The aim of the present study was to investigate the influence of parasympathetic receptor blockade on the heart rate performance curve (HRPC). Twenty healthy male subjects performed a first cycle ergometer test (F), showing a HRPC deflection of varying degree and direction. Subjects then in random order performed two additional cycle ergometer tests, one with atropine(A) and the other with placebo (P). Two lactate turn points (LTP1, and LTP2) were determined by means of linear regression turn point analysis. The degree and direction of the deflection of the HRPC was calculated mathematically as factor kHR (kHR>0 = downsloping of HPRC; kHR<0 = upsloping of HRPC). In comparison with that in F and P, HR in A was significantly higher at rest, LTP1, LTP2, and during recovery, but not at Powermax. An upsloping deflection of the HRPC was seen in only five cases in F and P, whereas in A 10 cases were observed (P < 0.05). In A, kHR was significantly lower than in F and P. A significant correlation for kHR was found among F, P, and A. Independent from parasympathetic receptor blockade and the HR at Powermax, the HR at LTP2 was lower in cases with negative kHR (upsloping). In A as well as in P a significant correlation was observed between kHR and HR at LTP2. The individual time course of HRPC is reproducible and may be independent of parasympathetic activity.
Department of Sportsphysiology, University of Vienna, Vienna, AUSTRIA; Departments of Sports Sciences and Internal Medicine, Karl Franzens University, Graz, AUSTRIA; Center for Cardiac Rehabilitation, Bad Schallerbach, AUSTRIA, and the Human Performance Laboratory, Department of HPER, University of North Dakota, Grand Forks, ND
Submitted for publication March 1997.
Accepted for publication September 1997.
Address for correspondence: Serge P. von Duvillard, Ph.D., Director-Human Performance Laboratory, Department of HPER, University of North Dakota, P. O. Box 8235, Grand Forks, ND 58202-8235 E-mail:Vonduvil@badlands.nodak.edu.