Hypothesis
Because metformin dampens inflammation, adding it to 14 weeks of supervised resistance training would augment the muscle response in healthy adults aged 65 and over.
What failed
Among 94 randomized participants the placebo group gained more lean body mass (p = .003) and thigh muscle mass (p < .001), and more thigh muscle area (p = .005) and density (p = .020), than the metformin group, with strength gains trending lower on metformin; fibre hypertrophy and satellite-cell and macrophage abundance were unaffected.
Broken assumption
Suppressing training-related inflammation helps rather than hinders muscle hypertrophy.
Why
The authors report that metformin raised AMPK signalling and tended to blunt the training-induced rise in mTORC1 signalling, and that placebo but not metformin lowered the type I fibre percentage.
From the published paper: Walton et al. Aging Cell, 2019. ↗CC BY