Integrated Neuromuscular Physiology Laboratory, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, CANADA.
Med Sci Sports Exerc. 2023 Mar 1;55(3):430-439. doi: 10.1249/MSS.0000000000003070. Epub 2022 Oct 21.
With acclimatization to high altitude (HA), adaptations occur throughout the nervous system and at the level of the muscle, which may affect motor unit (MU) characteristics. However, despite the importance of MUs as the final common pathway for the control of voluntary movement, little is known about their adaptations with acclimatization.
Ten lowlanders and Sherpa participated in this study 7 to 14 d after arrival at HA (5050 m), with seven lowlanders repeating the experiment at sea level (SL), 6 months after the expedition. The maximal compound muscle action potential (M max ) was recorded from relaxed biceps brachii. During isometric elbow flexions at 10% of maximal torque, a needle electrode recorded the MU discharge rate (MUDR) and MU potential (MUP) characteristics of single biceps brachii MUs.
Compared with SL, acclimatized lowlanders had ~10% greater MUDR, ~11% longer MUP duration, as well as ~18% lower amplitude and ~6% greater duration of the first phase of the M max (all P < 0.05). No differences were noted between SL and HA for variables related to MUP shape (e.g., jitter, jiggle; P > 0.08). Apart from lower near-fiber MUP area for Sherpa than acclimatized lowlanders ( P < 0.05), no M max or MU data were different between groups ( P > 0.10).
Like other components of the body, MUs in lowlanders adapt with acclimatization to HA. The absence of differences between acclimatized lowlanders and Sherpa suggests that evolutionary adaptations to HA are smaller for MUs than components of the cardiovascular or respiratory systems.
随着对高海拔（HA）的适应，神经系统和肌肉水平都会发生适应性变化，这可能会影响运动单位（MU）的特征。然而，尽管 MU 作为控制自主运动的最终共同途径非常重要，但对于适应高海拔环境时它们的适应性变化却知之甚少。
10 名低地人和 10 名夏尔巴人在抵达 HA（5050 米）后 7 至 14 天参加了这项研究，其中 7 名低地人在探险 6 个月后在海平面（SL）重复了实验。从放松的肱二头肌记录最大复合肌肉动作电位（M max ）。在以最大扭矩的 10%进行等长肘部弯曲时，针电极记录肱二头肌单个 MU 的 MU 放电率（MUDR）和 MU 潜力（MUP）特征。
与 SL 相比，适应的低地人 MUDR 增加了约 10%，MUP 持续时间增加了约 11%，M max 的幅度降低了约 18%，第一阶段的持续时间增加了约 6%（均 P <0.05）。与 MUP 形状相关的变量（例如抖动、抖动；P > 0.08）在 SL 和 HA 之间没有差异。除了夏尔巴人的近纤维 MUP 区域低于适应的低地人（P <0.05）之外，两组之间的 M max 或 MU 数据没有差异（P > 0.10）。
与身体的其他组成部分一样，MU 也会随着低地人对 HA 的适应而发生适应性变化。适应的低地人和夏尔巴人之间没有差异表明，MU 对 HA 的进化适应比心血管或呼吸系统的组成部分要小。
