Ventilation parallels plasma potassium during incremental and continuous variable intensity exercise.
The aim of the present investigation was to examine the relationship between plasma potassium (K+) and ventilation (VE) during incremental and prolonged continuous exercise which varied between low and moderate intensity. Seven well-trained male cyclists who had a mean maximal aerobic power (VO2max) of 69.4 +/- 2.9 ml/kg/min were recruited to participate as subjects. The graded incremental exercise bout was composed of 3 min stages set to elicit 40, 50, 60, 70, 80 and 90% VO2max. The continuous variable intensity exercise consisted of 30 min of cycling at 45% VO2max and then 6 x 16 min periods which consisted of cycling for 8 min at 75% VO2max and 8 min at 45% VO2max. During prolonged continuous exercise, VE and plasma K+ changed in a coordinated manner between the low and moderate intensity exercise bouts with the responses during the moderate intensity intervals being significantly greater (p < 0.05) than the responses during the low intensity intervals. During the incremental exercise test, a strong positive relationship between VE and plasma K+ concentration was found for each subject. However, a positive relationship and slope was also found when the VE/K+ ratio was correlated with exercise intensity (r = 0.90-0.99). This indicates that with increasing exercise intensity, the rise in VE becomes increasingly greater than the rise in plasma K+. These findings suggest that the plasma K+ concentration contributes to but may not be the sole determinant of ventilatory regulation during exercise.