Did you know that your heart doesn’t beat to a perfect rhythm? Here’s why you should start paying attention to how irregular your heartbeat is:
- Tracking your heart rate variability (HRV) is a good way to monitor recovery from training.
- It’s now easier than ever to measure your HRV! You can use your phone and don’t need a pesky chest strap.
- Being more in tune with your recovery helps you train smarter and perform better in the long run!
All this talk of HRV got your heart racing? Check out the following guest article by Marco Altini, PhD, Data scientist, Entrepreneur | Full bio below
Physiological stress & Heart Rate Variability
Heart rate variability (HRV) is an important marker of an individual’s physiological stress level. In particular in the context of training, intense exercise is a strong stressor, therefore leading to higher physiological stress, which can be captured with HRV, for example in the form of acute drops post high intensity activity, which can last for up to 48 hours post-exercise. This is part of the rationale behind measuring HRV to better understand our body’s response to training and optimize recovery. By combining HRV with other parameters and contextual information related to lifestyle and training, we can better understand the big picture, see how an athlete is adapting (or not adapting) to a specific training block, and try to make changes to avoid overtraining, eventually leading to better performance.
Due to recent technological improvements in terms of computation power and accessibility to high quality wearable technology we are seeing all sorts of applications making use of HRV today, from optimizing performance in sports, to monitoring psychological stress in the workplace.
While HRV is a powerful tool and can be very helpful in better understanding physiological responses to both acute and chronic stressors, interpreting HRV data at the individual level can be challenging. This article focuses on practical ways to acquire and interpret HRV data in the context of monitoring training load and optimizing performance, using HRV4Training as an example.
What’s HRV, why it matters and how to start collecting data
Practically speaking, our heart does not beat at a constant frequency. So even if we measure our pulse, and get a 60 beats per minute reading, it doesn’t mean we have a beat every second. The time differences between beats are slightly different, they can be 0.9 seconds, 1.2 seconds, and so on. When we talk about HRV, we talk about ways to quantify this variation between heart beats.
This explains also why HRV, is not a single number, and there is sometimes a bit of confusion on different metrics to measure HRV since we can quantify these beat to beat differences in different ways. However, especially in the context of using HRV to monitor physiological stress, the community settled on one specific feature which is called rMSSD. It’s a time domain feature, easy to compute. So most commercial tools or apps, will provide you with either rMSSD or with a transformation of rMSSD to make the value a bit easier to interpret, for example scaling it between approximately 1 and 10 or 1 and 100. This is also what HRV4Training does, when providing what I called Recovery Points.
What does HRV represent?
Let’s take a step back and talk a bit about the autonomic nervous system. The autonomic nervous system regulates many body functions, mainly unconsciously, such as respiration, the heart beating and so on, and consists of two branches, the sympathetic and parasympathetic branches.
The sympathetic branch, is in charge of the fight or flight response, while the parasympathetic branch promotes a rest and recovery. Making a few simplifications, since the autonomic nervous system maintains an adaptive state of balance in our body, we can better understand how we react to different stressors, by analyzing autonomic function.
This means we would expect higher parasympathetic activity under conditions of rest, when we are well recovered and rested. Since the autonomic system regulates the heart beating, we can use HRV as a proxy to autonomic function, and therefore use HRV as a way to measure how we react to stressors. This is where collecting HRV data can become very interesting, because we can, for example, start to figure out how much time our body needs to get back to normal after an intense workout or spot the early onset of a flu, as well as understand how our body is reacting to big stressors like intercontinental travel or other life situations.
How to get started with collecting your HRV data
Up to a few years ago, HRV was used mainly by academic researchers working at the intersection of sport, health and medicine. Many of these experts were able to show links between HRV and performance as well as recovery or training load and chronic disease.
However, in the recent past many new, affordable and user-friendly tools have been developed. These tools typically rely on commercially available heart rate monitors (e.g. a Polar chest strap) to analyze data, compute HRV and provide guidance to the user. Most of these apps rely on spot measurements of about 1 minute.
The latest developments go even a step further in terms of usability and accessibility. With apps likeHRV4Training, HRV can be computed accurately without the need for any external sensor or device. The main advantage is the increased compliance and reduced cost. The techniques used by HRV4Training have also been validated, showing equivalency with not only a chest strap but also electrocardiography in the context of measuring heart rate and heart rate variability. (Reference)