Most everyone knows that a lower resting heart rate is good and that getting your heart rate up during exercise is also beneficial for this most important muscle. If one undergoes a “cardiac stress test” to look for signs of heart disease, one of the components of that evaluation is to exercise in order to raise the heart rate while measuring blood pressure, electrocardiogram, and other factors.
Nowadays, wearable electronics have increased the number of parameters people can measure throughout the day and use the data gathered to monitor health, predict disease, and guide treatment. Some elements have been incorporated into watches or bracelets, linked to apps on our phones, and even uploaded to physicians, peer groups for the more competitive, or even health alert services if one has a potentially life-threatening condition. Parameters measured include steps walked, distance covered, flights of stairs climbed, calories burned, and pulse rate at various times. One of the newer items is “heart rate variability” (HRV). This data point measures how the time between each heartbeat varies throughout the day and is a window into broader issues.
The autonomic nervous system controls things like how the cardiovascular and digestive system work and is divided into two parts, sympathetic, which drives the fight-or-flight response, and parasympathetic, which does the opposite, setting one up for relaxation. In harmony with the autonomic system are opposing hormones that flood our body, chemical messengers that do similar things to the autonomic nervous system. If there is an appropriate stimulus for the response – a tiger chasing you merits a fast pulse rate – then all is well and good. But if the response is to a false stimulus, such as stress at work or home, or a poor sleep cycle, the physical response of an overactive sympathetic system has potential long-term negative effects on every part of your body.
HRV is a simple and non-invasive way of keeping an eye on the state of balance of your autonomic nervous system and hormonal balance – when in a relaxed, or healthy state, the HRV is high and when in a stressed, or unhealthy state, it is low, which is associated with an increased risk of illness, and even death.
An elevated HRV suggests that one may be more resistant to the negative effects of stress and heart disease and provides a very easy and transparent way of looking at your lifestyle and how it affects your overall health status.
Classically, HRV was calculated from a conventional, medical-grade electrocardiogram, an expensive machine that is validated regularly by medical engineers in the healthcare environment. The over-the-counter phones and apps may not have the same degree of validation but are certainly getting more accurate with time.
If you start monitoring your HRV as I have, you will note that during a period of high stress, the numbers are low and when exercising regularly, the numbers climb. Adjusting lifestyle parameters by simple things like relaxation tools such as yoga, quiet breathing, or taking a walk in a park shows immediate benefits, which of course encourages one to make further positive adjustments. Of interest, one study found that listening to the soothing sounds of Native American flute music had a positive effect on HRV. One of my favorite relaxation albums is a recording by R. Carlos Nakai; I recommend it wholeheartedly – pun intended!
HRV has also been shown to decline in diseases like diabetes, cancer, and serious infections, implying that it is an interesting representative of a declining state of health.
To be clear, though, HRV is just one parameter and must be taken in conjunction with every other observation. In an aircraft, RPM is a valuable metric, but just because you see a high number, that doesn’t mean you are flying high – you could have brakes applied and be firmly on the ground! So, if you want to fly high and well, keep an eye on all aspects of your health, including HRV!