Reading time: 3 min

What’s more heartwarming in the wintertime than struggling up close to the fireplace, drinking a cup of hot cocoa while watching your favorite movie? Well, how about going for a run or hike in fresh, mountain snow, or taking a walk on your neighborhood parkway as snowflakes flutter down upon your eyelashes?

While wintery terrain may give you cold feet, it’s all warm and fuzzy when it comes to your heart. And here are six tips to help keep your heart warm this winter.

1. Winterize it

Cold weather can put a large strain on the heart, especially if you aren’t used to it. Cold temperatures cause your blood vessels and arteries to shrink, restricting blood flow and reducing oxygen to the heart. Due to this, your heart has to pump harder to move the blood through the narrowed vessels. When this happens, your blood pressure and heart rate increase.

And as we know, a sudden spike in blood pressure – especially when paired with outdoor exertion, can have scary, even life threatening consequences.

In order to avoid this, make sure that your heart is in good shape before winter by implementing a regular cardiovascular exercise regimen well before the winter months.

2. Dress appropriately

You wouldn’t wear a winter coat, gloves and hat in the middle of summer for the simple reason that it would cause your body to overheat. The same principle applies to wintertime. Shorts and a tank out in the freezing cold would cause your body temperature to plummet.

By dressing appropriately in moisture wicking layers with your head and hands covered, you will be able to last a lot longer out there in the cold, and your heart rate will be less variable.

3. Warm up

Temperature extremes are not good for the cardiovascular system. Both the extremes of heat and cold can cause changes in the body that may have lasting negative effects and could even lead to death.

This is why it is important to warm up before entering the cold so you can to get your heart pumping blood, easing the transition as you acclimate to the weather. Doing so will also lessen the shock to your cardiovascular system.

4. Drink fluids

Drinking plenty of water helps the heart pump blood through the blood vessels to the muscles more easily, according to the American Heart Association. Simply put, if you’re hydrated, your heart won’t need to work as hard.

And while you won’t sweat as much in the cold because your body is keeping water in to keep your body temperature up, rather than using it to cool you off, you still do sweat. Plus, the air that we breathe in the wintertime has less moisture in it, and our lungs need to use the water in our bodies to moisturize it, according to an Dr. Steven T. Devor – Director of Performance Physiology for MIT and OhioHealth.

So, continue to drink your water, and lots of it!

5. Eat heart healthy foods

Along with drinking plenty of water, it is important to eat heart healthy foods like fish, nuts, berries, and green vegetables to make sure that your heart is in tip-top shape as you exercise during the cold, winter months.

6. Know your limits and listen to your body

Exercising outdoors is awesome because you get to experience this time of year the best possible way. However, with extreme temperatures brings risks both to your heart and body. If you begin to shiver, it is time to bring things indoors because this is the first sign of hypothermia.

And there is nothing wrong with exercising in a temperature regulated room. Nothing at all.

Reading time: 5 min

From maintaining a healthy weight to living longer, eating healthy offers many benefits for our long-term wellbeing. The foods we eat also have a major impact on our heart — especially for those who suffer from a high heart rate.

Having a high heart rate is a dangerous condition that can increase a person’s risk for heart attack, stroke, and cardiovascular disease, all while shortening their life expectancy. Here’s what you should know about heart rate, plus the best foods that lower heart rate and improve quality of life.

Why Does Low Heart Rate Matter?

Heart rate fluctuates throughout the day depending on a person’s activity. According to Harvard Health Publishing’s Howard LeWine, M.D., walking around, lying down, and sitting all require different amounts of effort, which will cause the heart to beat at different rates.

Regardless of this change in activity level, a person’s resting heart rate — the number of heart beats per minute at rest — stays consistent over time. For example, a person’s resting heart rate will be consistent each night during sleep, regardless of the activity they engaged in that day.

Heart rate is an important predictor of health. Some people, such as athletes or pregnant women, are expected to have a lower or higher heart rate, respectively. Age and hormonal fluctuations also affect how fast a person’s heart beats.

When an average person’s resting heart rate falls outside the normal range — 60-90 beats per minute — it can signify a serious health problem. Having a high heart rate is called tachycardia, and there are many types of increased heart rates.

