Ive herd people talk about that you should'nt rund after working out in the gym,Does any one know why?I herd it was something to do with muscles not recovering propery.
Also would this also count for swimming?
Well youir muscles need some down time after a work out, that's when they build themselves back up after you've destroyed them in the gym. If you do more exercise your muscles wont rebuild and you'll just be breaking them down more and you wont see the benfits of the gym.
Most gym/resistance work will not prevent you from going for a run to be honest (which is what I think you're getting at).
If you've been doing weighted squats/lunges/Romanian deadlifts, stuff like that, you may want to give your legs the day off, but for the most part you won't be using the same muscle groups. So long as you aren't using the same fatigued muscles the very next day, you can normally avoid damage or even catabolism. Legs recover quickly and running, despite being knackering and hard on the joints, doesn't fatigue the muscles in the same way targeted resistance training would, hence it's possible to run 6 days in a week without doing any harm to your muscles.
I mostly avoid swimming since I have the buoyancy of a DU shell, but unless you're really beasting yourself doing lengths; I can't see how it will cause damage to your muscles.
Again I apply the disclaimer that I could be full of sh*t.