Role of intramuscular afferent fibers in the ventilatory response to dynamic exercise in humans

Eight subjects, aged 26.5 ± 3.7 yrs, performed incremental workload cycling to investigate the interaction of skeletal muscle ergoreceptors in eliciting a ventilatory stimulus response to exercise. Each subject performed three bouts of exercise: control (exercise - no intervention); exercise with thigh cuff inflation to 90 mmHg (to reduce venous outflow and stimulate metaboreceptors); and exercise with application of lower-body positive pressure (LBPP) to 45 mmHg (to stimulate mechanoreceptors). Measurements of ventilation (V_E, L·min^-1), change in intramuscular pressure (ΔIMP, mmHg), and pH were collected. CONTROL CUFFS LBPP Watts V_E pH ΔIMP V_E pH ΔIMP V_E pH ΔIMP Rest*14.3 7.38 0.0 13.9 7.38 0.0 13.9 7.38 0.0 67W 30.4 7.37 1.1 29.2 7.37 0.4 37.4 7.37 4.48*137W 48.7 7.36 1.7 51.0 7.37 1.3 57.7 7.36 48.9*200W 67.8 7.33 2.0 76.9a 7.36*1.8 90.9*7.36*50.1*(*Significance from control at p<0.05; a Significance from control, p =0.08; Rest*- no interventions. Mean data is presented.) From these data, we conclude that stimulation of ergoreceptors generates a ventilatory stimulus to exercise.