Volitional Weight-Lifting in Rats Promotes Adaptation via Performance and Muscle Morphology prior to Gains in Muscle Mass.
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.
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA.
Erik P
EP
Rader
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA.
G Roger
GR
Miller
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA. ; West Virginia University School of Medicine, Department of Neurology, WV, USA.
Robert D
RD
Chetlin
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA.
Oliver
O
Wirth
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Morgantown, WV, USA.
Brent A
BA
Baker
fiber cross-sectional area; fiber number; operant conditioning; resistance exercise; stereology