Figure 1.

Schematic of muscle synergy combination. Each muscle synergy is a time-invariant unit vector across muscles (W), and scaled by a time-varying activation coefficient (C). The waveforms from the synergies are linearly summed to explain the EMGs normalized to maximum voluntary contraction (MVC) of the muscles. The quantities whose variability are correlated to performance measures here – W, trial maximum of C (C_max), and time interval between C_max's of synergy pairs – are marked by blue asterisks. Figure adapted from [42].