INFLUENCE OF RESPIRATORY AFFERENTS UPON THE PROPRIOCEPTIVE REFLEX OF SKELETAL-MUSCLES IN HEALTHY HUMANS

Relationships between respiratory afferents and the motor drive to ske letal muscles are well documented in animals, but human data are scarc e. Tonic vibratory response (TVR) elicited by mechanical tendon vibrat ions were explored in an arm (extensor digitorum, ED) and a leg (vastu s lateralis, VL) muscle, in healthy subjects. Tendon vibrations were d elivered during unloaded breathing and after 10 breathing cycles while the subject breathed through an inspiratory or expiratory resistive l oad in order to activate respiratory afferents. Inspiratory loaded bre athing significantly enhanced TVR in ED and VL muscles whereas the eff ects of expiratory loading depended on the vibrated muscle (increased TVR in ED; decreased TVR in VL). These results suggest that inspirator y muscle afferents activated during inspiratory loading facilitate the gamma motor drive to arm and leg muscles whereas the activation of pu lmonary vagal afferents during expiratory loading can exert a facilita ting or suppressive influence on the gamma motor drive, depending on t he limb muscle group. (C) 1997 Elsevier Science Ireland Ltd.