Flexible Adaptation

By Paul Salmon, Ph.D.

Mindfulness is a great tool for learning about things that would otherwise escape our attention. A common practice is just sitting quietly and following the breath ... breathing in, breathing out ... in a cycle that repeats over and over again. If you do this consistently, and on a regular basis, you begin to notice patterns that are otherwise easily overlooked. A world of interesting things to explore can open up, if only we are willing to pay attention. Becoming sensitive to such subtle inner states would be especially helpful for anyone involved in fitness and athletic training as a means of refining performance skills and avoiding injury.

Here's an interesting pattern to explore. If you sit quietly for a few minutes and allow the breath to deepen and relax, you will move into a state of relaxation in which both breathing and heart rate decrease. Most of us have experienced this frequently enough so it comes as no surprise. What is especially interesting about breathing that can be detected in this state is that your heart rate varies in a subtle, but predictable and meaningful way. In brief, as you inhale, your heart rate will increase momentarily; on the outbreath, heart rate decreases.

This pattern is an indication that heart rate and breathing are linked, and the effect is extremely predictable. The term for this is 'respiratory sinus arrhythmia,' and despite the word 'arrhythmia' it's a normal and healthy phenomenon. The effect is well known in archery and riflery, where you're taught to release the arrow or pull the trigger while exhaling when heart rate slows down momentarily. The effect is quite pronounced in states of deep relaxation and meditation.

This relationship between heart rate and breathing illustrates a more general, and very important principle: the heart is, or should be, sensitive to changes in both the internal and external environment and is capable of responding on a moment-by-moment basis to changing demands during episodes of stress (including exercise) or states of relaxation. This can be measured by determining the average variation in time between a particular segment of each cardiac cycle. Of course, breathing speeds up and slows down as well under such circumstances, again illustrating how these systems are coupled.

This kind of flexible responsiveness in heart rate, known as heart rate variability or HRV, is something that you're unlikely to pay much attention to, since it occurs automatically in response to varying demands on the cardiovascular system. However, it has been the focus of considerable research in recent years. In general, studies have shown that low HRV (that is, a lack of response variation) is common in people with high levels of perceived stress and a range of anxiety disorders, including panic attacks and post-traumatic stress disorder. It is also an index of vulnerability to adverse cardiac events. Finally, HRV tends to decrease with age, consistent with an overall decrease in flexibility with which we respond to changing circumstances.

From a health perspective, people who exercise regularly and are physically fit generally tend to show greater heart rate variability. This suggests that one of the benefits of regular exercise for the cardiovascular system may be greater flexibility in response to imposed demands. In other words, your system appears to be better adapted at responding to change, which helps avoid chronically high states of activation that can be extremely taxing in terms of both physiological and psychological factors. The key point? Exercise may not only be beneficial because it gets your heart rate up, but it may promote more effective adaptation and energy conservation in response to the challenging circumstances of everyday life.

Paul Salmon, Ph.D., is an associate professor at the University of Louisville, specializing in exercise psychology. Paul is a member of the Kentuckiana HealthFitness Advisory Board.