ISSN:
1439-6327
Keywords:
Exercise-induced vagal inhibition
;
Exertion
;
Humans
;
Overshoot
;
Transients
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The influence of respiration on the mean blood pressure $$\bar P_{\text{a}}$$ and R-R interval responses at the onset of dynamic exercise was studied in 15 healthy subjects who performed 4 s of unloaded cycling at 1.5–2.0 Hz, 4 s of Valsalva manoeuvre at 5.3 kPa, and a combination of both, each during a 12-s long apnoea at total lung capacity. The R-R intervals were obtained from the electrocardiogram,P a was measured continuously by finger plethysmography, and intra-oral pressure was used to estimate the changes in intrapleural pressure. There was an immediate and significant shortening of the R-R intervals during exercise [mean (SE): 790 (20) to 642 (20) ms] that was not modified when Valsalva manoeuvre was added [783 (28) to 654 (21) ms]. Although 4 s of exercise alone did not alterP a [13.8 (0.5) to 13.7 (0.7) kPa], this may indicate a pressor response, since $$\bar P_{\text{a}}$$ decreased during apnoea alone. When exercise was performed simultaneously with Valsalva manoeuvre, $$\bar P_{\text{a}}$$ increased significantly [13.6 (0.4) to 15.8 (0.5) kPa] and of similar magnitude during Valsalva alone [13.2 (0.4) to 15.3 (0.7) kPa]. In conclusion, 4 s of unloaded cycling elicited a fast R-R shortening with no change in $$\bar P_{\text{a}}$$ from rest. A concomitant Valsalva manoeuvre had no effect on the R-R interval response but caused a marked increase in $$\bar P_{\text{a}}$$ . From these findings, it is suggested that respiratory influences should be controlled in studies concerned with the cardiovascular responses at the onset of dynamic exercise.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00571453
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