Menstrual Cycle Phase-Based Interval Training Yields Distinct Muscle Changes in Female Athletes

Advances in mass-spectrometry(MS)-based technologies have leveraged our understanding of skeletal muscle responsiveness to exercise in humans. However, there is a lack of such data in females, particularly pertaining to female athletes and menstrual cycle phase-based sprint interval training(SIT) despite its efficacy and popularity. Here, we present a comprehensive proteomic analysis of skeletal muscle adaptations to high-frequency SIT during different menstrual cycle phases in female athletes. We randomized 49 eumenorrheic females to either high-frequency SIT in the follicular(FB) or luteal phase(LB) over one menstrual cycle comprising eight sessions of 6x30-s all-out efforts. Twenty-five completed the intervention with verified cycles. MS-based proteomics revealed notable differences in muscle adaptations to phase-based SIT. LB suppressed mitochondrial pathways of the tricarboxylic acid cycle and electron transport chain while enriching ribosomal complexes. Conversely, FB enriched filament organization and skeletal system development. Mitochondrial repression during LB was linked to reduced [V]O2max, whereas exercise capacity improved in FB only. Our findings show that synching high-frequency SIT with menstrual cycle phases induces distinct muscle adaptations and affects phenotype in eumenorrheic female athletes.