Dai Wen-tao, Zhang Fei-ruo, Wang Zheng-lun, Yang Lei
School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi. 2006 Apr;24(4):201-4.
To evaluate the influence of the frequency, the weight and the motion angle on the stress and the fatigue of the forearm extensors in repetitive wrist extending at low force loading level with surface electromyography (SEMG).
Sixteen male college student volunteers were recruited for the experiment. Eight tasks of wrist extending were performed for 20 minutes respectively in given weight (1.96, 4.90 N), frequency (8.0, 33.3 moves/minute) and motion angle (45 degrees, 90 degrees). The static wrist extending at the level of 20% maximum voluntary contraction (MVC) were performed before and after each task for 2 up to 3 seconds, and the SEMG signals of extensor carpi ulnaris muscle (ECU) and extensor digitorum (ED) were recorded and analyzed.
The weight loading level was approximately equal to 1.40% or 3.50% of the MVC force. The mean power frequency (MPF) and the median frequency (MF) were decreased with the increase of 3 kinds of loading levels. The decrease of MPF of the muscle ED was significant (P < 0.05 or P < 0.01). The MF was decreased with the increase of angle and weight loading levels (P < 0.05 or P < 0.01). The root mean square (RMS) value of SEMG could be divided into 3 or 4 groups with significant difference. All three kinds of loads had positive correlation with amplitude of SEMG according to the stepwise regression analysis.
The fatigue level of ED is the highest. The primary load factor for the forearm extensors is the frequency followed by the weight and the angle. MF, MPF and RMS can be used as sensitive indexes for evaluating the stress and the fatigue of the forearm extensors during repetitive performance at lower force loading level.
采用表面肌电图（SEMG）评估在低负荷水平下重复腕伸展时，频率、重量和运动角度对前臂伸肌应力及疲劳的影响。
招募16名男性大学生志愿者参与实验。分别在给定重量（1.96、4.90 N）、频率（8.0、33.3次/分钟）和运动角度（45度、90度）下进行8项腕伸展任务，每项任务持续20分钟。在每项任务前后进行2至3秒的20%最大自主收缩（MVC）水平的静态腕伸展，记录并分析尺侧腕伸肌（ECU）和指伸肌（ED）的SEMG信号。
重量负荷水平约等于MVC力的1.40%或3.50%。随着三种负荷水平的增加，平均功率频率（MPF）和中位频率（MF）降低。指伸肌的MPF降低显著（P<0.05或P<0.01）。MF随着角度和重量负荷水平的增加而降低（P<0.05或P<0.01）。SEMG的均方根（RMS）值可分为3或4组，差异显著。根据逐步回归分析，所有三种负荷与SEMG幅度均呈正相关。
指伸肌的疲劳程度最高。前臂伸肌的主要负荷因素是频率，其次是重量和角度。MF、MPF和RMS可作为评估低负荷水平重复运动时前臂伸肌应力及疲劳的敏感指标。
