The Connection Between Fatigue and Low Heart Rate Variability

Feeling constantly knackered is a common complaint I get in my therapy room. You might be relieved to know that emerging science is giving us some interesting answers.

A fascinating link between fatigue and a physiological metric known as heart rate variability (HRV) is becoming apparent. A low HRV can be a red flag from your body that its ability to manage stress is compromised, which can show up as persistent tiredness.

Understanding this connection is the first step towards increasing your HRV which might just help you reclaim your energy levels.

Strap in! This is a long one and includes information on hypermobility later down in the article.

What is Fatigue and Heart Rate Variability?

Fatigue is more than just feeling sleepy. It's a state of bone level weariness, persistent low energy, and a reduced capacity for physical and mental activity. We sometimes refer to it as burnout. It can be brought on by:

• Inadequate sleep especially a lack of deep sleep connected to high or poorly functioning cortisol (stress hormones)

• Chronic stress

• Underlying medical conditions such as POTS, dysautonomia and symptomatic hypermobility

• Psychological distress

• It is rooted in the nervous system, when our system gets stuck in fight-flight, or functional freeze. And can be more common in the neurodivergent population.

Heart Rate Variability (HRV) is a measure of the variation in time between each of your heartbeats. This variation is controlled by your autonomic nervous system (ANS), which has two main branches: the sympathetic nervous system (your "fight-or-flight" response) and the parasympathetic nervous system (your "rest-and-digest" response).

A healthy, flexible nervous system is constantly making subtle adjustments to your heart rate in response to your environment and internal state. Even your inhale and exhale. (A fun thing to do if you have a smart watch is to watch your heart rate slightly shift as you breathe - maybe that’s just my idea of fun!)

A flexible nervous system results in a higher HRV, revealing a healthy balance between the sympathetic and parasympathetic systems. This means your body can efficiently switch between states of stress and relaxation as it needs to. Helping you digest food, rest, sleep, exercise, focus, connect with others, self-regulate.

But, if you have a low HRV, meaning the ANS isn’t functioning flexibly, you’ll be stuck in one state, one branch of the nervous system. And this typically is the fight-flight branch, the sympathetic state. This constant state of high alert can be a significant contributor to feelings of fatigue. (In some instances, we may end up stuck in the dorsal vagal part of the parasympathetic branch which could be related to feelings of depression. But for today, we’re talking about the sympathetic branch).

Either way, you wind up feeling absolutely bone weary tired.

Why Low HRV Equates to Fatigue

When your body is in a prolonged state of stress or distress, whether from work pressure, emotional turmoil, or even excessive physical training without enough recovery time, your sympathetic nervous system remains active. It’s like you’re driving with your foot constantly on full gas, never applying the brakes. This leads to a less variable heartbeat, like a metronome - you know, those beat timers that musicians use - resulting in low heart rate variability.

Being stuck in sustained fight-flight mode is incredibly draining. Your body is constantly primed for a threat that never materialises, leading to a cascade of physiological responses that consume energy. Never allowing you to fully switch off and rest.

Think about it. It’s like you’re on a treadmill of stress you can’t get off of, forced to move at the same pace, day in day out. You’d soon get tired, right?

This can show up as:

• Mental and Physical Exhaustion: The constant state of arousal eats into your energy reserves, leaving you feeling tired and unmotivated.

• Poor Sleep Quality: A dominant sympathetic nervous system can make it difficult to fall asleep and stay asleep, preventing the deep, restorative rest your body needs to recover.

• Impaired Recovery: Low HRV is a sign that your body isn't switching into its rest and digest mode, which is crucial for repairing tissues and replenishing energy stores after physical or mental exertion.

• Increased Inflammation: Chronic stress and a low HRV have been linked to higher levels of inflammation in the body, which can further contribute to feelings of fatigue as well as chronic pain.

In essence, a low HRV can be seen as an objective indicator of your body's struggle to cope with the cumulative load of stress, with fatigue being the primary and most debilitating symptom.

How to Increase Your Heart Rate Variability and Combat Fatigue

Fortunately, you can actively work to increase your HRV and, by extension, improve your energy levels. What good news! The key is to help your body become more flexible, not physically flexible (although dynamic flexibility is good for easing chronic pain) but nervous system flexible. This allows you to move back into the parasympathetic branch of your nervous system, the ventral vagal state.

