The secret to getting a firm butt is adding more resistance to recruit medium and large fast-twitch fibers. The body responds quickly when challenged with heavier weights than it's accustomed to. Give your butt a boost with these two easy moves.

1. Single-Leg Squats: Stand in front of a bench with your feet about shoulder width apart. Prop your right foot behind you on top of the bench, then lower your body with your left foot, throwing your hips back until your upper thigh is parallel to the floor. Push yourself back to the starting position. Do 2 sets of 10 reps for each leg. More squats you'll like.

2. Reverse Lunge: Stand with your legs hip distance apart and feet parallel. Step back with your right leg about 3-4 feet (depending on your height), landing on the ball of your foot with your heel elevated off of the floor. Slowly lower your body weight down into a lunge. Your front knee should be directly over your heel creating a 90-degree angle thigh to shin, and the back leg should be straight but not hyper-extended. You back knee should never touch the floor. Drive your body weight through your left heel and straighten your left leg to a standing position, contracting your left buttocks, quadriceps and hamstring. At the same time lift your right foot off the floor and lift your right knee up to hip level. Repeat the movement with the right foot. If you are doing this exercise with weights, hold them firmly by your sides. Repeat the reverse lunge with the other leg performing the appropriate number of reps for your level.