Integrating circadian biology and resistance training: time-of-day effects on hypertrophy, hormonal flux and the muscle transcriptome in bodybuilders
DOI:
https://doi.org/10.47197/retos.v74.118121Keywords:
Circadian Physiology, Resistance Training Hypertrophy, Chronotype, Skeletal Muscle Transcriptomics, mTOR and Ribosome BiogenesisAbstract
Introduction: Circadian rhythms influence muscle metabolism and gene expression, suggesting that training time-of-day may shape hypertrophic and molecular adaptations. Evidence in trained individuals, however, remains limited.
Objective: To compare the effects of morning versus evening resistance training on hypertrophy, performance, endocrine markers, sleep, and skeletal-muscle transcriptomics in bodybuilders.
Methodology: In a randomized parallel-group trial, 112 trained males were assigned to 12 weeks of supervised training either in the morning (07:00–09:00) or evening (17:00–19:00). Primary outcome was change in vastus lateralis CSA (MRI). Secondary outcomes included lean mass (DXA), strength, hormones, sleep (actigraphy), chronotype, and RNA-seq profiling.
Results: Evening training produced a greater VL-CSA increase (+8.2% vs +6.0%; p=0.04) and stronger induction of mTOR- and ribosome-related transcriptional pathways (FDR < 0.05). Chronotype moderated hypertrophic responses.
Discussion: Training time influenced phenotypic and molecular adaptations, with evening sessions eliciting broader anabolic signaling.
Conclusion: Evening resistance training yields modestly greater hypertrophy and distinct transcriptomic responses; aligning training with chronotype may enhance outcomes.
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Copyright (c) 2025 Mohammed Nadim Abd, Jihad Mohammed Hassan Al Eqabi, Haider Radhi Raheem Alsaedi, Bareq Rahman Hashim Alfadhli
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