Starting Position: Lie on your side on a mat/floor with your legs extended straight away from your body. Hold your feet together in neutral position (at 90 degrees to your shinbone) and your lower arm bent and positioned under your head for support, while the upper arm rests upon your upper hip. Your hips and shoulder should be aligned vertically to the floor. Your head should be aligned with your spine.
Upward Phase: Exhale and gently raise the upper leg off the lower leg while keeping the knee extended and the foot in a neutral position (avoid flexion and extension). The hips should remain vertical to the floor and the knee of the raised leg should point straight away from you (do not rotate upward towards the ceiling or downward towards the floor). Continue raising the leg until the hips begin to tilt upwards or until your feel tension develop in your low back or oblique muscles.
Downward Phase: Gently inhale and slowly return your raised leg to your starting position in a 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.