Figure 3.

Extraction of the dynamic components within the averaged EMG records (see detailed description in the text). The same procedure was applied to analyse the reactions in both the flexor (A) and extensor (B) muscles. First, the amplitude of the static component E_st was determined by averaging the EMG activities over 2 s periods ΔT₁ prior to the end of the hold phases in the test movements. Finally, the time course of the static components in the EMGs was assumed to repeat the time course of the angle changes in the corresponding joint; Equation (5) had been proposed for its description (shown by the gray lines in the second row from top). The dynamic EMG components were determined using the difference between the initial EMG record and the static component evaluation E_st. In flexors, the resulting dynamic components E_dyn = E−E_st predominantly include two different waves of activity connected directly with the phases of active muscle shortening (D_P) or lengthening (D_R). If the E_dyn traces are compared with the first derivative of the movement records (dα_e/dt), one can conclude that the durations of D_P and D_R waves exceed the durations of the movement phases. Therefore, for the correct assessment of the areas of the components, the integration times were elongated 1.5 times with respect to the duration of the derivative waves (lines Δt₁ and Δt₂ in the bottom panels, dα_e/dt graphs). The EMG calibration is given in % of MVC.