Perhaps the most common type of tachycardia is atrial fibrillation, which is caused by irregular electrical impulses in the upper heart chambers. Atrial fibrillation is a sign of weak contractions in the upper chamber of the heart (the atria). Atrial flutter is an associated condition marked by a rapidly beating atria and a normal heart rate.

A high heart rate doesn’t always cause symptoms, and seeking professional medical advice is sometimes the only way to diagnose this condition properly. When symptoms are present, they can include shortness of breath, lightheadedness, rapid pulse, heart palpitations, chest pain, and fainting. If you’re unable to exercise because of these factors, it’s a sign that it’s time to take control of your heart health. So what happens if you don’t intervene?

The Role of Heart Rate in Heart Attack and Disease


Having a high heart rate can affect everyday life by contributing to daytime fatigue, low fitness levels, and obesity. Yet it’s particularly dangerous because it puts people at higher risk for developing heart disease or suffering from additional cardiovascular disorders.

A high heart rate is linked to health issues like heart disease, stroke, and cardiac arrest. Research also shows that having an above-normal heart rate increases a person’s chance of death, regardless of whether they’re physically fit or generally deemed healthy. This study, which measured 3,000 middle-aged men, found that for every additional 10-22 beats per minute, a man’s chance of death increased by 16%.

Causes of High Heart Rate

The most common causes of high heart rate are hypertension (high blood pressure) and coronary artery disease — both of which can be controlled by lifestyle factors. In particular, things like chronic stress and excessive use of caffeine are all modern factors that contribute to high heart rate.

Additional risk factors that elevate resting heart rate include excessive alcohol consumption and alcoholism, taking certain medications, smoking cigarettes, and taking recreational drugs. High blood pressure is another common cause of high heart rate.

Medical professionals have understood the correlation between lifestyle and heart health for quite some time, but recent research shows that high heart rate can be caused by a variety of genetic factors.

For example, a heart study led by cardiologist Pim van der Harst found 64 gene locations that influence heart rate, suggesting that genes and gene location influence both heart rate and life expectancy more than previously thought. Congenital heart defects, which can be caused at birth or after heart surgery, can also cause the heart to beat irregularly.

Diet plays a significant role in high heart rate because the foods we eat affect our blood pressure. Alcohol and stimulants are especially hard on the heart because they cause dehydration and are considered toxic to the body. This means the heart has to work harder to remove them — leading to an increase in heart rate.

Foods high in fat and sugar also cause an increased heart rate, primarily because they contribute to being overweight or obese, which places more pressure on the heart.

Foods That Lower Heart Rate

silver metal knife 2007335

Despite the role of chronic and genetic factors in heart health, changing one’s diet to include more healthy foods is the quickest and most effective way a person can achieve a lower heart rate and improve overall healthLowering your heart rate can reduce the risk of heart disease, heart attack, and stroke while helping lower blood pressure. Here are the nutrient-dense foods that lower heart rate, reduce heart disease, and boost longevity.

Whole Grains

Whole grains are an important element of a heart healthy diet and offer many health benefits. A diet high in whole grains has been shown to reduce cholesterol, blood pressure, and blood sugar levels.

Whole grains have also been shown to reduce the risk of stroke, type 2 diabetes, and heart disease — all of which are associated with high heart rate. Whole grains also work to keep you full for longer. This can reduce the risk of overeating to help an overweight person lose extra pounds and reduce excess strain on the heart.

Simple, heart-healthy, whole-grain swaps and substitutes include choosing whole wheat flour instead of refined white flour, oatmeal, bulgur, whole wheat pasta, and barley. They are all examples of healthy whole grains to incorporate into your diet.

Green Vegetables, Leafy Greens, and Fruit

Green vegetables and leafy greens are especially beneficial for cardiovascular health because they contain vitamin K1. Eating high amounts of vitamin K1 can protect against high heart rate and an enlarged heart. It has also been shown to reduce high cholesterol. Fruits and vegetables are low-fat foods that contain fiber, which is known to lower both cholesterol and high blood pressure.

One study found that eating 10 servings of fruit and vegetables a day can lower your risk of cardiovascular disease by 28% while reducing the risk of premature death by 31%. Aside from leafy greens, apples, pears, citrus fruits, cruciferous vegetables, green beans, and peppers were shown to offer the best heart benefits.

Blueberries, which are high in anthocyanins (the phytochemicals that give blueberries their color) have also been shown to improve heart health. Specifically, blueberries have been shown to decrease blood pressure, improve blood vessel function, and reduce the risk of cardiovascular disease.

