The evolution of fatigue associated with isometric contraction in toad sartorius.

1. The development of fatigue in isolated toad sartorius undergoing short, periodic, isometric tetani of controlled duration, was studied. Stimulation was direct and curare was used.2. In the great majority of cases extratension decreased very regularly towards a steady value, following a simple exponential equation.3. The final steady tension (expressed as percentage of the maximum) and the constant of exponential decay varied as simple functions of the mean frequency of stimulation and their product was a constant.