These days, you can monitor many aspects of your own health and fitness with tracking devices. Monitoring your heart rate is pretty standard but there’s another measure that you should be aware of. It’s called heart rate variability. What is it and why would you want to monitor it?
Research shows that heart rate variability is a marker of health and well-being. At a physiological level, it’s a measure of how much variability there is in the time between heartbeats. Greater heart rate means that the time between each beat of your heart fluctuates more than someone with low heart rate variability. What’s more, greater heart rate variability is a marker of better cardiovascular functioning. That’s because your heart rate is ultimately controlled by your autonomic nervous system or automatic, nervous system. Your autonomic nervous system is divided into two components: the parasympathetic and the sympathetic nervous system. These two components of the autonomic nervous system opposed one another.
The “Fight or Flight” and “Chill” Components of Your Nervous System
Your sympathetic nervous system is the portion of the autonomic nervous system that speeds up your heart rate and raises your blood pressure. It’s activated during times of stress and when you need to take action. It’s, appropriately enough, referred to as the “fight or flight” component. You can imagine why this portion of the nervous system evolved. In early times, primitive humans needed to be able to escape from a giant bear lumbering toward them or another predator. When the sympathetic nervous system activity predominates, your heart rate speeds up, your pupils dilate, blood pressure rises, and your airways open up. This prepares you to take action – to fight the threat or get out of the way!
In contrast, your parasympathetic nervous system is the “chill” component or your autonomic nervous system. This is the portion that slows your heart rate and lowers your blood pressure. It’s most active when you’re relaxed and after eating a meal. You also have more parasympathetic nervous system activity when you enter into a state of meditation.
When you’re stressed out or anxious, it can impact the balance between the sympathetic and parasympathetic components of the autonomic nervous system and this leads to a reduction in heart rate variability. In other words, there’s less variation between the timing of each heartbeat because stress has shifted the two components out of sync. In contrast, if you’re healthy, relaxed, and in good spirits, your heart rate variability will likely be higher. Good heart rate variability is a sign that your autonomic nervous system is doing its job of staying balanced – and that’s good for your health.
What’s more, studies show that low heart rate variability is linked to higher mortality. It’s a sign that your nervous system is having a hard time adjusting to the demands placed on it and may not be as resilient as it should be. Heart rate variability can also decline when you over-train. Overdoing the exercise without giving your body enough rest and recovery time can trigger imbalances in the autonomic nervous system that show up as a drop in heart rate variability. So, you can follow your own heart rate variability to monitor for signs of overtraining. A drop in heart rate variability is a marker of stress in general, including the stress of overtraining. It’s also a marker of fatigue.
Heart rate variability typically declines with age as the autonomic nervous system becomes more sluggish at switching between sympathetic and parasympathetic activity. However, aerobic exercise slows the decline in heart rate variability associated with aging. So, regular exercise without overtraining can help you retain better heart rate variability.
Devices That Measure Heart Rate Variability
It’s not hard to see how heart rate variability is a good tool for monitoring how you’re responding to stress and whether you’re overtraining. But, how do you measure it? It used to be that you had to hook yourself up to an electrocardiogram to check heart rate variability. These days, you can use a heart rate device at home to measure heart rate variability. Some of these devices use a chest strap that you wrap around your chest while others use a finger sensor. Now, you can also purchase apps that compute HRV without using an external sensor.
If you buy a device to monitor heart rate variability, do your research first. It’s not clear how accurate these devices really are, but the technology is improving all the time. Regardless of which device you choose, it’s important to learn to use it properly. Factors like body position and the time of day you measure can impact heart rate variability. That’s why you should be consistent about when you measure it and do it in the same position every time. First thing in the morning works well. Also, what you eat, caffeine, nicotine, and prior exercise can alter heart rate variability. Other factors that affect it are age, gender, genetics, and whether you have other chronic health conditions.
The best time to measure HRV is in the morning when you first wake up. The app or sensor will measure heart rate variability for one minute and record the value. As you continue to measure it over time, the app compares your current heart rate variability to previous value to alert you if changes have taken place. It’s best to measure HRV consistently for several weeks to establish a good baseline. Once you know your baseline, you can monitor for changes like a sharp drop in heart rate variability that might indicate that you’re overtraining or that your body is dealing with more stress than usual.
The Bottom Line
Heart rate variability is an effective way to monitor the health of the autonomic nervous system. Stress, including the stress of overtraining, can reduce heart rate variability. Fortunately, you can monitor for changes in heart rate variability using easy-to-use devices and apps. Do your research before choosing a device, as there are a variety of options available.
References:
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Exp Ther Med. 2016 May; 11(5): 1531–1536.
Journal of Strength and Conditioning Research: July 2014 – Volume 28 – Issue 7 – p 1896–1905.
J Strength Cond Res. 2018 Mar;32(3):716-725. doi: 10.1519/JSC.0000000000001662.
American Council on Exercise. “ACE-sponsored Research Study: The Perfect Pushup”
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