Here are some evidence-based strategies:

1. Prioritise Good Quality Sleep:

• Consistent Sleep Schedule: Go to bed and wake up around the same time each day (yes, even on weekends!) to regulate your body's internal clock and stop yourself feeling like you’re constantly jetlagged.

• Create a Relaxing Bedtime Routine: Wind down with calming activities like gentle stretching, meditation, the 478 breath, reading, taking a warm bath or shower, or listening to soothing music.

• Optimise Your Sleep Environment: Ensure your bedroom is dark, quiet, and cool. Use an eye mask if that helps. Invest in a good, supportive mattress and pillows.

2. Engage in Regular Physical Activity (with adequate recovery):

• Aerobic Exercise: Activities like brisk walking, jogging, cycling, and swimming have been shown to improve HRV. But choose an activity that works for your body and fitness level. And always have a rest day in between, especially if you are hyper mobile or have dysautonomia.

• Interval Training: Short bursts of intense exercise followed by recovery periods can also be beneficial, but it's very important to listen to your body and not overtrain.

• Strength Training: Regular resistance training can also positively impact your autonomic nervous system. And has the added bonus of being good for your joints and bone density and strength, which helps us produce more red blood cells and reduces pain over time.

• Active Recovery: Incorporate light activities like gentle (I call it ambling) walking, yin yoga, or stretching on your rest days to aid recovery without adding significant stress.

3. Manage Stress Effectively:

• Mindfulness and Meditation: Regular practice can help calm your nervous system and shift it towards a more parasympathetic state, and has a positive impact on brain waves.

• Deep Breathing Exercises: Slow, diaphragmatic breathing can have an immediate impact on your HRV. A simple technique is to inhale for a count of four, hold for a count of four, and exhale for a count of six. Or simply make your exhale longer than your inhale which immediately puts on your vagal brake (like you’re slowing down a car)

• Spending Time in Nature: "Forest bathing" or simply being in green spaces has been shown to reduce stress and improve HRV.

• Yoga and Tai Chi: These practices combine physical postures, breathing techniques, and moving in a meditative state to aid relaxation.

• Vagal Toning: You can tone the vagus nerve with simple exercises, such as humming or singing, eye movements, yawning, and neck rotations.

4. Focus on a Balanced Diet:

• Nutrient-Rich Foods: Eat whole foods like fruits, vegetables, lean proteins, pulses, grains and healthy fats.

• Omega-3 Fatty Acids: Found in fatty fish like salmon, as well as in flaxseeds and walnuts, these have been linked to improved HRV.

• Hydration: Staying well-hydrated is essential for optimal physiological function, including heart health. And reduces fatigue instantly.

5. Limit Alcohol and Caffeine:

• Alcohol: Can significantly lower your HRV, especially when consumed close to bedtime, as it disrupts your sleep architecture. Even one glass of wine can cause us to wake up in the wee hours and not be able to return to slumber!

• Caffeine: While it can provide a temporary energy boost, excessive caffeine intake can keep your sympathetic nervous system in a heightened state and cause arrhythmic heart beats

6. Cold Exposure:

• Cold Showers or Face Splashes: Brief exposure to cold water can stimulate the vagus nerve which can increase heart rate variability.

Shifts in HRV will be temporary to start with, but as with any kind of toning of a body part, over time the results will become more permanent. The key is, as ever, consistency, and showing up regularly. This doesn’t mean a rigid routine, or pushing yourself through pain, discomfort, menstrual pain or tiredness. It means prioritising what works for you. Adjusting for the season, where you are in your menstrual cycle, and what else is going on in your life. Doing well is on a good enough basis, not a perfect basis.

Hypermobility, POTS, Autonomia and HRV

Yes, there is a significant and increasingly recognised link between low heart rate variability (HRV) and joint hypermobility. This connection is rooted in a frequent co-occurrence of hypermobility and a dysfunction of the autonomic nervous system, known as dysautonomia. Low HRV is a key physiological marker of underlying dysautonomia.

If you are neurodivergent, you may well have come across information on hypermobility and dysautonomia already. But if you haven’t, or you don’t relate to being neurodivergent, read on, as I think you’ll find this very interesting - and potentially revealing!

What Is Hypermobility?

Joint hypermobility refers to the ability of joints to move beyond the normal range of motion. For many, this is asymptomatic - meaning, you have no symptoms or difficulties.

