Nutrients, Vol. 17, Pages 3672: Hydration Responses to Pre-Exercise Sodium Hyperhydration at Rest and During Cycling in the Heat and Across Menstrual Cycle Phases
Nutrients doi: 10.3390/nu17233672
Authors:
Lilia Convit
Liliana Orellana
Julien D. Périard
Amelia J. Carr
Stuart Warmington
Ashwin K. V. Mruthunjaya
Angel A. J. Torriero
Rhiannon M. J. Snipe
Purpose: This study examined hydration responses to sodium hyperhydration in female athletes at rest and during cycling across the early follicular and mid-luteal phases of the menstrual cycle. Methods: Twelve cyclists/triathletes consumed 30 mL·kg−1 fat-free mass fluid with either sodium chloride (7.5 g·L−1) or placebo (sucrose) 2 h before 75 min of steady-state cycling (60% VO2peak) and a 200 kJ time trial (TT) in a hot environment (34 °C, 60% RH). Body mass was measured, and urine was collected every 30 min, whilst blood samples were taken hourly pre-exercise, post-steady-state, and post-TT. Results: During pre-exercise, sodium hyperhydration increased fluid retention (509.0 mL, 95% CI: [349.0, 669.0]; p < 0.001), while reducing urine volume (−107.4 [−146.7, −68.1] mL; p < 0.001). During exercise, body mass loss was lower with sodium during steady-state (−0.20%; p = 0.001) and TT (−0.15%; p = 0.037), but sweat rates were reduced with sodium only during steady-state (−0.08 L·h−1; p = 0.001). Exploratory analyses showed greater effects in the early-follicular phase, with reductions in body mass loss (−0.26%; p = 0.004), sweat rate (−0.1 L·h−1; p = 0.003), and post-TT arginine vasopressin (−10.8 [−19.2, −2.3] pg·mL−1; p = 0.013). Conclusions: Sodium hyperhydration effectively enhanced fluid retention and reduced body mass loss during exercise in the heat. While no consistent main effects of menstrual cycle phase were observed, some phase-specific differences emerged, particularly in the early-follicular phase. These findings highlight the importance of monitoring hydration responses across the menstrual cycle and tailoring strategies to individual needs, rather than applying universal phase-specific recommendations.
Purpose: This study examined hydration responses to sodium hyperhydration in female athletes at rest and during cycling across the early follicular and mid-luteal phases of the menstrual cycle. Methods: Twelve cyclists/triathletes consumed 30 mL·kg−1 fat-free mass fluid with either sodium chloride (7.5 g·L−1) or placebo (sucrose) 2 h before 75 min of steady-state cycling (60% VO2peak) and a 200 kJ time trial (TT) in a hot environment (34 °C, 60% RH). Body mass was measured, and urine was collected every 30 min, whilst blood samples were taken hourly pre-exercise, post-steady-state, and post-TT. Results: During pre-exercise, sodium hyperhydration increased fluid retention (509.0 mL, 95% CI: [349.0, 669.0]; p < 0.001), while reducing urine volume (−107.4 [−146.7, −68.1] mL; p < 0.001). During exercise, body mass loss was lower with sodium during steady-state (−0.20%; p = 0.001) and TT (−0.15%; p = 0.037), but sweat rates were reduced with sodium only during steady-state (−0.08 L·h−1; p = 0.001). Exploratory analyses showed greater effects in the early-follicular phase, with reductions in body mass loss (−0.26%; p = 0.004), sweat rate (−0.1 L·h−1; p = 0.003), and post-TT arginine vasopressin (−10.8 [−19.2, −2.3] pg·mL−1; p = 0.013). Conclusions: Sodium hyperhydration effectively enhanced fluid retention and reduced body mass loss during exercise in the heat. While no consistent main effects of menstrual cycle phase were observed, some phase-specific differences emerged, particularly in the early-follicular phase. These findings highlight the importance of monitoring hydration responses across the menstrual cycle and tailoring strategies to individual needs, rather than applying universal phase-specific recommendations. Read More