We explored the organization of motor units recorded in the flexor digitorum superficialis into stable groups (MU-modes) and force-stabilizing synergies in spaces of MU-modes. Young, healthy participants performed one-finger and three-finger accurate cyclical force production tasks. Two wireless sensor arrays (Trigno Galileo, Delsys, Inc.) were placed over the proximal and distal portions of the muscle for surface recording and identification of motor unit action potentials. Principal component analysis with Varimax rotation and factor extraction was used to identify MU-modes. The framework of the uncontrolled manifold hypothesis was used to analyze inter-cycle variance in the space of MU-modes and compute the index of force-stabilizing synergy. Multiple linear regression between the first MU-mode in the three-finger task and the first MU-modes in the three single-finger tasks showed no differences between the data recorded by the two electrodes suggesting that MU-modes were unlikely to be synonymous with muscle compartments. Multi-MU-mode synergies stabilizing task force were documented across all tasks. In contrast, there were no force-stabilizing synergies in the three-finger task analyzed in the space of individual finger forces. Our results confirm the synergic organization of motor units in single-finger tasks and, for the first time, expand this result to multi-finger tasks. We offer an interpretation of the findings within the theoretical scheme of control with spatial referent coordinates expanded to the analysis of individual motor units. The results confirm trade-offs between synergies at different hierarchical levels and expand this notion to intra-muscle synergies.

我们探索了在屈肌浅表中记录的运动单位组织成稳定组（MU 模式）和 MU 模式空间中的力稳定协同作用。年轻、健康的参与者执行了单指和三指精确的循环发力任务。两个无线传感器阵列（Trigno Galileo，Delsys，Inc.）放置在肌肉的近端和远端部分，用于表面记录和识别运动单位动作电位。使用 Varimax 旋转和因子提取的主成分分析来识别 MU 模式。不受控流形假设框架用于分析MU模式空间中的周期间方差并计算力稳定协同指数。三指任务中的第一个 MU 模式与三个单指任务中的第一个 MU 模式之间的多元线性回归显示两个电极记录的数据之间没有差异，这表明 MU 模式不太可能与肌肉隔间。在所有任务中记录了多 MU 模式协同稳定工作组。相比之下，在单个手指力空间中分析的三指任务中没有力稳定协同作用。我们的结果证实了单指任务中运动单元的协同组织，并首次将这一结果扩展到多指任务。我们提供了对控制理论方案内的研究结果的解释，空间参考坐标扩展到对单个运动单元的分析。