Ask a PT

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Posted - 01/16/2007 :  19:32:11  Show Profile  Reply with Quote
Our user asked: "Hello, When a sprinter suddenly stops accelerating upon pulling his hamstring, what reflex is he relying on to prevent further damage? - crossed extensor - flexor - golgi tendon - muscle spindle stretch Thank you for your time."

Ask a PT Response: "It has been awhile since I have had to break down a motion and look at the various occurences involved at the levels of the muscles and joints. I'll try my best to answer your question. Lets consider what happens with the structures involved at the knee. In looking at the knee, the quadricpes and hamstrings are the muscles which are mainly involved with sprinting. The forces which are generated by these muscles are a function of its velocity. Therefore, this requires both concentric and eccentric contractions of both muscles. A concentric contraction is active shortening of a muscle, while an eccentric contraction is an active lengthening of a muscle. With a sudden stop when sprinting you will be eccentrically contracting your hamstrings to assist you in achieving the neuromotor control with coming to a stop. The hamstring tendon can become more strained as a result of this. The ACL and its mechanoreceptors will most likely assist in achieving this task as well. Looking even deeper at this situation, I believe that the Golgi Tendon Organs are most likely involved as they are most sensitive to changes that result from either stretch or contraction of a muscle. The GTO reflex is an inhibitory disynaptic reflex meaning it inhibits its own muscle and excites its antagonist. In this case inhibiting the hamstring and exciting the quadriceps. I hope this answers your question. Thank you for using CyberPT."