Do we have a body battery?

Modern activity trackers and everyday language seem to push the idea that we have one, finite energy 'source' that depletes over time—or with certain activities—and can only be restored through physical rest. When working with fatigue, it's clear we need to be more flexible in how we think about batteries, as it more closely represents how energy works. 

It feels more accurate to think of our bodies as having multiple batteries and these differ from person to person, both in type and capacity. Some people notice a ‘social battery’ that drains more quickly than others; this may be more likely if they are introverted or neurodiverse. The same person might have a larger or smaller ‘physical battery’ or a ‘cognitive battery’.  When given the chance to label their batteries, some people call one of their batteries  ‘family’—particularly the parents of young, bouncy children or ‘sensory’, reflecting challenges many have in multi-sensory environments like open-plan offices, cafes, or groups of people.  Many people find that using devices and social media is so draining it deserves a battery of its own! 

What’s more, energy capacity isn’t fixed. People often notice their battery capacity fluctuates over time, challenging the idea of a single, unchanging amount of charge. Capacity for many people does in fact increase over time, and with rehabilitation. 

What Recharges Your Specific Batteries? 

Being outside and connecting to nature is often restorative for different types of battery drain

I find it incredibly useful to work with people to identify their individual batteries and understand what restores each one. Often, it's useful to discuss a common belief that physical rest or meditation is the only way to recharge. Different types of activities can replenish different batteries, and people have more options than they realise.  After my own experience of Long Covid, which affected my voice, I definitely noticed a 'voice' battery as well as a 'noisy environment' battery. I don't have to lie down to restore my voice battery, I just have to stop talking and perhaps consider any stress that might be making things worse. 

One client, for example, had always believed the only way to recharge was to retreat to a dark room and sleep. Over time, he discovered other forms of restoration. Walking, for instance, became a way to restore his social battery, meaning he no longer needed to rest before or after social interactions which he once thought was essential. He described this as a 'total game changer'. It's also important to note that sometimes, for example during acute illness, that all of the batteries are drained at the same time and lying down in a dark room is exactly the right response. 

Similarly, what restores one person might surprise them: cooking, crafting, or even socialising after a cognitive task can help some batteries recharge. Being outside and connecting to nature is often restorative for different types of battery drain. Meeting a friend might recharge a physical battery. Conversely, activities often thought of as restful like watching TV may not restore energy at all. Some people (although less common) can even be recharged by playing video games. It's all much more nuanced than people appreciate, and keen observation helps a great deal. 

Does that make my watch 'Body Battery' feature useless? 

Having said that one, finite battery isn't the way the body works, I have also seen that the 'body battery feature' of some smart watches can be very useful to some people. Using a combined measure of stress, heart rate variability, sleep, rest, and activity, the watch algorithms use this data to come up with a figure between 0 and 100. This can give users an instant score in any given moment. It can sometimes also give little tips like 'time to rest.' I find these measures very interesting, and some people swear by them and find them very useful in their fatigue management, especially those who find it hard to tune into their body's physical signals. Personally, I find the measure way too simplistic, and would encourage using such a measure as only one of many objective and subjective indicators of fatigue to help guide activity. 

Written by Founding Director and Specialist Physiotherapist, Jessica Sands