Beta1-adrenoceptor mediated origin of the heart rate performance curve deflection.
OBJECTIVE
The deflection of the HR performance curve (HRPC) has been described as an objective marker of submaximal exercise performance. HR response to incremental cycle ergometer exercise is shown to be neither linear nor uniform and a physiological explanation of the deflection phenomenon is lacking. We hypothesized that differences in the beta1-adrenoceptor site are the source of these differences. The aim of the study was to investigate the influence of the highly selective beta1-adrenoceptor (beta1-AR) antagonist bisoprolol (Bi) on the HRPC in young healthy male subjects with different HR response patterns.


METHODS
Sixteen subjects were treated in randomized order with Bi or a placebo (Pl) in two separate trials. HR response during incremental cycle ergometer exercise was compared between the two trials. Blood lactate concentration (La) and ventilatory variables were measured throughout both tests.


RESULTS
Bi changed the direction of the HRPC more in subjects with a regular, s-shaped response pattern under placebo than those with a nonregular or linear pattern. The influence of Bi on the HR at the second lactate turn point was significantly related (R = 0.78; P < 0.001) to the pattern of the HRPC in Pl conditions.


CONCLUSIONS
We suggest that differences between the subjects with regular s-shaped versus nonregular HRPC may be due to differences at the beta1-AR site. The origin of the HRPC deflection is mediated in part by the beta1-AR sensitivity.
Hofmann
Peter
P
Institute of Sports Science, University of Graz, Graz, Austria.
Wonisch
Manfred
M
Pokan
Rochus
R
Schwaberger
Günther
G
Smekal
Gerhard
G
von Duvillard
Serge P
SP
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D017298:Bisoprolol / Q000494:pharmacology*; D005080:Exercise Test; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007773:Lactates / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D018342:Receptors, Adrenergic, beta-1 / Q000502:physiology*
D000319:Adrenergic beta-Antagonists; D007773:Lactates; D018342:Receptors, Adrenergic, beta-1; D017298:Bisoprolol