• supine exercise;
  • trained muscle;
  • detrained muscle;
  • left ventricular volume;
  • sympathetic nervous activity

In 11 healthy subjects (8 M, 3 F, age 21–59 years), left ventricular end-diastolic and end-systolic volumes (LVEDV and LVESV) were measured noninvasively by isotope cardiography together with arterial blood pressure, central venous pressure (CVP), catecholamines and atrial natriuretic factor (8 subjects) during submaximal exercise with a habitually active or trained (tr) and a detrained (dtr) leg, respectively. Exercise was performed as supine bicycling at 2 different absolute workloads with each leg in a randomized order. At the lowest workload, small but significant increases in heart rate (107–112 bpm), plasma norepinephrine (2.1–2.4 nmol · l−1), arterial blood pressure (systolic blood pressure (SBP) 168–172 mmHg) and contractility (SBP/LVESV) as well as left ventricular ejection fraction (0.71–0.74) and estimated myocardial efficiency (29.0–30.1%) were found during dtr exercise compared with tr exercise. LVESV (39–34 ml) and peak ejection time (154–134 ms) were both reduced. At the highest workload, SBP (175–180 mmHg) and CVP (1.8–3.1 mmHg) were increased for dtr exercise compared with tr exercise. It is concluded that only modest differences in the central hemodynamic response upon exercise with tr and dtr muscles could be demonstrated, in contrast to preliminary findings. The results from the lowest exercise load support the hypothesis that peripheral factors related to the actual state of training strongly influence the central hemodynamic response to exercise. The blunting of the results on the second workload might be caused by influence from the preceding exercise load. The smaller than expected differences, generally, could be caused by the experimental conditions (supine exercise) as well as variations in the state of detraining in the subjects.