Movement begins when the hip flexors of the horizontal leg contract to lift that leg to vertical. At the same time, a slow lengthening of the hip and knee extensors of the vertical leg allows gravity to flex the hip and knee joint of that leg. The result moves the vertical foot along the vertical line. The lower abdominals pull to align the lower spine as the vertical leg stretches upward. The vertical variant position requires slight adduction of the flexed leg. Sculling is at mid depth, near the lateral line.