J Appl Physiol. 2011 Jul 28. [Epub ahead of print]
Effects of high- and low-velocity resistance training on the contractile properties of skeletal muscle fibers from young and older humans.
Claflin DR, Larkin LM, Cederna PS, Horowitz JF, Alexander NB, Cole NM, Galecki AT, Chen S, Nyquist LV, Carlson BM, Faulkner JA, Ashton-Miller JA.
Source
1University of Michigan.
Abstract
A two-arm, prospective, randomized, controlled trial study was conducted to investigate the effects of movement velocity during progressive resistance training (PRT) on the size and contractile properties of individual fibers from human vastus lateralis muscles. The effects of age and gender were examined by a design that included 63 subjects organized into four groups: young (20 to 30 yrs) males and females, and older (65 to 80 yrs) males and females. In each group, half of the subjects underwent a traditional PRT protocol that involved shortening contractions at low velocities against high loads, while the other half performed a modified PRT protocol that involved contractions at 3.5× higher velocity against reduced loads. Muscles were sampled by needle biopsy before and after the 14-week PRT program and functional tests were performed on permeabilized individual fiber segments isolated from the biopsies. We tested the hypothesis that, compared with low-velocity PRT, high-velocity PRT results in a greater increase in the cross-sectional area (CSA), force and power of type 2 fibers. Both types of PRT increased the CSA, force and power of type 2 fibers by 8-12%, independent of the gender or age of the subject. Contrary to our hypothesis, the velocity at which the PRT was performed did not affect the fiber-level outcomes substantially. We conclude that, compared with low-velocity PRT, resistance training performed at velocities up to 3.5× higher against reduced loads are equally effective for eliciting an adaptive response in type 2 fibers from human skeletal muscle.