Responses to moderate and low sodium diets during exercise-heat acclimation.
This investigation examined whether low sodium (Na+) (LNA; 68 mEq Na+.d-1) or moderate Na+ (MNA; 137 mEq Na+.d-1) intake allowed humans to maintain health, exercise, and physiologic function during 10 days of prolonged exercise-heat acclimation (HA). Seventeen volunteers, ages 19 to 21, consumed either LNA (n = 8) or MNA (n = 9) during HA (41 degrees C, 21% RH; treadmill walking for 30 min.h-1, 8 h.d-1 at 5.6 km.h-1, 5% grade), which resulted in significantly reduced heart rate, rectal temperature, and urine Na+ for both groups. There were few between-diet differences in any variables measured. Mean plasma volume in LNA expanded significantly less than in MNA by Days 11 and 15, but reached the MNA level on Day 17 (+12.3 vs. +12.4%). The absence of heat illness, the presence of normal physiologic responses, and the total distance walked indicated successful and similar HA with both levels of dietary Na+.
Armstrong
L E
LE
University of Connecticut, Human Performance Laboratory, Storrs 06269-1110.
Hubbard
R W
RW
Askew
E W
EW
De Luca
J P
JP
O'Brien
C
C
Pasqualicchio
A
A
Francesconi
R P
RP
D000064:Acclimatization; D000328:Adult; D001810:Blood Volume; D015992:Body Mass Index; D001833:Body Temperature Regulation; D003889:Desert Climate; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D008297:Male; D012982:Sodium, Dietary / Q000008:administration & dosage*; D016482:Urinalysis; D014882:Water-Electrolyte Balance
D012982:Sodium, Dietary