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 crossover design
In healthy adult humans undergoing standardized resistance training, compare muscle protein synthesis and hypertrophy outcomes between sessions where metabolites (lactate, H+, Pi) are artificially elevated via infusion or occlusion versus control sessions with normal metabolite levels, while matching volume and intensity. Double-blind, placebo-controlled, within-subject crossover trial with muscle biopsy sampling
Determine whether artificially increasing intramuscular metabolites during a single bout of resistance exercise alters acute muscle protein synthesis rates compared to a control condition with normal metabolite accumulation. Longitudinal cohort study with controlled metabolic manipulation
Assess whether chronic, repeated artificial elevation of metabolites during resistance training leads to greater hypertrophy than training without such elevation over a prolonged period. Mechanistic in vivo human study with pharmacological blockade
Test whether blocking the physiological response to metabolites (e.g., via sodium bicarbonate to buffer H+ or inhibitors of swelling pathways) alters hypertrophy outcomes despite normal training-induced metabolite accumulation. Case-control study comparing high vs. low metabolite responders
Determine whether individuals who naturally experience high metabolite accumulation during resistance training show greater hypertrophy than low accumulators, despite matched training volume and intensity.