Abstract

Structural and functional strength of a muscle immediately after an experimentally created strain injury was examined to provide clinically relevant information for early treatment of muscle strain injuries. The EDL muscles of 12 adult male rabbits were studied. Contractile force and shortening, and peak load were determined for control muscles. A nondisruptive strain injury was created by stretching the experimental muscles just short of complete rupture. Contractile force generation and shortening, and peak load were determined after the experimental injury. Peak load was 63 and elongation to rupture was 79 for experimental muscles relative to controls. Statistically significant lower values for contractile force generation and shortening were also seen in the EDL muscles. Histologic and gross examinations revealed that incomplete disruptions occurred near the distal muscle-tendon junction. The experimental data suggest clinical implications, such as 1) a muscle-tendon unit is significantly more susceptible to injury following a strain injury than normal muscle, 2) early return to the uncontrolled environment of athletic competition may place the injured muscle at risk for further injury, and 3) therapeutic regimens designed to achieve early return to competition may further increase the risk for additional injury by eliminating protective pain mechanisms. Although decrements in peak load and elongation to failure are less than in normal muscle, the values seem high enough to allow functional rehabilitation post-injury. Verf.-Ref.