Morel Baptiste, Lapole Thomas, Liotard Cyril, Hautier Christophe
EA 7424, F-42023, Laboratoire Interuniversitaire de Biologie de la Motricité, Universite de Lyon, Université Jean Monnet Saint-Étienne, Saint-Étienne, France.
Movement-Interactions-Performance, MIP, EA 4334, F-72000, Le Mans Université, Le Mans, France.
Front Physiol. 2019 Jul 16;10:875. doi: 10.3389/fphys.2019.00875. eCollection 2019.
During high intensity exercise, metabosensitive muscle afferents are thought to inhibit the motor drive command to restrict the level of peripheral fatigue to an individual's critical threshold. No evidence exists of an individual relationship between peripheral fatigue and the decrease in voluntary activation reached after prolonged all-out exercise. Moreover, there is no explanation for the previously reported large decrease in voluntary activation despite low metabolic stress during high force contractions. Thirteen active men completed two maximal intensity isokinetic knee extension tests (160 contractions) under conditions of low force - high velocity and high force - low velocity. Neuromuscular testing including maximal torque, evoked torque and voluntary activation, was done every 20 contractions. The exponential modeling of these variables over time allowed us to predict the stable state (asymptote) and the rate of decrease (curvature constant). For both high and low force contractions the evoked torque and voluntary activation asymptotes were negatively correlated ( = 0.49 and = 0.46, respectively). The evoked torque asymptotes of the high and low force conditions were positively correlated ( = 0.49). For the high force contractions, the evoked torque and voluntary activation curvature constant were negatively correlated ( = 0.43). These results support the idea that a restrained central motor drive keeps peripheral fatigue under this threshold. Furthermore, an individual would show similar fatigue sensibility regardless of the force generated. These data also suggest that the decrease in voluntary activation might not have been triggered by peripheral perturbations during the first high force contractions.
在高强度运动期间，代谢敏感型肌肉传入神经被认为会抑制运动驱动指令，以将外周疲劳水平限制在个体的临界阈值。目前尚无证据表明外周疲劳与长时间全力运动后自愿激活的降低之间存在个体关联。此外，对于先前报道的在高负荷收缩期间尽管代谢压力较低但自愿激活却大幅下降的情况，尚无解释。13名活跃男性在低负荷 - 高速度和高负荷 - 低速度条件下完成了两次最大强度等速膝关节伸展测试（160次收缩）。每20次收缩进行一次神经肌肉测试，包括最大扭矩、诱发扭矩和自愿激活。对这些变量随时间的指数建模使我们能够预测稳定状态（渐近线）和下降速率（曲率常数）。对于高负荷和低负荷收缩，诱发扭矩和自愿激活渐近线均呈负相关（分别为(r = 0.49)和(r = 0.46)）。高负荷和低负荷条件下的诱发扭矩渐近线呈正相关（(r = 0.49)）。对于高负荷收缩，诱发扭矩和自愿激活曲率常数呈负相关（(r = 0.43)）。这些结果支持了这样一种观点，即受限的中枢运动驱动将外周疲劳保持在该阈值以下。此外，无论产生的力量如何，个体都表现出相似的疲劳敏感性。这些数据还表明，在最初的高负荷收缩期间，自愿激活的降低可能不是由外周扰动触发的。
