Drive corresponding motor neurons on swing & Reflex loops operating on them especially. Stretch flexes, cutaneous reflexes (extensive thrust reinform activity in extensor burst gen while leg bearing weight) Propriospinal (in spinal) regulate reflex strength of swing & stance. Spinoreticulothalamic neurons have pain-related neurons near central canal so when very painful stimulus, tends to turn on some of these locomotor networks. So is foot stimulated, get increased flexion than normal, functional since means hit obstacle and increase flexion to get over it instead of stepping on hid. So dif connections in spinal cord, presynaptic inhibition, easy for ns to change signal effect. Swing when in air, not supporting weight: f starts w toe coming off ground (pure flexion, leg suspended in air) E1 when foot brought back to ground (extension, mostly passive gravity doing work so minimal muscle activity) Flexor burst generator: flexion phase of swing has a fixed duration, regardless of speed of locomotion ex.