Figure 2.

Young, trained mice exhibited a significant increase in maximum distance running (250%, P < 0.001), maximal running speed (23%, P = 0.03), in comparison to age‐matched untrained mice (A). In contrast, both trained and untrained old mice demonstrated similar endurance and maximal speed. Muscle fibre composition of gastrocnemius revealed a 2.5‐fold increase (P = 0.02) and 30% increase in the Type I and Type IIa fibres (P = 0.03) in trained young mice, respectively, where these were absent in aged muscles (B). RNA seq analysis gastrocnemius muscles revealed 96 and 146 to be differentially regulated with exercise treatment in young and old mice, respectively, without any overlap, where 85% of the top 20 most upregulated genes in exercised young mice were the transcriptional targets of HIF1A (C). The exercise training led to a 50% decrease in PHD2 protein levels (P = 0.006) with corollary increase in the HIF1A and PGC‐1a protein levels in muscle of young mice (D).