Improved body composition and fat oxidation from LCHF diet potentially negate expected performance decrement from reduced carbohydrate use late in exercise for nonelite runners. An acute decrease in training capacity is expected; however, if performance improvement is not exhibited after 3 wk, diet cessation is suggested for negative responders.

Context:The behaviors and beliefs of recreational runners with regard to hydration maintenance are not well elucidated.Objective: To examine which beverages runners choose to drink and why, negative performance and health experiences related to dehydration, and methods used to assess hydration status.Design: Cross-sectional study. Setting: Marathon registration site. Patients or Other Participants: Men (n = 146) and women (n = 130) (age = 38.3 ± 11.3 years) registered for the 2010 Little Rock Half-Marathon or Full Marathon. Intervention(s):A 23-item questionnaire was administered to runners when they picked up their race timing chips.Main Outcome Measure(s): Runners were separated into tertiles (Low, Mod, High) based on z scores derived from training volume, expected performance, and running experience. We used a 100-mm visual analog scale with anchors of 0 (never) and 100 (always). Total sample responses and comparisons between tertile groups for questionnaire items are presented. Results:The High group (58±31) reported greater consumption of sport beverages in exercise environments than the Low (42 ± 35 mm) and Mod (39 ± 32 mm) groups (P < .05) and perceived sport beverages to be superior to water in meeting hydration needs (P < .05) and improving performance during runs greater than 1 hour (P < .05). Seventy percent of runners experienced 1 or more incidents in which they believed dehydration resulted in a major performance decrement, and 45% perceived dehydration to have resulted in adverse health effects. Twenty percent of runners reported monitoring their hydration status. Urine color was the method most often reported (7%), whereas only 2% reported measuring changes in body weight.Conclusions: Greater attention should be paid to informing runners of valid techniques to monitor hydration status and developing an appropriate individualized hydration strategy.Key Words: dehydration, sport beverages, hydration monitoring Key Points• Most runners had experienced performance decrements that they attributed to dehydration. Almost half the runners had sustained heat-related illness symptoms that they related to dehydration.• Despite these adverse events, few participants monitored their hydration levels or used specific hydration plans.• Better dissemination of accurate scientific information about appropriate hydration practices may increase runners' safety.

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.

Carbohydrate mouth rinse (CMR) is a novel method proposed to enhance endurance performance lasting ≤ 60 min. The current study examined the influence of CMR on anaerobic performance tasks in 11 collegiate female soccer players after an overnight fast. Athletes completed two experimental sessions, during which carbohydrate (CHO; 6% maltodextrin) or taste- and colour-matched placebo (PLA) mouth-rinse solutions were administered in a counterbalanced, double-blinded design. Three rounds of a 5-min scrimmage bout and series of performance tests including a single countermovement vertical jump (1VJ), a set of four consecutive vertical jumps, a 72-m shuttle run (SR72) and 18-m sprint comprised each trial. Thirst sensation (TS), session TS, ratings of perceived exertion (RPE) and session RPE were assessed as secondary outcomes. The first SR72 approached significance (p = 0.069), but no significant between-trials differences were observed for any of the mean performance tasks. The highest 1VJ scores did not differ for the first (CHO = 47.3 ± 3.4, PLA = 47.7 ± 3.5 cm; p = 0.43), second (CHO = 48.0 ± 4.1, PLA = 47.9 ± 3.5 cm; p = 0.82) or third bout (CHO = 47.4 ± 3.9, PLA = 48.1 ± 3.9 cm; p = 0.26). TS approached significance (p = 0.053) during the first bout. No significant differences (p > 0.05) were found for any of the perceptual variables. Current results fail to support ergogenic influence of CMR on anaerobic performance tasks in collegiate female athletes.

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.