Start in a full plank position - shoulders, elbows & wrists are stacked - arms straight - skates hip distance apart - heels pointing upwards - core engaged - weight distributed evenly between hands and feet - roll one leg in towards the chest bending at the knee - reverse the action and roll the same leg backwards extending the leg, simultaneously roll the opposite leg in towards the chest bending at the knee - alternate legs with a rhythmic action - continue for 1 minute.