Originally Posted by
datlas
Hey
MoAlpha I have a muscle cramp issue. It's probably a variation of the usual muscle over-exertion cramps, but these cramps have been having a delayed onset.
Typical history is I go on a long, hard ride (like yesterday), but don't cramp on the ride. I come home and rest for an hour or two...at which point ANY minor muscle movement of lower extremities causes severe muscle cramps. This happened yesterday and was VERY unpleasant and it lasted for at least a few hours. Involved mostly quads/hamstrings/calf/flexor hallucis longus (big toe goes up with severe pain in side of calf). I don't know if there is much to do other than stretch and accept it, but any ideas on the pathophysiology and more importantly, treatment for these?
I have exactly the same thing. In fact, last night I rolled over into a huge hamstring spasm which I somehow managed to stretch and will into subsiding.
According to the prevailing theory, the cause is hyperactivity of the muscle stretch reflex, which, as you may remember, goes from the muscle spindles (muscle length receptors) to the spinal segment via the 1a afferents, which excite the alpha motoneurons back to the same muscle monosynaptically, causing muscle shortening, as in the classic tendon reflexes we test in the clinic. However, in the fatigued state, hyperexcitability in somewhere in the afferent side of the loop can send the muscle into spasm in response to a minor stimulus.
There is an opposing system composed of the Golgi tendon organs (contraction force detectors) which inhibit the spinal motoneurons via the 1b afferents and an inhibitory interneuron. This is the system we recruit by stretching. I believe there is also evidence that it is under-active in the exercise-fatigued state.
Why this happens I don’t think anyone knows. However, there are fairly good cross sectional studies looking at serum chemistry in athletes after hard events and there are no correlations with cramping. This doesn’t rule out helpful pharmacological effects of stuff like Mg++, which may be helpful in nocturnal cramping unrelated to exercise, but that may have a different mechanism.
That’s all what I can tell you, but it’s a cool area and I was a board certified clinical neurophysiologist in my yoot, so I’ll keep looking into it.