Differences of Fatigability in Human Skeletal Muscles

研究了5 ~ 7例男性肩外展肌、肘屈肌、肘伸肌、膝关节屈肌、膝关节伸肌、足底屈肌和背屈肌等肌收缩力水平与肌肉疲劳发生时间的关系。耐力任务在最大自主收缩（MVC）的5、10、15、20、30、40和50%的收缩水平下进行。相对力（F %MVC）与耐力时间或疲劳时间（“darui”）和疼痛（“itai”）外观（T min）曲线拟合如下公式：logT = a +博客(f - k), 30 0 k < < = =。在耐力时间内，最拟合方程中的常数k、a、b分别为肩部内收肌3、2.02、-1.22，肘关节屈肌0、4.33、-2.52，肘关节伸肌2、3.05、-1.81，膝关节屈肌0、3.05、-1.63，膝关节伸肌8、1.96、-1.23，足底屈肌0、4.53、-2.47，背屈肌0、4.51、-2.48。在疼痛出现时，肩外展肌分别为2、1.64和-1.09，肘关节屈肌分别为0,3.33和-1.99，肘关节伸肌分别为2,2.25和-1.43，膝关节屈肌分别为0,2.94和-1.78，膝关节伸肌分别为8,1.35和-0.96，足底屈肌分别为0,3.88和-2.16，背屈肌分别为0,3.90和-2.24。在检查的肌肉群中，肩外展肌是最容易疲劳的。最不容易疲劳的是足底屈肌和背屈肌，其次是肘关节屈肌。在高收缩水平时，膝关节伸肌容易疲劳，而在非常低的收缩水平时，膝关节伸肌相对无疲劳。膝关节屈肌在高收缩水平时相对不疲劳，在低收缩水平时变得疲劳，并且表现出与肘关节伸肌相似的疲劳。

The relationship between force level of isometric contraction and time until three indices of muscular fatigue was studied for the shoulder abductors, elbow flexors, elbow extensors, knee flexors, knee extensors, plantar flexors and dorsiflexors in 5-7 males. Endurance tasks were performed at the contraction levels of 5, 10, 15, 20, 30, 40 and 50% of the maximal voluntary contraction (MVC). The relative force (F %MVC) versus the endurance time or the time of tiredness("darui") and pain("itai") appearance (T min) curves were fitted to the following equation; logT=a+blog(F-k), 0<=k<=30. In the endurance time the constants k, a and b in the most fitted equation were 3, 2.02 and -1.22 for the shoulder adbuctors, 0, 4.33 and -2.52 for the elbow flexors, 2, 3.05 and -1.81 for the elbow extensors, 0, 3.05 and -1.63 for the knee flexors, 8, 1.96 and -1.23 for the knee extensors, 0, 4.53 and -2.47 for the plantar flexors, and 0, 4.51 and -2.48 for the dorsiflexors, respectively. In the time of pain appearance these values were 2, 1.64 and -1.09 for the shoulder abductors, 0, 3.33 and -1.99 for the elbow flexors, 2, 2.25 and -1.43 for the elbow extensors, 0, 2.94 and -1.78 for the knee flexors, 8, 1.35 and -0.96 for the knee extensors, 0, 3.88 and -2.16 for the plantar flexors, and 0, 3.90 and -2.24 for the dorsiflexors, respectively. In the examined muscle groups, the shoulder abductors were the most fatigable. The least fatigable were the plantar flexors and dorsiflexors, followed by the elbow flexors. The knee extensors were fatigable at higher contraction levels, and relatively fatigueless at very low contraction levels. The knee flexors, which were relatively fatigueless at higher contraction levels, became fatigable at lower contraction levels, and showed similar fatigability as the elbow extensors.