Meeting Abstract
Many skeletal muscles exist ensheathed in tight fitting connective tissue compartments comprised of epimysium and overlying fascia. It has been shown that freeing a muscle from this compartmental fascia via surgery has a negative impact on muscle force production; however, reports on the effects of introducing artificial constraining materials that exaggerate a muscle’s in situ environment have been contradictory, with some reporting increases in muscle performance while others report decreases. Here, we sought to quantitatively describe the effects of artificially constraining a skeletal muscle during contraction. Using a force transducing servomotor and fixed-length contractions, we determined the length-tension characteristics of freshly dissected Lithobates catesbeianus (bullfrog) plantaris muscles in the presence and absence of snug-fitting plastic tubes that encased the muscle belly. We then explored the impact of these constraining tubes on work production during force-controlled, shortening contractions. Constraining the belly of a skeletal muscle decreased its ability to generate force across all regions of the L-T curve, with reductions as high as 25%. In shortening contractions, constricted muscles performed less work on the servomotor arm when compared with the unconstricted condition. Although the physiological mechanism by which muscle performance is influenced remains unclear, our results indicate that adding artificial constraints to the muscle belly can have a detrimental effect on force and work production. These findings, taken alongside reports of the detrimental effects of disrupting anatomical compartments that surround muscles in vivo, imply that there is an optimal shape in which to confine a contracting skeletal muscle that yields maximal muscle performance. Supported by NIH grant AR055295.