However, when it is accompanied by other symptoms like chronic pain and muscle stiffness, fatigue, and joint instability, it may be diagnosed as a Hypermobility Spectrum Disorder or, in more specific cases, a type of Ehlers-Danlos Syndrome (EDS), most commonly the hypermobile type (hEDS).

These are genetic connective tissue differences that affect collagen, the protein that provides structure to skin, joints, blood vessels, and organs.

There are tests that are conducted by GPs to screen for hypermobility, such as looking at your flexibility by getting you to do a forward fold or touch your thumb to your wrist. They may also look at skin flexibility. But not all hyper mobile people will have these markers. This is often because muscles have to work extra hard and become stiff and overworked to compensate for loose joints. And whether you have stretchy skin or not depends on a number of factors.

The Link to Dysautonomia

There is a very strong association between hypermobility and dysautonomia, which is a malfunction of the Autonomic Nervous System (ANS). Remember that the ANS is responsible for regulating involuntary bodily functions like heart rate, blood pressure, digestion, and temperature control.

In individuals with hypermobility, it is suggested that the softness of connective tissue affects blood vessels, making pooling blood in the lower torso more likely, and the nerves that help regulate autonomic functions. This leads to a dysregulated nervous system.

Low HRV as a Marker of Dysautonomia

As discussed, HRV is a direct measure of how well your ANS is functioning. A healthy, adaptable, and flexible ANS results in a high HRV, indicating a good balance between sympathetic and parasympathetic states.

In the context of hypermobility-related dysautonomia, the sympathetic system even more likely to be in a state of overdrive while the parasympathetic system is underactive. This is whether you’re stressed, overworked, or just living life relatively normally. As a hyper mobile person, you end up stuck in the sympathetic branch even if you’re not stressed out.

This imbalance leads directly to low HRV. The heart beats in a more metronomic, less adaptable way, reflecting a body that is in a constant state of underlying stress.

I’ll tell you a little story. I’m hyper mobile and I have dysautonomia. I didn’t know this until the last few years, but I REALLY felt it when I was pregnant with both my children, especially my first.

When I became pregnant with my first child, I was at the time very active, attending and teaching regular yoga classes each week and dancing regularly. Once pregnancy hit I could no longer exercise. I couldn’t stand for any length of time before getting dizzy and feeling light headed. The additional strain having a baby put on my body made it impossible for me to function as I once had.

I’ve experienced periods of burnout and exhaustion throughout my life. But I didn’t realise it was related to dysautonomia until the last few years. Now I’m in perimenopause, and again it is much more noticeable to me that I cannot drive myself with the same energy that I used to, just as I felt when I was pregnant.

Whereas I could just about muddle through when I was ‘normal’ (as in not pregnant or in perimenopause). Having to take time off sick from work at times to recover from mysterious bouts of chronic fatigue. When those additional strains on my body were included, I had to do a complete lifestyle change.

This is why I now work for myself, exercise my way, and can no longer teach physical classes like yoga or ballet even monthly, let alone weekly!

Postural Orthostatic Tachycardia Syndrome (POTS)

You may have noticed I mentioned POTS earlier in this article. POTS is a very common form of dysautonomia seen in the hypermobile population. Although of course with all of these chronic conditions it is still difficult to get diagnosed even though I believe it is far more common than the medical sector would have us believe.

POTS is characterised by a significant increase in heart rate upon standing, accompanied by other symptoms that include:

• Dizziness and lightheadedness on standing

• Palpitations randomly

• Brain fog (often confused with perimenopause or PMT)

• Fatigue (often you’re sent for tests of fibromyalgia, especially if you also have chronic pain, which hyper mobile people usually do)

• Shortness of breath not related to physical exertion

• Shakiness or feeling like your body is kind of vibrating

Studies on people with POTS, a large percentage of whom also have symptomatic hypermobility, HSD or hEDS, consistently show markers of autonomic dysfunction, including lower heart rate variability, when compared with healthy controls. Usually with sympathetic (fight-flight) dominance.

So, if you have low heart rate variability it might be worth considering that you may be hyper mobile and have dysautonomia. And if you get dizzy when you stand up quickly, you might also want to throw POTS into the mix, which is a form of dysautonomia.

A low HRV is related to being stuck in your sympathetic, fight-flight mode. Whether you are hyper mobile or not. You can do something about it. Just be careful if you are hyper mobile or dysautomic to go gently and to always listen to your body. And if you are in doubt, speak to your GP.