Four square hopping is an exercise that I often incorporate into the late stages of the rehab process in working with runners rebounding from injury. This drill challenges the runner from a plyometric and neuromuscular control standpoint. If the performer demonstrates proficiency with this drill I'm confident as their therapist that they are prepared to initiate a graded return to running program. Once they have mastered the baseline drill they can progress to hopping without pausing  between each jump as is seen in the second video. Prerequisites to perform four square hopping include the following: 1) no signs nor symptoms of inflammation, 2) ability to fully weight bear through the previously injured region, 3) ability to balance on each leg in a wobble free manner, 4) ankle dorsiflexion of 20+ degrees with the knee flexed 45 degrees, 5) tolerance to eccentric closed chain contractions of the quadriceps, 6) adequate control of the lower extremity in the frontal and transverse planes, and 7) adequate hip and trunk control. Lastly, ensuring the runner is in an appropriately cushioned and defect free shoe is helpful in the case of awkward landings.