Blangsted Anne Katrine, Søgaard Karen, Christensen Hanne, Sjøgaard Gisela
Department of Physiology, National Institute of Occupational Health, Lersø Parkallé 105, 2100, Copenhagen, Denmark.
Eur J Appl Physiol. 2004 Mar;91(2-3):253-8. doi: 10.1007/s00421-003-0979-z. Epub 2003 Oct 21.
The overall aim was to investigate the effect of psychosocial loads on trapezius muscle activity during computer keying work and during short and long breaks. In 12 female subjects, surface electromyography (EMG) was recorded bilaterally from the upper trapezius muscle during a standardized one hand keying task-interspaced with short (30 s) and long (4 min) breaks-in sessions with and without a combination of cognitive and emotional stressors. Adding psychosocial loads to the same physical work did not increase the activity of the trapezius muscle on either the keying or the control side, both of which remained at median and static EMG activity levels of around 5% and 2.5% of the maximal voluntary electrical activity (EMG(max)), respectively. The difference between the keying and the control side was significant; and further the control side activity was significantly increased above resting level. During both short and long breaks, exposure to psychosocial loads also did not increase the activity of the trapezius muscle either on the side of the keying or the control hand. Of note is that during long breaks the muscle activity of the keying side as well as that of the control side remained at the same level as during the short breaks, which was increased above resting level. This was to be seen from the static and the median EMG activity levels as well as gap times, the overall mean values being: 0.4%EMG(max), 1.1%EMG(max), and 50% in gap time, respectively.
psychosocial loads are not solely responsible for increased non-postural muscle activity; and increasing the duration of breaks does not per se cause muscle relaxation.
总体目标是研究心理社会负荷对计算机按键工作期间以及短期和长期休息期间斜方肌活动的影响。在12名女性受试者中，在标准化单手按键任务期间，双侧记录上斜方肌的表面肌电图（EMG），该任务间隔有短（30秒）和长（4分钟）休息时间，实验分有和没有认知与情绪应激源组合的两种情况进行。在相同的体力工作中增加心理社会负荷，并不会增加按键侧或对照侧斜方肌的活动，两者的肌电图活动水平分别维持在最大自主电活动（EMG(max)）的中位数和静态水平，约为5%和2.5%。按键侧和对照侧之间的差异显著；此外，对照侧的活动显著高于静息水平。在短期和长期休息期间，接触心理社会负荷也不会增加按键侧或对照侧斜方肌的活动。值得注意的是，在长期休息期间，按键侧和对照侧的肌肉活动与短期休息期间保持在同一水平，且高于静息水平。这可以从静态和中位数肌电图活动水平以及间隙时间看出，总体平均值分别为：0.4%EMG(max)、1.1%EMG(max)和间隙时间的50%。
心理社会负荷并非导致非姿势性肌肉活动增加的唯一原因；增加休息时间本身并不会导致肌肉放松。
