C57BL/6 neuromuscular healthspan scoring system.

Developing a scoring system based on physiological and functional measurements is critical to test the efficacy of potential interventions for sarcopenia and frailty in aging animal models; therefore, the aim of this study was to develop a neuromuscular healthspan scoring system (NMHSS). We examined three ages of male C57BL/6 mice: adults (6-7 months old, 100% survival), old (24-26 months old, 75% survival), and elderly group (>28 months old, ≤50% survival)-as well as mice along this age continuum. Functional performance (as determined by the rotarod and inverted-cling grip test) and in vitro muscle contractility were the determinants. A raw score was derived for each determinant, and the NMHSS was then derived as the sum of the individual determinant scores. In comparison with individual determinants, the NMHSS reduced the effect of individual variability within age groups, thus potentially providing an enhanced ability to detect treatment effects in future studies.