Fasciculation frequency changes at different length of relaxed muscle.

We have studied, in chronically denervated muscles, fasciculation potentials (FPs) which were clearly identified when the muscles were either relaxed or passively stretched. The frequency of 10 FPs was determined in both positions in seven patients. In stretched muscles, two FPs were no longer recorded, and the mean FP frequency decreased significantly (P < .01). There was also a decrease of the FP amplitude. As FPs are frequently associated with ordinary muscle cramps, stretching of the muscle may lessen the frequency of FPs by the same mechanism which stops cramps.