Hey Is it bad to do cardio after weight training when you want to build muscles?
There is research to promote both views on what is best for muscle gains. I think you have to find the right balance for your body. Me personally, when i want to stay lean will do a light warmup steady state cardio for 5 - 10 mins before hitting the weights. Then hit the cardio again post weight training. When I want to gain weight I save cardio for only 2 days out of the week.
The best is to do it on different days. But if you have to do it on one day, it's better to do cardio before muscle workout. Only then and if you want to gain muscles! If you have other goals, it might be better to change the sequence. Just think about, which muscles you want to gain - legs, arms, chest...
Of course you can finish your session with a slightly cardio training, but it may not be long and fast in this case.