Mean (SD) R
values between predicted and actual EMG signals. (A) Mean R2 values across different muscles during unloaded (open bars) and loaded (filled bars) movements. ANOVA indicated no significant effect on R2 of movement type but a significant effect of muscle (P < 0.001) and a significant interaction (P < 0.001) between the factors muscle and movement type. Post hoc analysis indicated a significant (P < 0.01) difference (*) in R2 when comparing loaded to unloaded movements for just two muscles: brachialis and brachioradialis (muscle abbreviations as in Figure 1). (B) Effect of training set on predictions of different test data sets. Each bar represents mean (SD) R2 value across all subjects and muscles for each training set/test set combination. R2 for the condition in which the training set was obtained from unloaded movements and used to predicted loaded-movement EMG was significantly lower (P < 0.05, *) than that of all the other conditions. In addition, R2 values for the condition in which the training set was obtained from loaded movements but used to test unloaded movements were significantly lower (P < 0.05, **) than that when training and test sets both included included loaded movements (bar 2).