As athletes, we walk a fine line between training hard to make fitness gains and pushing our bodies to breaking point.
If you’re training at a high level, it’s important to have objective measures in place to tell you if you’re overdoing it. Otherwise, you risk illness or injury which will put the brakes on your progression.
Heart rate variability is one way to determine whether you are hitting a sustainable volume and intensity, or whether your body needs you to dial things back.
What Is Heart Rate Variability
Heart rate variability is a measure of the time between each heartbeat.
Although many people may assume that a regular heartbeat is desirable, a higher variation in time between each beat is actually a sign of a healthy heart and is therefore common in athletes.
In fact, it’s when your heart rate variability decreases that you may be overtraining or overstressed.
This is because heart rate variability is influenced by two branches of the nervous system - the parasympathetic branch (sometimes called rest and digest) and the sympathetic branch (sometimes called fight or flight).
The heart is simultaneously being told to slow down by the parasympathetic branch, but also to speed up by the sympathetic branch (fight or flight), which leads to a high heart rate variability when the nervous system is balanced.
When heart rate variability is low, this indicates that the body’s sympathetic nervous system could be overactive and that levels of stress hormones such as adrenaline and cortisol which are triggered by exercise may still be high.
How Can You Use Heart Rate Variability
The time between heartbeats will vary by just a few fractions of a second, so it is almost impossible to track heart rate variability without technology.
Thankfully, many fitness trackers and smartwatches now track heart rate variability and give you a tangible score of how stressed you are.