Fig. 3.

Activation patterns of antagonistic muscles in the normal and MPTP states of Monkey Z. A,Normal; B, MPTP.Top, Output of accelerometer attached to the wrist of the working arm. Bottom, EMG recording from biceps and triceps of the working arm. Calibration: horizontal, 1 sec; vertical (accelerometer traces), 0.5 g (=490 cm × sec⁻²). Scale of EMG is arbitrary. Note the tri-phasic pattern of muscle activation (biceps leading) in the normal voluntary movement, in contrast to the completely overlapping co-contraction in the MPTP movements.