On rest days...

[w3ssam]

is it ok to do light cardio and push-ups/sit ups? i usually dont but is it ok if you do or will this hinder gains?

[Big H]

The point of rest days are just that; rest. As long as your not working or hitting the muscle groups you hit on your last workout then its not going to be that bad for you. I usually do cardio on my off-days, but not a lot especially when cutting. Push-ups after Chest day can be counter-productive, but working abs is fine if you want.

Keep it light and keep it short.

[khalid a.k.a Genocide]

I try not to do anything fitness wise on my rest days. Since my workout intensity (and weights) is high I really just try to lay back and chill on my non-workout days. But like BigH said, light cardio is ok to do it on your rest days, nothing wrong with that.

[Shaolin Temple]

I advise doing at least light cardio. However, there are plenty people I know that do intense aerobic workout during "rest" days (65% to probably near 80% MHR) or even intense anerobic workouts like basketball or soccer (75% to close to 90%) for 30 to 45 minutes. It's effective in burning fat. So if you want to burn fat and probably hinder muscle gains a bit, it's fine. Celebrities do it to burn away fat and get down below or around 8% to 10% body fat levels.

Even if you bulk, doing light cardio (brisk walk - 50% MHR) or light jog @60% MHR, it wouldn't hinder gains IMO.