Effect of muscle coactivation on spinal feedback processing

Determine whether and how muscle coactivation of agonist and antagonist muscles alters the processing of spinal short-latency proprioceptive feedback circuits (SLRmechanical) during upper-limb motor tasks that involve mechanical perturbations.

Background

The paper reviews decades of work on proprioceptive feedback processing and highlights that most experiments have used background loads to pre-excite one muscle while reciprocally inhibiting its antagonist, thereby emphasizing reciprocal patterns of muscle activity. Muscle coactivation, in contrast, requires simultaneous excitation of agonist and antagonist muscles and thus fundamentally different neural control.

Because coactivation engages both muscle groups, the authors argue that it is difficult to generalize findings from reciprocal activation paradigms to coactivation, leaving uncertain how even the fastest spinal circuits process proprioceptive input when muscles are coactivated.