I think it's like any new activity. New muscle usage causes soreness, and after a while you don't get sore anymore. Make sure your body is supported and you're not hunched over or tense. Take frequent breaks and stretch your fingers. I knit English style and can go for hours without getting sore, but when I got back into knitting after years away, my hands ached at night.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry