Can calisthenics affect muscle memory in regard to piano playing?

“Muscle memory” is a misnomer. It refers to motor learning. The types of things committed to “muscle memory” are things like how you sit, hold your hands, and strike the keys. The things that become automatic whenever you play. Memorizing music is a different kind of memory all together and I wouldn’t worry about calisthenics. Practicing piano for hours/day is hard enough on your body that any other non-injurious activities you do to improve strength, flexibility, and endurance should balance out the harm playing piano is doing to your body. The best tip I ever picked up for memorizing music is to memorize it from the end rather than from the beginning. Most people memorize the first section, then the first+second section, then the first+second+third section etc. The reason this is all wrong is because you learn the beginning sections so well you can play them in your sleep but don’t spend nearly as much time on the last sections. Also, if you do have a memory slip and have to pick up from where you left off you won’t be used to starting in the middle of the piece and playing to the end. If you memorize the last section of your piece; then the 2nd from last+last section, then 3rd from last+2nd from last+last section etc. instead of getting weaker as you play your piece you will get stronger. Since the end of the piece is the last thing they will hear it is the most important part to nail (other than a cadenza anyway). Also, practicing this way you will be used to playing to the end from any point so if you do have a memory slip and have to play from there you will have already practiced playing from that point to the end. I don’t think your workouts are hurting your memory unless you are doing them so intensely that you are over-training and running yourself down.