Omega-3 Fatty Acids


Omega-3s are healthy fats found in a variety of plant foods and fish. Omega-3 fatty acids are one of the best foods to lower heart rate and reduce the risk of cardiac arrest. There are three main types of Omega-3s. These include alpha-linolenic acid (ALA), which is found in plant oils, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), both of which are found in fish like salmon, mackerel, and tuna.

Omega-3s keep heart rate low while reducing the risk of irregular heartbeat, slowing down the buildup of artery plaque, and lowering blood pressure. Aside from eating fish, plant foods that contain essential fatty acids include ground flaxseeds, chia seeds, soybeans, and tofu. Walnuts also contain high amounts of Omega-3s, with almonds, macadamia nuts, hazelnuts, and pecans coming in second. Avocado, olives, and olive oil are also known to be high in ALA omega-3s.

Eating for a Healthy Heart

Heart rate plays a vital role in a person’s overall health. While athletes, pregnant women, and people with congenital heart defects are expected to have an abnormal heart rate, people outside of these categories should have a resting heart rate between 60-90 beats per minute. Having a heart rate above this range can put a person at risk for a variety of life-threatening diseases and conditions, including heart disease, heart failure, and heart attack.

Fortunately, eating healthier foods is one of the most effective ways a person can reduce their risk of disease and extend their life expectancy. Leafy greens, fruits, whole grains, and items rich in Omega-3s are all examples of foods that lower heart rate and improve overall quality of life.

Reading time: 4 min

What is it?

Heart rate is defined as the number of contractions of the heart, expressed in beats per minute (bpm). The heart rate is a function of local electrical signals in the cardiac cells, neural inputs, and hormonal influence.

Heart rate changes in response to stressors in order to increase circulation of blood, often by increasing cardiac output. This increase in cardiac output helps meet the demands of physiological responses to stress.

Therefore, heart rate can be a valuable metric in understanding the cumulative stress (e.g. emotional and physical stress) that is placed on the body.

How it’s measured

Heart rate can be measured through palpation, electrocardiography (ECG), and photoplethysmography (PPG). Biostrap measures heart rate using PPG, which captures pulse waves of blood flow using red and infrared light. By using the count of pulse waves per unit of time, heart rate in bpm can be obtained.

Heart rate can be measured during activity (active heart rate). However, resting heart rate (RHR) is most often used to clinically assess cardiovascular health, since extraneous stress on the cardiovascular system is absent. RHR can be subject to acute stress, including observation bias. Therefore, passive collection of RHR through wearables, particularly during sleep, allows for minimizing error that may artificially raise RHR.

Correlation with health conditions

Chronically increased resting heart rate has been correlated with many diseases and their outcomes, particularly hypertension, obesity, cardiovascular diseases, cancer, and metabolic disorders, among others. In many cases, the increased heart rate is not itself a contributor to the disease progression, but rather a signal that there are down-stream effects of the underlying disease.

Acutely increased resting heart rate may be an indication of altered blood flow, reduced plasma volume, psychological stress, activity, infection, and thermal stress. Monitoring heart rate trends can alert when heart rate has changed acutely, but may not be indicative of the cause of the increase. In times where no change in RHR is expected such as during sleep, follow-up evaluation may be warranted.

What is a “normal” range?

<60 bpm = Bradycardia
60-100 bpm = “Normal”
>100 = Tachycardia

A “normal” RHR is considered to be 60-100 beats per minute. Factors that may influence resting heart rate values include:

  • Fitness level
  • Room temperature
  • Body position
  • Emotional stress
  • Body size and/or composition
  • Use of medications

A resting heart rate below 60 bpm is considered “bradycardia”, but may be common, particularly in individuals with good cardiovascular fitness or individuals taking certain medications. In the case of cardiovascular fit patients, the stroke volume of the left ventricle is increased, meaning heart rate may decrease in order to have the same cardiac output, according to the Fick principle. Alternatively, this could be a result of problems with the sinoatrial node or damage to the heart as a result of a cardiovascular event or disease.

A resting heart rate over 100 is considered “tachycardia”, which is often correlated with increased risk for cardiovascular diseases. Increased HR at rest may result in increased work by the heart, as well as indicating an issue with other physiological pathways. If the RHR is closer to 150 bpm or higher, this may be indicative of a condition such as supraventricular tachycardia (SVT) requiring medical attention. 

