Here is the study Palumbo mentioned
R. Grace Walton et al.
Metformin blunts muscle hypertrophy in response to progressive resistance exercise training in older adults: A randomized, double‐blind, placebo‐controlled, multicenter trial: The MASTERS trial. Aging December 2019. Volume18, Issue6 e13039
Abstract
Progressive resistance exercise training (PRT) is the most effective known intervention for combating aging skeletal muscle atrophy. However, the hypertrophic response to PRT is variable, and this may be due to muscle inflammation susceptibility. Metformin reduces inflammation, so we hypothesized that metformin would augment the muscle response to PRT in healthy women and men aged 65 and older. In a randomized, double‐blind trial, participants received 1,700 mg/day metformin (N = 46) or placebo (N = 48) throughout the study, and all subjects performed 14 weeks of supervised PRT. Although responses to PRT varied, placebo gained more lean body mass (p = .003) and thigh muscle mass (p < .001) than metformin. CT scan showed that increases in thigh muscle area (p = .005) and density (p = .020) were greater in placebo versus metformin. There was a trend for blunted strength gains in metformin that did not reach statistical significance. Analyses of vastus lateralis muscle biopsies showed that metformin did not affect fiber hypertrophy, or increases in satellite cell or macrophage abundance with PRT. However, placebo had decreased type I fiber percentage while metformin did not (p = .007). Metformin led to an increase in AMPK signaling, and a trend for blunted increases in mTORC1 signaling in response to PRT. These results underscore the benefits of PRT in older adults, but metformin negatively impacts the hypertrophic response to resistance training in healthy older individuals. ClinicalTrials.gov Identifier: NCT02308228.
1. There was a trend for blunted strength gains in metformin that did not reach statistical significance.
Note- the blunted strength gains were not considered statistically significant.
2. Metformin did not affect fiber hypertrophy, or increases in satellite cell or macrophage abundance with Progressive Resistance Training (PRT).
3, In the full study with PRT, metformin does not affect fiber hypertrophy, but inhibits increased type I fiber frequency, without significantly affecting satellite cell expansion.
4. Metformin led to an increase in AMPK signaling, and a trend for blunted increases in mTORC1 signaling in response to PRT.
Limitations of this study which are very important to consider, this trial did not include sedentary control groups. Therefore, we are unable to draw conclusions regarding the effects of metformin alone on muscle mass and strength in generally healthy older adults. The effects of metformin in frail elderly, alone or in combination with resistance exercise, need further study. Although metformin appears to preserve lean mass in sedentary diabetic patients (Lee et al.,
2011),it would be important to know whether metformin affects muscle mass and strength gains with PRT in older diabetic patients. Our study was not designed to address these issues, and the majority of our cohort was nonobese and free from metabolic disease. Another thing to consider is what happens when you include testosterone and hGH? We do know that testosterone administration greatly decreases AMPK signaling and increases mTORC1 signaling. Increases in hGH and IGF-1 also do the same.
So for those who are doing steroids and even hGH, how significant would metformin negatively impact the hypertrophic response to resistance training?