Abstract：
The aim of the present study was to investigate the acute effect of caffeine or quercetin ingestion on motor unit firing patterns and muscle contractile properties before and after resistance exercise. High-density surface electromyography (HDs-EMG) during submaximal contractions and electrically elicited torque in knee extensor muscles were measured before (PRE) and 60 min after (POST1) ingestion of caffeine, quercetin glycosides, or placebo, and after resistance exercise (POST2) in ten young males. The Convolution Kernel Compensation technique was used to identify individual motor units of the vastus lateralis muscle for the recorded HDs-EMG. Ingestion of caffeine or quercetin induced significantly greater decreases in recruitment thresholds (RTs) from PRE to POST1 compared with placebo (placebo: 94.8 ± 9.7%, caffeine: 84.5 ± 16.2%, quercetin: 91.9 ± 36.7%), and there were significant negative correlations between the change in RTs (POST1-PRE) and RT at PRE for caffeine (rs = - 0.448, p < 0.001) and quercetin (rs = - 0.415, p = 0.003), but not placebo (rs = - 0.109, p = 0.440). Significant positive correlations between the change in firing rates (POST2-POST1) and RT at PRE were noted with placebo (rs = 0.380, p = 0.005) and quercetin (rs = 0.382, p = 0.007), but not caffeine (rs = 0.069, p = 0.606). No significant differences were observed in electrically elicited torque among the three conditions. These results suggest that caffeine or quercetin ingestion alters motor unit firing patterns after resistance exercise in different threshold-dependent manners in males.
摘要：
本研究的目的是研究咖啡因或槲皮素摄入对抵抗运动前后运动单位放电模式和肌肉收缩特性的急性影响。在摄入咖啡因之前（PRE）和之后（POST1）60分钟测量亚最大收缩期间的高密度表面肌电图（HDs-EMG）和膝关节伸肌的电引起的扭矩，槲皮素苷，或安慰剂，10名年轻男性进行抵抗运动(POST2)后。卷积核补偿技术用于识别记录的HDs-EMG的股外侧肌的各个运动单位。与安慰剂相比，摄入咖啡因或槲皮素可导致从PRE到POST1的募集阈值（RTs）显着降低（安慰剂：94.8±9.7％，咖啡因：84.5±16.2%，槲皮素：91.9±36.7%），咖啡因（rs=-0.448，p<0.001）和槲皮素（rs=-0.415，p=0.003）的RTs（POST1-PRE）和PRE时的RT变化之间存在显着负相关，但不是安慰剂（rs=-0.109，p=0.440）。安慰剂（rs=0.380，p=0.005）和槲皮素（rs=0.382，p=0.007）在PRE时观察到放电率（POST2-POST1）和RT之间的显着正相关，但不是咖啡因（rs=0.069，p=0.606）。在这三种情况下，电引起的扭矩没有显着差异。这些结果表明，咖啡因或槲皮素的摄入会在男性以不同的阈值依赖性方式进行抵抗运动后改变运动单位的射击模式。
