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, Michelle B. Lopez, Gregory R. Cox, Joanne N. Caldwell Odgers, Ricardo J.S. Costa

Research output: Contribution to journalArticleResearchpeer-review

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% V˙ 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.

Original languageEnglish
Pages (from-to)2105-2118
Number of pages14
JournalEuropean Journal of Applied Physiology
Volume119
Issue number9
DOIs
Publication statusPublished - 1 Sep 2019

Keywords

  • Cycling
  • Endurance
  • Plasma osmolality
  • Plasma volume
  • Running
  • Salt
  • Sweat

Cite this

@article{32828d4f04c6452ab091b7347eea2044,
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",
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{\%} V˙ 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",
author = "McCubbin, {Alan J.} and Lopez, {Michelle B.} and Cox, {Gregory R.} and {Caldwell Odgers}, {Joanne N.} and Costa, {Ricardo J.S.}",
year = "2019",
month = "9",
day = "1",
doi = "10.1007/s00421-019-04199-2",
language = "English",
volume = "119",
pages = "2105--2118",
journal = "European Journal of Applied Physiology",
issn = "1439-6319",
publisher = "Springer-Verlag London Ltd.",
number = "9",

}

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. / McCubbin, Alan J.; Lopez, Michelle B.; Cox, Gregory R.; Caldwell Odgers, Joanne N.; Costa, Ricardo J.S.

In: European Journal of Applied Physiology, Vol. 119, No. 9, 01.09.2019, p. 2105-2118.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Impact of 3-day high and low dietary sodium intake on sodium status in response to exertional-heat stress

T2 - a double-blind randomized control trial

AU - McCubbin, Alan J.

AU - Lopez, Michelle B.

AU - Cox, Gregory R.

AU - Caldwell Odgers, Joanne N.

AU - Costa, Ricardo J.S.

PY - 2019/9/1

Y1 - 2019/9/1

N2 - 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˙ 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.

AB - 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˙ 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.

KW - Cycling

KW - Endurance

KW - Plasma osmolality

KW - Plasma volume

KW - Running

KW - Salt

KW - Sweat

UR - http://www.scopus.com/inward/record.url?scp=85070848227&partnerID=8YFLogxK

U2 - 10.1007/s00421-019-04199-2

DO - 10.1007/s00421-019-04199-2

M3 - Article

VL - 119

SP - 2105

EP - 2118

JO - European Journal of Applied Physiology

JF - European Journal of Applied Physiology

SN - 1439-6319

IS - 9

ER -