Multiplicity of the afferent pathways mediating the exercise pressor reflex.

The cardiovascular responses to isometric contraction of the triceps surae muscle of one leg were determined before and after transecting the ipsilateral L7 or L6 and S1 spinal roots. Sectioning only the L7 spinal root slightly attenuated the pressor, but not the heart rate response induced by skeletal muscle contraction, while cutting the L6 and S1 spinal roots (L7 intact) had no effect on the cardiovascular changes. This indicates that there is multiplicity in neural afferent pathways that mediate the exercise pressor reflex.