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- Title
Impact of 3-day high and low dietary sodium intake on sodium status in response to exertional-heat stress: a double-blind randomized control trial.
- Authors
McCubbin, Alan J.; Lopez, Michelle B.; Cox, Gregory R.; Caldwell Odgers, Joanne N.; Costa, Ricardo J. S.
- Abstract
<bold>Purpose: </bold>To determine the impact of altering dietary sodium intake for 3 days preceding exercise on sweat sodium concentration [Na+], and cardiovascular and thermoregulatory variables.<bold>Methods: </bold>Fifteen male endurance athletes (runners n = 8, cyclists n = 7) consumed a low (LNa, 15 mg kg-1 day-1) or high (HNa, 100 mg kg-1 day-1) sodium diet, or their usual free-living diet [UDiet, 46 (37-56) mg kg-1 day-1] for 3 days in a double-blind, randomized cross-over design, collecting excreted urine (UNa) and refraining from exercise. On day 4, they completed 2 h running at 55% [Formula: see text]O2max or cycling at 55% maximum aerobic power in Tamb 35 °C. Pre- and post-exercise blood samples were collected, and sweat from five sites using absorbent patches along the exercise protocol.<bold>Results: </bold>UNa on days 2-3 pre-exercise [mean (95% CI) LNa 16 (12-19) mg kg-1 day-1, UDiet 46 (37-56) mg kg-1 day-1, HNa 79 (72-85) mg kg-1 day-1; p < 0.001] and pre-exercise aldosterone [LNa 240 (193-286) mg kg-1 day-1, UDiet 170 (116-224) mg kg-1 day-1, HNa 141 (111-171) mg kg-1 day-1; p = 0.001] reflected sodium intake as expected. Pre-exercise total body water was greater following HNa compared to LNa (p < 0.05), but not UDiet. Estimated whole-body sweat [Na+] following UDiet was 10-11% higher than LNa and 10-12% lower than HNa (p < 0.001), and correlated with pre-exercise aldosterone (1st h r = - 0.568, 2nd h r = - 0.675; p < 0.01). Rectal temperature rose more quickly in LNa vs HNa (40-70 min; p < 0.05), but was similar at the conclusion of exercise, and no significant differences in heart rate or perceived exertion were observed.<bold>Conclusions: </bold>Three day altered sodium intake influenced urinary sodium excretion and sweat [Na+], and the rise in rectal temperature, but had no effect on perceived exertion during moderate-intensity exercise in hot ambient conditions.
- Subjects
ENDURANCE athletes; ATHLETES; AEROBIC capacity; SODIUM; RATE of perceived exertion; HEART beat; SODIUM metabolism; COMPARATIVE studies; CROSSOVER trials; DIGESTION; EXERCISE; SODIUM content of food; HEAT; PHYSIOLOGICAL effects of heat; RESEARCH methodology; MEDICAL cooperation; PERSPIRATION; PHYSICAL fitness; RESEARCH; RUNNING; WATER-electrolyte balance (Physiology); EVALUATION research; RANDOMIZED controlled trials; BLIND experiment; METABOLISM
- Publication
European Journal of Applied Physiology, 2019, Vol 119, Issue 9, p2105
- ISSN
1439-6319
- Publication type
journal article
- DOI
10.1007/s00421-019-04199-2