Isometric contractile properties of the extraocular muscles of the monkey.

Isometric contractile properties were measured for three superior rectus muscles, one inferior rectus muscle, and three levator muscles, all obtained from monkeys. These are the first reported measurements for the superior rectus and levator muscle on any mammalian species and the first reported for a primate on the inferior rectus. The levator muscle was shown to be a fast muscle, like other extraocular muscles. Time to peak tension and time to relax to one-half peak tension were short for each muscle tested and were similar to those found for extraocular muscles of other mammalian species. The data for the ratio of peak twitch tension to peak tetanic tension are not reliable because there is evidence that the muscle fibers were damaged.