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Phase transition in a healthy human heart rate
Ken Kiyono1, Zbigniew R Struzik, Naoko Aoyagi
1Educational Physiology Laboratory, Graduate School of Education, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Physical Review Letters
|August 11, 2005
Summary
Human heart rate variability exhibits critical dynamics during daily activity. This criticality breaks down during strenuous exercise and sleep, indicating a biological phase transition in heart rate control.
Area of Science:
- Physiology
- Complex Systems
- Nonlinear Dynamics
Background:
- Healthy human heart rate (HR) exhibits complex fluctuations.
- These fluctuations share characteristics with physical systems near a critical state.
- Understanding HR control is crucial for health and disease.
Purpose of the Study:
- To investigate the criticality characteristics of human heart rate variability.
- To identify conditions under which these characteristics change.
- To explore the implications for understanding heart rate control.
Main Methods:
- Analysis of heart rate fluctuations in healthy individuals.
- Examination of criticality hallmarks, specifically highly correlated fluctuations.
- Comparison of HR dynamics during usual daily activity, prolonged strenuous exercise, and sleep.
Main Results:
- Highly correlated fluctuations, a hallmark of criticality, were observed only during usual daily activity.
- A dramatic breakdown of these criticality characteristics occurred during prolonged, strenuous exercise and sleep.
- This breakdown is reminiscent of continuous second-order phase transitions.
Conclusions:
- The human heart rate control system exhibits a dynamical phase transition.
- This is the first reported discovery of such a phenomenon in a biological control system.
- Findings provide a key to understanding HR regulation in health and disease.