Research Paper Volume 18 pp 213—233

The lack of ATF5 rescues the age-related decline in muscle mass but reduces overall endurance performance. Phenotypic characteristics between genotypes and age were assessed, including (A) body weight (g), and muscle weights, (B) TA, (C) Gastrocnemius, (D) Soleus, (E) Heart weight, normalized for body weight (mg/g). Muscle endurance was assessed over the course of an acute contractile activity 9-minute in situ protocol, where the gastrocnemius muscle was stimulated at 0.25, 0.5 and 1 tetanic contractions per second (TPS). Muscle endurance, expressed as the percentage of max/initial force (t=0) in both (F) young and (G) aged mice, comparing phenotypic differences between genotypes. A¶¶ P<0.01, A¶¶¶ P<0.001, main effect of age; G¶ P<0.05, G¶¶ P<0.01, G¶¶¶¶ P<0.0001, main effect of genotype; AxG¶ P<0.05, AxG¶¶ P<0.01, interaction between age and genotype, Two-way ANOVA (n=6-20/group); Tukey’s post-hoc analyses, Young WT vs. Young ATF5 KO, Aged WT vs. Aged ATF5 KO, Young WT vs. Aged WT, Young ATF5 KO vs. Aged ATF5 KO, Young ATF5 KO vs. Aged WT, Young WT vs. Aged ATF5 KO. Tukey’s post-hoc: *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001. Data are means ± SD.