The Bow Flex is probably one of the more effective machines. It offers many different types of resistance and countless exercises that you can do to give you total body, core muscle strengthening.
Machines that allow compound exercises will work best, rather than an isolated muscle group. Try to find something that would let you get a few kinds of exercises in.
Remember, machines are only effective if you use them regularly, and push yourself on them. That being said, the three best machines to use for results are stairmaster, treadmill or stationary bike.
