Key result
Atropine increases upsloping heart rate performance curve deflection by ~100% versus placebo.
Why the study?
The influence of parasympathetic receptor blockade on the heart rate performance curve (HRPC) was not well understood.
Does parasympathetic receptor blockade with atropine alter the heart rate performance curve in healthy male subjects?
RCT (n=20)
random order
Does parasympathetic receptor blockade with atropine alter the heart rate performance curve in healthy male subjects?
Parasympathetic blockade with atropine alters the heart rate performance curve, though the individual time course remains reproducible.
Answers are grounded in this paper and cite their sources.
Requires accounting for parasympathetic tone in HR curve interpretation; extends evidence on autonomic determinants during exercise.
Parasympathetic receptor blockade and the heart rate performance curve. Med. Sci Sports Sci., Vol. 30. No. 2, pp. 229-233, 1998. 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 Power(max). 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 Power(max), 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.
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Pokan et al. (1998) conducted an RCT in Healthy (n=20). Atropine vs. Placebo was evaluated on Upsloping deflection of the heart rate performance curve (p=<0.05). Parasympathetic receptor blockade with atropine increased the incidence of upsloping deflection of the heart rate performance curve compared to placebo.
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