Hormonal
Mechanical tension is the primary and sufficient stimulus for load-induced human skeletal muscle hypertrophy, whereas acute hormonal spikes, metabolic stress, and cell swelling ('the pump') do not meaningfully contribute to the hypertrophic process.
To build muscle, prioritize mechanical tension through resistance training (lifting weights with progressive overload). Do not design your workouts around chasing a 'pump' or relying on metabolic stress (high reps, short rest) as primary drivers, as these do not add to hypertrophy beyond what mechanical tension provides. Similarly, do not expect natural acute hormonal spikes to drive growth; they are not required for hypertrophy to occur.
Mechanical tension is widely recognized as the primary stimulus underlying the molecular mechanisms that influence muscle hypertrophy induced by resistance training. ... Claims that acute hormonal responses, metabolic stress, cell swelling or 'the pump' meaningfully contribute to hypertrophy are not supported by scientific evidence.
Why this rating
Based on a comprehensive review of multiple human studies, including unilateral training models and meta-analyses, showing no correlation between acute hormonal/metabolic changes and hypertrophy.
Source
Load-induced human skeletal muscle hypertrophy: Mechanisms, myths, and misconceptions
Derrick W. Van Every et al. · Journal of sport and health science/Journal of Sport and Health Science · 2025
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