Four-Way Hip Extensions

Another surprise in this study was the multi-hip (or four-way) extension. This exercise (which involves that weird looking machine on a platform at the gym) targets the hamstrings as well as the gluteus maximus and medius. This machine can be a little strange to use, so get a trainer or helpful gym-goer to help you with the adjustments if you need to. How to do it:

1. Stand on the platform, sideways to the roller pad and make sure the pad is up high.
2. Swing the inside leg over the roller pad so that it's resting on the back of the thigh.
3. Hold onto the handles to help keep your balance, and keep the abs in and the torso straight.
4. Press the roller pad down with your thigh until the heel is out behind you (knee slightly bent)
5. Don't arch the back!
6. Slowly bring the leg back and repeat all reps before switching sides.
7. Perform 1 to 3 sets of 10 to 16 reps according to your fitness level and goals.

Quadruped Hip Extensions

Surprisingly, quadruped hip extensions (or a bent-leg raise while on all-fours) came out on top for targeting the gluteus maximus. This exercise really allows you to contract the muscles of the glutes. How to do it:

1. On hands and knees, keep the abs tight as you lift one leg up, knee at a 90-degree angle throughout the movement.
2. Keep lifting the leg until the bottom of the foot faces the ceiling and the hip, thigh and knee are all in alignment and parallel to the floor.
3. Don't arch the back and keep the neck straight.
4. Lower back down and repeat for all reps before switching sides.
5. Add ankle weights for more intensity or, as in this example, hold a light dumbbell behind the knee.
6. Perform 1 to 3 sets of 10 to 16 reps according to your fitness level and goals.

Back Extensions on the Ball

Using a ball for back extensions will give you more range of motion than you get on the floor and you'll also have a balance challenge since the ball is unstable. You may want to prop your feet against the wall to get more leverage.

1. Lie down with the ball under the belly and hips, legs straight out behind you (or knees bent for a modification).
2. Place the hands behind the head or under the chin - you can also keep the hands resting on the ball if you need a modification.
3. Round down over the ball and then squeeze the lower back to lift the chest off the ball.
4. Raise up until the body is straight (don't hyperextend), lower down and repeat for 1-3 sets of 10-16 reps.

http://exercise.about.com/od/strengthtrainingworkouts/ss/backexercises2_2.htm