Why do musicians need to do fitness exercises?
While not all musicians may need to do fitness exercises, certain exercises target different muscle groups that can help to improve your physical stamina and ability when playing an instrument. In addition, musicians who exercise can also help to develop and fine-tune their coordination which in turn can lead to greater musicianship.
What are some exercises that I can do if I play the drums?
There are multiple exercises that you can do if you are a drummer. Those include:



Walking
Walk fast, take big steps, move your arms back and forth while walking. This way of walking is really good for your legs, feet, arms and wrists when you play drums. To maximize the benefits, push your backfoot hard on the ground when you walk. This is good for your ankles when you play drums.



Biking
Biking is especially good exercise for drummers. While biking, you use your feet and legs a lot, like when drumming. Moving your feet on bike pedals is similar to moving your feet on drum pedals. Biking can help you learn to control your foot and leg muscles better.



Jumping rope
Jumping rope isn't easy, but it is good exercise. You use your legs, feet, arms and wrists, which are important for drummers. Don't do it too much at first, because it can be a pretty exhausting task. 



These are some exercises that you potentially could do as a drummer, but it's up to you to decide.