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Related Experiment Videos

Cardiorespiratory responses to cyclic triangular ramp forcings in work load.

K Niizeki1, Y Miyamoto

  • 1Department of Electrical and Information Engineering, Faculty of Engineering, Yamagata University, Yonezawa, Japan.

The Japanese Journal of Physiology
|January 1, 1991
PubMed
Summary

This study examined physiological responses during cyclic ramp exercise. Slower exercise ramps initially caused asymmetric responses in ventilation and cardiac output, which normalized with subsequent cycles.

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Area of Science:

  • Exercise Physiology
  • Cardiorespiratory Function

Background:

  • Understanding the dynamic physiological responses to exercise is crucial for assessing cardiorespiratory fitness.
  • Investigating the influence of exercise intensity and protocol on these responses can reveal underlying control mechanisms.

Purpose of the Study:

  • To investigate the dynamic responses of minute ventilation, heart rate, cardiac output, oxygen uptake, and carbon dioxide output.
  • To determine the effect of different ramp slopes on the mean response times (MRTs) and response asymmetry during cyclic ramp exercise.

Main Methods:

  • Six healthy male subjects performed cyclic ramp exercise on a cycle ergometer in a sitting position.
  • Three ramp slopes (33.3, 20, and 14.3 W/min) were applied up to 100 W.
  • Exponential function with time delay was used to calculate MRTs for physiological variables.

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Main Results:

  • Mean response times (MRTs) for the ascending phase of the first cycle were longer with decreasing ramp slopes for most variables.
  • Significant response asymmetry was observed in the first cycle, particularly for respiratory variables, which diminished in subsequent cycles.
  • Cardiac output showed less asymmetry compared to respiratory variables, and a strong correlation was found between MRTs for ventilation and carbon dioxide output.

Conclusions:

  • Exercise intensity, specifically ramp slope, influences the dynamic cardiorespiratory response and introduces transient asymmetry.
  • The normalization of responses in later cycles suggests adaptive mechanisms that overcome initial asymmetries.
  • Cardiodynamic or humoral factors likely play a role in the coupled dynamic responses of ventilation and carbon dioxide output.