We investigated the influence of autonomic blockade (AB) on the left ventricular (LV)
diastolic function at rest (R) and during bicycle exercise (EX) in eight endurance-trained
(TR) and ten untrained subjects (UT). Two-dimensional and M-mode echiocardiography
at the parasternal long axis were performed at rest and during an exercise protocol,
which consisted of two stages of 50 and 100 W. Using the digitized data from the M-mode
echocardiogram, the normalized maximal increase in LV dimension during the rapid filling
phase (nmD) was calculated according to Hortnagl. Additionally the ECC was recorded
at R and during Ex 60min after this first test. 0.02 mg kg body mass-1 propanolol and 0.04 mg - kg body mass-1 atropine were injected intravenously over a 5-min period and the test procedure was
repeated as described above. Before AB nmD increased significantly from resting values
to 100 W in both groups, whereas nmD tended to be lower in UT compared to TR. During
AB nmD of UT was rather unchanged at R and during EX compared to pre-blockade conditions.
In contrast nmD of TR was slightly reduced and this difference was significant at
100 W. No major difference in nmD between the TR and UT group could be observed during
AB. Before and during AB HR of TR were significantly lower at rest, 50 and 100 W compared
to UT. We conclude that the enhanced diastolic relaxation observed in endurance athletes
seems to be due to a training-induced adpation of the au tonomic nervous system.
Key words
Diastolic function - exercise - training adaptation - autonomic blockade
