Facial muscle tension influences lung airway resistance; limb muscle tension does not.

In healthy adult subjects, operantly conditioned increases in facial (frontalis) muscle tension produce increased lung airway resistance, whereas conditioned facial muscle relaxation results in decreased airway resistance. Conditioned increases and decreases in limb (brachioradialis) tension do not affect airway resistance. The latter finding rules out general muscular events and mitigates against metabolic agents as explanations of the airway resistance changes associated with facial tension change and suggests that the facial muscles influence airway resistance through the operation of a neural reflex.