[Changes in plasma electrolytes during exercise in normal subjects--with special reference to the concentration of potassium and inorganic phosphate (Pi)].
In 8 healthy adults, changes in plasma electrolyte levels (Na+, Cl-, Ca2+, Pi and lactate) and respiratory parameters (VE, VO2 and VCO2) were examined during incremental exercise on a treadmill. Na+, Cl- and Ca2+ increased significantly near the end of maximal exercise and the early phase of the recovery period. Considering the 14% decrease in plasma volume, the increases in Na+, Cl-, and Ca2+ were not significant, while the increases in K+, Pi and lactate were significant. During incremental exercise, the concentration of K+ significantly correlated with minute ventilation (r = 0.994, p < 0.0001). Two minutes after the completion of exercise, K+ decreased below the pre-exercise level. The inflection point of VE on VO2 appeared earlier than that of K+ on VO2. The results suggest that some other factor which may contribute to the control of ventilation during exercise should be considered in addition to K+. Lactate and Pi began to increase 5 and 8 minutes, respectively, after the start of exercise. Even after the completion of exercise, these two parameters remained significantly higher than the pre-exercise level. During incremental exercise, the concentration of Pi increased concomitantly with time, and significantly correlated with VE. On the other hand, in the early stage of exercise, the concentration of lactate remained at the pre-exercise level. These results suggest that the increase in plasma Pi is responsible for the state of metabolism in the muscle in addition to lactic acidosis.
Iwato
S
S
Department of Internal Medicine, Koshigaya Hospital, Dokkyo University School of Medicine, Saitama, Japan.
Nagao
K
K
Ichiwata
T
T
D000328:Adult; D004573:Electrolytes / Q000097:blood*; D015444:Exercise; D005080:Exercise Test; D006801:Humans; D007773:Lactates / Q000097:blood; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000097:blood*; D011188:Potassium / Q000097:blood*
D004573:Electrolytes; D007773:Lactates; D010710:Phosphates; D011188:Potassium