What is Garmin’s Body Battery and how does it work?

We’ve all had those days where we feel a bit more lethargic. But how can you tell when that’s just a momentary bout of sluggishness, or a sign from your body that you need to take things easy for a little while? 

Step forward, Body Battery. Garmin describes it as an “energy monitoring system”, designed to help you keep track of your energy levels through the day.

It shows you the impact of physical activity, stress, relaxation and sleep on your body, and can also give you an idea of how prepared your body is for physical exertion. Are you ready to take on a challenging workout or do you need to focus more on recovery?  

“Both mental and physical strain is good for you – to a certain limit.”

That’s what Garmin’s Body Battery tells you. Over time, you’ll be able to build up a picture of what causes your energy levels to be depleted and what helps to restore them (hint: it’s good quality sleep).

It’s similar to the Fitbit app’s Daily Readiness Score (although you have to pay for Fitbit Premium to access this insight, while Garmin offers Body Battery for free). 

Body Battery works by monitoring physical activity, stress, rest and sleep, and combining the influence of these four factors to produce a score. Specifically, your device will track your stress levels, activity data and heart-rate variability (HRV), to decide how much your battery has been charged or drained. 

Garmin Body Battery levels: 

0-25: Low 

26-50: Medium 

51-75: High 

76-100: Very high 

The higher the score, the more ready your body is for challenging activities, while a lower score may suggest that it’s time to try to take things easy. 

Garmin uses this difference in heart-rate rhythm as an indirect indicator of stress. Increased heart-rate variability means lower stress. And stress is one of the main factors that depletes your energy.  

In basic terms, the more stress you’re under, the faster your battery score will deplete. Body Battery doesn’t differentiate between different types of stress – whether that’s intense exercise, being in a loud pub, discovering that someone has eaten the last biscuit in the packet, or missing your flight home.

But as Garmin says: “Your phone is made for use. There is no sense extending the battery life by not using it. The same is true of your body. It is made for use and both mental and physical strain is good for you – to a certain limit.”

In other words, you should expect your energy levels to reduce over the course of the day, and exercise can, over time, make your Body Battery score more resilient to stress as you become fitter. 

Rest and relaxation are key to increasing your Body Battery score, and sleep is by far the most important factor. It’s no coincidence that your Body Battery score will likely be at its highest just after you wake up, and lowest just before bedtime.

According to Garmin: “Quiet, restful moments and short naps during the day can boost your energy levels, but real, quality sleep time is when the magic happens.” 

Garmin also emphasises the importance of a good bedtime routine in improving your energy. Drinking alcohol or caffeine in the evening, or doing an intense workout shortly before bedtime, are all factors that can negatively influence your Body Battery score, if they interfere with your sleep quality.  

Body Battery offers a quick insight into some of the data your Garmin device captures. But Body Battery is at its most accurate the more you wear your running watch or fitness tracker.

It needs a minimum of five to seven days’ worth of data to start providing you with a score. If you wear your device 24/7, it will be able to more accurately monitor how your energy levels are depleted and restored.

And if you don’t wear it enough, you simply won’t get a score. But once you do have a score, what do you do with the data?  

Given that Garmin primarily produces devices with a fitness focus, the most obvious use for the Body Battery is to gauge what kind of physical activity your body is ready for. A high Body Battery score means you’re likely to cope better with more intense activities and workouts, while a lower score may mean that your body is fatigued, and in need of something more restorative such as yoga, or a walk.  

It can also help identify patterns and situations that impact your score. For example, are there certain nights where your energy levels don’t recharge as much as usual? Does that correlate with a night where you consume alcohol, or have a late night for some reason? It doesn’t mean you need to change your behaviours, but it can be instructive if you’re trying to understand why you feel better on some days than others. 

Garmin’s Body Battery can also offer a clue that you may be about to get sick. Your immune system will often kick into gear before you start showing any symptoms of illness, but your Garmin device may be able to spot the impact this has on your heart-rate variability. If you notice that your usual exercise felt a bit harder than normal, or that your score is dropping faster than usual, it could be a sign that you’re getting ill. 

You don’t necessarily need Body Battery to tell you when you’ve got a cold, or that you’re feeling tired. It’s more beneficial as a tool to support you in knowing when to push yourself and when to take things a little easier. No matter what level of fitness you’re at, having a better understanding of your own body can help you make better lifestyle choices and optimise your exercise and recovery schedules.