Your butt shape is determined by a number of factors, including the size of your gluteal muscles and the amount of fat you have. Some women appear to have a flat butt because they have poor posture, lack mass in the hip or have a genetic placement of the pelvis that predisposes them to more of a pancake shape.
You can improve the shape of your butt with exercises. Corrective exercises focus on improving your posture, while strength exercises help you increase muscle mass. Integrate both types of exercise in your workouts for the greatest benefits.
Posterior Pelvic Tilt
The posterior pelvic tilt is a postural deviation where your pelvis is tilted backward, causing your lower spine to decrease its natural extension. This causes your upper spine and shoulder girdle to round forward to maintain your center of gravity, causing your butt to appear flat and droopy. Side effects include weak hip, back, shoulder and abdominal muscles -- and pain in the back and neck, along with tight chest muscles.
Increase lumbar extension through correct posture exercises to push your pelvis slightly back, giving you the appearance of a shapelier butt. Seated overhead raises are a stretching exercise to help improve this postural deviation.
How to: Stand with your right foot in front of you with both feet pointing forward. Lace your fingers together and extend both arms in front of you with your hands facing toward you. Raise your arms over your head and turn your hands so that they are facing up. Tighten your left buttock to stabilize your pelvis, and do not move your torso as you stretch. You should feel your lower back extend slightly. Hold this position for five to six deep breaths. Switch leg positions and repeat the stretch.
Build Your Glutes for a Rounder Butt
Your butt muscles -- the glutes -- and fat tissue provide the shape of your butt, as well as support for your lower body when you stand and move. Weight training stimulates muscle growth in your butt, giving your buttocks greater definition.
Exercises that work your glutes include squats, deadlifts, lunges and jumping exercises. For most strength exercises, the National Academy of Sports Medicine recommends two to three sets of eight to 15 repetitions. Use weight that feels heavy by the end of your chosen number of reps. Train on three non-consecutive days each week for at least four weeks to see any significant muscle growth.
A sedentary lifestyle can cause your body to lose muscle mass and impact your posture. Sitting with poor ergonomics for a long period of time, such as sitting with a rounded spine and hunched shoulders, can lead to a flatter butt. Engaging in regular activities, such as hiking, swimming and dance can supplement the corrective exercise and strength training, which will teach you how to move better, preventing further postural deviation in the hip.
Remember that genetics also play a role in determining the shape of your buttocks. While you can add some perk to a flat pair with exercise, remember that not everyone will develop the backside of a Kardashian. Build up your glutes with postural and strength moves, but keep your expectations in line with your body type's potential.