Figure 4

Mean (SD) R ² 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).