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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.

The aim of this study was to compare daily hydration profiles of competitive adolescent swimmers and less active maturation- and sex-matched controls. Hydration profiles of 35 competitive adolescent swimmers (male n = 18, female n = 17) and 41 controls (male n = 29, female n = 12) were monitored on 4 consecutive days. First morning hydration status was determined independently by urine specific gravity (USG) and urine color. Changes in fluid balance were estimated during the school day and in training sessions after adjusting for self-reported urine losses and fluid intake. Urinalyses revealed consistent fluid deficits (USG >1.020, urine color ≥5) independent of activity group, sex, and day of testing (hypohydration in 73–85% of samples, p > .05). Fluid balance and intake were observed over typical school days in males and females from the 2 groups. During training, male swimmers lost more fluid relative to initial body mass but drank no more than females. Although both activity groups began each testing day with a similar hydration status, training induced significant variations in fluid balance in the swimmers compared with controls. Despite minimal fluid losses during individual training sessions (<2% body mass), these deficits significantly increased fluid needs for young swimmers over the school day.

This study determined the fluid balance of elite female basketball players before and during competition. Before and during 2 international games, 17 national-level players (age 24.2 ± 3 yr, height 180.5 ± 6 cm, mass 78.8 ± 8 kg) were assessed. Fluid-balance assessment included pregame hydration level as determined by urine specific gravity (USG), change in body mass during the game, ad libitum intake of water or sports drink, and estimated sweat losses. Mean (± SD) USG before Game 1 was 1.005 ± 0.002 and before Game 2 USG equaled 1.010 ± 0.005. Players lost an average of 0.7% ± 0.8% and 0.6% ± 0.6% of their body mass during Games 1 and 2, respectively. In each game, 3 players experienced a fluid deficit >1% of body mass, and 1 other, a fluid deficit >2%. Sweat losses in both games, from the beginning of the warm-up to the conclusion of the game (~125 min with average playing time 16–17 min), were approximately 1.99 ± 0.75 L. Fluid intake in Game 1 and Game 2 equaled 77.8% ± 32% and 78.0% ± 21% of sweat losses, respectively. Most players were hydrated before each game and did not become meaningfully dehydrated during the game. It is possible that the players who experienced the highest levels of dehydration also experienced some degree of playing impairment, and the negative relationship between change in body mass and shooting percentage in Game 2 provides some support for this notion.

A palatable flavor is known to enhance fluid intake during exercise; however, a fear of excessive kilojoule intake may deter female athletes from consuming a sports drink during training sessions. In order to examine this issue, we monitored fluid balance during 9 separate training sessions undertaken by junior elite female netball players (n = 9), female basketball players (n = 7), and male basketball players (n = 8). The beverages tested were water, a regular carbohydrate-electrolyte beverage (6.8% CHO, 18.7 mmol/L Na, 3.0 mmol/L K, 1130 kJ/L), and an identical tasting, low kilojoule electrolyte beverage (1% CHO, 18.7 mmol/L Na, 3.0 mmol/L K, 170 kJ/L). Each subject received each of the 3 drinks at 3 separate training sessions, in a randomized, balanced order. Subjects were aware of the beverage provided. Change in body mass over the training session was used to estimate body fluid change, while voluntary fluid intake was determined from the change in weight of drink bottles used in each session. The overall fluid balance on drinks classified as regular, low kilojoule, and water was -11.3 ml/h (95%CI -99.6 to 77.0), -29.5 ml/h (95%CI -101.4 to 42.5) and -156.4 ml/h (95%CI -215.1 to -97.6), respectively. The results indicate that, overall, better fluid balance was achieved using either of the flavored drinks compared to water. These data confirm that flavored drinks enhance fluid balance in a field situation, and suggest that the energy content of the drink is relatively unimportant in determining voluntary fluid intake.

