It can be so tiring to play in a marching band. Especially percussion...first of all the drums aren't exactly light to carry around. Plus your hands get sore pretty quickly. I played cymbals last year in marching band. Having the stupid things strapped around your wrists (even with gloves) and having to hold them up for long rehearsals wasn't so fun. I'm sure carrying the bass drum isn't a walk in the park either, so I see where you are coming from. It is definitely a challenge.I suggest that if you are having a lot of pain, talk to your percussion instructor. You may be holding excess tension in your arms when playing and if there is such a problem, playing hours on end will only magnify it. The only way I can see it being bad for your piano playing is if you do damage to your hands or arms. Definitely try and minimize tension when playing. This may sound strange, but stretching out your wrists and massaging your hands before playing and during breaks may help.