Much of the weight I am trying to lose is around my middle. So, when I run, do situps, or do pushups, I feel a quite a strain in my lower back (also, running has been hard on my knees). I know that swimming is really low impact, but I don't have time to go to a pool. Any suggestions of ways in which I can exercise and maximize fat burned without straining my back?
I always suggest yoga or pilates for folks with back problems. It will strengthen your core and help your back. As for the other, perhaps you should consider race walking instead of running. Or even cycling. Either option will give you a good workout but be easier on your knees.