Abstract：
It is important to understand the effects of rapid changes in weight on neuromuscular functions of combat athletes. The purpose of this case study was to investigate time-course changes in muscle strength, muscle size, and neural input during rapid weight loss in a professional boxer. One professional male boxer (26 yr) participated in two matches during measurements: welterweight (66.6 kg; weight loss: WL) and super welterweight (69.85 kg; control: CON). His muscle contraction properties and body composition were measured from 6 wk (baseline) before the matches to 1 wk after them. Maximal voluntary isometric knee extension torque, muscle cross-sectional area (mCSA) of the vastus lateralis using ultrasound, and high-density surface electromyography of the vastus lateralis during submaximal ramp-up contraction were measured. Individual motor units were identified, and modified discharge rates were calculated from a regression line between the recruitment threshold and discharge rates at 60%-70% of maximum torque according to the baseline value. His body weights for WL and CON decreased from 70.80 and 71.42 kg at the baseline to 68.75 and 71.36 kg immediately before the matches, respectively. Muscle strength changed little for either match. For WL, skeletal muscle mass and mCSA decreased, but there was no decrease for CON. The modified motor unit discharge rate for WL increased immediately before the match compared with other periods but did not change for CON. After rapid weight loss, neural input increased to compensate for lost muscle mass, and muscle strength was maintained.NEW & NOTEWORTHY This case study found that neural input to muscle, which was evaluated by high-density surface electrocardiography, increased to compensate for the decline of body weight and muscle mass and to maintain muscle strength during rapid weight loss, while neuromuscular characteristics were not markedly changed during no significant weight loss.
摘要：
了解体重快速变化对战斗运动员神经肌肉功能的影响很重要。本案例研究的目的是调查肌肉力量的时程变化，肌肉大小,在职业拳击手中快速减肥过程中的神经输入。一名职业男拳击手（26岁）在测量期间参加了两场比赛：中量级（66.6公斤；体重减轻：WL）和中量级（69.85公斤；对照：CON）。从比赛前6周（基线）到比赛后1周测量他的肌肉收缩特性和身体组成。最大自愿性等距膝盖伸展扭矩，使用超声波测量股外侧肌的肌肉横截面积（mCSA），并测量了最大斜升收缩期间股外侧肌的高密度表面肌电图。确定了单个电机单元，和修正后的出院率是根据基线值在最大扭矩的60%-70%时从募集阈值和出院率之间的回归线计算的.他的WL和CON体重从基线时的70.80和71.42公斤下降到比赛前的68.75和71.36公斤，分别。两次比赛的肌肉力量变化不大。对于WL，骨骼肌质量和mCSA减少，但CON没有减少。与其他时段相比，WL的修改后的电动机单位放电率在比赛前立即增加，但对于CON则没有变化。快速减肥后，神经输入增加以补偿丢失的肌肉质量，肌肉力量得以维持。这个案例研究发现，神经输入到肌肉，通过高密度体表心电图进行评估，增加以补偿体重和肌肉质量的下降，并在快速减肥期间保持肌肉力量，而在无明显体重减轻期间，神经肌肉特征没有明显变化。
