Figure 4. Selected gene transcripts associated with p53/p21 axis of autophagy and the relationship to the PERK arm of the UPR. Gene transcripts associated with p53/p21 axis are elevated at baseline (A) and decreased 18h post-exercise (B) in older compared to younger adults. Correlations between gene transcripts associated with the PERK arm of the UPR and p53/p21 axis post-exercise (C) in young (bottom left) compared to older (upper right) adults. The correlation matrix heat maps demonstrate significant positive (dark red) and negative (dark blue) relationships between the fold-change from baseline to 18h post-exercise for the individual gene transcripts associated with the UPR pathway in young and older adults. *Significantly (p ≤ 0.05) different between groups. Data bars are presented as mean ± SEM.