Personalized Hydration Strategy Attenuates the Rise in Heart Rate and in Skin Temperature Without Altering Cycling Capacity in the Heat

Abstract

The optimal hydration plan [i.e., drink to thirst, ad libitum (ADL), or personalized plan] to be adopted during exercise in recreational athletes has recently been a matter of debate and, due to conflicting results, consensus does not exist. In the present investigation, we tested whether a personalized hydration strategy based on sweat rate would affect cardiovascular and thermoregulatory responses and exercise capacity in the heat. Eleven recreational male cyclists underwent two familiarization cycling sessions in the heat (34°C, 40% RH) where sweat rate was also determined. A fan was used to enhance sweat evaporation. Participants then performed three randomized time-to-exhaustion (TTE) trials in the heat with different hydration strategies: personalized volume (PVO), where water was consumed, based on individual sweat rate, every 10 min; ADL, where free access to water was allowed; and a control (CON) trial with no fluids. Blood osmolality and urine-specific gravity were measured before each trial. Heart rate (HR), rectal, and skin temperatures were monitored throughout trials. Time to exhaustion at 70% of maximal workload was used to define exercise capacity in the heat, which was similar in all trials (p = 0.801). Body mass decreased after ADL (p = 0.008) and CON (p < 0.001) and was maintained in PVO trials (p = 0.171). Participants consumed 0 ml in CON, 166 ± 167 ml in ADL, and 1,080 ± 166 ml in PVO trials. The increase in mean body temperature was similar among trials despite a lower increase in skin temperature during PVO trial in comparison with CON (2.1 ± 0.6 vs. 2.9 ± 0.5°C, p = 0.0038). HR was lower toward the end of TTE in PVO (162 ± 8 bpm) in comparison with ADL (168 ± 12 bpm) and CON (167 ± 10 bpm), p < 0.001. In conclusion, a personalized hydration strategy can reduce HR during a moderate to high intensity exercise session in the heat and halt the increase in skin temperature. Despite these advantages, cycling capacity in the heat remained unchanged.

Effect of a cajuína hydroelectrolytic drink on the physical performance and hydration status of recreational runners

“…The participants in this study lost less than 1% of body mass, indicating that they finished the time-to-exhaustion test at a satisfactory level of hydration ( Sawka et al, 2007 ). Thus, the data from the present study indicate that the methodological protocol of the ingested water volume was adequate, as it was done individually, which is more suitable to prevent dehydration than ad libitum methods ( Melo-Marins et al, 2018 ). Considering the data regarding the loss in body mass, the sweating rate was between 1 and 1.25 L/h, also without showing statistical difference between the conditions evaluated.…”

Skin-interfaced microfluidic sweat collection devices for personalized hydration management through thermal feedback

“…57 As sweat rates and electrolyte concentrations vary greatly during training and competition, personalized fluid and electrolyte replenishment strategies based on individualized sweating profiles are required. 16,58 Fig. 5a shows the practical application of the devices in human trials, including sweat capture, collection, and automatic feedback to the user.…”

Personalized Hydration Strategy Improved Fluid Balance and Intermittent Exercise Performance In The Heat

“…Players were required to ingest the PHS solution within an hour of practice, finally resulted in a -0.95%BML, whereas drink adlibitum resulted in -1.14%BML [20]. Melo-Marins et al applied a PHS solution offset 80% of sweat loss during a time to exhaustion cycling at 70% of the maximal workload, resulted in a -0.2%BML compared to ad-libitum CON with a (-1.0%BML) [21]. In addition, Bardis et al prescribed PHS to offset total sweat loss in a 30-km cycling resulted in a -0.5% BML compared to ad-libitum a -1.8%BML [22].…”