This investigation examined the influence of two levels of dietary sodium (Na+) intake on intramuscular and extracellular potassium (K+) content. Nine unacclimatized college males exercised. (90 minutes of treadmill walking, 5.6km/hr, 6X grade) in an environmental chamber maintained at 40.1( + .05)°C and 23.5( + . 4) %RH, during two 8-day dietary-acclimation regimens. The first regimen employed a high Na+ diet (399mEq/day), the second a low Na+ diet (98mEq/day); both diets contained 80mEq K+/day. Total body K+ stores increased during the high Na+ diet (+138mEq, 4.1%) and the-low Na+ diet (+114mEq, 3.4%). By day 8 (D8) of both treatments, subjects exhibited a significantly lower (p<.O5) mean heart rate and rectal temperature. Oxygen consumption and sweat rate were unaltered but sweat responsiveness (ml/hr/°c) progressively increased during the acclimation trials. Plasma volume increased +16.3% (D4) and +10.7% (D8) under the high Na+ diet and only +3.0% (D4) and +7.0% (D8) under the low Na+ diet. The low sodium diet was associated with a significantly higher (p<.05) mean heart rate (D3-D5), higher rectal temperature (D3-D6), lower sweat responsiveness (D2) and a delayed plasma volume expansion (D4)--resulting in less effective heat removal. The total content of K+, Na+, and C1- in plasma changed isoosmotically with plasma volume. The diets were associated with equivalent urine K+ excretion, and. during exercise in the heat both diets resulted in significantly decreased urine K+ losses. Muscle K+ and sweat K+ concentrations were not altered by dietary intervention or acclimation trials. Total muscle water-was significantly increased, in accord with Na+ and Cl- increases, on D8 of the low Na+ diet only. It was concluded that dietary intake of Na+, in combination with 8 days. of exercise in the heat and heavy sweating, does not significantly diminish the intramuscular K+ or total body K+ content.
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/174841 |
| Date | 03 June 2011 |
| Creators | Armstrong, Lawrence E. |
| Contributors | Craig, Bruce W. |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | ix, 100 leaves : ill. ; 28 cm. |
| Source | Virtual Press |
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