A number of conditions can affect your heart rate including arrhythmias which can cause the heart to beat too fast, too slow, or with an irregular rhythm.

The Biostrap Buzz

Sign up to our email newsletter to receive curated content on the latest news in digital health and health optimization. Plus, special access to Biostrap offers and community updates.

Interpreting trends

Resting heart rate, measured over time, provides insights into cardiovascular changes in response to lifestyle or disease progression. Since RHR responds relatively quickly to lifestyle changes, tracking resting heart rate over time is recommended in order to monitor positive and negative health changes.

Although RHR alone is not enough to diagnose any particular disease, the American Heart Association recommends lowering resting heart rate as much as possible. Exercise training, dietary changes, meditation, and reducing stress are examples of ways to reduce RHR. The decrease in heart rate reflects increased cardiovascular efficiency and decreased systemic stress.

Increases in RHR over time could be an indication of negative cardiovascular changes, and may warrant follow-up testing or lifestyle intervention. 


In a clinical study, the Biostrap PPG-based resting heart rate measurement matched within 1 +/- BPM to the reference research grade ECG.

In a small real-world cohort of elderly people, the standalone Fibricheck AF algorithm can accurately detect AF using Wavelet wristband-derived PPG data. Results are comparable to the Alivecor Kardia one-lead ECG device, with an acceptable unclassifiable/bad quality rate. This opens the door for long-term AF screening and monitoring.


  1. Lakatta EG, Vinogradova TM, Maltsev VA. The Missing Link in the Mystery of Normal Automaticity of Cardiac Pacemaker Cells. Annals of the New York Academy of Sciences. 2008;1123(1):41–57. doi:
  2. Brack KE, Coote JH, Ng GA. Interaction between direct sympathetic and vagus nerve stimulation on heart rate in the isolated rabbit heart. Experimental Physiology. 2004;89(1):128–139. doi:
  3. Furnival CM, Linden RJ, Snow HM. The inotropic and chronotropic effects of catecholamines on the dog heart. The Journal of Physiology. 1971;214(1):15–28.
  4. Sneddon G, Mourik R van, Law P, Dur O, Lowe D, Carlin C. P177 Cardiorespiratory physiology remotely monitored via wearable wristband photoplethysmography: feasibility and initial benchmarking. Thorax. 2018;73(Suppl 4):A197–A197. doi:10.1136/thorax-2018-212555.334
  5. Lequeux B, Uzan C, Rehman MB. Does resting heart rate measured by the physician reflect the patient’s true resting heart rate? White-coat heart rate. Indian Heart Journal. 2018;70(1):93–98. doi:10.1016/j.ihj.2017.07.015
  6. Paul Laura, Hastie Claire E., Li Weiling S., Harrow Craig, Muir Scott, Connell John M.C., Dominiczak Anna F., McInnes Gordon T., Padmanabhan Sandosh. Resting Heart Rate Pattern During Follow-Up and Mortality in Hypertensive Patients. Hypertension. 2010;55(2):567–574. doi:10.1161/HYPERTENSIONAHA.109.144808
  7. Aune D, Sen A, ó’Hartaigh B, Janszky I, Romundstad PR, Tonstad S, Vatten LJ. Resting heart rate and the risk of cardiovascular disease, total cancer, and all-cause mortality – A systematic review and dose-response meta-analysis of prospective studies. Nutrition, metabolism, and cardiovascular diseases: NMCD. 2017;27(6):504–517. doi:10.1016/j.numecd.2017.04.004
  8. Lee DH, Park S, Lim SM, Lee MK, Giovannucci EL, Kim JH, Kim SI, Jeon JY. Resting heart rate as a prognostic factor for mortality in patients with breast cancer. Breast Cancer Research and Treatment. 2016;159(2):375–384. doi:10.1007/s10549-016-3938-1
  9. Hillis GS, Woodward M, Rodgers A, Chow CK, Li Q, Zoungas S, Patel A, Webster R, Batty GD, Ninomiya T, et al. Resting heart rate and the risk of death and cardiovascular complications in patients with type 2 diabetes mellitus. Diabetologia. 2012;55(5):1283–1290. doi:10.1007/s00125-012-2471-y
  10. Jiang X, Liu X, Wu S, Zhang GQ, Peng M, Wu Y, Zheng X, Ruan C, Zhang W. Metabolic syndrome is associated with and predicted by resting heart rate: a cross-sectional and longitudinal study. Heart. 2015;101(1):44–49. doi:10.1136/heartjnl-2014-305685
  11. Lee B-A, Oh D-J. The effects of long-term aerobic exercise on cardiac structure, stroke volume of the left ventricle, and cardiac output. Journal of Exercise Rehabilitation. 2016;12(1):37–41. doi:10.12965/jer.150261
  12. Target Heart Rates Chart. [accessed 2021 Apr 15].
  13. Reimers AK, Knapp G, Reimers C-D. Effects of Exercise on the Resting Heart Rate: A Systematic Review and Meta-Analysis of Interventional Studies. Journal of Clinical Medicine. 2018;7(12). doi:10.3390/jcm7120503
Reading time: 3 min

