Engage core, move opposite arm and leg. Mistakes: Arching back, not controlling movements.
Engage core, reach side to side. Mistakes: Not engaging core, not reaching far enough.
Move knees to chest in plank position. Mistakes: Dropping hips, not engaging core.
Lift legs to 90 degrees, engage core. Mistakes: Using momentum, not engaging core.
Hold plank position on side, engage core. Mistakes: Collapsing hips, not engaging core.
Hold plank position, engage core. Mistakes: Sagging hips, not engaging core.