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Garmin Body Battery: What is it and why should you care?

How does Garmin's Body Battery measure energy levels? Allow us to explain.
By
February 15, 2022
garmin venu 2 review body battery
Jimmy Westenberg / Android Authority

Garmin Body Battery is a feature on Garmin devices that aims to offer insight into your energy and readiness for training. The feature is available on a number of watches from the company. But is it really a useful feature? How does it work? Allow us to explain.

How Garmin Body Battery works

According to Garmin’s website, Body Battery combines heart rate variability (HRV), stress, and activity data to calculate the user’s likely energy reserves. It uses this information to generate a number between 1-100, where 100 is maximum energy.

HRV is a useful measurement of sympathetic nervous system dominance. The sympathetic nervous system is responsible for the “fight or flight” response and is associated with increased heart rate, suppressed immunity, digestion, and anxiety, among other things. Normally, when we exhale, we become slightly more parasympathetic, meaning our body slightly relaxes. This is indicated by a slight decrease in heart rate, providing us with “variability.”

If the heart rate does not change as much during exhalation — if variability is low — it suggests the body is too stressed to calm itself down. This tends to correlate with physiological arousal, illness, toxicity, psychological stress, hunger, or incomplete recovery.

Stress and activity

Garmin says HRV data is then combined with stress. This is derived from the HRV data, but it’s possible to see in the screenshots (above) how the two metrics interact. Broadly, more stress = a rapidly draining battery, as you would expect.

Activity levels can help to contextualize this data. If you have been training intensively for five days in a row, there is a higher likelihood that you should be tired.

Sleep data also factors into your Body Battery score. Garmin suggests the best way to recharge your battery is to get a good night’s sleep while wearing the device.

Crucially, Garmin Body Battery relies on cumulative data. If you have a very restful day, this will be viewed in light of your prior activity. This is important: one night of poor sleep does not immediately equate to low energy. However, five nights of missed sleep start to rack up.

With the Garmin Venu 2 series, the company rolled out improvements to its Body Battery algorithms based on user feedback. It’s now far more difficult to achieve a Body Battery score of 100.

Why Garmin Body Battery is useful

A woman sleeps in bed while she wears the Garmin Lily Sport Edition smart watch on her left wrist.
Lily Katz / Android Authority

So, how useful is Garmin Body Battery? The answer will depend very much on your personal usage. Many people find Body Battery is a fairly accurate representation of their subjective energy levels. This makes it a helpful aid in decision-making.

Knowing how hard to train on any given occasion is important, as simply continuing to push through when fatigued can break down the body without giving it an opportunity to recover. This can lead to overtraining — or under-recovery — which is considered, by some, to be the more accurate term.

See also: The best Garmin running watches you can buy

At the very least, adequate recovery time is necessary to ensure the best results from training. Weight training, for example, is biphasic. While we provide the stimulus for growth in the gym, it is actually during our anabolic rest time that the muscles repair and grow. Similar processes allow for nervous system adaptations. Going harder for longer is not always the solution.

Likewise, management of the Garmin Body Battery may teach better energy management in general. It may help users adopt healthy habits. As they say: That which is measured, improves.

Finally, tools like Body Battery allow us to identify trends. If you find your score is consistently lower than you would like, you can begin to look for ways to improve it. Perhaps you are sensitive to that blue light from your phone before bed and this is reducing the restoration you get during sleep? Perhaps you should give up the nightcap? These are all factors you may be able to notice when looking at your scores.

garmin venu 2 review garmin connect body battery stress
Jimmy Westenberg / Android Authority

We should also recognize the limitations of these tools. The best indicator of recovery, after all, is the way your own body feels. The best way to know whether or not to train on a given occasion is simply to listen to what those systems are telling you.

There are many more factors that contribute to a readiness to train — factors that can’t possibly be measured by Garmin Body Battery. Your Body Battery score might be high, but if you have picked up an injury or if you’re suffering from a migraine, you shouldn’t train.

Above all else, listen to what your body is telling you about your recovery.

Moreover, Body Battery is primarily a reflection of HRV. While the score might also take other factors into account, such as activity and sleep, these should already be reflected in your HRV.

Nor is this feature entirely unique. Other devices, such as the Oura Ring 2 or Whoop Strap, have a similar ability to measure HRV and output a “readiness” score. Fitbit also debuted a similar feature called Daily Readiness Score on the Fitbit Charge 5.

Body Battery also requires the user to wear the device consistently, including at night, with only short breaks to charge. When you stop using the tool, you will see dotted lines appear on the graph. This indicates estimated values that are generated as a combination of population data and individual trends. If you stop wearing the watch for several hours, however, it will reset the score. In other words? Body Battery is a commitment if you want to see the most accurate information. This will be off-putting to some users, especially those that own the bulkier Garmin products.

Garmin devices with Body Battery

Garmin Forerunner 55 review body battery graph
Jimmy Westenberg / Android Authority

If you want to give Garmin Body Battery a try, you can find it on any of the following compatible devices:

Once you begin wearing the device, it can take 5-7 days for it to learn your habits and adapt accordingly.