Sweat rate and electrolyte losses have a large inter-individual variability. A personalized approach to hydration can overcome this issue to meet an individual’s needs. This study aimed to investigate the effects of a personalized hydration strategy (PHS) on fluid balance and intermittent exercise performance. Twelve participants conducted 11 laboratory visits including a VO_2max test and two 5-day trial arms under normothermic (NOR) or hyperthermic (HYP) environmental conditions. Each arm began with three days of familiarization exercise followed by two random exercise trials with either a PHS or a control (CON). Then, participants crossed over to the second arm for: NOR+PHS, NOR+CON, HYP+PHS, or HYP+CON. The PHS was prescribed according to the participants’ fluid and sweat sodium losses. CON drank ad libitum of commercially-available electrolyte solution. Exercise trials consisted of two phases: (1) 45 min constant workload; (2) high-intensity intermittent exercise (HIIT) until exhaustion. Fluids were only provided in phase 1. PHS had a significantly greater fluid intake (HYP+PHS: 831.7 ± 166.4 g; NOR+PHS: 734.2 ± 144.9 g) compared to CON (HYP+CON: 369.8 ± 221.7 g; NOR+CON: 272.3 ± 143.0 g), regardless of environmental conditions (p < 0.001). HYP+CON produced the lowest sweat sodium concentration (56.2 ± 9.0 mmol/L) compared to other trials (p < 0.001). HYP+PHS had a slower elevated thirst perception and a longer HIIT (765 ± 452 s) compared to HYP+CON (548 ± 283 s, p = 0.04). Thus, PHS reinforces fluid intake and successfully optimizes hydration status, regardless of environmental conditions. PHS may be or is an important factor in preventing negative physiological consequences during high-intensity exercise in the heat.

Background and objectives: Research investigating hydration strategies specialized for women’s soccer players is limited, despite the growth in the sport. The purpose of this study was to determine the effects of fluid balance and electrolyte losses in collegiate women’s soccer players. Materials and Methods: Eighteen NCAA Division I women’s soccer players were recruited (age: 19.2 ± 1.0 yr; weight: 68.5 ± 9.0 kg, and height: 168.4 ± 6.7 cm; mean ± SD), including: 3 forwards (FW), 7 mid-fielders (MD), 5 defenders (DF), and 3 goalkeepers (GK). Players practiced outdoor during spring off-season training camp for a total 14 practices (WBGT: 18.3 ± 3.1 °C). The main outcome measures included body mass change (BMC), sweat rate, urine and sweat electrolyte concentrations, and fluid intake. Results: Results were analyzed for comparison between low (LOW; 16.2 ± 2.6° C, n = 7) and moderate risk environments for hyperthermia (MOD; 20.5 ± 1.5 °C, n = 7) as well as by field position. The majority (54%) of players were in a hypohydrated state prior to practice. Overall, 26.7% of players had a %BMC greater than 0%, 71.4% of players had a %BMC less than −2%, and 1.9% of players had a %BMC greater than −2% (all MD position). Mean %BMC and sweat rate in all environmental conditions were −0.4 ± 0.4 kg (−0.5 ± 0.6% body mass) and 1.03 ± 0.21 mg·cm⁻²·min⁻¹, respectively. In the MOD environment, players exhibited a greater sweat rate (1.07 ± 0.22 mg·cm⁻²·min⁻¹) compared to LOW (0.99 ± 0.22 mg·cm⁻²·min⁻¹; p = 0.02). By position, DF had a greater total fluid intake and a lower %BMC compared to FW, MD, and GK (all p < 0.001). FW had a greater sweat sodium (Na+) (51.4 ± 9.8 mmol·L⁻¹), whereas GK had the lowest sweat sodium (Na+) (30.9 ± 3.9 mmol·L⁻¹). Conclusions: Hydration strategies should target pre-practice to ensure players are adequately hydrated. Environments deemed to be of moderate risk of hyperthermia significantly elevated the sweat rate but did not influence fluid intake and hydration status compared to low-risk environments. Given the differences in fluid balance and sweat responses, recommendations should be issued relative to soccer position.

