Absolutely not. I think there's a thread here, somewhere, discussing this. Up until 2 years ago I was lifting weights 3 times a week at the gym.
@ costicina -> he's spot on.
i won't go into my treatise on all things stupid regarding the mythology surrounding muscular development but i will sucker punch the undying faulty logic that is workout=muscle='muscle bound'=stiff unflexible schmuck who can't even scatch their backside....
i am actualy in argument FOR a more than mild fitness and bodybuilding approach to for musicians but we just need to be smart about certain things.
1. we must pay super careful attention to strength and muscle imabalance, that is we must be very vigilent on working opposing and antagonist movements equally or counter to existing over use (so like for men, who love to do many bench pressing movements, they should be doing pull ups and rowing movements like crazy to make sure and develop the rear kinetic chain musculature enough that posture is maintained otherwise you get a tightness in the front from too much anterior work and this actually pulls the shoulders forward and down. a big no no that WILL affect your playing among other things.).
2. we must address the fact that we as pianists don't have the luxury of playing while standing, so when your are sitting for many hours per day (this includes when you sit for non piano too), this is a very unatural thing to do as far as how we are put together and our bodies just do not like it. you are essentially havingyour hips out of plane relative to the midline of the body BUT unlike a natural movement when this would be accompompanied by a lengthening of the hamstrings and a counter contraction of your quads, we have a bent leg at 90 degrees so the hamstring is in a shortened position for a very long time, with little to no quad activation. what happens over time is that a progressive shortening of the hamstring will begin to pull on the lower hips where they insert at the pelvis, this begin to shift the 'hip area' into an anterior til, and since the top end is connected to all sorts of goodies, i.e. your back muscle insert and attach in the upstairs area, it begins to pull on the lower back muscles. this is the classic cause of a lat of people with low back problems and why many of them injure themselves when they bend over to pick something up off the ground incorrectly (they attempt to lengthed an already length back muscle and since hams are tight, boom, pulled x,y,z). so we need to make sure and work MORE the hip and hamstring muscles to help counter act this tendency (i.e. lots of deadlifts, springting, squating, etc.).
3. we need to pay attention to hand and forearm health (this is a way long topic so i'll just leave it at that, i'll only say that from experience i make it a point not to go super uber heavy and deadlift more than 285 lbs or approx 130 kg close to a performance or too often as this will definately have some collateral tightness in the hands that can affect your playing but it is temporary. and still there are ways to train heavy while keeping in mind our need to relaxed hands and arms)
4. i am not entirely conviced stretching is absolutely neccesary (but it can help some). if you are working themuscles through a FULL range of motion and are addressing the balance issues i mentioned up top, flexibility will come on its own.-
i could go on and on but these are just some issues we can and need to address that actually make 'bodybuilding' good and necessary for our art.
also consider this thread. at the end of the day we as performers should want to put our best selves in front of our audience, we're there for them, part of that enjoyable live performance is a complete package, composed confident, competant musical playing, and when possible look your best. all things being equal, human nature is pretty much dominant and attractive and fit and musical is going to be more enjoyable vs frumpy/unattractive and flabby and musical. generally speaking of course.
typos be dammed i need some coffee before i get online, it's too early.
ok i'm off my soap box now. sorry for the book. the end.