Effects of cold stimulation of human skin on motor unit activity.
Effects of cold stimulation of human skin on motor unit activity.
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人体皮肤冷刺激对运动单位活动的影响。
DOI：
10.2170/jjphysiol.47.341
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
M. Yona
中科院分区：
文献类型：
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作者：
M. Yona
这项研究检查了运动单位（MU）的募集阈值以及维持冷感的影响，冷感介导皮肤受体的冷反射激活，这是通过用冷空气冷却皮肤产生的。在持续 3 秒的缓慢斜坡收缩（2.52 +/- 0.13 kg/s）期间测量人类二头肌运动单位阈值力的变化，同时使用固定在 -10 摄氏度的冷却箱不断降低受试者肌肉上的皮肤温度。激活肌肉上的皮肤温度范围约为 33-25 摄氏度。在相同的试验中，在两个受控的过程中对 MU 活动进行了采样。 30% 自愿等长斜坡收缩 (VIRC)，皮肤温度变化为 31、29、27 和 25 摄氏度。获得了 5 名受试者的 51 个 MU 的募集行为数据。随着皮肤温度为 25°C，阈值力降低，总共有 13/51 个 MU 被新招募。此外，从对照 (Tc) 到 25°C 的每个温度，有 38/51 个 MU 出现斜坡收缩。7/38 个 MU 的阈值力不受皮肤冷刺激的影响，但其他 MU 受刺激的影响更大。随着皮肤温度的降低，12/38 MU 的阈值力降低，19/38 MU 的阈值力增加。这些数据表明，阈值力的增加或不变会影响低振幅和低阈值力 MU (LT-MU)，而阈值力的减小会影响高振幅和高阈值力 MU (HT-MU)。所有受试者中 MU 在 Tc 下的阈值力与四个冷却温度之间是相关的。然而，除了 27-25 摄氏度外，不同回归线的斜率（系数）均随着皮肤温度的降低而明显下降（p > 0.05）。因此，这些结果表明，与外周传入神经有突触连接的 HT-MU 之间的一些募集阈值可能会发生变化，因为皮肤传入输入在所有 MU 中的贡献程度不同。
This study examined the recruitment threshold of motor units (MUs) and the effects of a maintained cold sensation that mediates the cold reflex activation of the cutaneous receptors, produced by cooling skin with cold air. The changes of the threshold force of the motor units in the human biceps muscle were measured during a slow ramp contraction (2.52 +/- 0.13 kg/s) for 3 s, while the skin temperature on the subject's muscle was continuously reduced using a cooling box fixed at -10 degrees C. The temperature range of the skin on the activated muscle was about 33-25 degrees C. In the same trials, MU activities were sampled during two controlled 30% voluntary isometric ramp contractions (VIRCs) with changes in the skin temperature to 31, 29, 27, and 25 degrees C. Data on recruitment behavior were obtained for 51 MUs in 5 subjects. A total of 13/51 MUs were newly recruited by the decrease of threshold force with the skin temperature at 25 degrees C. Also, 38/51 MUs appeared among a ramp contraction at each temperature from control (Tc) to 25 degrees C. The threshold forces of 7/38 MUs were not affected by cold stimulation to the skin, but other MUs were more affected by the stimulation. The threshold forces of 12/38 MUs were decreased and those of 19/38 MUs were increased with the reduction in skin temperature. These data suggest that either an increase or no change of the threshold force affects the low-amplitude and low-threshold-force MUs (LT-MUs), and a decrease in the threshold force affects the high-amplitude and high-threshold-force MUs (HT-MUs). The threshold force of the MUs at Tc vs four cooling temperatures was correlated in all subjects. The slope (coefficient) of the different regression line, however, clearly decreased with the reduction in skin temperature except for 27-25 degrees C (p > 0.05). Therefore, these results suggest that some recruitment thresholds might change among the HT-MUs that have synaptic connections with the peripheral afferent, because the cutaneous afferent input does not contribute to the same extent at all MUs.