Gene expression
APPENDIX, AFTEREFFECTS
The use of a gene expression‐based measure of biological age has the added advantage of facilitating additional transcriptomic analyses, which could shed light on the mechanisms underlying exercise's effect on aging processes. However, in an untargeted genome‐wide expression analysis, 12 HIIT sessions had only modest effects on gene expression.Although there were transcriptomic effects associated with HIIT, less than 100 genes displayed a fold change greater than 1.5 or less than 0.5, the values typically used to identify DEGs. This DEG count is less than the amount required for subsequent higher‐order bioinformatic analyses such as a functional enrichment analysis.While these modest findings may seem surprising given the systemic physiological changes induced by exercise, it is important to remember that this trial examined the effects of a 1‐month HIIT protocol on steady‐state expression levels. The follow‐up blood draw occurred approximately 48 h after the final exercise session, meaning that whole‐genome expression was assessed while the participants were not experiencing the acute physiological aftereffects of exercise. Given the small dose and duration of our exercise protocol and the small sample size, this modest between group effect may not be surprising.The 48‐h delay in follow‐up blood collection was specified to minimize changes in inflammatory processes and cell composition following the last exercise bout. This helped isolate a more accurate picture of “per cell” transcriptional changes rather than transitory changes in cell composition. This is necessary because acute exercise modifies the presence of all major leukocyte populations in peripheral blood as a result of sympathetic stimulation, shear stress, inflammatory signaling, and other processes (Peake et al., An exploratory genome‐wide discovery analysis using more liberal fold change cutoff values (greater than 1.2 or less than 0.8) revealed 1075 upregulated transcripts and 1778 downregulated transcripts potentially associated with HIIT (Appendix The raw transcript count per genome feature for all samples is available in Appendix 