Muscle metaboreceptors in hemodynamic, autonomic, and ventilatory responses to exercise in men.

A muscle metaboreceptor (ergoreceptor) contribution to the hemodynamic and autonomic responses to exercise is well recognized, but a ventilatory component remains controversial. Control handgrips were compared with handgrips followed by 4-min regional circulatory occlusion of the exercising muscles to isolate the metaboreceptor role in blood pressure, autonomic tone (spectral analysis of R-R and blood pressure variability), and ventilatory responses to exercise in 11 normal subjects. Exercise responses were maintained after the effort by metaboreflex activation in systolic pressure (136.2 +/- 3.5 vs. 123.0 +/- 4.3 mmHg, P < 0.05), ventilation (19.0 +/- 2.6 vs. 8.5 +/- 0.4 l/min, P < 0.0005), and sympathetic discharge to the heart and circulation (elevated low-frequency components of R-R interval, 1,747.5 +/- 309.2 vs. 1,085.9 +/- 259.1 ms2, P < 0.05, and systolic pressure variability, 45.3 +/- 3.9 vs. 26.5 +/- 4.4 mmHg2, P < 0.005). We conclude that metaboreflex contributes to the sympathetic, hypertensive, and hyperpneic responses to exercise in normal subjects.