Fig. 1. Experimental apparatus used to measure oxygen consumption and work. Muscle (mu) was mounted in a cylindrical glass chamber (bound by broken lines) surrounded by a temperature controlled water jacket (wj). One end of the muscle was attached to a rigid, stainless-steel arm (ra) secured to the stainless-steel chamber lid (cl). The other end was attached to a stainless-steel pin (pn) that passes through a narrow aperture in the lid and was connected to the arm of an ergometer (er). A glass-encapsulated magnetic stir bar (sb) was used to mix the saline in the chamber. An oxygen probe (op) enters the chamber through a sealed side port. A temperature probe (tp) was placed adjacent to the chamber. To flush the chamber, saline entered through a port in the bottom (arrow) and exited through the hole in the chamber lid; diameter of holes in chamber lid and bottom are exaggerated for illustration purposes. Chamber lid and bottom formed a tight seal with the walls of the chamber using rubber O-rings. The rigid arm and pin connected to the ends of the muscle were attached to fine magnet wires outside the chamber (not shown) and used to stimulate the muscle. The rigid arm was insulated along its length with polyethylene tubing to minimize stray current in the chamber.