Previous studies have shown that skeletal muscle is more susceptible to contraction-induced injury and recovers more slowly after the initial injury in aged animals. Purpose: To investigate if aging affects the ability of skeletal muscle to adapt to repeated exposures of maximal stretch-shortening cycles (SSCs). Methods: Dorsiflexor muscles of old (30 months, N= 5) and young (12 weeks, N = 6) Fischer 344 × Brown Norway rats were exposed 3 times per week for 4.5 weeks to a protocol of 80 maximal stretch-shortening cycles (60 deg/s, 50 deg range of motion) per exposure in vivo. Performance was characterized by isometric performance, negative, positive, and net work, and stretch-shortening parameters (peak force and minimum force at each exposure interval (fourteen exposures). Results: The isometric force (p = 0.455), peak force (p = 0.761), and minimum force (p = 0.853) was not statistically different between groups at the start of the exposure. During the chronic exposure, those forces responded differently with age (p = 0.0003, 0.0081, and 0.0011 respectively) and were significantly different with age at the end of the exposure period (p <0.0001 for all parameters). Negative work and positive work were also not different between groups at the start of the exposure (p = 0.455 and 0.475, respectively). During the chronic exposure, both negative and positive work responded differently with age (p = 0.0044 and 0.0011, respectively) and resulted in significantly different magnitudes at the end of the exposure period (p <0.0011 for both parameters). There was also a significant increase in all performance parameters from the initial to the final exposure in the young animals (p <0.05), but a concomitant decrease in the old animals in all parameters (p <0.05) except negative work. Conclusions: A chronic exposure of SSCs results in a significant performance increase in young animals, and significant performance decrease in old animals. These findings indicate that aging impairs the ability of skeletal muscle to adapt to repetitive mechanical loading.