Skeletal Muscle Transcriptomic Responses to Chronic Concurrent Exercise Training

Combining resistance and endurance exercises in a training regime (concurrent training) can impair improvements in muscle hypertrophy, strength, and power compared to resistance training alone. Here we aimed to characterize skeletal muscle transcriptomic changes following chronic concurrent training to determine whether contraction-induced gene expression may reveal molecular underpinnings explaining impaired adaptations. Eighteen young, healthy male participants underwent 12 weeks of resistance, endurance, or concurrent training. Maximal strength, aerobic capacity, and anaerobic power were assessed. Transcriptomics were performed on skeletal muscle biopsies obtained pre and post-intervention. Improvements to maximal anaerobic power are impaired with concurrent and endurance training. Gene expression related to plasma membrane structures was enriched while gene expression related to regulation of mRNA processing and protein degradation was suppressed with concurrent training. Considerable overlap of gene expression related to extracellular matrix remodeling was observed between concurrent and endurance training. Our results provide the first comprehensive comparison of unique and overlapping gene sets enriched following chronic resistance, endurance, and concurrent training, and reveals pathways that may have implications in relation to impaired adaptations when undertaking concurrent training. Overall design: The study employed a parallel-groups design where participants were stratified according to lean body mass (LBM) and allocated to either a resistance only (RES), endurance only (END) or concurrent resistance and endurance exercise training (CET) group for 12 weeks. Measures of maximal strength, aerobic capacity, and anaerobic power, as well as body composition were performed pre- and post-intervention. Resting biopsies were obtained from the vastus lateralis muscle pre-intervention, after weeks 2 and 8 of exercise training, and post-intervention. For the duration of the intervention, all participants consumed a high-protein diet (2 g·kg-1·d-1). The study was approved by the Australian Catholic University Human Research Ethics Committee and was carried out in accordance with the latest revision of the Declaration of Helsinki. This trial was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12617001229369).