Effects of high and low velocity muscle contraction on myosin heavy chain mRNA and protein expression in conjunction with muscle performance in the elderly
Title: Effects of high and low velocity muscle contraction on myosin heavy chain mRNA and protein expression in conjunction with muscle performance in the elderly
Introduction: Aging decreases skeletal muscle mass and contractile ability. This decreases the capacity for an individual to successfully carry out activities of daily living, eventually leading to physical disability. Recent research demonstrates that when compared to conventional resistance training, high velocity resistance training (HVRT) may be more effective in slowing or reversing age related declines in skeletal muscle. However, there is currently a paucity of research which has aimed to investigate the transcriptional and translational events taking place within senescent skeletal muscle in response to HVRT.
Purpose: To examine the velocity specificity of resistance training by directly comparing changes in muscle transcription, translation, performance, and function in older adults.
Methods: Twenty-six older adults were randomized to partake in 6 weeks of either low velocity resistance training (LVRT) or HVRT. Subjects underwent pre- and post-training strength and functional testing. A subsample of subjects also underwent subcutaneous needle biopsies of the vastus lateralis pre- and post-training.
Results: From baseline to post-training, there were several significant (P < 0.05) differences in muscle performance and functional characteristics in LVRT (n = 13) and HVRT (n = 13) groups. Our results demonstrate HVRT provides a greater number of muscular enhancements when compared to LVRT, particularly under conditions of high velocity muscle contraction. MyHc-a mRNA showed a significant (P < 0.01) decrease (.93-fold ± 0.12) in LVRT and a significant (P < 0.01) increase (2.0-fold ± .62) in HVRT. MyHc-IIa mRNA showed a significant (P < 0.05) increase (1.2-fold ± 0.01) in HVRT. MyHc-IIx mRNA showed a significant (P < 0.01) decrease (0.99-fold ± 0.004) in LVRT). MyHc-b/slow had a significant (P< 0.05) decrease in HVRT (1.0 ± 0.12 vs 0.84 ± 0.13, pre v post). MyHc-IIx decreased (P < 0.01) in LVRT (1.0 ± 0.06 vs 0.87 ± 0.06, pre vs post).
Conclusion: HVRT is emerging as the optimal training stimulus for the older adult. The present study demonstrates, in addition to increased muscular performance and functional outcomes, HVRT may also evoke a favorable (i.e., slow-to-fast) transcriptional and translational response in MyHC.