Starting Position: Lie on your side on a mat/floor with your legs lengthened straight away from your body. Stack your feet in neutral position. Your lower arm can be bent and placed under your head for support. Your upper arm rests upon your upper hip. Your hips and shoulders should be stacked up and aligned vertically to the floor. Your head should be aligned with your spine. Engage your abdominal muscles to support your spine.
Upward Phase: Exhale. Gently raise the upper leg off the lower leg. Keep the knee straight and the foot in a neutral position. Do not allow the hips to roll forward or back. Both knees should be "looking" straight ahead. Continue raising the leg until the hips begin to tilt, the waist collapses into the floor or until your feel tension develop in your low back or oblique muscles.
Downward Phase: Gently inhale and return the leg to your starting position in a slow, controlled manner. After completing your set, roll over and repeat with the opposite leg.
A common mistake is raising the leg too high in this exercise. Given the design of the hip joint, the thigh can only abduct (move out sideways) to 45 degrees. Any movement beyond that position involves movement of the entire hip and no longer targets the muscles intended for this exercise.