INTERRELATIONSHIP BETWEEN PLASMA POTASSIUM CONCENTRATION, PULMONARY VENTILATION AND ELECTROCARDIOGRAPHIC CHANGE DURING AND AFTER HIGHLY INTENSE EXERCISE

Objective: The purpose of this investigation was to induce elevated pl asma concentrations of potassium (K+) efflux from active muscle cells during intense muscular exercise. The relationship between K+, pulmona ry ventilation (V(E)) and EKG changes, specifically T-wave amplitude. is presently controversial. Design: Repeated measures design. Setting: Human performance laboratory. Participants: Twelve volunteer trained recreational cyclists (10 males. mean age 31.9 +/- 7.4, and 2 females, mean age 27.5 +/- 0.7, mean Vo2max 571.2 +/- 6.4 ml. kg . min-1). Out come Measure: Subjects performed 10 min of pedaling at 90 rpm, yieldin g a power output of 45 W. min-1 on a mechanically braked cycle ergomet er as a warm-up. Each exercise stage was 2 min in duration, beginning at 135 W and increased by 45 W thereafter until voluntary exhaustion. Respiratory gas exchange measures were obtained every 10 sec. Venous b lood samples for K+ and lactate (LA-) determination were drawn at rest , at the end of stage 2, all subsequent stages, and during 3 and 10 mi n of recovery. EKG recordings were concurrent with venous sampling. Re sults: Statistical analyses for V(E) vs. K+, respiratory exchange rati o (RER) vs. K+ and RER vs. LA- revealed neither significant change nor an associative relationship from stages 1-3. However, stages 4-8 were statistically significant (p < .05) and highly correlated. No relatio nship was found between K+ change and T-wave amplitude during exercise or recovery. Conclusion: These data indicate a strong relationship be tween selected respiratory gas exchange measures and K+ during interme diate to highly intense exercise.