Starting position lying flat on your back with your legs straight up
in an "L" position. Freeze your knees throughout the exercise.
Hold your arms out to the sides, palms down to stabilize yourself.
Maintaining an "L" position with your knees locked, swing your legs to
one side without hitting the floor. Then swing back up in the
other direction, duplicating the same movement to the other side.
prior to getting used to the exercise, you can hold your arms with a
wide grip on a barbell or even the bottom of a couch. It can
also be beneficial to move your butt as close as possible to a wall or
other barrier. This helps you to focus on maintaining the "L"
position as you fatigue.