STARTING POSITION:
Stand straight, spread your feet at shoulder width apart. Contract your pelvic floor and core while keeping your chest up.
MOVEMENT:
In a pendular movement, raise your right foot until your feel the stretch in your hamstring. Continue the movement moving your right foot backwards until you feel the stretch in your hip flexors. Repeat the movement for the specified amount of repetitions and then repeat with the other leg.
TIPS: While your are doing the exercise, move only the legs, make sure you don't move any other part of your body. Your head and chest should always look forward.