Heart Rate Variability and the Big Picture
The metric that could revamp everything about how you train (and recover)
If you’ve never heard of HRV (heart-rate variability), you’re not alone. And you may also know nothing about the inconsistency of your heartbeat. Yep, that’s right; your 60-bpm resting heart rate is not 60 evenly-spaced-out beats. In fact, heart-rate beat timing is all over the place. While the metrics have long been oversimplified, in general, the more variance you experience between each heartbeat, the healthier you are. But why?
HRV and the Autonomic Nervous System
Before we go any further, let’s clear up some common misconceptions. Heart rate variability (HRV) and heart rate are not the same. Heart rate variability measures the variations in the time between each heartbeat while heart rate simply measures the total number of beats per minute.
When measured correctly and over a prolonged period, HRV is a good measurement of the health of your autonomic nervous system, the part of your body than manages automatic processes like digestion, nutrient delivery, energy regulation, sexual function, heartbeat, etc. How well this system functions is directly related to how well you recover between hard efforts.
Dr. Ashley Stewart, a psychophysiology and applied neuroscience specialist who has studied HRV, says to think about the heart beat like a car in drive. Your parasympathetic nervous system (rest and digestion system) is the brake and the sympathetic nervous system (fight or flight) is the gas. "What pushes the gas and the brake is a beautifully complex orchestration of neurobiological mechanisms," she says. "These orchestrations cause changes in heart rate and in it’s variability over time."
The brake and gas allow the car to move faster or slower, depending on how and where you're driving. She adds, "The ability of the nervous system to allow and readily experience these orchestrated events means the heart can have dynamic system function, a hallmark of health. If the heart can readily adapt to internal and external environmental changes, it can essentially 'bend without breaking.'"
In short, variation is a good thing. And the more variation you have, the higher your HRV. The higher your HRV, the more capable your body is at adapting to and recovering from stress.
HRV and Training
According to Jason Moore, founder of Elite HRV, one of the most popular HRV monitoring apps on the market (it’s also free), HRV is your system’s diagnostic check; it’s the big picture of your systemic health.
As you train, you want your HRV scores to increase because it most often indicates a higher aerobic capacity. Conversely, if HRV decreases over time, it's often an indication that you’re accumulating too much stress, which could be a result of overtraining.
Still, while a handful of studies exist about HRV and training for recreational endurance athletes, Stewart says that at the elite level we still have a long way to go. With intense training loads, sometimes the correlation between HRV and fitness doesn’t quite match up. "Accuracy and consistency of measurement over time present enough of a barrier in research," she says. "Factoring in intra-individual differences complicates things even more but is imperative, especially in the case of athletic and cardiovascular performance in endurance athletes."
That being said, since most of us aren't Olympians, learning how to track and use your HRV to support your training makes sense. It will help you understand your overall health and more accurately forecast training.
Find your baseline and work from there. You'll need a heart-rate-monitoring chest strap (like this one from GARMIN, which can pair with a GARMIN watch) and an app like Elite HRV that uses an advanced algorithm to customize your results.
Measure HRV first thing in the morning, ideally before you get out of bed and certainly before you’ve had any coffee. It only takes a minute or two, but you need to do it every day for at least a week to get an accurate reading based on your unique physiology.
Plan high-intensity workouts (intervals, tempos, etc.) on days where your HRV is higher. Let’s say your average reading is 45. If you perform hard workouts on days when your s is more like 50 or 55, you’ll not only have a better workout, but you’ll also experience more fitness gains, at least according to a recent study of recreational endurance runners.
A lower HRV score indicates you need more time to recover. Think about how much you train per week. Is it three hours? Four? 10? Even if you spend 10 (OK, that’s a lot), there are still over 150 hours left in the week, which means that most of your time is spent recovering. Utilizing HRV values to monitor recovery helps you to maximize that time and experience the most benefit.
The bottom line? It’s not even really about training. It’s about self-awareness, according to Moore. “You do not measure just to measure stuff, you measure to learn more about yourself and to maximize your health."