So I've been playing classical piano for 20 years now (I'm only 23). I'm very advanced and study with a Van Cliburn silver medalist currently. I finished a piano performance degree last May, and actually had to take a year off of piano while I completed my music education degree. I'm starting to get back into the habit of practicing about 4 hours a day, and I've noticed a tightness in my left hand. There isn't pain per se, it's just very tight after say, 20 minutes of doing scales, and when I try to perform arpeggios it also becomes very tight in the hand and forearm. I'm not sure if this is because I'm just out of shape and need to take things very slowly, or if there is an underlying medical condition (say tendinitis or carpal tunnel).
For my senior recital in college, I performed Barber's Sonata Op. 26. It's a difficult piece and I practiced for about 6 or 7 hours a day for about 3 months to master the piece (especially the fugue). If you're familiar with the piece, there is a lot of pounding on the hands, and I'm worried that I might have done some damage (although I'm not sure why I would be experiencing this a year later)?
Any advice on what I should do? Does this sound like I'm just out of shape, or is it tendinitis? Thank you!