Heart rate variability has become one of the most popular new fitness metrics. More people are using HRV to monitor their health, thanks to increased knowledge about HRV and the introduction of next-generation wearables such as Hanu.
There’s a bit of a learning curve to tracking HRV. HRV data is not the same as breathing and heart rates – it can’t be interpreted on the spot– at least without context. Instead, it needs to be collected and analyzed over time.
If you are an active, health-conscious individual using some form of HRV tracking device, you have likely noticed that your HRV ranges tend to be pretty fluid. Let’s look at why this is the case and how to best use this data to develop a closer relationship with your nervous system.
“Life is about rhythm. We vibrate, our hearts are pumping blood, we are a rhythm machine, that’s what we are.” – Mickey Hart.
What Affects Your Heart Rate Variability?
Your heart is the main pump of the body. It’s a global coordinator in maintaining synchronicity between body functions. Because of the need to maintain harmony and balance physiologically, the heart does not preserve the same rhythm from one heartbeat to the next.
It reacts to different stimuli by increasing or decreasing its rhythm. Let’s put this in perspective—your nervous system must attend to trillions of processes in any given second.
Heart rate variability is a metric that represents the subtle fluctuations in between each heartbeat. There are a variety of factors contributing to these slight fluctuations. Your heart rate is adjusted to facilitate improved blood flow and circulation. Researchers call the alignment of your heart rate, mind, and emotions ‘heart coherence’.
Your heart rate variability represents how adaptive your body is. Your HRV should fluctuate regularly, as this dynamic shifting represents your body’s ability to effectively modulate between action and rest. Studies have repeatedly shown us that less variable HRV trends are associated with improved risk of heart problems, mental health issues, and even mortality rates.
Your HRV is directly linked to your autonomic nervous system (ANS), which governs the body’s stress response system and connects to your heart activity. When you need to perform, this system activates the stress response, which secretes hormones, dilates blood vessels, and prepares the body for action. This system is responsible for the opposite reaction that calms you down and enables natural healing mechanisms during rest.
Some of the main factors that influence your HRV levels include:
Some crucial mechanisms in your body affect the variability of your heart rate. One of the most important is your circadian rhythm. Your circadian rhythm is your body’s natural time clock that helps to keep your body “in sync.”
Studies have shown that consistent sleep schedules and healthy exposure to light in the morning and dark in the evening help keep the body balanced. When your circadian rhythm is balanced, your body knows when to take action and rest.
A more variable HRV score represents the heart’s ability to switch between these two responses more readily. It also enables the body to spend less energy adjusting, as it becomes in tune with when you need to be ready to perform and when it is time to rest and recover.
Another note regarding circadian rhythm is that HRV will change significantly throughout the day. Indeed, you will notice a higher HRV in the morning (after a restful sleep since the nervous system has had a chance to recover) and a lower HRV in the afternoon. The dynamic shift and changes in the secretion of sympathetically arousing hormones, glucocorticoids (cortisol), and neurotransmitters like norepinephrine and epinephrine, are responsible for these differences.
Breathing plays a considerable role in your HRV. Inhaling increases your heart rate, and exhaling decreases it.
Breathwork is a powerful tool for triggering your body’s natural healing mechanisms through activating the parasympathetic nervous system. The PNS is the autonomic nervous system’s division that calms the body down and prepares it for rest and digestion. When you engage in deep breathing or other exercises such as apnea tables, you hone your body’s ability to calm down and respond to stress, leading to a more variable HRV.
Studies have recently shown inflammatory cytokines in the body can contribute to a low HRV score. While cytokines are a regular type of cell used in the immune response to trigger healing during infections, an excess of cytokines can build up due to stress, poor diet, and other factors. In the long term, chronic inflammation can lead to immune dysfunction and excessive strain on the heart.
Inflammation tells your body it needs to react and heal the inflamed area. When too much inflammation builds up, you can imagine the pressure it places on your heart and brain.
The heart communicates with the body and brain through its natural chemical messengers, commonly known as hormones. Hormones are responsible for various action cascades in the body that help rebuild muscle, preserve cognitive function, and even prepare the body for action. Depending on the external stimuli and the current state of your physiology, the brain and heart coordinate the release of these different chemical messengers to fulfill their respective roles.
A great example of a class of hormones that have an impact on HRV is thyroid hormones. They also affect the ANS we mentioned by altering the sympathetic response. Other chemicals or neurotransmitters, such as Acetylcholine, trigger the opposite side of this response and prepare the body for rest and healing.
Stress plays a significant role in the HRV fluctuations you will notice over time. For example, chronic stress causes your body’s sympathetic (fight or flight) response to become overactive, resulting in a less variable HRV trend over time.
High levels of stress are linked to both elevated levels of glucose in the blood as well as reduced parasympathetic nervous system activity (the body’s system that helps it rest and recover). When stress throws this system off, the heart’s variability becomes much less adaptable – that is, it is less able to stay balanced and return to rest after it becomes stressed.
While stress has some adverse effects on the body in high doses, a healthy amount of stress is necessary if you want to be healthy and adaptable.
While chronic stress is undeniably bad for your health, understanding that utilizing certain forms of stress is critical to maintaining your health. Cardio workouts, weight lifting, and cold therapy are examples.
These forms of stress activate your stress response system and train your body to modulate between stress and rest. As such, when you encounter an acute stressor, you will likely see a dip in HRV. HRV may be lower for a short time or a long time, depending on how stressful the event was.
So – Why Do Your HRV Levels Fluctuate So Much?
If you’ve been tracking your HRV for a while or just started, you’ll have noticed that it fluctuates.
These fluctuations result from all the different actions your body is taking behind the scenes throughout your day.
All the factors above are constantly working to stay in equilibrium and provide a healthy balance of action and recovery. When you exercise or become stressed, your heart rate increases in response to higher demand for blood flow – resulting in a suppressed HRV. When you meditate or sit down for the evening, your body switches into rest mode (if you don’t carry your stress with you!) – resulting in an increased HRV.
A more variable heart rate means your body adapts well to experiences and modulates efficiently between action and rest. Your circadian rhythm is an essential factor. By enabling it to get into a rhythm, you remove a stressor and improve your body’s ability to efficiently distribute energy between action and repair.
So if you have noticed your HRV fluctuating all the time, don’t worry – this is normal! Not only will you see fluctuations day-to-day, but with Hanu, you will see fluctuations on a second-by-second basis!
It’s not the short-term variabilities that paint the picture of your health – it’s the long-term trends your data displays. With this in mind, keep progressing with your health and fitness goals and keep an eye on whether or not the HRV readings you get from your Hanu device are becoming more variable.