Elite and recreational athletes alike are increasingly using their heart rate data to guide their training. In addition to using heart rate zones as a measure of exercise intensity, heart rate variability is being used to judge athlete readiness and recovery needs. 

In this blog we’ll explain exactly what your resting heart rate (RHR) and heart rate variability (HRV) are, explore how your personal DNA can affect both, and share some of the recommendations being followed by FitnessGenes members to improve theirs. 

What is RHR and HRV? 

Your RHR is the number of heartbeats in one minute when you are at rest. A low RHR is a positive training adaptation to exercise as the heart becomes stronger and more efficient at delivering blood around the body. 

Adults typically have a RHR of 60-100 beats per minute (bpm)^[1], however, it is not uncommon for trained athletes to have a RHR of below this range. Five-time Tour de France winner Miguel Indurain even had a RHR of just 28 bpm! A RHR above 100 indicates that the heart is having to work hard to sustain normal function and can indicate an increased risk of cardiovascular conditions.

Your HRV is a measure of how much the time between each heartbeat varies. The variety between heartbeats is influenced by two competing systems within your autonomic nervous system - the network of nerves that control unconscious processes such as heart rate, blood pressure, and breathing. 

While your parasympathetic nervous system - known as the ‘rest and digest’ side - tells your heart to slow down, the sympathetic nervous system - known as the ‘fight or flight’ side - instructs it to speed up^[2]. Greater variation in your HRV, therefore, shows that your body is responding to both inputs and your nervous system is well balanced. Smaller variation suggests that one system is dominating this balance and that your body is less primed to handle the physical stress of exercise.

Through progressive endurance training you can expect your RHR and HRV to move in opposite directions. Your RHR will fall as your cardiovascular efficiency increases and your HRV will climb as you establish greater balance between your parasympathetic and sympathetic nervous systems. 

How does your DNA affect your RHR and HRV?

Both your RHR and HRV are influenced by a variety of lifestyle factors including your age, sex, and training level. However, they can also be affected by the genetic variants that you inherit. 

The FitnessGenes Resting Heart Rate and Heart Rate Variability report analyses 9 variants across 8 genes that have been shown to influence RHR and HRV. Taken collectively using a polygenic risk score^[3], these 9 variants have been found to explain up to 1.13% and 2.4% of the variance in RHR and HRV respectively.  

By understanding which variants our members carry, we can then organise them between individual groups, otherwise known as bands, that highlight their relative risk:

1. Low genetic risk

2. Moderate genetic risk

3. Moderately high genetic risk

4. High genetic risk

Those members who are grouped within the ‘low genetic risk’ band carry the fewest genetic risk variants linked to a higher RHR and lower HRV. The number of genetic risk variants present progressively increases across the subsequent bands, with members grouped within the ‘high genetic risk’ carrying the greatest number of variants linked to a higher RHR and lower HRV. 

For those members who are grouped within the ‘high genetic risk’ band, their collection of variants are associated with a RHR of up to 5.5 BPM more than someone without any risk variants. That’s almost 8,000 more beats per day! With the heart having to work harder, this increase in RHR is associated with an 8.3% higher risk of cardiovascular disease and a 9.4% higher risk of mortality from all causes.

Through our analysis, we found that a combined 40% of our members carry variants that place them within either the moderately high genetic risk (31%) or high genetic risk band (9%). For these members, it’s of increased importance that they follow recommendations that will lower their RHR and increase their HRV. 

Recommendations to improve your RHR and HRV

As with all FitnessGenes reports, Resting Heart Rate and Heart Rate Variability provides our members with actionable recommendations that they can incorporate into their daily schedule. Our recommendations relate to five key areas of health and fitness: exercise, nutrition, supplements, behaviour and lifestyle. 

Here are some examples of the recommended that have been saved by our members this week:

1. If you are able to monitor your HRV, take a rest day or opt for low-intensity training on days when your morning HRV is low. 

Lower waking HRV has been correlated with poorer exercise performance, particularly during moderate to high-intensity exercise. Lower-intensity exercise or active recovery on these days would be more beneficial. 

2. Try some hatha yoga a few evenings a week. 

Hatha yoga has been shown to significantly improve your HRV, which can enhance your endurance performance.

3. Moderate your alcohol intake. 

Alcohol prevents the parasympathetic nervous system from helping your body rest during sleep, which leads to lower HRV in a dose-dependent way. Two drinks have a significantly greater effect on HRV compared to one drink. 

4. Focus on adequately rehydrating after exercise. 

You can make your own rehydration drink by mixing 200ml squash with 800ml water and adding a large pinch of salt. Dehydration can lower your HRV and slow your recovery after exercise. 

Understand your personal genetic risk

Want to know if you carry genes linked to elevated RHR and lower HRV? If you have existing DNA data from alternative providers including 23andMe or Ancestry.com, you can find out immediately through our DNA upload service. Alternatively, you can take a FitnessGenes DNA analysis test, with your results delivered within 4-6 weeks. 

Resting Heart Rate and Heart Rate Variability is just one of 11 endurance-related reports that you receive with FitnessGenes. You’ll also gain insights into your red blood cell production, caffeine response, VO2 max trainability, and more. Learn more about how you can work with your DNA to achieve your next PB by exploring our Endurance category. 

References 

1. https://www.bhf.org.uk/informationsupport/heart-matters-magazine/medical/ask-the-experts/pulse-rate
2. https://www.healthline.com/health/parasympathetic-nervous-system
3. https://www.genome.gov/Health/Genomics-and-Medicine/Polygenic-risk-scores