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

• Published in: European journal of applied physiology 2019-09, Vol.119 (9), p.2105-2118
• Main Authors: McCubbin, Alan J., Lopez, Michelle B., Cox, Gregory R., Caldwell Odgers, Joanne N., Costa, Ricardo J. S.
• Format: Article
• Language: English
• Subjects: Adult; Aldosterone; Biomedical and Life Sciences; Biomedicine; Body water; Cross-Over Studies; Dietary intake; Double-Blind Method; Double-blind studies; Drinking - physiology; Excretion; Exercise; Exercise - physiology; Heart rate; Heart Rate - physiology; Heat stress; Heat Stress Disorders - metabolism; Heat Stress Disorders - physiopathology; Heat-Shock Response - physiology; Hot Temperature; Human Physiology; Humans; Male; Occupational Medicine/Industrial Medicine; Original Article; Physical Endurance - physiology; Physical training; Running - physiology; Sodium; Sodium - metabolism; Sodium, Dietary - administration & dosage; Sports Medicine; Sweat; Sweat - metabolism; Sweating - physiology; Urine; Water-Electrolyte Balance - physiology
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-019-04199-2

Purpose To determine the impact of altering dietary sodium intake for 3 days preceding exercise on sweat sodium concentration [Na + ], and cardiovascular and thermoregulatory variables. Methods 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% V ˙ O 2max or cycling at 55% maximum aerobic power in T amb 35 °C. Pre- and post-exercise blood samples were collected, and sweat from five sites using absorbent patches along the exercise protocol. Results 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