Cardiovasc Diabetol. 2014 May 15;13:93. doi: 10.1186/1475-2840-13-93.
Effects of metformin and exercise training, alone or in association, on cardio-pulmonary performance and quality of life in insulin resistance patients.
Cadeddu C1, Nocco S, Lucia C, Deidda M, Bina A, Fabio O, Bandinu S, Cossu E, Baroni MG, Mercuro G
RESULTS:
Cardiopulmonary exercise test showed a significant increase of peak VO2 with metformin and exercise together.
Very rarely, metformin may cause a life-threatening condition called lactic acidosis. Your risk of lactic acidosis increases with other medical conditions, including congestive heart failure (CHF), kidney failure, and liver problems, including liver failure and cirrhosis (see Metformin and Lactic Acidosis for more information, including possible symptoms of lactic acidosis).
This “rarity” is estimated at 4 of 100 people. Do ya feel lucky, Punk?
By the way, some evidence suggest metformin rips holes in the pancrease to make it more sensitive, thus forcing the user to switch to insulin forever. But you wont find that in the "unbiased" (lol) government studies. Stick with ALA and IGF-LR.