Seasonal variation in muscle fatigue in the sartorius muscle of the frog Rana pipiens

Abstract

The goal of this study was to determine whether seasonal variation occurs in the rates of fatigue development and force recovery in the frog sartorius muscle. The data were gathered from different experiments performed during a 6-year period (1983–1989). All frog sartorius muscles were stimulated to fatigue with tetanic contractions at the rate of 1/s for 3 min. The decrease in tetanic force after 1.5 and 3 min of stimulation was relatively consistent throughout the year. The only significant difference occurred in the muscles tested in September and October, which were less fatigue resistant than those tested in December. Following fatigue, muscles were stimulated at the rate of one contraction every 100 s, so that the recovery of tetanic force could be followed. A large and significant seasonal variation was observed in the recovery period. Frog sartorius muscles tested between March and July recovered their tetanic force at a faster rate than those tested between August and October. It was shown that the highest capacity to recover force coincides with the time of the year when frogs are the most active.