[Effect of change of plasma K+ and pH value induced by exercise on muscle fatigue and surface EMG].
OBJECTIVE
This study was undertaken to explore the relationship between plasma K+, H+ and muscle fatigue as well as electromyogram changes.


METHODS
Fourteen male students enrolled as the subjects of this study performed two exercise tests of different intensity (200 W; 120 W) on a cycle ergometer till being fatigued. The plasma K+, pH value and electromyography (EMG) of active and inactive muscles during 10 s isometric contraction fixed load were measured before exercise and at 0, 5, 10, 20 minutes after exercise.


RESULTS
Both plasma K+ and mean power frequency (MPF) of the active muscles changed significantly (P<0.01) after exercise, but recovered in 20 minutes and were highly negatively correlated. Plasma pH at 20 minutes after 200 W exercise was significantly lower than that at rest (P<0.01), but did not change after 120 W exercise, and no correlation was found between pH and EMG. Integral electromyography (IEMG) of inactive muscles at 20 minutes after 120 W exercise was significantly lower than that at rest (P<0.05).


CONCLUSIONS
The results showed that high extra cellular K+ concentration for exercise is one of the main factors inducing fatigue and MPF decrease of the active muscles as well as IEMG decrease of the inactive muscle, but H+ is not a main factor for fatigue and it has no direct effect on EMG.
He
Wei
W
Department of Occupational Health, West China School of Public Health, Sichuan University, Chengdu 610041, China.
Wang
Mian-zhen
MZ
Wang
Zhi-ming
ZM
D000328:Adult; D004576:Electromyography; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D011188:Potassium / Q000097:blood*
D011188:Potassium