Fig. 1: Muscle mass and function progressively decline in male C57BL/6JRj mice during aging.

a Body mass for 8, 14, 18, 22, 24, 26, and 28 months-old mouse groups. EchoMRI measurements of b fat and c whole-body lean mass. d Absolute muscle mass for quadriceps (QUAD), gastrocnemius (GAS), tibialis anterior (TA), plantaris (PLA), extensor digitorum longus (EDL) and soleus (SOL) averaged across both limbs. e Body, lean and fat mass as well as muscle tissue and organ mass in 28 months-old mice normalized to the mean of 8, 14, and 18 months-old groups. The mean percentage loss in mass relative to body mass is reported above each data set. The color scheme designates the direction of changes and significance: gray is not different (p-value > 0.10), red is increased (p-value < 0.05), blue is decreased (p-value < 0.05), light red is a trend for increased (0.05 < p-value < 0.10). f Recordings of all-limb grip strength. Isolated EDL muscle function parameters, including g force-frequency curve (left) and fatigue response to multiple stimulations (right); and twitch time-to-peak tension in (h) and half relaxation time in (i). Group numbers of biological replicates are: n = 9–13 in (a–f); n = 7–12 in (g) (left); n = 5–11 in (g) (right) and n = 7–12 in (h-i). For statistical comparisons 8, 14, and 18 months-old groups were pooled and compared with each of the other four groups. One-way ANOVAs with Dunnett’s post hoc tests were used to compare between 8 and 18 months data and the other four groups. *, ** and *** denote a significant difference between groups of p-value < 0.05, p-value < 0.01 and p-value < 0.001, respectively. Trends (0.05 < p-value < 0.10) are denoted by # or the p-value specified. Colored asterisks refer to the group of comparison. All values were visualized as mean ± standard error of the mean (SE).