Biocircuitry linked to exercise adaptations: impact of dose and inter-individual response heterogeneity

In a randomized, dose-response trial, we used molecular and phenomic profiling to compare responses to traditional (TRAD) endurance plus resistance training and high-intensity tactical training (HITT). Ninety-four participants (18-27 years) completed 12 weeks of TRAD or HITT followed by 4 weeks of detraining. While in vivo phenotype improvements were not dose-dependent, a few dose-dependent ex vivo muscle adaptations were overshadowed by wide-ranging inter-individual response heterogeneity (IRH). To address this, we established minimum clinically important difference (MCID) scores to classify participants by their attainment of MCIDs for functional muscle quality (fMQ) and cardiorespiratory fitness (CRF). Using differential gene expression (DGE) of muscle and exosomal microRNAs (miRs) and higher-order singular value decomposition (HOSVD), we mapped the molecular and phenomic biocircuitry of IRH. Nine miRs emerged as robust features of training adaptability, providing new insights into the integrated biocircuitry driving exercise adaptations and response heterogeneity.