Phosphoproteomics uncovers exercise intensity-specific signaling networks underlying high-intensity interval training in human skeletal muscle

In response to exercise, protein kinases and signaling networks are rapidly engaged in skeletal muscle to maintain energy homeostasis. High-intensity interval training (HIIT) induces superior or similar health-promoting skeletal muscle and whole-body adaptations compared to prolonged, moderate-intensity continuous training (MICT). However, the exercise intensity-specific signaling pathways underlying HIIT versus MICT are unknown. Ten healthy male participants completed bouts of work- and duration-matched HIIT and MICT cycling in randomized crossover trials. Mass spectrometry-based phosphoproteomic analysis of human muscle biopsies mapped acute signaling responses to HIIT and MICT, identifying 14,931 phosphopeptides and 8,509 phosphosites. Bioinformatics uncovered >1,000 phosphosites significantly regulated by HIIT and/or MICT, including 92 and 348 respective HIIT-specific phosphosites after 5 and 10 min and >3,000 total phosphosites significantly correlated with plasma lactate. This first human muscle HIIT signaling network map has revealed rapid exercise intensity-specific regulation of kinases, substrates and pathways that may contribute to HIIT's unique health-promoting effects.