The aim was to analyze the influence of competitive round on muscle strength, body-fluid balance, and renal function in elite badminton players during a real competition. Body mass, jump height during a countermovement jump, handgrip force, and urine samples were obtained from 13 elite badminton players (6 men and 7 women) before and after the 2nd-round and quarterfinal matches of the national Spanish badminton championship. Sweat rate was determined by using prematch-to-postmatch body-mass change and by weighing individually labeled fluid bottles. Sweat rates were 1.04 ± 0.62 and 0.98 ± 0.43 L/h, while rehydration rate was 0.69 ± 0.26 and 0.91 ± 0.52 L/h for the 2nd round and quarterfinals, respectively. Thus, dehydration was 0.47% ± 1.03% after the 2nd round and 0.23% ± 0.43% after the quarterfinals. There were no differences in prematch-to-postmatch jump height, but jump height was reduced from 37.51 ± 8.83 cm after the 2nd-round game to 34.82 ± 7.37 cm after the quarterfinals (P < .05). No significant differences were found in handgrip force when comparing prepost matches or rounds, although there were significant differences between dominant and nondominant hands (P < .05). The succession of rounds caused the appearance of proteinuria, hematuria, glycosuria, and higher nitrite and ketone concentrations in urine. Rehydration patterns during a real badminton competition were effective to prevent dehydration. A badminton match did not affect jump height or handgrip force, but jump height was progressively reduced by the competitive round. Badminton players’ renal responses reflected diminished renal flux due to the high-intensity nature of this racket sport.

The purpose of this study was to examine the gastric emptying and rehydration effects of hypotonic and hypertonic glucose-electrolyte drinks after exercise-induced dehydration. Eight healthy males lost ~1.8% body mass by intermittent cycling and rehydrated (150% of body mass loss) with a hypotonic 2% (2% trial) or a hypertonic 10% (10% trial) glucose-electrolyte drink over 60 min. Blood and urine samples were taken at preexercise, postexercise, and 60, 120, 180, and 240 min postexercise. Gastric and test drink volume were determined 15, 30, 45, 60, 90, and 120 min postexercise. At the end of the gastric sampling period 0.3% (2% trial) and 42.1% (10% trial; p < .001) of the drinks remained in the stomach. Plasma volume was lower (p < .01) and serum osmolality was greater (p < .001) at 60 and 120 min during the 10% trial. At 240 min, 52% (2% trial) and 64% (10% trial; p < .001) of the drinks were retained. Net fluid balance was greater from 120 min during the 10% trial (p < .001). When net fluid balance was corrected for the volume of fluid in the stomach, it was greater at 60 and 120 min during the 2% trial (p < .001). These results suggest that the reduced urine output following ingestion of a hypertonic rehydration drink might be mediated by a slower rate of gastric emptying, but the slow gastric emptying of such solutions makes rehydration efficiency difficult to determine in the hours immediately after drinking, compromising the calculation of net fluid balance.

Little data exists on drinking behavior, sweat loss, and exercise intensity across a competitive handball tournament in elite female athletes. Heart rate (HR), fluid balance and sweat electrolyte content were assessed on 17 international players across a 6-day tournament involving 5 games and 2 training sessions played indoors (23 ± 2 °C, 30 ± 2% relative humidity). Active play (effective) mean HR was 155 ± 14 bpm (80 ± 7.5% HR_max) with the majority of time (64%) spent exercising at intensities >80% HR_max. Mean (SD) sweat rates during games were 1.02 ± 0.07 L · h^-1 and on 56% of occasions fluid intake matched or exceeded sweat loss. A significant relationship was observed between estimated sweat loss and fluid intake during exercise (r ₂ = .121, p = .001). Mean sweat sodium concentration was 38 ± 10 mmol · L^-1, with significant associations observed between player sweat rates and time spent exercising at intensities >90% HR_max (r ² = .181, p = .001). Fluid and electrolyte loss appear to be work rate dependent in elite female handball players, whom appear well capable of replacing fluids lost within a tournament environment. Due to large between-athlete variations, a targeted approach may be warranted for certain players only.