I've been getting pretty good at hitting the gym 4-5 times a week but I do mostly cardio. I don't know what to add for strenth training as I never really do it. I've been good at alternating arms and legs and adding in abs most of the time (I use the exercise ball). I'm not a huge fan of free weights but I'm don't know if its because I don't do them often. Any suggestions on a good routine? How often should I be doing them and for how long?