Overactive Synergists Cheat Sheet

by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, H/FS

Brookbush Institute's Human Movement Science Rule #5: -

What is an overactive synergist?

An overactive synergist is a muscle that has disrupted normal recruitment patterns by adopting a more active role during joint motion; generally as a compensation for an inhibited or weak prime mover.  This phenomenon occurs at any joint where postural dysfunction or movement impairment has altered joint motion.

How does this occur?

Adaptive shortening of a muscle will generally result in hypertonicity (overactivity) of that muscle.  Over-activity alters normal reciprocal inhibition.  This alteration decreases neural drive (activity) of the functional antagonist (opposing muscle); most often the prime mover of the opposing action.  This leads to a decrease in force output for the inhibited action.  The loss is compensated for by increasing neural drive to synergistic muscles.  If this faulty motor pattern is reinforced and a movement impairment (postural dysfunction) develops, these synergists will adopt a new, compensatory level of tonicity (over-activity).

Why does this occur?

Simply, it has to.  Every time postural dysfunction leads to changes in length/tension relationships - muscles will shorten, antagonists will be inhibited, and synergists will have to step-up.  Think of synergists like the 3 interns you had