Kilbom A, Hägg G M, Käll C
National Institute of Occupational Health, Division of Applied Work Physiology, Solna, Sweden.
Eur J Appl Physiol Occup Physiol. 1992;65(1):52-8. doi: 10.1007/BF01466274.
A group of 5 women and 11 men walked on a treadmill, each carrying a weight in the right hand. In separate experiments, the mass was varied to give total exhaustion within 3 min, 5 min, 9 min, and 13 min. In additional experiments 50% and 25% of the masses leading to exhaustion after 5 min were used, and these were stopped after 16 min. Heart rate (fc) and systolic blood pressure (BPs) were measured noninvasively. There was a consistent increase in fc x BPs during the experiments leading to exhaustion, while steady-states were obtained in the nonexhausting trials. An electromyogram (EMG) was recorded with cutaneous electrodes over the flexor carpi ulnaris and flexor digitorum superficialis muscles and the number of zero crossings (ZC) of the EMG signal per time unit were analysed. As the subjects approached exhaustion, the number of ZC declined exponentially, reaching approximately 50% of their initial values. In the nonexhausting experiments, however, the decline was slower and less marked, and during the second half of the experiment the number of ZC increased again. Subjectively, endurance was underestimated by all the subjects. It was concluded that cardiovascular and muscle criteria of fatigue in carrying coincided. Prolonged carrying in one hand of more than 6 kg or 10 kg for young healthy women and men respectively should not be recommended, since it could lead to cardiovascular non steady-states and EMG signs of fatigue.
一组5名女性和11名男性在跑步机上行走，每人右手都拿着一个重物。在不同的实验中，改变重物的质量，以使受试者在3分钟、5分钟、9分钟和13分钟内达到完全疲劳。在另外的实验中，使用了导致5分钟后疲劳的重物质量的50%和25%，并在16分钟后停止。通过无创方式测量心率（fc）和收缩压（BPs）。在导致疲劳的实验过程中，fc×BPs持续增加，而在未导致疲劳的试验中获得了稳定状态。用皮肤电极记录尺侧腕屈肌和指浅屈肌的肌电图（EMG），并分析单位时间内EMG信号的过零次数（ZC）。随着受试者接近疲劳，ZC数量呈指数下降，降至初始值的约50%。然而，在未导致疲劳的实验中，下降较慢且不太明显，并且在实验的后半段，ZC数量再次增加。主观上，所有受试者都低估了耐力。得出的结论是，负重时心血管和肌肉疲劳标准是一致的。对于年轻健康的女性和男性，分别不建议单手长时间负重超过6公斤或10公斤，因为这可能导致心血管非稳定状态和EMG疲劳迹象。
