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Heart rate variability & how devices can glean your health from it

Heart rate variability & how devices can glean your health from it

A gadget that tracks your lub-dubs might just enable you understand your body well and also tackle anxiety and stress
Representational image | Shutterstock

Your heart might do  its occasional little jigs for a host of reasons:  before cracking a submission at the nick of time, while a deadline looms, or when it is getting late for an important interview, to name a few.  

Now, imagine living in that state on a loop. Before you know it, your stress level would be soaring, and you might need help. Fortunately, with research in health-related technology or health tech, people can monitor any variation in their heartbeat and possibly seek timely intervention.  

Heart rate variability (HRV), as it is known, is being looked at among researchers as a potential indicator of health issues like stress and anxiety. Happiest Health helps you to know all about this measure.

What is HRV? 

Heart rate variability is the measure of the difference in time between two heartbeats. It is usually calculated in milliseconds, with the average deviation between the two being between 20 milliseconds and 200 milliseconds.  

A healthy resting heart ideally beats between 60 and 100 times per minute. A lower rate implies that the heart is working efficiently, and the individual has a good cardiovascular capacity. However, a person can have a pulse considered to be in the healthy range, but still suffer from anxiety, mental health issues, and heart conditions. Luckily, medical researchers have found an indicator, the heart rate variability or HRV that can alert one to these conditions.  

HRV is controlled by the autonomic nervous system (ANS) which also controls other critical functions such as respiration, digestion, blood pressure, urination, sexual arousal, pupil dilation, and reflex actions such as swallowing, coughing and sneezing.  

How experts use this data 

Vellore-based cardiologist Dr K Sabapathy says HRV can vary depending on one’s physiological or pathological condition. “A diabetic patient might have a low HRV, while a person under physical stress can also have a low HRV. There are multiple formulas cardiologists use to obtain the correct feedback from HRV, [which is] usually tracked through an electrocardiogram [ECG],” he says.  

A new health metric?   

Scientists believe that HRV can indicate a healthy ANS. This is also why manufacturers of many fitness and wearable devices have included sensors to measure HRV in their watches and activity trackers.  

The companies claim that by monitoring HRV, users can get insights into stress, fatigue, recovery and can even predict how much they are allowed to exert during their next physical activity.  

“Our wearables collect more than 25,000 data points on a daily basis and work by monitoring variations in heart rate or body temperature. The data these devices collect could provide people with information on which to base decisions to seek medical advice or treatment,” says Vishal Gondal, Founder and CEO, GOQii, a smart wearables company based in Menlo Park, California, USA.  

The smart devices use sensors to capture vital parameters such as heart rate, heart rate variability, blood pressure, SpO2 levels and sleep. “Since the pandemic broke out, wearables such as smart watches have become an essential commodity to help detect vital parameters and help individuals to monitor themselves. They are designed almost like a doctor in your hand,” adds Gondal.  

Caution on external signals 

Dr Sabapathy offers a word of caution. He strongly advises that wearables be used only as reference points for HRV as they collect a lot of data where external stimuli could be acting on HRV. 

“HRV is a method to assess the proper functioning of the ANS, and smart wearables might not be able to differentiate if the stressors are caused by physiological or pathological factors. It is important to consult a doctor before misinterpreting these readings,” points out Dr Sabapathy. 

Factors influencing HRV 

  • Circadian rhythms, age and gender: Your sleep cycle, age and gender can have an impact on HRV. Hence it would be a good idea to first consult your doctor, understand what to expect in terms of HRV tracking, and then begin it. Here, it would be a confusing scenario if you measured your HRV against those of friends or activity groups, as there is a good chance that the figures can vary. 
  • Medical condition: Individuals who have been diagnosed with issues pertaining to the lungs, kidneys and heart could have lower HRVs. Mental issues such as panic attacks, anxiety, post-traumatic stress disorders, anorexia, borderline personality disorder and depression can also affect HRV. 
  • Intensive exercises: Do not be surprised by a lower HRV reading if you have been overtraining, or are involved in extreme sports such as marathons, intense CrossFit sessions or long treks. Induced pain can also cause a low HRV reading owing to the activation of the sympathetic nervous system.
  • Climatic conditions: A hot climate has been shown to increase the activity of the sympathetic nervous system. However, the same might not be true for moderately cold conditions.  

What users say 

A few users say that tracking heart rate variability has helped them to have a more disciplined life and avoid exertion. “Ever since I became pregnant, I constantly monitor my heart rate variability and sleep cycle on my smartwatch to track my stress levels,” says Vidhyashri S Rao of Bengaluru. The head of marketing at Hotel Chancery Pavilion says she reduces her activities if her device shows a low number.  

Bengaluru-based Anees Rahman points out how certain lifestyle changes have affected his HRV. “I was surprised to see that my HRV levels improved slightly two weeks after I quit smoking.”  

How to read it 

Timing is everything: Experts advise measuring right after waking up in the morning. This is because the nervous system is responsive to almost any stimuli at that time. Also, transitory, short-term stressors will be relatively low. Measuring the HRV randomly during the day might not be the most effective. 

HRV can also be measured throughout the night, when the person is in complete rest, and external factors are not at play.  

Fixing a time: Choose a device in which you can set a time to track the heart rate. HRV is closely linked to the duration of time it measures, i.e. more data while at rest or sleep can provide near-accurate figures. The minimum recorded time is 5 minutes. However, certain devices measure HRV at regular intervals at rest, and such data can provide the best feedback.  

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