P&P #39. The Myotatic Setch Reflex May Not Facilitate Joint Protection in Certain Situations
We all learn and accept that the myotatic and other reflexes serve as involuntary control mechanisms to prevent a joint from being taken beyond its safe anatomical range of movement. However, during actions such as elbow, shoulder and knee flexion near their respective ends of range, the myotatic action either is insignificant or too slow to prevent the joint from being hyperflexed, particularly if the joint is heavily or rapidly loaded.
Test this for yourself by bouncing in a full squat position or have someone forcibly flex your forearm further while your elbow is fully flexed. Similar apparent inadequacies of reflex protection occur during many rotational actions about the joints. In fact the effectiveness of reflex protection seems to diminish in many cases as the end of joint range is reached, when it would appear logical that reflex protection should be greater and more rapid. Does this imply deficiencies in the reflex systems of the human body? Can these deficiencies be overcome by appropriate training? Does this imply that humans were not intended to perform loaded or rapid end-of-range movements?
Does this not suggest that current rehabilitation with slow terminal action or isokinetic mid-range resistance does not adequately address the underlying neuromuscular mechanisms? Is our understanding of protective reflex mechanisms sufficient for us to understand human movement or prescribe exercise competently?
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