At the gym, you might have heard a few of us talking about heart rate variability (HRV). Read on for the scoop and how you can use it in your life.
– Heart rate variability (HRV) describes the changes in the amount of time between heart beats.
– HRV has been shown to be an accurate & non-invasive way to determine a person’s overall health and longevity because it is a reflection of the autonomic nervous system’s ability to adapt.
– The higher the HRV (on average), the better that person’s body can manage stress (physical or emotional, real or perceived, internal or external, etc). This is translated to better ability to perform (athletically or in a stressful work or home environment).
– Changes in HRV have been correlated to 9 of the 10 top causes of death. Only “road injury” is excluded.
– HRV can be improved through sleep, proper exercise for your abilities, better nutrition, improved fitness levels, decreased emotional and environmental stress.
– A person’s HRV trend is more important than any one reading, so consistency of readings is crucial for measuring progress.
A deeper dive:
Heart rate variability has been studied since the 1970s, but the application was limited to people who had access to EKG equipment and could spend several hours hooked up to a machine. Today’s chest strap-based heart rate monitors make this information accessible to everyone from the elite athlete to the the average Joe.
Below is an image of an echocardiogram. The uppermost point of each beat is referred to as “R” and is part of the QRS Complex. To measure heart rate variability, the heart rate monitor must transmit the R-R intervals (the time between each “R”). Most wrist-based monitors don’t transmit the R-R intervals. The Polar H10 chest straps do, and have Bluetooth technology.
Our bodies work very hard to maintain a particular status quo (“homeostasis”). Since maintaining the status quo covers things like body temperature, heart rate, blood sugar levels, pH levels, and many others, you’re correct in assuming that our body has must adapt frequently to any number of stressors that might tip the scales of balance in our systems. To combat the stressors, our nervous system has two branches that work simultaneously, but in varying levels of dominance depending on the situation.
Many people have heard of “fight or flight” and that refers to the sympathetic nervous system (SNS). The other system is the parasympathetic nervous system (PSNS) and is often called the “rest & digest” system. As you might suspect, the fight or flight system speeds up the heart rate and the rest & digest system slows it down. In terms of heart rate variability, a lot of changes (high variability) means that both systems are doing their thing – and that is a good thing!
Stress isn’t always a bad thing. A new workout program is a stressor and creates positive adaptations within the body when executed well. Stress also comes from social stress, physical stress, emotional, or enviromental. Each of these stressors impacts your body and its ability to respond. When the body is overwhelmed by the growing levels of stress layering on top of each other (“allostatic load”), then heart rate variability will decrease.
Higher variability means your nervous system is adapting favorably to the various stimuli it receives. A low variability means one system is working in dominance. Depending on the circumstances, low variability can be good or bad. If you are being chased by a bear, variability should be low with “fight or flight” SNS dominance. If you are meditating, low variability with “rest and digest” PSNS dominance is good.
If you are going through an average suburban life and routinely have low HRV, that is not good. That indicates you are overstressed, unhealthy and reducing your potential life span!
Heart rate variability is best interpreted by looking at trends over several days per week. A single measurement or infrequent measurements are rather irrelevant because HRV can be impacted by so many different factors. When analyzing trends, large changes in HRV (abnormally low and abnormally high HRV trends) can indicate critical health problems.
Extreme changes in HRV has been correlated with nearly every major cause of death in the US, except “road injury.” These causes of death include heart disease, cancer, stroke, Alzheimer’s, chronic lung disease, and diabetes among others. Many of these diseases are linked to an imbalance of nervous system dominance. Temporary imbalances are normal, but chronic low HRV can indicate decreased adaptability and thus, degradation of systems.
Improving your HRV can be as simple as taking time to rest: improved sleep patterns, meditation or yoga, active recovery, full body mobility work or other low intensity activities. Improved nutrition habits help the body recover and repair and can lead to body composition changes (less fat & more muscle). Drinking enough high quality water and clean air also improve HRV.
Determining your HRV is as easy as using an app (I recommend downloading the Elite HRV app, available for Apple and Android) and your Polar chest strap (make sure it is Bluetooth). Within 30 minutes of waking each morning, strap on the chest strap – be sure to put water on the sensors – lie down and start up the app. It will connect to your strap, you click START and spend the next 3 minutes or so lying there. The app does all the work.
The key is to be consistent. One reading is essentially irrelevant. The magic lies in watching trends. The Elite HRV app provides your sciencey data, but will also do the complicated interpretations for you and provide a “readiness” score from 1 to 10, with 10 being a great score. (See image below for a screenshot from the Elite HRV app).
I hear you asking, “How do I apply all this HRV data?” Did you start a new training program? Did you start a new diet? Did you start a new job? All these things are potential stressors. If you start a new training program and your HRV doesn’t change much, then it’s possible your program isn’t challenging enough. If your HRV plummets and doesn’t recover after a few days, then you might’ve over-extended yourself.
There are a lot of factors to consider when analyzing HRV and I can help you navigate it, if you choose to see how your body is responding to your lifestyle.