Fig. 1.

Voluntary torque (thick line) and rectified surface EMG of the vastus lateralis muscle (thin line) time traces, obtained from a representative subject during an isometric voluntary knee extension performed as fast and forcefully as possible. The arrow and diamond at time 0 ms indicate the start of voluntary torque development. The shaded area under the voluntary torque trace reflects the vTTI₄₀, calculated the first 40 ms after onset of torque development. The horizontal bar indicates the 40 ms immediately preceding the onset of torque development (i.e., from −40 to 0 ms) for which the root mean square (RMS) of the surface EMG was calculated. Subsequently, both vTTI₄₀ and RMS_−40–0 were normalized to the steady state maximal isometric knee extension condition at the day of testing