Ventilation Parallels Plasma Potassium During Incremental and Continuous Variable Intensity Exercise

Abstract

The aim of the present investigation was to examine the relationship between plasma potassium (K⁺) and ventilation (V̇E) 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 (V̇O₂max) 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% V̇O₂max. The continuous variable intensity exercise consisted of 30 min of cycling at 45% V̇O₂max and then 6 × 16 min periods which consisted of cycling for 8 min at 75% V̇O₂max and 8 min at 45% V̇O₂max. During prolonged continuous exercise, V̇E 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 V̇E and plasma K⁺ concentration was found for each subject. However, a positive relationship and slope was also found when the V̇E/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.

Key words

Exercise hypernea - blood lactate - heart rate