Electromyogram Activation Reflects Property of Isochrony Phenomenon During Cyclic Human Arm Movement

Hiroshi Yokoyama, Rie Kurai, Isao Nambu, Yasuhiro Wada

Abstract: The isochrony principle is a well-known phenomenon, whereby the speed of human arm movement is regulated to increase as its planned trajectory distance increases. The isochrony principle is observed in many studies, but its relationship with the motor planning process has never been explained. To address this issue, we attempt to explain the relationship between the isochrony principle and trajectory planning based on observable physiological information. Assuming that electromyography (EMG) reflects the temporal aspect of motor commanded signals, we directly evaluated the EMG changes during cyclic arm movement to consider the physiological mechanism underlying the isochrony phenomenon. Our presented result suggested the tendency that duration-average of the EMG change is equal, regardless of the differences in the movement distance. Its tendency suggest experimental evidence that human arm trajectory is planned to ensure constant EMG changes, rather than for equalization of movement durations.