Cardiovascular and catecholamine responses to static exercise in partially curarized humans

Neural control of the circulation was evaluated during static exercise in 19 subjects by the determination of heart rate (HR), mean arterial pressure (MAP), cardiac output (CO) and plasma catecholamines. Influence from central command was evaluated during contractions with weakened muscles following partial curarization and reflex influence from metaboreceptors was assessed by post-exercise muscle ischaemia. Static handgrip increased HR and more so MAP and CO and MAP remained elevated during post-exercise muscle ischaemia. With partial curarization plasma catecholamines were also increased (P < 0.05). Two-leg extension increased all variables and during post-exercise muscle ischaemia elevations of HR, MAP and CO were maintained (P < 0.05). With partial curarization HR, MAP and plasma noradrenaline were even greater during the contraction. With the involvement of both legs during static exercise, reflex influence from the muscles elevated blood pressure by way of HR and CO and the importance of central command was detectable for HR and MAP as plasma catecholamines became elevated. However, the results indicate a separation between a central command influence on HR and CO related to an increase in plasma catecholamines during a handgrip, while the reflex influence on blood pressure was directed towards total peripheral resistance.