Fig. 2.

Comparison of recruitment and fatigue between FOS and FES. a Comparison of electrical and optical stimulation for CL control. CL-FES uses a more constant stimulation profile as compared to the growing profile of CL-FOS, corresponding to its motor unit recruitment pattern. b System response (black) to cyclic CL square wave pattern (red) alternating between rest and plantar flexion (FOS: 1.25 ms PW, 40 Hz, T_i = 5E−6 s⁻¹, K_p = 1E−2; FES: 100 µs PW, 40 Hz, T_i = 4E−4 s⁻¹, K_p = 5E−3). Percent change in stimulation (blue) calculated by comparing the peak value during each cycle with the value during the first cycle. c Percent error in system response from desired angle for FES and FOS systems over the time course of stimulation. These representative data were drawn from trials performed in rats