Heart Rate Variability as a Marker of ANS Activities
HRV is based on the time difference between each heartbeat (R-wave) (as above), i.e. the beat-to-beat variability.
Each R-wave represents a contraction of the heart and corresponds to the pulse. The beat-to-beat variability is affected by autonomic nervous system activity.
Each R-wave represents a contraction of the heart and corresponds to the pulse. The beat-to-beat variability is affected by autonomic nervous system activity.
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Normally the heartbeat should vary from beat to beat under direct control of both the SNS and PNS (the SNS speeds and the PNS slows the heart rate). HRV is the result of the interaction between these 2 systems. It is accepted by scientists that this interaction at the heart is a reflection of ANS balance or imbalance in the body in general. For example, SNS dominance at the heart is therefore an indication of a general sympathetic dominance in the autonomic nervous system.
This would indicate a system under chronic stress and a vulnerability to further stresses. An overactive ANS is an indicator of a system under current stress, with a balanced ANS being important to effective stress coping. More recent research highlights how our personality and thought processes influence health and also HRV. Sustained positive effective states lead to a clear and definable mode of physiological function that appears to facilitate the body’s natural regenerative processes. |
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Physiological coherence – a sine-wave-like pattern in the heart rhythm, increased heart/brain synchronisation and entrainment between diverse physiological systems occurs after positive thought focus, and positive emotions can produce extended periods of this physiological entrainment.
A healthy physiological system has the following characteristics:
Attenuated physiological variability is associated with a lack of psychological and behavioral flexibility in response to environmental demand. A reduction in HRV is therefore not only an indication of a lack of physiological variability, but also in its broad sense a reflection of reduced psychological and behavioral flexibility.
Although our understanding of the meaning of HRV is far from complete, it seems to be a marker of both dynamic and cumulative load. As a dynamic marker of load, HRV appears to be sensitive and responsive to acute stress. Under laboratory conditions, mental load (including making complex decisions, and public speech tasks) have been shown to lower HRV. As a marker of cumulative wear and tear, HRV has also been shown to decline with the aging process.
Although resting heart rate does not change significantly with advancing age, there is a decline in HRV, which has been attributed to a decrease in efferent vagal tone and reduced beta-adrenergic responsiveness. By contrast, regular physical activity (which slows down the aging process) has been shown to raise HRV, presumably by increasing vagal tone.
In short, HRV appears to be a marker of two processes, relevant to the conceptualization of allostatic load: (1) frequent activation (short term dips in HRV in response to acute stress); and (b) inadequate response (long-term vagal withdrawal, resulting in the over-activity of the counter-regulatory system –in this case, the sympathetic control of cardiac rhythm).
Several studies have now suggested a link between negative emotions (such as anxiety and hostility) and reduced HRV. Cross-sectional association between anxiety and reduced HRV (as assessed by two time-domain measures). Lower HRV in individuals who were “highly anxious” according to the Minnesota Multiphasic Personality Inventory.
A healthy physiological system has the following characteristics:
- Efficient neural control
- Rhythmic physiological variability within normal limits
- Greater response-potential to challenge
- Greater range of response behavior
Attenuated physiological variability is associated with a lack of psychological and behavioral flexibility in response to environmental demand. A reduction in HRV is therefore not only an indication of a lack of physiological variability, but also in its broad sense a reflection of reduced psychological and behavioral flexibility.
Although our understanding of the meaning of HRV is far from complete, it seems to be a marker of both dynamic and cumulative load. As a dynamic marker of load, HRV appears to be sensitive and responsive to acute stress. Under laboratory conditions, mental load (including making complex decisions, and public speech tasks) have been shown to lower HRV. As a marker of cumulative wear and tear, HRV has also been shown to decline with the aging process.
Although resting heart rate does not change significantly with advancing age, there is a decline in HRV, which has been attributed to a decrease in efferent vagal tone and reduced beta-adrenergic responsiveness. By contrast, regular physical activity (which slows down the aging process) has been shown to raise HRV, presumably by increasing vagal tone.
In short, HRV appears to be a marker of two processes, relevant to the conceptualization of allostatic load: (1) frequent activation (short term dips in HRV in response to acute stress); and (b) inadequate response (long-term vagal withdrawal, resulting in the over-activity of the counter-regulatory system –in this case, the sympathetic control of cardiac rhythm).
Several studies have now suggested a link between negative emotions (such as anxiety and hostility) and reduced HRV. Cross-sectional association between anxiety and reduced HRV (as assessed by two time-domain measures). Lower HRV in individuals who were “highly anxious” according to the Minnesota Multiphasic Personality Inventory.
