Coordination of arm and leg movements.

<p>A – arm and leg kinematics and EMGs in one representative participants performing hand-walking at 2 km/h and voluntary air-stepping. The left portion of each panel shows the oscillations of left upper and lower limbs accompanied by respective EMG activity of some representative muscles. Grey areas demarcate single limb cycles defined separately for arms and legs as the time between two consecutive maxima in the a-p displacement of the respective endpoint. The right portion of each panel displays the Fourier spectra derived from the signals on their left. Dashed lines show the position of the first five multiples of the fundamental frequency (f1) whose percentage of variance explained is displayed (PV_f1). B – mean (±SD, n = 9) peak frequencies of EMGs and corresponding arm (upper plot) and leg (middle plot) kinematic patterns for hand-walking at different speeds and for voluntary leg air-stepping (vol.). Lower plot represent the phase (relative to the onset of leg cycle) of the first harmonic for leg EMGs and thigh and shank elevation angles (zero corresponds to the cosine function with zero time shift). Only EMGs with peak activity greater than 2 µV and PV_f1>20% were included in this analysis.