Effect of normalization method on the estimated level of muscle activation.

Data from each participant (n = 25, 18 males) of electromyographic activity (EMG) in each contraction level normalized to maximal EMG as a function of voluntary activation (panels A-C), EMG normalized to Mmax as a function of voluntary activation (panels D-F), and EMG normalized to maximal EMG as a function of EMG normalized to Mmax (panels G-I) for soleus (SO, panels A, D, G), medial gastrocnemius (MG, panels B, E, H) and lateral gastrocnemius (LG, panels C, F, I) muscles. Slopes of lines in panels G-I indicate scaling factors for participants and muscles.