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 plasma concentrations of potassium (K+) efflux from active muscle cells during intense muscular exercise. The relationship between K+, pulmonary ventilation (VE) and EKG changes, specifically T-wave amplitude, is presently controversial.


METHODS
Repeated measures design.


METHODS
Human performance laboratory.


METHODS
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).


METHODS
Subjects performed 10 min of pedaling at 90 rpm, yielding a power output of 45 W.min-1 on a mechanically braked cycle ergometer 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 blood 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 min of recovery. EKG recordings were concurrent with venous sampling.


RESULTS
Statistical analyses for VE vs. K+, respiratory exchange ratio (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 relationship was found between K+ change and T-wave amplitude during exercise or recovery.


CONCLUSIONS
These data indicate a strong relationship between selected respiratory gas exchange measures and K+ during intermediate to highly intense exercise.
von Duvillard
S P
SP
Division of Cardiovascular Research, University of Massachusetts at Lowell 01854.
LeMura
L M
LM
Szmedra
L
L
Di Vico
P
P
D000328:Adult; D001642:Bicycling; D002245:Carbon Dioxide / Q000097:blood; D004562:Electrocardiography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008451:Maximal Voluntary Ventilation; D010100:Oxygen / Q000097:blood; D011188:Potassium / Q000097:blood*; D011659:Pulmonary Gas Exchange
D002245:Carbon Dioxide; D011188:Potassium; D010100:Oxygen