It is always preferable doing some exercise rather than no exercise at all, but your results will be even better if you cross train. In many cases, when you go to a gym, you will see people on the treadmills and stationary bikes, and other people lifting weights. Most of the time you will never see those two groups cross over, and that is where the opportunity for greater gain is lost. If you can lift three hundred pounds, but can’t walk up a flight of stairs without getting winded; that is a serious problem. If you can run a 5 minute mile, but struggle carrying bags of groceries to the car; THAT is a problem. You want overall fitness; not just in specific areas. By cross training, you will address the strength and aerobic capacity of your body, and appreciate those improvements in your day-to-day activities. In the end, isn’t that what you want? You don’t go to the gym just because you enjoy going to the gym. You go to make yourself stronger, get in better shape, and then see and experience the results of your hard work when you are not at the gym.