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Randomized Controlled Trial
. 2019 Sep;119(9):2105-2118.
doi: 10.1007/s00421-019-04199-2. Epub 2019 Aug 3.

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

Alan J McCubbin  1 , Michelle B Lopez  2 , Gregory R Cox  3 , Joanne N Caldwell Odgers  2 , Ricardo J S Costa  4
Affiliations
Randomized Controlled Trial

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

Alan J McCubbin et al. Eur J Appl Physiol. 2019 Sep.

Abstract

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% [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.

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 < 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.

Conclusions: 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.

Keywords: Cycling; Endurance; Plasma osmolality; Plasma volume; Running; Salt; Sweat.

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References

    1. Alcock R, McCubbin A, Camões-Costa V, Costa RJS (2018) Case study: providing nutritional support to an ultraendurance runner in preparation for a self-sufficient multistage ultramarathon: rationed versus full energy provisions. Wilderness Environ Med 29(4):508–520. https://doi.org/10.1016/j.wem.2018.06.004 - DOI - PubMed
    1. Armstrong LE, Costill DL, Fink WJ (1985) Effects of dietary sodium on body and muscle potassium content during heat acclimation. Eur J Appl Physiol Occup Physiol 54(4):391–397 - DOI
    1. Baker LB (2017) Sweating rate and sweat sodium concentration in athletes: a review of methodology and intra/interindividual variability. Sports Med 47(Suppl 1):111–128. https://doi.org/10.1007/s40279-017-0691-5 - DOI - PubMed - PMC
    1. Baker LB, Barnes KA, Anderson ML, Passe DH, Stofan JR (2016) Normative data for regional sweat sodium concentration and whole-body sweating rate in athletes. J Sports Sci 34(4):358–368. https://doi.org/10.1080/02640414.2015.1055291 - DOI - PubMed
    1. Baker LB, De Chavez PJD, Ungaro CT, Sopeña BC, Nuccio RP, Reimel AJ, Barnes KA (2018) Exercise intensity effects on total sweat electrolyte losses and regional vs. whole-body sweat [Na+], [Cl−], and [K+]. Eur J Appl Physiol. https://doi.org/10.1007/s00421-018-4048-z (in press) - DOI - PubMed - PMC

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