According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.
Randomized Controlled Trial (RCT) with mechanical tension isolation
In healthy adult humans, compare muscle hypertrophy after resistance training with mechanical tension preserved but hormonal/metabolic stress minimized (e.g., via blood flow restriction without metabolic burn, or low-load high-tension protocols with pharmacological suppression of systemic stress responses) versus standard resistance training with full hormonal/metabolic stress. Measure muscle cross-sectional area via MRI over 12 weeks. Mechanistic human biopsy study with pathway inhibition
In healthy humans undergoing resistance training, administer localized inhibitors of mTORC1 (e.g., rapamycin analog) or FAK (e.g., PF-573228) via intramuscular injection to one limb, while the contralateral limb receives placebo. Measure hypertrophy and signaling pathway activation via muscle biopsies pre- and post-8 weeks of training. Isolated mechanical stimulation in human myotubes with hormonal/metabolic control
Use human primary myotubes in vitro subjected to controlled mechanical stretch (mimicking resistance training tension) in the absence of serum, hormones, or metabolic stressors (e.g., low glucose, no lactate), and measure hypertrophy markers (e.g., myosin heavy chain expression, cell size) compared to unstretched controls. Longitudinal observational study with mechanical tension quantification
Track 100 individuals over 6 months performing varied resistance training regimens, using wearable sensors to quantify mechanical tension (force x displacement) and blood/urine biomarkers for hormonal/metabolic stress (cortisol, lactate, IGF-1). Correlate tension metrics with muscle growth while statistically controlling for stress biomarkers. Case study of individuals with hormonal insensitivity
Examine muscle hypertrophy in individuals with rare genetic conditions causing complete insensitivity to key hormones (e.g., androgen insensitivity syndrome, GH receptor mutations) who engage in regular resistance training, to determine if hypertrophy occurs without hormonal signaling.