运动所致血浆K+和血pH值的变化对肌肉疲劳和表面肌电图的影响

目的探讨血K^ 、H^ 与肌肉疲劳和肌电变化的关系。方法对同一批受试者在200W和120w蹬功率车之前和运动至疲劳后即刻、5min、10min、20min时，测定血浆K^ 、血pH值以及活动肌和非活动肌定量负荷等长收缩10s的肌电图(EMG)。结果两次运动后血浆K^ 和活动肌平均功率频率(AM—MPF)均明显改变(P＜0．01)，二者高度负相关，并在20min时基本恢复。200W运动后20min内血pH值一直明显低于安静值(P＜0.01)，但在120w运动后无变化，并与肌电无相关关系。120W运动后20min内的非活动肌积分肌电图值(IM—IEMG)明显低于安静值(P＜0．05)。结论细胞外高K^ 是肌肉疲劳和AM—MPF下降的主要因素之一，并可能也是IM—IEMG下降的原因之一。H^ 不是疲劳形成的主因，并对肌电无直接影响。

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). Conclusion 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.