Bend the right leg and place a tennis or lacrosse ball behind the right knee, squeezing it, so it doesn't fall. Lift the right knee up and out to the side, externally rotating your right hip for a clamshell. Lift and lower the right leg a couple of inches for a pulse, using the core to help lift the leg. Stand on the left foot with the right foot placed on a glider or towel, feet hip-width apart. Stand on the left foot with the right foot placed on a glider or towel, feet hip-width apart.