Load-induced human skeletal muscle hypertrophy: Mechanisms, myths, and misconceptions

Mechanical tension is widely recognized as the primary stimulus underlying the molecular mechanisms that influence muscle hypertrophy induced by resistance training. Despite this, several outdated or overstated concepts continue to persist, both in the scientific literature and in the practical application of resistance training coaching and program design. Claims that acute hormonal responses, metabolic stress, cell swelling or "the pump" meaningfully contribute to hypertrophy are not supported by scientific evidence. Additionally, the concept of sarcoplasmic hypertrophy as a distinct and functionally meaningful contributor to hypertrophy lacks strong evidence. In this review, we critically evaluate several persistent misconceptions and contrast them with evidence-based mechanistic insights into load-induced hypertrophy. Specifically, we discuss the role (or lack thereof) of systemic hormones, metabolites, and cell swelling in promoting muscle hypertrophy. We also critically review the concept of sarcoplasmic hypertrophy and propose that it is not a meaningful contributor to muscle hypertrophy. Lastly, to translate knowledge for trainees and coaches, we discuss the upper limit of muscle hypertrophy and provide readers with evidence-based, reasonable expectations for muscle hypertrophy. We aimed, through this review, to use scientific evidence to enhance our understanding of what drives muscle hypertrophy and provide an evidence-based framework for resistance exercise training.