Individual raw data used in the analysis.

The detailed distribution of muscle activity within the biceps brachii (BB) muscle during isometric contraction as contraction intensity increases is not yet fully understood using multichannel surface electromyography (EMG). This study aimed to elucidate the distribution of muscle activity within the BB muscle during isometric contractions using monopolar and bipolar recording methods with multichannel surface EMG. The participants were 23 healthy young adults who performed a gradually increasing load task involving right elbow flexion for 10 seconds. The results showed that muscle activity was higher in the proximal medial area from the middle region with the monopolar recording method, and higher in the central medial area with the bipolar recording method as contraction intensity increased. These results with the monopolar recording method were consistent with previous reports regarding the increased shortening rate of the BB muscle from the middle to the proximal area and the migration of the innervation zone. Therefore, the monopolar recording method of multichannel surface EMG is considered more suitable for clarifying the detailed distribution of muscle activity within the same muscle.采用多通道表面肌电图（multichannel surface electromyography, EMG）技术，目前尚未完全明确随收缩强度递增时，肱二头肌（biceps brachii, BB）内部肌肉活动的详细分布特征。本研究旨在借助多通道表面肌电图的单极记录法（monopolar recording method）与双极记录法（bipolar recording method），阐明等长收缩（isometric contraction）过程中肱二头肌内部的肌肉活动分布情况。本研究招募23名健康青年受试者，要求其完成持续10秒的右侧肘关节屈曲渐进式负荷任务。研究结果显示：随着收缩强度提升，采用单极记录法时，肌肉活动在中部区域至近端内侧区域的范围内水平更高；而采用双极记录法时，肌肉活动在中央内侧区域更高。单极记录法所得的上述结果，与既往关于肱二头肌从中部区域向近端区域缩短速率提升、神经支配区（innervation zone）迁移的研究报道相符。因此，多通道表面肌电图的单极记录法被认为更适用于阐明单块肌肉内部肌肉活动的详细分布特征。