Piedrahita Hugo, Oksa Juha, Malm Christer, Sormunen Erja, Rintamäki Hannu
Human Work Sciences Department, Luleå University of Technology, 97187, Luleå, Sweden.
Eur J Appl Physiol. 2008 Sep;104(2):183-91. doi: 10.1007/s00421-007-0657-7. Epub 2007 Dec 20.
The present study was designed to find out if cooling and/or clothing affect the vertical trajectories and muscle function of the upper arm during repetitive light work. Twelve female subjects performed a one-handed lifting task for 60 min while standing in front of a table with six target angles (30 degrees to 220 degrees ). The experiment was carried out in a climatic chamber in three different conditions: at 10 degrees C (C), at 25 degrees C (TN), and at 10 degrees C dressed in cold-protective clothing (C(p)). Skin and rectal temperatures were measured continuously. The vertical trajectories of the head, shoulder, elbow, and wrist on the right side of the body were recorded. Muscular strain (averaged EMG, a-EMG) and EMG gaps in eight muscles on the right upper arm were measured. The variation of the vertical trajectory amplitude of the upper arm measured from the elbow was significantly higher (at 200 degrees ) both at C and C(p) (50 and 25% respectively) and in shoulder (at 220 degrees angle) at C (33%) compared with TN (P < 0.05). Both C and C(p) increased a-EMG and reduced the number and duration of EMG gaps significantly in all muscles studied. In conclusion, in repetitive tasks the high mean vertical trajectory and changes in the amplitude of the trajectory of the upper arm at C and C(p) compared with TN were associated with increased muscular strain and reduced number of EMG gaps (more continuous activation of given muscle fibers). The changes in trajectories may serve as indicator of a risk for local muscle fatigue.
本研究旨在探究在重复性轻度工作期间，降温及/或着装是否会影响上臂的垂直轨迹和肌肉功能。12名女性受试者站在一张有六个目标角度（30度至220度）的桌子前，进行单手举重任务60分钟。实验在气候舱内的三种不同条件下进行：10摄氏度（C）、25摄氏度（TN）以及穿着防寒服处于10摄氏度（C(p)）。连续测量皮肤和直肠温度。记录身体右侧头部、肩部、肘部和腕部的垂直轨迹。测量右上臂八块肌肉的肌肉应变（平均肌电图，a-EMG）和肌电图间隙。与TN相比，在C和C(p)条件下，从肘部测量的上臂垂直轨迹振幅变化在200度时显著更高（分别为50%和25%），在C条件下肩部在220度角时也显著更高（33%）（P < 0.05）。C和C(p)均显著增加了所有研究肌肉的a-EMG，并减少了肌电图间隙的数量和持续时间。总之，在重复性任务中，与TN相比，C和C(p)条件下上臂较高的平均垂直轨迹和轨迹振幅变化与肌肉应变增加及肌电图间隙数量减少（特定肌纤维更持续的激活）相关。轨迹变化可能是局部肌肉疲劳风险的一个指标。
