It won't put any significant amount of muscle on your legs unless your using a high amount of weight. Very unlikely since Tae Bo is mostly done without weight. Tae bo is aerobic so basically its just repetition which will slim and tone your muscles. Lifting weights adds to muscle but an aerobic workout will generaly add a negligible amount of muscle which will only be of benefit to you as the more lean mass you have the more calories you need to burn throughout the day to maintain. So keep on doing your workouts and remember when your doing your kicks make sure you don't over extend your knees and slightly bend your supporting leg for better balance. Never lock them out it just doesn't add to the workout.