Fig. 4

Measurements of the force produced by the quadriceps muscle group in subject P3 during Experiment 1, under two conditions: a) moderate electrical stimulation intensity (80 mA) and b) high electrical stimulation intensity (130 mA). Forces produced by the quadriceps muscle group under SDSS and SES electrode configurations are represented by red and blue lines, respectively. Horizontal black lines indicate the time to fatigue (TTF), and the shaded areas under the force-time curves represent the force-time integral (FTI)