With more sensors connected to our bodies, technology can now measure and give us feedback on the subtle things happening in our bodies and impact on our performance. After a few weeks of wearing my new Apple Watch, I casually watched all the health data show up on my iPhone. Then my Garmin Edge started to tell me about 10 minutes into my ride whether I was fatigued or not. Generally, it was a pretty accurate indicator of how I felt, but what did that data really mean? Was there a useful tool I wasn't aware of? I started doing some poking around. The short answer is yes: Measuring and comparing your Heart Rate Variability (HRV). HRV is as an assessment of your fatigue or rest level with science behind it, and it is a useful tool to optimize your training.
The Science behind HRV
What is it? HRV is the physiological phenomenon of the variation in the time interval between heartbeats. It is measured by the variation in the beat-to-beat interval. Your heart does not beat in a perfectly regular rhythm. Beat-to-beat variations in your heart rate are healthy and normal.
Research has shown that the HRV results will be a key indicator on how well rested you are. This is especially true for athletes. The stress level one feels is a function of many variables to include training load, sickness, alcohol use, nutrition, sleep, and air quality just to name a few. Research has shown that HRV is a great biomarker to understand your life, but there are a few things you need to do to help make the most of it.
1. The first is consistency. Measuring it at the same time of the day and in the same situation–sitting, standing etc. The best is to measure it while standing in the morning just after you wake up.
2. Next, you need to understand the context of the results. Just finished a big ride? A few too many cocktails last night? Changed your diet? Is your new job stressful? These will all impact the results.
3. Lastly, you need to get a solid baseline by measuring over a 5-day period to make the most of the HRV data. After this, you can monitor the trends and understand the context to understand how it has changed.
How do You measure HRV?
One easy way is to use your heart rate monitor strap and connect it to an app like Elite HRV or Bioforce, both available in the App store for Apple and Android phones. If you have a
Garmin Edge, you’re in luck. Garmin has a feature that allows you to check your HRV manually. The stress level range is from 0 to 100, where 0 to 25 is a resting state; 26 to 50 is low stress; 51 to 75 is medium stress; and 76 to 100 is a high stress state. Knowing your stress level can help you identify stressful moments throughout your day.
There are other tools that measure HRV, like Apple Watch, which measures randomly throughout the day so it is less effective because you need to measure it at the same time every day to get a better reading. You can force an Apple Watch to take a reading by running the “Breathe” app on your watch for a minute, but the data doesn't populate the Health app right away. I found the Apple Watch to be useful as a general, but pretty accurate, trend tool.
I’m a data nerd, so I have been using the Elite HRV app and connected it to my Strava account for $5. It pulls all my Strava exercise data and uses it in its algorithms to assess trends and rested or fatigues periods. This set up tells me when it's best to go hard and when it’s better to stay in easier zone 2 efforts. For the Wahoo users, the Wahoo TICKR transmits HRV measurements via Bluetooth to your favorite app.
How to Apply Insights
HRV will provide athletes insight on what behaviors or areas of life impact your well being. It can also determine your level of effort for a given day. Have a negative trend? Maybe it's time for a day off or an active recovery instead of intervals. Have a positive trend? Maybe that's the day to push yourself. It's a great tool to determine how training and different behaviors in your life can be affected over time.
By regularly tracking your HRV and pursuing different modifications to your lifestyle through nutrition, workouts and other life changes, you will see different results. HRV helps you understand your behavior and know when a change is a good one.
For a deeper dive on the science behind HRV to assess your level of fatigue and target your training, here's a reference article. Now, go for a ride!
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