The purpose here is to stimulate the "hip lock" position of single leg stance, ie to train away the hip drop of stance phase of running.
The drill is done by stepping laterally over a stick held at the height of the tibial tuberosity whilst holding a weight rigidly overhead. The cue is to push the weight towards the ceiling with each step.
The weight held overhead provides a vertical compression down the upper limb, through the shoulder girdle into the spine to facilitate reflex stabilisation.
The reach towards the ceiling can only be done by using the weightbearing hip to "get taller". This creates lateral hip stability, locking the hip into an abducted position, facilitating contralateral hip flexion. The extension at the weightbearing hip and spine leads to reflex stabilisation, permitting expression of hip flexion mobility.
Dropping the wrist, elbow, shoulder or neck into flexion. Flexion is associated with increased mobility of the segments we want to be stable. Cue eyes up, head up, stiff wrist, stiff elbow, punch the sky.
Progression: the hip lock walking drill.