I’ve seen this asked in forums quite a lot, and, for the most part, it comes from a misconception about drumming and the (supposed) strength that it takes.
Drumming, by itself, does not build muscle. But it can tone muscles and build endurance, which is a different thing.
Intense drumming - like in intense heavy metal situations or hard bop -, especially when you do it live in 90 minute sets or so, definitely counts as cardio exercise. And, as we all know, cardio does not build a lot of muscle, but it can definitely tone it (ever seen a muscular marathon runner? Neither have I).
Like running, intense drumming in long sets can improve cardiovascular health, lower blood pressure, boost your mood, strengthen your immune system and improve brain power. Of course, other things in your life should be aligned in order for this to have the greatest impact. Eating McDonald’s and then drumming an entire Slayer set every day won’t help you.
In terms of brain power and health, drumming has been shown to help in treatment of Parkison’s disease, since drumming builds a very strong connection between brain signals and your entire body’s muscles.
So while drumming can contribute to muscle development, especially in the arms, shoulders, calves and core, it's not comparable to weightlifting or resistance training in terms of building muscle mass.
The repetitive motion and the need to maintain rhythm and force can engage and strengthen these muscle groups. However, for significant muscle building, drumming should be complemented with more traditional strength training exercises.
So, keep drumming, but also, if you can, go to the gym 💪
