If you sit a lot (e.g. because you want absolutely to finish a shawl ;-)), you can easily get pain in the arms, wrists, shoulders, neck…
;-)
If you stretch a little in between, it won’t get so severe, I’ve tried it before ;-)
Links:
Crafters Stretches (Suggested Stretch Combinations – What Aches?)
Here at unikatissima:
Pain From Crafting