Volitional weight-lifting in rats promotes adaptation via performance and muscle morphology prior to gains in muscle mass.
Rader EP; Miller GR; Chetlin RD; Wirth O; Baker BA
Environ Health Insights 2014 Oct; 8(Suppl 1):1-9
Investigation of volitional animal models of resistance training has been instrumental in our understanding of adaptive training. However, these studies have lacked reactive force measurements, a precise performance measure, and morphological analysis at a distinct phase of training - when initial strength gains precede muscle hypertrophy. Our aim was to expose rats to one month of training (70 or 700 g load) on a custom-designed weight-lifting apparatus for analysis of reactive forces and muscle morphology prior to muscle hypertrophy. Exclusively following 700 g load training, forces increased by 21% whereas muscle masses remained unaltered. For soleus (SOL) and tibialis anterior (TA) muscles, 700 g load training increased muscle fiber number per unit area by -20% and decreased muscle fiber area by -20%. Additionally, number of muscle fibers per section increased by 18% for SOL muscles. These results establish that distinct morphological alterations accompany early strength gains in a volitional animal model of load-dependent adaptive resistance training.
Animals; Models; Force; Training; Measurement-equipment; Muscles; Muscle-function; Morphology; Weight-factors; Muscles;
Author Keywords: operant conditioning; resistance exercise; fiber cross-sectional area; fiber number; stereology
Erik P. Rader, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA
Environmental Health Insights