Could be. Unless your knees or back are screaming with pain...
Basically, if you are riding painfree you are doing it most likely right.
If you joints hurt you are doing something wrong (unless you have some kind of other condition/illness.). Pains can be usually remedied by changing technique.
Sore muscles are good - means you are riding hard. Now go get a beer and chug it while riding with no handbrake.