What is it?

Active heart rate is the rate at which the heart beats during activity or exercise. Heart rate is a highly responsive physiological measure, since it is in part responsible for increased cardiac output. Increasing cardiac output is vital during increased physical activity, since the metabolic demand is higher. It is important to note that heart rate is a response variable to many factors and therefore, the utility in measuring heart rate is to measure the body’s physiological reaction to the work being performed.

How is it measured?

There are many ways to measure heart rate during physical activity, but some are more reliable than others. The typical ‘gold standard’ method is through electrocardiography, whether 12-lead or single-lead. Many commercially available single-lead ecg-based chest straps are available and common among research groups due to their wireless nature, although 12-lead ECGs remain more popular among clinical settings due to the increased depth of information. 

Additionally, photoplethysmography can be used to measure pulse waves to obtain heart rate. Due to the nature of different wavelengths utilized during PPG measurements, green light LED appears to be best at detecting pulse waveforms during exercise, although still subject to some error. Red and infrared light appear to be highly prone to motion artifacts, and are not recommended for active heart rate monitoring. 

The Biostrap ecosystem contains both a chest-worn ECG-based heart rate monitor as well as a green light PPG sensor worn on the arm. The Biostrap EVO device, equipped with red and infrared PPG does not record during exercise due to motion artifacts. Therefore, the Biostrap activity heart rate monitors are recommended for use during activity to obtain proper active heart rate. 

Correlation with health

Use of heart rate during activity and exercise is not recommended for or capable of diagnosing medical conditions. However, heart rate during activity and exercise can provide a lot of information about cardiovascular health and performance. 

Increasing metabolic demand should lead to an increase in aerobic metabolism, thereby requiring increased oxygen delivery to the muscle tissues being used. This oxygen is vital for producing ATP (energy) to contracting skeletal muscles. Cardiac output (CO), as mentioned before, is the ability to supply oxygen to the contractile tissues; CO is a product of heart rate and stroke volume.

Therefore, when the heart becomes more efficient at pumping blood, increasing the stroke volume, heart rate will decrease to equal the same level of cardiac output. Typically, when examining individuals during exercise, a lower heart rate at an equivalent workload suggests increased cardiovascular health.

There are many other metrics that are designed to extract data from activity, particularly among sports and performance realms (e.g. rate of change, cardiac drift, heart rate reserve, and many more), but most will be beyond the scope of this review. 

The Biostrap Buzz

Sign up to our email newsletter to receive curated content on the latest news in digital health and health optimization. Plus, special access to Biostrap offers and community updates.

Normal Values

In theory, any value existing between resting heart rate and maximal heart rate are ‘typical’ values for exercising. Because exercise intensity is linearly related to heart rate, heart rate is often a reflection of relative intensity of physical activity. 

While many still suggest a percentage of maximal heart rate as a proxy of activity intensity, the heart rate reserve method (Karvonen method) is widely considered the most accurate method of monitoring intensity through active heart rate. The primary reason this is recommended is that 0% ‘work’ (sedentary) should equate to resting heart rate, but would be 0 beats per minute when using percent of maximum heart rate. 

Karvonen Formula

Heart Rate Reserve (HRR) = Maximum heart rate (MHR) – Resting heart rate (RHR)

%HRR is above resting heart rate. 

Monitoring Trends

In general, performing the same task, an individuals’ heart rate should be lower after cardiovascular fitness adaptations. 

