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The effects of concentric and eccentric training in murine models of dysferlin-associated muscular dystrophy.

INTRODUCTION
Dysferlin-deficient murine muscle sustains severe damage after repeated eccentric contractions.


METHODS
With a robotic dynamometer, we studied the response of dysferlin-sufficient and -deficient mice to 12 weeks of concentrically- or eccentrically-biased contractions. We also studied whether concentric contractions before or after eccentric contractions reduced muscle damage in dysferlin-deficient mice.


RESULTS
After 12 weeks of concentric training, there was no net gain in contractile force in dysferlin-sufficient or -deficient mice, whereas eccentric training produced a net gain in force in both mouse strains. However, eccentric training induced more muscle damage in dysferlin-deficient versus -sufficient mice. Although concentric training produced minimal muscle damage in dysferlin-deficient mice, it still led to a prominent increase in centrally-nucleated fibers. Prior exposure to concentric contractions conferred slight protection on dysferlin-deficient muscle against damage from subsequent eccentric contractions.


DISCUSSION
Concentric contractions might help dysferlin-deficient muscle derive the benefits of exercise without inducing damage. This article is protected by copyright. All rights reserved.