Reduced non-bicarbonate skeletal muscle buffering capacity in mice with the mini-muscle phenotype

Abstract

Muscle pH decreases during exercise, which may impair function. Endurance training typically reduces muscle buffering capacity due to changes in fiber type composition, but existing comparisons of species that vary in activity level are ambiguous. We hypothesized that High Runner (HR) lines of mice from an experiment that breeds for voluntary wheel running would have altered muscle buffering capacity as compared with their non-selected control counterparts. We also expected that six days of wheel access, as used in the selection protocol, would reduce buffering capacity, especially for HR mice. Finally, we expected a subset of HR mice with the "mini-muscle" phenotype to have relatively low buffering capacity due to fewer type IIb fibers. We tested non-bicarbonate buffering capacity of thigh muscles. Only HR mice expressing the mini-muscle phenotype had significantly reduced buffering capacity, females had lower buffering capacity than males, and wheel access had no significant effect.