However, many variables can influence heart rate during exercise that may alter this trend. Heat, emotional stress, caffeine consumption, movement economy, and dehydration are just some of the factors that can influence day-to-day variation in exercise heart rate at the same workload.

Cardiovascular adaptations may decrease the reactivity of heart rate to some of these influences, so a trend towards a lower heart rate should still be observed over time. 

Of note, this should not be confused with active heart rate during a single exercise bout. Heart rate should remain proportional to intensity, and thus depends on the workload applied to the activity. In theory, at a constant workload, heart rate should remain constant; however, in practice, long bouts of activity can lead to cardiac drift, which is a dissociation between heart rate and workload. This is common in lesser-trained individuals, particularly with factors that affect thermoregulation, but is also common in dehydration, hot environments, nutritional stress,  and other fatigue-related factors that influence heart rate. 

Reading time: 4 min

Resting Heart Rate can be a strong indicator of overall health and fitness—here are the essentials on why you should measure it and how to lower it. 

For decades, athletes and trainers have tracked Resting Heart Rate (RHR) as an indicator of athletic performance. However, RHR is an important biometric for everyone to track as it is an indicator of overall health.

Resting Heart Rate is a measure of how many times the heart beats per minute (bpm) while at rest. It is often measured while standing, sitting or lying down; however, it is best to track it passively while sleeping, as acute stress can highly influence it. 

What is a Normal Resting Heart Rate?

The average adult will have an RHR between 60-100 beats per minute, while athletes are likely to rest somewhere between 40-60 bpm. And the lower, the better, as RHR indicates the health of the heart leading to overall longevity, lower risk of heart attack, higher energy levels, metabolic efficiency and athletic endurance.

A resting heart rate below 60 bpm is considered “bradycardia”, but may be common, particularly in individuals with good cardiovascular fitness or individuals taking certain medications. Alternatively, this could be a result of problems with the sinoatrial node or damage to the heart as a result of a cardiovascular event or disease.

A resting heart rate over 100 is considered “tachycardia”, which is often correlated with increased risk for cardiovascular diseases. Increased HR at rest may result in increased work by the heart, as well as indicating an issue with other physiological pathways. If the RHR is closer to 150 bpm or higher, this may be indicative of a condition such as supra-ventricular tachycardia (SVT) requiring medical attention.

What Affects Resting Heart Rate?

  1. Regular Exercise: It’s important that whatever the exercise may be, it should increase heart rate for an extended period of time.
  1. Hydration: Staying hydrated helps with blood viscosity and allows the blood to flow through the body more easily, exerting less stress on the heart.
  2. Sleep: During consistent, uninterrupted sleep, the body rests, repairs, and recovers. Poor or inconsistent sleep can be a large contributor to elevated RHR, putting stress on the heart.
  3. Diet.:A balanced diet full of healthy fats, whole foods, good sources of protein and fiber as well low sodium, inflammatory oils and processed foods help keep the arteries clear, leading to lower RHR and less work for the heart.
  4. Stress: Both acute and chronic stress have a significant impact on the heart by increasing RHR. It’s important to incorporate healthy habits and routines to keep stress and anxiety at bay and help maintain a healthy RHR.
  5. Weight: Extra body weight puts stress on the body and heart. 
  6. Room Temperature: The hotter the body temperature, the faster the heart beats. 
  7. Use of Medications: Treatments for asthma, high blood pressure, thyroid and more can cause changes in heart rate and rhythm. 

Why Measure Resting Heart Rate?

As with most biometrics, Resting Heart Rate offers insights into your overall health, indicating general well-being as well as potential health risks which can inform your daily lifestyle choices.

Tracking consistently over time can be beneficial to watch for changes. As previously mentioned, working to lower your RHR is generally beneficial for overall health. This is because the decrease in heart rate reflects increased cardiovascular efficiency and decreased systemic stress. An increase in RHR over time could be an indication of negative cardiovascular changes, and may warrant follow-up testing or lifestyle intervention.

For athletes, knowing your RHR as well as your Maximum Heart Rate (MHR) can help dictate heart rate based training zones. Spikes in RHR can indicate when overtraining has occurred and an athlete should take a rest day, something else in a training regiment is amiss, or can even indicate an oncoming cold or illness.

The Biostrap Buzz

Sign up to our email newsletter to receive curated content on the latest news in digital health and health optimization. Plus, special access to Biostrap offers and community updates.

