Context: Metformin is a simple, very safe, and very common diabetic drug that appears to improve all-cause mortality and have some positive health effects in the average person, even if minor (such as improving blood glucose levels and insulin resistance), thereby slightly lengthening human lifespan and improving the process of aging. For this reason it has been touted as an anti-aging drug by many, and is taken by many non-diabetics for this purpose.

However, there have been more studies surfacing recently that show that it can make exercise less beneficial, of which the link in OP is a piece of evidence in favor of this.

For those interested in other interesting substances in this area, I suggest looking into Acarbose and Rapamycin, but there's many others that seem pretty cool, even if highly speculative. Also adding after reading a child comment to this, Peter Attia is one of the many great people worth following in this area, with a very high-quality information-dense podcast.