See which leg is stronger.

1. Lie on your back, knees bent, feet flat on the floor. Place the ball between your hands and knees. Keep your arms straight.

2. Begin by first moving the ball back and forth gently between your hands and knees. Keep your spine long, and your skull on the floor without arching your neck or lower back. This placement activates your core.

3. Raise your head, neck, and shoulders off the floor, without pressing too hard with your hands. The spine should remain stable on the ground, without arching. Keep your tail bone firmly on the floor. Repeat this 8-10 times.

From 101 Ways to Work Out On the Ball

Just like normal leg extension, except done one leg at a time.

Same as standard lying leg curls, just done one leg at a time.

Sit on a bench with feet flat on the floor. Sit straight with shoulders back and down. Tighten your abs, focusing on the lower part to provide solid support. Keeping your lower body and the pelvis stable, on exhale, rotate the upper body to the right. Inhale and return to center. Exhale and turn to the left. Inhale and return to center.

Start by standing upright, holding dumbbells in each hand.

Keeping the dumbbell close to your body, raise them by bending your elbows slowly. Keep your forearm parallel with your body, not like a bicep curl.

Lower back to starting position.

For a complete description and pics: http://www.usmc-mccs.org/fitnessrec/downloads/Daily16.pdf

3. Daily 16 Conditioning Excercise Descriptions -> #3.