation or hematological responses were noted in either gender group. Under these experimental conditions, chronic LCLT supplementation increased CHO oxidation in males during exercise but this was not observed in females.