Differences of Fatigability in Human Skeletal Muscles

本文研究了5-7名男性肩外展肌、肘屈肌、肘伸肌、膝屈肌、膝伸肌、跖屈肌和背屈肌等长收缩力与三项肌肉疲劳指标出现时间的关系。耐力任务在最大随意收缩（MVC）的5，10，15，20，30，40和50%的收缩水平下进行。将相对力（F %MVC）对耐受时间或疲劳（“darui”）和疼痛（“itai”）出现时间（T min）的曲线拟合为以下方程：logT=a+blog（F-k），0 ≤ k ≤ 30。在耐力时间中，最佳拟合方程中的常数k、a和B分别为：肩收肌3、2.02和-1.22，手肘屈肌0、4.33和-2.52，手肘伸肌2、3.05和-1.81，膝屈肌0、3.05和-1.63，膝伸肌8、1.96和-1.23，跖屈肌分别为0、4.53和-2.47，背屈肌分别为0、4.51和-2.48。在疼痛出现时，肩外展肌的这些值分别为2、1.64和-1.09，手肘屈肌为0、3.33和-1.99，手肘伸肌为2、2.25和-1.43，膝屈肌为0、2.94和-1.78，膝伸肌为8、1.35和-0.96，背屈肌分别为0、3.90和-2.24。在所检查的肌肉群中，肩外展肌最易疲劳。最不容易疲劳的是跖屈肌和背屈肌，其次手肘屈肌。膝伸肌在较高的收缩水平下易疲劳，而在非常低的收缩水平下相对不疲劳。膝屈肌在较高的收缩水平下相对不疲劳，在较低的收缩水平下变得疲劳，并且表现出与手肘伸肌相似的疲劳性。

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.