Hydration affects multiple aspects of basketball performance, but few investigations have examined the hydration profiles of collegiate basketball players. We examined multiday prepractice hydration status of 11 male and 11 female NCAA (National Collegiate Athletic Association) Division II basketball players' sweat losses, fluid intake, and how accurately players estimated their sweat losses. Urine-specific gravity (USG) was spontaneously assessed before 2 practices. Sweat losses and fluid intakes were measured during a conditioning practice (CP) and sport-specific practice (SP). After practices, players filled 1,030 ml practice bottles to estimate their sweat losses. Urine-specific gravity between practices exhibited a moderate correlation (r = 0.54; p = 0.012) and were consistently high (17% of samples = USG >1.030) with no difference in mean USG between men (1.026 ± 0.004) and women (1.022 ± 0.008). Athletes' estimations of their sweat loss volumes between CP and the longer SP were strongly correlated (r = 0.88; p < 0.001). Estimation error was high (absolute error for both practices = 71 ± 52%) and error direction varied greatly within men. Women consistently underestimated sweat losses by 63 ± 28% and 65 ± 20% during CP and SP. Sweat losses during SP equaled 2,471 ± 495 ml and 1,910 ± 441 ml for men and women, respectively, but high practice fluid intake limited body mass losses to 1.1 ± 0.6% by the end of practice. It is plausible that hypohydration is related to poor conceptualization of sweat losses. Simulating the methodology of this study could help identify chronically hypohydrated athletes and be used to educate on between-practice fluid needs.

The purpose of this study was to determine how accurately runners estimate their sweat losses. Male (n = 19) and female (n = 20) runners (41 ± 10 yr, VO2max 57 ± 9 ml · kg(-1) · min(-1) from the southeastern U.S. completed an ~1-hr run during late summer on a challenging outdoor road course (wet bulb globe temperature 24.1 ± 1.5 °C). Runs began at ~6:45 a.m. or p.m. Before and after running, participants filled race-aid-station paper cups with a volume of fluid they felt would be equivalent to their sweat losses. Total sweat losses and losses by percent body weight differed (p < .01) between men (1,797 ± 449 ml, 2.3% ± 0.6%) and women (1,155 ± 258 ml, 1.9% ± 0.4%). Postrun estimates (738 ± 470 ml) were lower (p < .001) than sweat losses (1,468 ± 484 ml), equaling underestimations of 50% ± 23%, with no differences in estimation accuracy by percentage between genders. Runners who reported measuring changes in pre- and postrun weight to assess sweat losses within the previous month (n = 9, -54% ± 18%) were no more accurate (p = .55) than runners who had not (n = 30, -48% ± 24%). These results suggest that inadequate fluid intake during runs or between runs may stem from underestimations of sweat losses and that runners who do assess sweat-loss changes may be making sweat-loss calculation errors or do not accurately translate changes in body weight to physical volumes of water.

Current American College of Sports Medicine (ACSM) guidelines recommend replacing 150% of sweat losses between training bouts separated by ≤12 hours, but little evidence exists concerning the implications of this strategy for runners. Participants (n = 13) in this study replaced 75% (1637 ± 372 mL) or 150% (3099 ± 850 mL) of sweat losses following an outdoor evening run (∼75 minutes; Wet-bulb-globe temperature (WBGT) = ∼27°C) and consumed a standardised evening meal and breakfast before completing an outdoor (WBGT = ∼23°C) 10-km time-trial the following morning. Urine was collected between runs and urine specific gravity (USG) was assessed pre-run. Significant differences were found in pre-run body mass (75% = 69.6 ± 9.2; 150% = 70.1 ± 9.3 kg; P = 0.02) and USG (75% = 1.026 ± 0.005; 150% = 1.014 ± 0.007; P < 0.001). Heart rate during 10-km run (168 ± 14 versus 168 ± 12 beats min(-1)) and post-run intestinal temperature (39.08 ± 0.52 versus 39.00 ± 0.70 °C) did not differ for 75% and 150%, respectively, despite an ∼3% performance improvement (75% = 47.28 ± 6.64; 150% = 45.93 ± 6.04 minutes; P = 0.001) due to a faster pace in the second half of the run with 150% replacement. Session rate of perceived exertion (RPE) was lower (P = 0.02) during 150% (7.5 ± 1.3) versus 75% (8.4 ± 0.9). Reluctant drinkers potentially hinder training quality between evening and morning runs in the heat, but copious urine production and difficulty in consuming recommended fluid volumes suggest fluid replacement <150% may be more ideal.

This study examined 24-h post-run hydration status and sweat loss estimation accuracy in college age runners (men = 12, women = 8) after completing a 1-h self-paced outdoor run (wet bulb globe temperature = 19.9 ± 3.0 °C). Sweat losses (1353 ± 422 mL; 1.9% ± 0.5% of body mass) were significantly greater (p < 0.001) than perceived losses (686 ± 586 mL). Cumulative fluid consumption equaled 3876 ± 1133 mL (218 ± 178 mL during) with 37% of fluid ingested lost through urine voids (1450 ± 678 mL). Fluid balance based on intake and urine production equaled +554 ± 669 mL at 12 h and +1186 ± 735 mL at 24 h. Most runners reported euhydrated (pre-run urine specific gravity (USG) = 1.018 ± 0.008) with no changes (p = 0.33) at hours 12 or 24 when both genders were included. However, USG was higher (p = 0.004) at 12 h post-run for men (1.025 ± 0.0070 vs. 1.014 ± 0.007), who consumed 171% ± 40% of sweat losses at 12 h vs. 268% ± 88% for women. Most runners do not need intervention concerning between bout hydration needs in temperate environments. However, repeated USG measurements were able to identify runners who greatly under or over consumed fluid during recovery. Practitioners can use multiple USG assessments as cheap method to detect runners who need to modify their hydration strategies and should promote assessment of sweat losses by change in body mass, as runners had poor perception of sweat losses.

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