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Responses to moderate and low sodium diets during exercise-heat acclimation
L E Armstrong1, R W Hubbard, E W Askew
1University of Connecticut, Human Performance Laboratory, Storrs 06269-1110.
International Journal of Sport Nutrition
|June 1, 1993
Summary
Both low and moderate sodium intake support health and exercise during prolonged heat acclimation. Dietary sodium levels did not significantly impact physiological responses or heat illness prevention.
Area of Science:
- Exercise Physiology
- Environmental Physiology
- Nutritional Science
Background:
- Heat acclimation (HA) is crucial for maintaining performance in hot environments.
- Dietary sodium intake is a key factor influencing physiological adaptations during HA.
- Understanding optimal sodium levels is essential for athletes and military personnel.
Purpose of the Study:
- To investigate the effects of low sodium (LNA) versus moderate sodium (MNA) intake on physiological function during prolonged exercise-heat acclimation.
- To determine if LNA or MNA intake supports health, exercise capacity, and physiological adaptations during 10 days of HA.
- To compare the impact of LNA and MNA on heart rate, body temperature, plasma volume, and urine sodium excretion.
Main Methods:
- Seventeen healthy young adults (19-21 years) underwent 10 days of controlled exercise-heat acclimation (41°C, 21% RH, 8 hours/day).
- Participants were assigned to either a low sodium (LNA; 68 mEq/day) or moderate sodium (MNA; 137 mEq/day) diet.
- Physiological variables including heart rate, rectal temperature, plasma volume, and urine sodium were monitored throughout the study.
Main Results:
- Both LNA and MNA groups exhibited successful heat acclimation, with significantly reduced heart rate, rectal temperature, and urine sodium.
- Plasma volume expansion was similar between groups by Day 17, despite a transiently smaller expansion in the LNA group.
- No significant differences in heat illness incidence or overall exercise performance were observed between the LNA and MNA dietary conditions.
Conclusions:
- Both low and moderate dietary sodium intakes are adequate for achieving successful heat acclimation in healthy young adults.
- Physiological adaptations and health maintenance during prolonged exercise in heat are not significantly compromised by a lower sodium intake within the tested range.
- These findings suggest flexibility in dietary sodium recommendations for individuals undergoing heat acclimation, provided other electrolytes are balanced.