We have recently reported that the baroreflex bradycardia due to stimulation of the aortic depressor nerve was blunted during voluntary static exercise in conscious cats and spontaneous contraction in unanesthetized decerebrate cats. Since the most blunted bradycardia occurred immediately before or when extending a forelimb prior to force development, central command is likely to contribute to the blunted baroreflex bradycardia at the onset of static exercise. However it remained unknown whether the blunted bradycardia was either due to the reduced sensitivity of the baroreflex stimulus-response curve or due to resetting of the curve toward a higher blood pressure. To solve this question, we examined the dynamic characteristics of the stimulus-response relationship between systolic (SAP) or mean arterial blood pressure (MAP) and heart rate (HR) before, at the onset of, and during the later period of voluntary static exercise in seven cats (n=348 trials) by decreasing and increasing arterial blood pressure with infusion of sodium nitroprusside and phenylephrine or norepinephrine. The slope of the MAP-HR curve significantly decreased at the onset of exercise to 48% of the preexercise value (2.9±0.4 beats/min/mmHg); the slope of the SAP-HR curve also decreased to 59% of the preexercise value. The threshold blood pressures of the stimulus-response curves, at which HR started to fall due to arterial baroreflex, were not affected at the onset of static exercise. On the other hand, the slopes of the SAP-HR and MAP-HR curves returned near the preexercise levels during the later period of exercise, while the threshold blood pressures of the stimulus-response curves were significantly elevated 6-8 mmHg. The maximal plateau level of HR was not different before and during static exercise, suggesting that an upward shift of the baroreflex stimulus-response curves is not appreciable. We conclude that central command is likely to attenuate the sensitivity of the cardiac component of arterial baroreflex at the onset of voluntary static exercise in conscious cats without shifting the stimulus-response curve.