I lifted pretty hard upper body while I was on accutane, as well as doing a lot of rehab for knee surgery. I did feel some aches and pains, but it could very well have been just because I was working hard. If you want to avoid joint soreness I'd recomend drinking a lot of water, taking anti-imflamitory pills like aleve, and taking glucosamine. Drinking a lot of water is always a good idea, and glucosamine supposedly promotes good joint health by keeping them lubricated. As far as the anti-imflam goes, soreness is a result of imflammation and you're more likely to get joint imflammation while taking accutane, because you're so dried out. This will treat the symptom, but not the problem. Just be careful though, because taking a lot of anti-imflammitories can be hard on your kidneys and Accutane puts a strain on all your organs as it is (even though it's hardest on the liver).