Figure 1. Motor unit (MU) recruitment and de-recruitment.

(A) The identified MU pool ranked on the recruitment order of one representative subject is shown with the underlying force profile (grey). Time points of recruitment (green) and de-recruitment (red) for each MU are marked. (B) Recruitment levels for MU1 and MU2 of the lower (blue) and higher threshold pair (red) across all subjects and days are shown with their median and quartiles. (C) Recruitment and de-recruitment threshold for the selected MUs across all days showed a significant relationship (p<0.001). Dashed line indicates the diagonal. The three subjects for whom no de-recruitment thresholds were determined were neglected in this correlation analysis.

Figure 1—figure supplement 1. High-density surface electromyogram (HDsEMG) from a single subject.

(A) HDsEMG at 10% maximum voluntary contraction (MVC) during the initial force task overlayed with the spike timing of the four selected motor units (MUs). Rectangles indicate a 10 ms window centred at the time of a detected MU action potential. (B) Spike-triggered average of the four selected MUs over 10 s at 10% MVC at the initial force task for four different locations i–iv. The locations are indicated on the schematic electrode layout on the right. Double differential signals are displayed for visualisation purposes.