Figure 2. Representative tracing from the interpolated twitch (ITT) experiment from one subject.

A: Interpolated twitch torque tracing. Supramaximal electrical stimuli were delivered at rest (pre-MVIC twitches), during (superimposed twitch torque, SITT), and after (post-MVIC twitches) a maximal voluntary isometric contraction (MVIC). Solid black line indicates torque tracing, grey line indicates electrical muscle stimulation (e-stim). B: Expanded view of first pre-MVIC twitch. Peak Twitch Force (PTF) was defined as the highest force value after dividing by patellar tendon moment arm length and normalizing to cross-sectional area. Rate of force development (RFD) and relaxation rate (RR) were calculated in the linear phases between 15 and 85% peak twitch torque (horizontal dashed lines) after dividing by patellar tendon moment arm length and normalizing to cross-sectional area. Post-activation potentiation was defined as the percent difference in peak pre-and post-MVIC twitch torques.