Heart Rate Variability: the new trend in fitness?

Author: Grow Team
Date: 15/01/2019
Category: Grow

Thanks to improvements in technology, fitness wearables have rapidly gone from glorified pedometers to truly amazing bits of kit that measure all kinds of things – from the quality of our sleep, stress levels, heart rate, effort exertion and more. The list of tools to help us be our fittest selves is ever-increasing, with some of the fanciest devices feeling like personal sports science labs that you can strap to your wrist, reeling off all kinds of fascinating stats (well, we find them fascinating, anyway!).


Although we’d never recommend getting too caught up in numbers, it can be really useful to keep an eye on some key stats when it comes to fitness. For example, hitting 10,000 steps a day is a great target to ensure you’re staying active, and monitoring your calorie intake and/or macros can be incredibly helpful if you have specific goals to reach.


One thing that some consumer devices are now starting to track is “heart rate variability”. This is the pause in between each heartbeat. Say you have a heart rate of 60 beats per minute – this doesn’t mean your heart is beating steadily once per second. The pause between beats may vary from say 0.95 to 1.05 milliseconds.


Why does that matter? Excellent question. Basically, HRV is a good indicator of how well your nervous system is functioning at a given moment in time. It can be used to assess whether you’re ready to smash an intense HIIT session or whether it might actually be better to take it steady with some gentle cardio and core work or a more recovery-focused session.


What does it measure? OK, let’s delve into a bit of science.


If you cast your mind back to science lessons at school, you should remember learning about the autonomic nervous system, that controls vital bodily functions that we’re not consciously aware of – like breathing regulation, pupil dilation and food digestion. This system is made up of two branches:

  • sympathetic – you can think of this as our “accelerator”, speeding up our body’s responses when faced with stress. It’s what controls our fight or flight response and gets us ready for exercise by speeding up our heart rate
  • parasympathetic – on the flip side, this is our body’s “brake”, used to slow things down and help us to recover. It’s most active during sleep and rest


The two systems work in tandem to keep our body balanced between high stress and relaxed states. There is a constant “push and pull” between the two, with our body’s reliance on each constantly changing depending on the situations we find ourselves in.


Back in caveman days, our fight or flight system was used to help us rapidly spring into action when faced with life or death situations, like being chased by lions – but in today’s modern world, our stressors are more likely to involve traffic jams and work deadlines. Unfortunately, our brains haven’t evolved as rapidly as our surroundings, so our fight or flight response is sometimes overstimulated by everyday problems. This can cause an imbalance, whereby our stress response is triggered too much, causing our body to rely heavily on the sympathetic branch, without using the parasympathetic branch to ensure adequate recovery. In the long term, this chronic stress can cause all sorts of problems like high blood pressure, loss of sleep and chronic fatigue.


An imbalance in the autonomic system, where the sympathetic branch is in overdrive, will cause there to be less “pushing and pulling” between the two systems. With the body relying more on the “accelerator”, HRV is likely to be driven down, meaning less variability between heart beats. A HRV monitor would detect this and suggest that a rest day could be in order.


Generally speaking, when measured at rest, low HRV indicates high stress and high HRV indicates a relaxed state or a state where stress is being tolerated well.


So, should you be measuring it? Not necessarily, but if you’re working out regularly, it is something that can help you to understand when to push it and when to hold back a little. It can increase your understanding of how your body is functioning, how well rested you are and what your workout should look like on a given day.


Encouraging a healthy HRV

It’s really important to have a healthy balance between your “rest and recover” and your “fight or flight” systems. Although the abundance of stressors in our modern life can make this difficult, there are some ways to help…

  1. Relaxation / mindfulness e.g. deep breathing, yoga, meditation, tai chi
  2. Exercise. Although exercise will usually trigger your sympathetic responses, by lowering the intensity it can also be used to combat stress. E.g. taking a long walk when stress symptoms rear their head
  3. Socialising. Spending time with others, relaxing and making use of a support network, is key for reducing the symptoms of stress
  4. SLEEP! This is super important. As well as its many other benefits, sufficient sleep is critical for entering the “rest and recovery” division of our autonomic nervous system. Adequate rest will help us to build muscle, recover from a tough workout, reduce stress hormones and generate energy ahead of the next session. Check out our blog all about sleep here 


HRV is still new on the scene, with consumer devices only just starting to pop up, but we reckon it’s going to be one of the next big trends in fitness. And while it’s not necessary to measure it, the increasing interest in HRV is demonstrating a wider trend, that is the growing awareness of the need to listen to our bodies when it comes to working out. There are days (probably those where, if you measured it, your HRV would be lower than usual) where you just don’t really feel like pushing yourself to the max. And that is absolutely fine! Not every workout should be a maximum effort, omg-I-can’t-do-another-burpee-sweat-fest.That’s why we always recommend mixing up your intense group training sessions with some more focused, steady sessions. And it’s why, if you’re not feeling 100%, our trainers will always adapt our group sessions for you if need be, to make sure that the workout works for you. Sweet!


Questions? Don’t hesitate to chat to the team

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