How to Lower RHR

It’s important to maintain an active lifestyle with regular aerobic exercise, a balanced diet, regular sleep and hydration. If your RHR is high, these are the first factors to assess. Beyond the basic lifestyle factors, a few other steps can be taken to significantly lower RHR:

  1. Smoking. Regular smoking increases stress on the heart and the cardiovascular system. Cutting back or eliminating this habit altogether may have a positive impact on not only reducing RHR, but on respiratory health and overall well-being as well.
  2. Manage Weight. Maintaining a healthy weight promotes increased metabolic and energy efficiency and decreases strain on the heart; hence lowering RHR.
  3. Meditation and breathwork. Controlled, long, and slow breathing can help regulate your heart rate and over time works to decrease RHR as well. 

Resting Heart Rate is an important measure of overall wellness for not only athletes but for anyone who wants to optimize their lifestyle. At Biostrap, we’re dedicated to putting you in control of your health by measuring biometrics at clinical-grade accuracy, so you can track and improve your performance and well-being better than ever.

Utilizing proprietary red and infrared photoplethysmography (PPG) sensors, Biostrap’s wrist-worn device captures high-integrity biometric measurements, including RHR, which have been successfully compared to gold standard medical devices.

We believe that the circumstances in which relevant biometrics are captured matter as well. Thus, our focus on nocturnal data collection. Sleep is when the body recovers from and adapts to daily stressors, which then dictates your resilience, recovery, and readiness to perform the following day. Measuring nocturnal RHR reflects some of these changes, providing you with the ultimate insight into how your daily choices impact your physical and mental health, and performance.

Reading time: 5 min

Do you know your sleeping heart rate, in other words nocturnal heart rate? If not, it might be time to find out. Several clinical studies have shown that resting heart rate is a key indicator of health, wellness, and longevity. Monitoring changes in your resting heart rate over time can also provide meaningful insight into changes in health.

Understanding your nocturnal heart rate is also important for determining your target heart rate zones, which can guide you to peak athletic performance. Here’s everything you need to know about your nocturnal heart rate — and how to improve it.

What Is Resting Heart Rate?

Heart rate is defined as the number of contractions of the heart, expressed in beats per minute (bpm). Heart rate can be measured during activity (active heart rate), but is most often clinically assessed at rest in the absence of extraneous stress and other factors. 

Resting heart rate is utilized to evaluate an individual’s cardiovascular health and function. While most healthy adults have a resting heart rate between 60 and 80 bpm, factors such as fitness level, body composition, room temperature, body position, stress, and use of certain medications can affect heart rate. 

‘Low’ Resting Heart Rate

A resting heart rate below 60 bpm is considered “bradycardia”, but may be common in individuals with good cardiovascular fitness or individuals taking certain medications. According to Dr. Jason Wasfy at Massachusetts General Hospital Heart Center. “In certain cases, a lower resting heart rate can mean a higher degree of physical fitness, which is associated with reduced rates of cardiac events like heart attacks.” In the case of individuals with good cardiovascular fitness, the stroke volume of the left ventricle is increased, meaning the heart rate may decrease while still maintaining adequate cardiac output.

In other cases, having a low resting heart rate could be indicative of an underlying health concern. According to the American Heart Association, bradycardia can lead to symptoms including lightheadedness, weakness, confusion, fatigue, and diminished exercise performance. Symptomatic bradycardia may indicate that an individual should seek immediate medical advice.

‘High’ Resting Heart Rate

A resting heart rate greater than 100 bpm is considered “tachycardia”, which is often correlated with increased risk of cardiovascular diseases due to chronic additional work placed on the heart. According to Healthline, tachycardia can be caused by anxiety, fatigue, electrolyte imbalance, overconsumption of alcohol or caffeine, drug use, or other underlying medical conditions.

The negative effects of a high resting heart rate were demonstrated in a study conducted by Copenhagen University Hospital. This study found a strong correlation between patients with higher resting heart rates (RHR) and risk of death, specifically a 10% increase risk of mortality for every additional 10 bpm.

Nocturnal Heart Rate

Unlike the traditional resting heart rate values obtained in normal clinical practice, nocturnal heart rate is obtained during sleep. It is normal for nocturnal heart rate values to be slightly lower than waking resting heart rate due to minimal factors impacting the value, and therefore represents a more valuable tool for trending over time to gain valuable insight into changes in your health and performance.

