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Lesser vagal withdrawal during isometric exercise with age
J A Taylor1, J Hayano, D R Seals
1Hebrew Rehabilitation Center for the Aged, Beth Israel Hospital, Boston, Massachusetts, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|September 1, 1995
Summary
Older adults show a reduced heart rate increase during isometric exercise due to an impaired ability to decrease cardiac vagal tone. This age-related decline is linked to lower baseline vagal activity.
Area of Science:
- Cardiovascular Physiology
- Aging Research
- Autonomic Nervous System Function
Background:
- Heart rate response to isometric exercise diminishes with age.
- The underlying physiological mechanisms for this age-related decline remain unclear.
- Cardiac vagal withdrawal is a key component of the heart rate response to exercise.
Purpose of the Study:
- To investigate if reduced cardiac vagal withdrawal is associated with the age-related decrease in heart rate response during isometric exercise.
- To compare cardiac vagal tone between young and older men during isometric exercise.
Main Methods:
- Assessed high-frequency R-R interval variability (an index of cardiac vagal tone) in healthy young and older men.
- Measured variables before and during isometric exercise to exhaustion.
- Analyzed heart rate, respiratory rate, and mean arterial pressure responses.
Main Results:
- Older men had lower baseline high-frequency amplitude (cardiac vagal tone) compared to young men.
- Only young men showed a significant decline in high-frequency amplitude during exercise.
- Smaller declines in cardiac vagal tone correlated with smaller heart rate increases during exercise.
Conclusions:
- The blunted heart rate response to isometric exercise in older adults is linked to an inability to further reduce already lower cardiac vagal tone.
- Reduced baseline cardiac vagal tone in older individuals contributes to their attenuated exercise heart rate response.