Temporal Response of Desmin and Dystrophin to Progressive Resistance Exercise

Abstract

PURPOSE: Our purpose was to investigate the adaptations of the cytoskeletal proteins desmin and dystrophin in relationship to known muscular adaptations of resistance exercise. We measured desmin, dystrophin, and actin protein contents, myosin heavy chain (MHC) isoform distribution, muscle strength, and muscle cross-sectional area (CSA) during 8 weeks of progressive resistance training and following a single bout of unaccustomed resistance exercise. METHODS: Muscle biopsies were taken from the vastus lateralis of 12 untrained men a week prior to exercise (week 0) and at weeks 1,2,4, and 8 following a single bout of exercise (n = 6), or at weeks 1, 2, 4 and 8 of the progressive resistance training program (n = 6). Desmin, dystrophin, and actin protein levels were determined with immunoblotting, and MHC isoform distribution was determined using SDS PAGE at each time point for each group. RESULTS: In the training group, the desmin:actin ratio significantly increased compared to week 0 beginning at week 4 (0.054 to 0.095, P < 0.0001) and continuing through week 8 (0.054 to 0.094, P < 0.0001). The desmin:actin ratio did not change at any time point for the single bout group. Actin and dystrophin protein contents were not changed in either group at any time point. The percentage of MHC type IIa increased and MHC type IIx decreased at week 8 in the training group with no changes occurring in the single bout group. Strength was significantly increased by week 2 (knee extension) and week 4 (leg press), and further increased at week 8 for both these exercises in the training group only. Muscle CSA was significantly increased at week 4 for type II fibers in the training group only (5719+/−382 and 6582+/−640, weeks 0 and 4 respectively, P < 0.05). Finally, a significant negative correlation was observed between the desmin:actin ratio and the percentage of MHC IIx (R = −0.31, P < 0.05, all time points from both groups). CONCLUSION: These data suggest a time course for muscular adaptation to resistance training in which desmin increases shortly after strength gains and in conjunction with hypertrophy, but prior to changes in MHC isoforms, while dystrophin remains unchanged.