Figure 1.

Original recordings from freshly biopsied skeletal muscle were obtained from the vastus medialis of the quadriceps muscle. Muscle strips approximately 2.5 cm long and approximately 3 mm wide were mounted in a tissue bath and slowly stretched to a pre-load force of approximately 25 mN. The tissue bath, containing Krebs-Ringer solution, was bubbled with carbogen at 37°C. Muscle strips were stimulated electrically in order to produce repeated muscle contractions (twitches). (A) A muscle strip of the patient showing a continuously increasing muscle contracture with absolutely no response to electrical stimulation, resulting from the loss of function of excitation-contraction coupling. (B) A muscle strip from a healthy subject. Note the stabilization of the baseline as well as the muscle contractions upon electrical stimulation.