When embarking on an exercise program it is natural to focus most of your attention on workouts because without the stimulus of appropriate exercise done at the correct frequency, intensity and for the right amount of time you will not make progress. However it is easy to lose sight of the fact that exercise is a stimulus and stressor and that progress actually occurs during recovery from exercise!
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So while providing the correct amount of exercise stimulus is important — optimizing recovery is as or more important. This is particularly the case as we get older because our ability to recover from exercise stress tends to decrease as we age. There are many factors which affect our ability to recover from and improve from exercise including adequate sleep, breathing patterns, hydration, nutrition, and mental ability to relax to name a few.
The art of exercise often comes down to knowing when you are training to much or too hard and NOT recovering adequately. This is particularly true as you get older and for serious athletes who must walk a knife edge between exercising enough and at a high enough intensity and allowing for adequate recovery.
The great news is that there is a highly accurate way to easily check your recovery status/stress response by monitoring heart rate variability or HRV for short. HRV refers to the fact that the time between each heartbeat continuously varies! The picture at the beginning of this article shows the variation in time between each beat of the heart measured with an electrocardiogram. Even though the time between each heart beat is always varying your heart rate as expressed as the number of heart beats per minute can be steady at times.
So for example, an average heart rate of 60 beats per minute (bpm) does not mean that the interval between successive heartbeats is exactly 1.0 sec, instead they may fluctuate/vary from 0.5 sec up to 2.0 sec. During exercise, HRV decreases as heart rate and exercise intensity increases. HRV also decreases during periods of mental stress.
As a general rule of thumb we want to see HIGHER Heart Rate Variability. Higher HRV indicates that your Autonomic Nervous System (ANS) is in a highly responsive state and able to quickly adjust to changes and challenges to optimize homeostasis (homeostasis refers the fact that any living thing must maintain a consistent internal environment to maintain life so your body must constantly adjust to changes such as increased temperature, muscle activity, lightness, darkness, etc. to keep all the cells and organs functioning)
HRV is regulated by the autonomic nervous system (ANS) which controls the function of our internal organs such as heart, lungs, intestines, level of arterial tension, etc. The ANS has two parts: Sympathetic and Parasympathetic.
The sympathetic nervous system is often considered the “fight or flight” system, while the parasympathetic nervous system is often considered the “rest and digest” system. In many cases, these systems have “opposite” actions where one system activates a physiological response and the other inhibits it.
Parasympathetic activity decreases heart rate and increases HRV, whereas sympathetic activity increases heart rate and decreases HRV. Recovery and stress relief is all about increased parasympathetic activity.
When there are inappropriately high levels of Sympathetic Activity and low levels of Parasympathetic Activity – particularly for prolonged periods of time – you cannot recover from stress and sooner or later you will begin to experience physiological symptoms and physical performance decrements.
HRV and Heart Disease
When your Parasympathetic Nervous System (PNS) is inhibited your HRV is low and directly influences stress on your heart. An under-active (PNS) and overactive Sympathetic Nervous System (SNS) is a direct cause of high blood pressure, inflammation, and heart disease. In fact research shows that the PNS activity of patients with heart disease is one-third lower, on average, than that of a healthy individual.
Measurement of HRV
Measurement of HRV allows you to know how your body is responding and adapting to all the stressors in your life including exercise BEFORE you experience symptoms or a decrease in physical performance. By measuring HRV each morning upon waking before you rise from bed or eat or drink anything you can very accurately track your recovery status/stress response. To measure your HRV you need a chest strap type heart rate monitor that puts out a Bluetooth Signal so it can connect to your mobile phone. Most chest strap monitors do put out a Bluetooth Signal. Then download one of several HRV apps for your phone such as this excellent app: https://elitehrv.com/
Follow the directions to set-up the app and connect your monitor to the app. Then in morning put on your monitor and let the app run for 2 minutes or so. Record the HRV numbers and look at them over a couple of days. It will take a few days before the numbers will become meaningful. Take notes on your workouts to see the correlations between your numbers and how you feel. The numbers are related to you and are not useful unless you can compare it to your previous data (furthermore, different apps use different algorithms, so the numbers between apps will be different, as well). You can use recommendations from the app as rough rules of thumb, but rely mostly on your numbers relative to previous numbers to track recovering and stress response.