Dantrolene sodium and fatigue of long duration.

A long-lasting impairment of muscular force generation follows fatiguing exercise (fatigue of long duration), the physiological basis of which is not well understood. To investigate the role of reduced calcium release in long-lasting fatigue, we examined the effects of dantrolene sodium, which selectively decreases calcium release from the sarcoplasmic reticulum. The drug impaired muscle function in a pattern identical to that of long-lasting fatigue. The results are consistent with either independent effects of dantrolene and exercise at the same site in the excitation-contraction coupling chain, or independent actions at separate serial sites.