You can find this exercise on page 52 of the book Synergistic Golf.
Exercise Type: DYNAMIC STRETCH
Exercise Category: ABDOMINALS, BALANCE, FLEXIBILITY, HIPS, LEGS - FEET, LOW BACK
Stand tall with hands on hips and feet hip distance apart. Inhale to prepare. Exhale and lift right knee straight out front. Inhale on lowering and exhale lifting the other leg. Maintain good posture lifting knees as high as possible. Repeat alternating legs 20x.