Long-term measurement of muscle function in the dog hindlimb using a new apparatus

The objective of this study was to develop an apparatus for reliable, reproducible, and minimally invasive measurements of long-term, myoneural function. Twenty conditioned dogs were anesthetized and placed supine with one hindlimb secured in a boot apparatus. The hindpaw was attached to a force transducer that was connected to a recorder for continuous monitoring of torque. Muscles within the anterolateral compartment were stimulated by percutaneous electrodes over the peroneal nerve near the fibular head. This elicited isometric dorsiflexion of the hindpaw. Twitch and tetanic torques correlated positively with dog weight whereas other skeletal-muscle function parameters (time to peak tension, one-half relaxation time, and endurance) were independent of dog weight. Muscle function results were consistent with an overall compartmental composition of 30% Type I and 70% Type II fibers. Repetitive testing of twitch and tetanic torques in the dog legs yielded coefficients of variance of 3-4% (intraday) and 7% (interday). Thus, about one-half of the interday variability may be accounted for by diet, exercise, and other physiological conditions that change daily. The apparatus was also used to detect myoneural degeneration following tourniquet ischemia. The results indicate that this procedure for evaluating muscle function yields reliable and quantitative results noninvasively, and thus allows long-term testing of muscle function in normal and diseased hindlimbs of dogs.