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Cardiovascular responses to active and passive cycling movements
A C Nóbrega1, J W Williamson, D B Friedman
1Harry S. Moss Heart Center, U.T. Southwestern Medical Center, Dallas 75235-9034.
Medicine and Science in Sports and Exercise
|June 1, 1994
Summary
Central command drives heart rate during active cycling (AC), while passive cycling (PC) increases stroke volume and mean arterial pressure. This highlights distinct physiological responses to different exercise types.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
Background:
- Understanding the physiological control mechanisms of cardiovascular responses during exercise is crucial.
- Distinguishing between active and passive limb movements provides insight into central and peripheral influences on cardiovascular regulation.
Purpose of the Study:
- To investigate the cardiovascular and metabolic responses to unloaded active cycling (AC) versus passive cycling (PC).
- To determine the role of central command versus peripheral feedback in regulating heart rate and stroke volume during different modes of cycling.
Main Methods:
- Ten healthy subjects underwent measurements of heart rate, mean arterial pressure, cardiac output, oxygen uptake, and muscle EMG during rest, AC, and PC.
- Stroke volume and peripheral vascular resistance were calculated.
- Passive cycling involved a second rider moving the subject's limbs.
Main Results:
- Oxygen uptake, perceived exertion, and muscle EMG were significantly higher during AC compared to PC.
- Cardiac output increased in both AC and PC, but via heart rate acceleration in AC and stroke volume increase in PC.
- Mean arterial pressure increased only during PC, suggesting a role for venous return or mechanoreceptor activation.
Conclusions:
- Central command appears to be the primary driver of heart rate response during dynamic exercise (AC).
- The increase in stroke volume and mean arterial pressure during passive cycling (PC) may be mediated by enhanced venous return and/or muscle mechanoreceptor stimulation.
- Active and passive cycling elicit distinct cardiovascular control strategies.
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