Effect of temperature and continuous stimulation on gastrocnemius of the frog

Abstract

Gastrocnemius muscles of the winter frog ( Rana pipiens) were stimulated directly, at a rate of 2/sec at temperatures of 10, 15, 20, 25, and 30 C and at 1/sec at 5 C. Isometric strain-gauge recordings showed that at all temperatures, when developed tension remained constant, the duration of contraction remained relatively unchanged, while the duration of relaxation progressively increased. The prolongation of relaxation was most rapid and striking at 5 C, becoming progressively less with increasing temperature. These findings suggest that relaxation may be the phase of greatest metabolic activity.