Bow flex is a great work out machine. You should use it at least three times a week and to avoid injusry start out by only using resistance that you can "lift" or push for 10-15 reps. Then after you have been working out for a month or more, you can start doing a set of heavy reps after doing 3 warm up sets of ten. Your heavy reps should be at a weight or setting that you can push two to three times any less too heavy any more too light.