Lower grip reflex (plantar, Babinski reflex) It is elicited when the thumb presses on the sole of the foot at the base of the II-III toes. The child produces plantar flexion of the toes (presses the toes against the foot). In healthy children, this reflex persists until 12-14 months of life. The absence of the lower grip reflex occurs when the spinal cord at the lumbar level is affected.