Training with very heavy weights while doing chest exercises will enlarge your muscle cells and decrease the size of the fat cells in your breasts, making it seem like you are losing your boobs. To decrease the impact of weight training on the shape and size of your breasts, vary your routine by incorporating different types of training methods such as circuit training and full-body workouts. Keeping the resistance at a light to moderate level further ensures you will tone up without excessively shrinking the fat cells in your breasts.
Follow an upper-body circuit training routine by including chest, back, biceps, triceps and aerobic exercises into one workout. By training all your upper-body muscles with aerobic intervals and resting for only 10 seconds between exercise stations, you tone up without focusing on your chest muscles so you can keep the size and shape of your breasts. Complete only two exercises per muscle group and three sets of 15 to 20 repetitions per exercise.
Vary the chest exercises you do by changing the exercises at every workout including dumbbell presses, pushups, dumbbell flies and machine chest flies. Change the incline of the bench as well, toning your pectoral muscles from various angles so you do not bulk up the center of your chest, keeping the size of your breasts while toning.
Do a lower-body, shoulder and abdominal circuit training workout two days after your upper body circuit, toning your lower body, deltoids and abs without exercising your upper body muscles too much in one week. Perform four exercises for your lower body, two exercises for your deltoids and two exercises for your abdominals. Complete four sets of 15 to 20 repetitions per exercise.
Perform a full-body workout for all your muscle groups two days per week with at least two days between your workouts. Full-body workouts minimize the number of exercises and sets you do for all your muscles, especially your chest, but are quite taxing because you are working your entire body.
Do four to five sets of 15 to 20 repetitions of only one exercise per muscle group, toning your body without losing your breasts.
Begin your second full body workout of the week in reverse order; for example, if you started your first workout of the week with chest and back exercises, do leg and shoulder exercises first at your second workout, toning your entire body without focusing on your chest muscles so you maintain the size of your breasts.