Laboratory of Physiomechanics of Locomotion, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy.
School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada.
Acta Physiol (Oxf). 2022 Apr;234(4):e13788. doi: 10.1111/apha.13788. Epub 2022 Jan 25.
Ascent to high altitude is accompanied by a reduction in partial pressure of inspired oxygen, which leads to interconnected adjustments within the neuromuscular system. This review describes the unique challenge that such an environment poses to neuromuscular fatigability (peripheral, central and supraspinal) for individuals who normally reside near to sea level (SL) (<1000 m; ie, lowlanders) and for native highlanders, who represent the manifestation of high altitude-related heritable adaptations across millennia. Firstly, the effect of acute exposure to high altitude-related hypoxia on neuromuscular fatigability will be examined. Under these conditions, both supraspinal and peripheral fatigability are increased compared with SL. The specific mechanisms contributing to impaired performance are dependent on the exercise paradigm and amount of muscle mass involved. Next, the effect of chronic exposure to high altitude (ie, acclimatization of ~7-28 days) will be considered. With acclimatization, supraspinal fatigability is restored to SL values, regardless of the amount of muscle mass involved, whereas peripheral fatigability remains greater than SL except when exercise involves a small amount of muscle mass (eg, knee extensors). Indeed, when whole-body exercise is involved, peripheral fatigability is not different to acute high-altitude exposure, due to competing positive (haematological and muscle metabolic) and negative (respiratory-mediated) effects of acclimatization on neuromuscular performance. In the final section, we consider evolutionary adaptations of native highlanders (primarily Himalayans of Tibet and Nepal) that may account for their superior performance at altitude and lesser degree of neuromuscular fatigability compared with acclimatized lowlanders, for both single-joint and whole-body exercise.
海拔升高伴随着吸入氧气分压的降低，这会导致神经肌肉系统的相互关联的调整。本篇综述描述了这种环境对神经肌肉疲劳性（外周、中枢和脊髓上）所带来的独特挑战，这些挑战对象包括通常居住在海平面附近（<1000 米；即低地居民）的个体，以及代表数千年来与高海拔相关的遗传适应性的本地高原居民。首先，将检查急性暴露于与高海拔相关的低氧环境对神经肌肉疲劳性的影响。在这些条件下，与海平面相比，脊髓上和外周疲劳性都增加了。导致表现下降的具体机制取决于运动范式和涉及的肌肉量。接下来，将考虑慢性暴露于高海拔（即 7-28 天的适应）的影响。随着适应，无论涉及多少肌肉量，脊髓上疲劳性都恢复到海平面值，而外周疲劳性仍高于海平面，除非运动涉及少量肌肉量（例如，膝关节伸展肌）。事实上，当涉及全身运动时，外周疲劳性与急性高海拔暴露没有区别，这是由于适应对神经肌肉性能的正面（血液学和肌肉代谢）和负面（呼吸介导）影响相互竞争的结果。在最后一节中，我们考虑了本地高原居民（主要是西藏和尼泊尔的喜马拉雅人）的进化适应，这可能解释了他们在高海拔地区的优异表现，以及与适应的低地居民相比，他们的神经肌肉疲劳性较小，无论是单关节运动还是全身运动。