Background: Both heat acclimation and neck cooling have been shown to alleviate heat stress and may help maintain exercise performance in the heat. However, no previous research has been determined their combined effects on thermal perception and physiological responses during exercise in the heat.Objective: To determine the effects of neck cooling applied before and after heat acclimation on physiological responses, thermal perceptions, and time to exhaustion exercise performance in the heat.Methods: Fourteen non-heat acclimated men completed a randomized crossover design, involving 10 consecutive days of heat acclimation exercise (HAE) in a controlled heat chamber (35 °C, 30%RH). Participants performed four time-to-exhaustion tests (TTE) with neck cooling (NC) or without (CON) before (Pre-NC and Pre-CON) and after HAE (Post-NC and Post-CON). The TTE test comprised an initial 30 min incremental phase (starting at 50%VO_2max, increasing 5% every 5 min) followed by a constant workload phase at 70%VO_2max until volitional exhaustion. Temperature from tympanic membrane (T_tym) and neck (T_neck), heart rate (HR), ratings of perceived exertion (RPE), thermal comfort (TC), thermal acceptability (TA), and thermal sensation (TS) were recorded at 5 min interval.Results: Following 10 days of HAE, participants exhibited a significant increase in local sweat rate (p = 0.002), and reductions in sweat sodium concentration (p = 0.04) and HR (p = 0.02). TTE performance exhibited significant main effects for both cooling (p = 0.003) and HAE (p = 0.002), while the interaction effect approached significance (p = 0.069). Comparing to the Pre-CON trial, the Post-NC had a significantly greater percentage improvement in TTE (17.3% ± 13.5%) than Pre-NC (3.4% ± 9.9%, p = 0.01) and Post-CON (4.9% ± 13.0%, p = 0.03). Moreover, thermal perception measures revealed significant main effects of cooling (TC: p = 0.01; TS: p < 0.001; TA: p = 0.003) and significant interaction effects (TC: p = 0.036; TS: p = 0.004; TA: p = 0.048), with the Post-NC exhibiting significantly improved TC and reduced TS compared to other groups.Conclusion: Neck cooling provides ergogenic effects in thermal perceptions and extends a greater improvement in time to exhaustion performance when applied after heat acclimation. These findings suggest that individuals should achieve physiological adaptation to the heat before neck cooling is introduced for perceptual or performance benefits.

Sweat rate and electrolyte losses have a large inter-individual variability, a personalized approach to hydration can overcome this issue to meet an individual’s needs. This study aimed to investigate the effects of personalized hydration strategy (PHS) on fluid balance and intermittent exercise performance. Twelve participants conducted 11 laboratory visits including a VO2max test and two 5-day trial arms under normothermic (NOR) or hyperthermic (HYP) environmental conditions. Each arm began with 3-day of familiarization exercise following by two random exercise trials with a either PHS or control (CON). Then, participants crossed-over to the second arm for: NOR+PHS, NOR+CON, HYP+PHS, and HYP+CON. The PHS was prescribed according to participants’ fluid and sweat sodium losses. CON drank ad-libitum of commercially-available electrolyte solution. Exercise trials consisted of two phases: 1) 45min constant workload; 2) high-intensity intermittent exercise (HIIT) until exhaustion. PHS had a significantly greater fluid intake compared to CON. HYP+CON produced the lowest sweat sodium concentration. HYP+PHS had a lower thirst perception and a longer HIIT compared to HYP+CON. Thus, PHS reinforces fluid intake and successfully optimizes hydration status, regardless of environmental conditions. PHS may be or is an important factor to preventing negative physiological consequences during high-intensity exercise in the heat.

The environment poses significant physiologic challenges to athletic performance. The purpose of this study was to investigate fluid balance and electrolyte losses in Chinese collegiate male soccer players during practices and games under different environments. Twelve male players were recruited across 38 practices (P) and 17 games (G) over a 9-month period, conducted in hot (H) and cool (C) environments, yielding four experimental conditions: G + H, P + H, G + C, and P + C. Fluid balance parameters comprised body mass loss (BML), urine specific gravity (USG), and sweat compositions. On-field running characteristics were collected only in games, including total distance covered (TD), number of sprints, fast run distance, accelerations, and decelerations. Pre-exercise USG indicated that > 50% of players began exercise in a hypohydrated status across four conditions. Players in G + C showed a higher proportion of ≥ 2% hypohydration, whereas players were overhydrated in G + H. Fluid balance parameters were significantly influenced by both exercise conditions and environments. Better running performance was found in G + C than G + H (p < 0.001). Both TD (r = -0.56, p < 0.001) and fast run distance (r = -0.54, p < 0.001) was inversely associated with %BML. Pre-exercise hypohydration remains a significant concern, regardless of exercise conditions or environments. TD and fast run distance may serve as practical indicators of post-game hydration status. Future guidelines aim at modifying drinking behaviors could help players maintain optimal hydration.