Neural coupling between the arms and legs during rhythmic locomotor-like cycling

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J Neurophysiol. 2006 Oct 25

Neural coupling between the arms and legs during rhythmic locomotor-

like cycling movement.

Balter JE, Zehr EP.

Rehabilitation Neuroscience Laboratory, University of ,

, Canada.

Neuronal coupling between the arms and legs allowing coordinated

rhythmic movement during locomotion is poorly understood. We used

the modulation of cutaneous reflexes to probe this neuronal coupling

between the arms and legs using a cycling paradigm. Participants

performed rhythmic cycling with arms, legs, or arms and legs

together (ARM & LEG).

We hypothesized that any contributions from the arms would be

functionally linked to locomotion and would thus be phase-dependent.

Reflexes were evoked by electrical stimulation of the superficial

peroneal nerve at the ankle and EMG was recorded from muscles in the

arms and legs. The main finding was that the relative contribution

from the arms and legs was linked to the functional state of the

legs.

For example, in TA the largest contribution from arm movement (57%

variance accounted for (VAF), p< .05) was during the leg power phase

while the largest from leg movement (71% VAF, p< .05) was during leg

cycling recovery.

Thus, the contribution from the arms was functionally gated

throughout the locomotor cycle in a manner that appears to support

the action of the legs. Additionally, the effect of arm cycling on

reflexes in leg muscles when the legs were not moving was relatively

minor; full expression of the effect of rhythmic arm movement was

only observed when both the arms and legs were moving.

Our findings provide experimental support for the interaction of

rhythmic arm and leg movement during human locomotion.