Cardiovascular, metabolic and plasma catecholamine responses to passive and active exercises

Eight healthy male volunteers (aged 19.6+/-3.0 years) were submitted to the unloaded active (AE) and passive (PE) cycling exercise-tests performed on an adapted cycle ergometer at a pedalling rate of 50 rpm. Intensity of acti ve exercise was about 10% of VO2 max. In the PE exercise test the ergometer was moved electrically. During both tests the systolic time intervals (STI ), stroke volume (SV), heart rate (HR), blood pressure (BP), oxygen uptake (VO2), rating of perceived exertion (RPE), electrical muscle activity (EMG) , plasma adrenaline (A), noradrenaline (NE) and blood lactate (LA) concentr ations were measured. Exercise induced changes in VO2, RPE and EMG were sig nificantly higher during AE than PE. Shortening of the pre-ejection period (PEP) and diminishing of the PEP to ejection time (ET) ratio were similar i n both types of exercise, whereas HR increased only during AE. A significan t increase in cardiac output (p<0.01) resulted from increased SV (p<0.01) d uring PE and from increased HR (p<0.01) during AE. MAP increased only durin g PE and it was higher than at rest and during AE (p<0.01). Absence of chan ges in SV and MAP during AE may be considered as a secondary effect of the decrease in TPR. Plasma catecholamines did not increase above resting value s in either type of exercise. Blood LA concentration increased during both PE and AE but it reached higher values (p<0.01) after the latter test. The present data suggest that the inotropic state depends on the mechanoreflexe s originated in skeletal muscles. However, contribution of changes in prelo ad to shortening of PEP can not be excluded.