Here is some reassurance for those of you who are doing ‘active recovery’ due to injury, surgery, etc.: Researchers have found that you don’t always have to lift heavy to get the strength and size gains you want. The study compared two groups of experienced lifters and had them either use lighter weights (50% of 1RM) x20-25 reps or use weights up to 90% of their 1RM x8-12 reps. At the end of 12 weeks, the gains in muscle mass and muscle fiber size were basically identical. The common link between the two: lifting to the point of fatigue. Don’t get me wrong, lifting heavy weight can be addictive and hitting a PR is incredibly satisfying. But if you’re needing to lift lighter…do it to the point of fatigue, and don’t worry that you will be losing all of the gains you have made.

https://www.mcmaster.ca/opr/html/opr/media/main/NewsReleases/Lightweightsarejustasgoodforbuildingmusclegettingstrongerresearchersfind.htm