Increases in intramuscular pressure raise arterial blood pressure during dynamic exercise

This investigation was designed to determine the role of intramuscular pres sure-sensitive mechanoreceptors and chemically sensitive metaboreceptors in affecting the blood pressure response to dynamic exercise in humans. Sixte en subjects performed incremental (20 W/min) cycle exercise to fatigue unde r four conditions: control, exercise with thigh cuff occlusion of 90 Torr ( Cuff occlusion), exercise with lower body positive pressure (LBPP) of 45 To rr, and a combination of thigh cuff occlusion and LBPP (combination). Index es of central command (heart rate, oxygen uptake, ratings of perceived exer tion, and electromyographic activity), cardiac output, stroke volume, and t otal peripheral resistance were not significantly different between the fou r conditions. Mechanical stimulation during LBPP and combination conditions resulted in significant elevations in intramuscular pressure and mean arte rial pressure from control at rest and throughout the incremental exercise protocol (P< 0.05). Conversely, there existed no significant changes in mea n arterial pressure when the metaboreflex was stimulated by cuff occlusion. These findings suggest that under normal conditions the mechanoreflex is t onically active and is the primary mediator of exercise pressor reflex-indu ced alterations in arterial blood pressure during submaximal dynamic exerci se in humans.