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Heart Rate Responses and Fluid Balance of Competitive Cross-Country Hang Gliding Pilots

Darren P. Morton

Purpose:

To evaluate the physiological challenges of competitive cross-country hang gliding.

Methods:

Seventeen experienced male pilots (age = 41 ± 9 y; mean ± SD) were fitted with a monitor that recorded heart rate and altitude at 0.5 Hz throughout a competitive fight. Fluid losses were evaluated by comparing pilot pre- and postfight mass.

Results:

The pilots’ displacement was 88.4 ± 43.7 km in 145.5 ± 49.4 min. Mean fight altitude was 1902 ± 427 m (range = 1363-2601 m) with a maximum altitude of 2925 ± 682 m (1870-3831 m). The mean in-fight heart rate of the pilots was 112 ± 11 bpm (64 ± 6% predicted HRmax). For all except one subject, heart rate was highest while launching (165 ± 12 bpm, 93 ± 7% predicted HRmax), followed by landing (154 ± 13 bpm, 87 ± 7% predicted HRmax). No statistically significant relationship was observed between heart rate during the launch and reported measures of state anxiety. Heart rate was inversely related (P < .01) to altitude for all pilots except one. Fluid loss during the fight was 1.32 ± 0.70 L, which approximated 0.55 L/h, while mean in-fight fluid consumption was 0.39 ± 0.44 L. Six pilots consumed no fluid during the fight.

Conclusions:

Even among experienced pilots, high heart rates are more a function of state anxiety than physical work demand. Fluid losses during fight are surprisingly moderate but pilots may still benefit from attending to fluid balance.

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Influence of Peak Menstrual Cycle Hormonal Changes on Restoration of Fluid Balance After Induced Dehydration

Paola Rodriguez-Giustiniani and Stuart D.R. Galloway

Maintenance of fluid balance is a major consideration for recreational exercisers and athletes ( Maughan et al., 1997 ). As hypohydration, defined as the uncompensated loss of body water, is known to influence exercise performance and health ( Evans et al., 2017 ), starting exercise in a euhydrated

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Sweat Characteristics and Fluid Balance Responses During Two Heat Training Camps in Elite Female Field Hockey Players

Paul S.R. Goods, Bradley Wall, Brook Galna, Alannah K.A. McKay, Denise Jennings, Peter Peeling, and Greig Watson

), indicating that players may not have been adequately rehydrating between sessions. This variability in fluid balance was recently confirmed in a study of 22 male field hockey players during a 10-day pre-Olympic training camp that included six matches (wet-bulb globe temperature range: 19.9 °C–30.4 °C

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Skimmed, Lactose-Free Milk Ingestion Postexercise: Rehydration Effectiveness and Gastrointestinal Disturbances Versus Water and a Sports Drink in Physically Active People

Luis F. Aragón-Vargas, Julián C. Garzón-Mosquera, and Johnny A. Montoya-Arroyo

conservation (%FC) were calculated, according to: • %FE: (TUV × 100)/fluid ingestion volume • %FC: 100%−%FE Net fluid balance (NFB) was calculated four times: preexercise, postexercise, postingestion, and 3 hr postingestion, using BM immediately prior to exercise, as follows: NFB time  = BM time – BM pre

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Fluid Balance and Sodium Losses During Indoor Tennis Match Play

Matthew J.E. Lott and Stuart D.R. Galloway

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.

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Comparison of Fluid Balance between Competitive Swimmers and Less Active Adolescents

Dean G. Higham, Geraldine A. Naughton, Lauren A. Burt, and Xiaocai Shi

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.

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Fluid Balance of Elite Female Basketball Players Before and During Game Play

Jason P. Brandenburg and Michael Gaetz

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.

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Effect of Preexercise Soup Ingestion on Water Intake and Fluid Balance During Exercise in the Heat

Neil M. Johannsen, Zebblin M. Sullivan, Nicole R. Warnke, Ann L. Smiley-Oyen, Douglas S. King, and Rick L. Sharp

Purpose:

To determine whether chicken noodle soup before exercise increases ad libitum water intake, fluid balance, and physical and cognitive performance compared with water.

Methods:

Nine trained men (age 25 ± 3 yr, VO2peak 54.2 ± 5.1 ml · kg−1 · min−1; M ± SD) performed cycle exercise in the heat (wet bulb globe temperature = 25.9 ± 0.4 °C) for 90 min at 50% VO2peak, 45 min after ingesting 355 ml of either commercially available bottled water (WATER) or chicken noodle soup (SOUP). The same bottled water was allowed ad libitum throughout both trials. Participants then completed a time trial to finish a given amount of work (10 min at 90% VO2peak; n = 8). Cognitive performance was evaluated by the Stroop color–word task before, every 30 min during, and immediately after the time trial.

Results:

Ad libitum water intake throughout steady-state exercise was greater in SOUP than with WATER (1,435 ± 593 vs. 1,163 ± 427 g, respectively; p < .03). Total urine volume was similar in both trials (p = .13), resulting in a trend for greater water retention in SOUP than in WATER (87.7% ± 7.6% vs. 74.9% ± 21.7%, respectively; p = .09), possibly due to a change in free water clearance (–0.32 ± 1.22 vs. 0.51 ± 1.06 ml/min, respectively; p = .07). Fluid balance tended to be improved with SOUP (–106 ± 603 vs. –478 ± 594 g, p = .05). Likewise, change in plasma volume tended to be reduced in SOUP compared with WATER (p = .06). Only mild dehydration was achieved (<1%), and physical performance was not different between treatments (p = .77). The number of errors in the Stroop color–word task was lower in SOUP throughout the entire trial (treatment effect; p = .04).

Conclusion:

SOUP before exercise increased ad libitum water intake and may alter kidney function.

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Effect of Flavor and Awareness of Kilojoule Content of Drinks on Preference and Fluid Balance in Team Sports

Michelle R. Minehan, Malcolm D. Riley, and Louise M. Burke

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.

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Effect of Drink Carbohydrate Content on Postexercise Gastric Emptying, Rehydration, and the Calculation of Net Fluid Balance

David J. Clayton, Gethin H. Evans, and Lewis J. James

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.