You’ve heard of heart rate zones and training by heart rate. Maybe you even know your resting heart rate can reflect how you’re recovering from, or adapting to, workouts. But what about heart rate variability? Are you using HRV, as the experts call it, in your training?
EXPLAINING HEART RATE VARIABILITY
“Practically speaking, our heart does not beat at a constant frequency,” says Marco Altini, PhD and creator of HRV4Training. “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 those beats — 0.9 seconds between two beats, and then 1.3 seconds between the next two and then 1-second flat — is what we’re talking about when we talk about heart rate variability.
Those differences matter because they’re indicative of what’s going on inside our body. It’s a bit complicated, but essentially your automatic nervous system regulates body functions. By analyzing the autonomous functions of our body — our heart rate variability, for example — we can understand how we’re responding to stress and how we’re recovering. More heart rate variability often means your body is responding well to minute changes second by second. Consistent high readings often mean you’re recovered, rested and ready to go.
“This is where collecting HRV data can become very interesting,” says Altini, “because we can, for example, better understand how much time our body needs to get back to normal after an intense workout or spot the early onset of a flu.”
WHY HRV MATTERS
It’s not hard to imagine why an increasing number of studies have correlated HRV with athletic performance. “Generally, people who are fitter have higher levels of HRV,” says Daniel Plews, PhD, a sports scientist working on heart rate variability. However, for the fittest athletes, this difference is less pronounced. In elite athletes, studies have shown performance can be worse when HRV is higher, because the body can be fatigued and HRV can spike after hard workouts or hard training blocks.
However, don’t get too attached to any universal rule, such as high numbers are always good. Athletes tend to perform best when their heart rate variability is within a normal range, whatever normal is. That means you need to know your normal to perform your best and respond accordingly.
MEASURING HEART RATE VARIABILITY
Measuring HRV is not quite as easy as counting your pulse, but it’s not as complicated as it sounds either. What most apps do is take a heart rate variability indices called rMSSD to make all those heart rate variability numbers into a simple or smaller number, says Plews. That rMSSD number can still range from 25–250 for a given person, but many apps also offer their own proprietary “recovery score” (typically out of 100) in addition to raw metrics.
READ MORE > HEART RATE MONITORING BASICS
Triathlon coach Alan Couzens recommends HRV4Training, which is the only app that can use the camera on your smartphone to measure HRV, but he also suggested ithlete and SweetBeat as proven apps and Kubios for those who want more in-depth numbers. The apps that don’t use a camera require you to put on a heart rate monitor strap for the period during which you’re measuring your HRV.
To get a good measurement, you should measure it at the same time each day and with the (more or less) same routine. “HRV will vary widely through the day so it is important to stick to same time and same circumstances,” says Couzens. He recommends measuring HRV each morning after your post-alarm bathroom trip. He also encourages his athletes to measure their heart rate variability while lying down. So make that trip to the bathroom and then lay back down for at least a minute to get an accurate measurement.
The key is to establish a baseline for yourself. “By doing this you can understand what is ‘out of the ordinary’ for you,” says Plews.
INCORPORATING HRV INTO YOUR TRAINING
Couzens has his athletes take a month to measure and watch the readings, but not use them. If it’s a normal month — not one where you’re racing an Ironman — it’ll give you a good average to start with.
Once you know your normal and how stable your HRV is, then you can start to make adjustments based on how it changes. Change generally means something’s going on. Couzens looks at two things: weekly and daily changes. “When the seven-day average numbers start to decline, it’s a good sign that a rest week is needed,” he says. On a daily basis, he uses it to fine-tune what type of workouts make sense. Some research has found athletes who trained in response to HRV — when their HRV numbers were low they would take an easy day and when it was higher they would do a harder workout — had a 7% increase in their VO2 max, while the group that trained a fixed hard/easy schedule improved by just 2%.
Couzens cautions people not to rely on solely HRV, since training is a puzzle made up of many pieces, and to focus more on the long-term trends and differences from baseline. The key is really to find out what your normal is and how your body responds to stress — training or life stress — and use HRV as one of many tools to help with recovery and performance. “For any athlete who truly commits to the process for a period of time, there is always some benefit,” says Couzens.
GEAR UP FOR YOUR NEXT WORKOUT