The squat thrust or up down is a calisthenic exercise. It typically is performed as follows:[1]
A variation is the alternate leg or split-squat thrusts. This is performed by starting in the same position as the normal squat thrust and then splitting the legs in motion; keeping on your toes during the exercise, take one leg from the rear, up towards the chest in a smooth motion, once the foot of this leg reaches the ground, the other leg should then start to come up towards the chest, and at the same time the leading leg should go back to the starting position.