I see people always run into the gym just to jump on a treadmill or piece of cardio equipment for 30-40 minutes and then finish with 10-15 minutes of weight lifting. That is not the way to workout. The reason why is simple, per minute of working out, weight lifting requires more energy usage than cardio. Therefore instead of burning up all of your energy on the cardio equipment, it would be best if you lifted fro 25-35 minutes, then finished off with 20-30 minutes of cardio for a great workout.