Your Heart Rate During Sleep and Sleep Apnea

Obstructive Sleep Apnea (OSA) is one of the most prevalent sleep disorders in the US with greater than 25 million confirmed cases and research suggesting a high prevalence of undiagnosed patients. During an apneic event, individuals experience a partial or complete collapse of their airway depriving them of oxygen for several seconds. In addition to sleep disturbances, this can lead to an acute change in heart rate and oxygen saturation. 

So what are some indications that you may have OSA? Kathleen Davis states that loud snoring, accompanied by restless sleep and daytime fatigue, could indicate the presence of sleep apnea.

According to Medline Plus, this sleep disorder can cause pauses in breathing that can last from a few seconds to several minutes, with a transition back to normal breathing marked by a gasp, snort or choke, which may startle the sleeper (and often their partner awake). These sleep disruptions have been credited for symptoms of daytime tiredness, even after a full night’s sleep, in patients with sleep apnea.

Fatigue and frustration aside, sleep apnea also affects nocturnal heart rate. “When you stop breathing while you sleep, your heart rate drops, and then your involuntary reflexes make you startle into a micro-arousal, which causes your heart rate to accelerate quickly,” says The National Sleep Foundation. In addition to elevated blood pressure, this rapid decrease and increase in heart rate may lead to an irregular heart rhythm, or cardiac arrhythmia.

Irregular Heart Rhythms and Risks

While irregular heartbeats can be caused by a variety of factors, more studies are revealing the direct relationship between cardiac arrhythmias and sleep disorders such as OSA. One of the most common types of arrhythmia, atrial fibrillation (AF) is marked by irregular contractions of the upper heart chambers.

According to a clinical study conducted at the University of Ottawa, researchers found that OSA may increase the risk of atrial fibrillation with secondary symptoms including palpitations, lightheadedness, weakness, fatigue, shortness of breath, and chest pain. Atrial fibrillation is also associated with stroke, heart failure, and other cardiovascular conditions. 

The Biostrap Buzz

Sign up to our email newsletter to receive curated content on the latest news in digital health and health optimization. Plus, special access to Biostrap offers and community updates.

Measuring Heart Rate

Maintaining a healthy cardiorespiratory system is important – but what are some ways you can measure your resting and nocturnal heart rate?

This can be accomplished with the old fashioned method of measuring your pulse rate with your fingertips placed on your wrist – just make sure you’ve had ample time to rest after a stressful event or exercise, and under controlled conditions. While this is cost effective (free) and can be done anywhere, there may be issues associated with reliability and these measurements cannot feasibly be performed during sleep. 

Electrocardiograms (ECG) are another method that are commonly used in clinical practice to measure electrical conductivity of the heart to measure its rate of contractions. While this is a relatively quick and very precise method for measuring heart rate and other important aspects of cardiovascular function, the most reliable form (12-lead ECG) is typically not available for the general population to track consistently over time.

Which brings us to perhaps the best solution for measuring resting and nocturnal heart rate in terms of cost, reliability, and availability- wearable technology. These cost-effective technologies unlock the ability for all to consistently track and monitor their heart rate over time to gain valuable insight into cardiovascular function. However, it is important that consumers seek a wearable technology that has proven accuracy compared to the gold standard ECG devices.

Improving Your Heart Rate

When it comes to improving your heart rate, maintaining a healthy body composition and regularly engaging in physical activity are key. According to Harvard Health Publishing, exercising within target heart rate zones can help to strengthen the heart and improve aerobic capacity. To safely and effectively train with heart rate zones, it is encouraged that individuals first seek clearance from their healthcare provider, and consider training under the guidance of a qualified fitness professional. 

Improve Your Nocturnal Heart Rate, Reduce Your Risks

Nocturnal heart rate is an important metric that helps quantify the efficiency of your cardiovascular system. Tracking your nocturnal heart rate over time and gaining knowledge of how certain behaviors are impacting trends can help develop an individualized lifestyle plan on the journey to optimal health and life performance.

Additionally, tracking heart rate may provide valuable insight or early detection of health conditions such as sleep disorders that can not impact your sleep quality, but may facilitate or exacerbate other health-related issues.

Maintaining positive habits such as consistently engaging in physical activity may help strengthen the body’s most vital muscle- the heart.