Fatigue: do friends & family free up your energy?

Date Published: 08.09.2022

New research directions from Wadham's Fellow in Human Sciences.

“Ouch!” Who knew the radiator was on? You yank your hand back, wincing.

Unpleasant as it was, pain protected you in this instance. The heat would have damaged your hand. Thanks to a jolt of pain, you removed it from harm’s way.

We owe pain a begrudging thanks but it’s not the only uncomfortable feeling the body uses to keep us safe. Prof. Emma Cohen and her team at the Social Body Lab are researching feelings of fatigue. In particular, the feelings that kick in during exercise. Go for a long enough run and tiredness will creep in, eventually becoming hard to resist. And at some point, you’ll surrender, dropping your run to a walk.

“From an evolutionary perspective,” Emma explains, “sensations of fatigue induced by physical activity or exercise are thought to be part of an energy regulation strategy that maintains expenditure within safe limits.”

After all, in succumbing to fatigue, you stopped spending energy. The body’s resources are limited and careful management of its energy is crucial for survival. It certainly was in our evolutionary past. Overspend your energy now and you may not have enough to fend off that tiger later. Fatigue keeps you safe by preventing you exhausting your energy supply.

But scientists know that neither pain nor fatigue are simple, brute mechanisms that entirely bypass your mind. What you believe, desire, intend etc can affect how you experience pain and fatigue.

The well-known placebo effect illustrates this. Participants told they’ve been given pain-killers, even when the pills are duds, still tend to report a decrease in pain. Similar effects are observed with fatigue. Emma notes one study where participants ingested a capsule they thought was a performance aid. It wasn’t. But they still experienced a performance boost. This was despite no perceived increase in how hard the exercise task felt. “It was easier to put the effort in, there wasn’t any tiredness creeping in,” one participant reported.

Emma explains what she thinks is going on here: believing that you have more energy available leads the body to be less cautious in letting you spend energy. After all, you don’t need to be stingy with something you have in abundance. Hence the feelings of fatigue produced are less intense, allowing you to exert harder and longer.

Believing that you have more energy available leads the body to be less cautious in letting you spend it.

But Emma and her team want to push this thought further. The participants in that study weren’t crazy to believe that something they ingest could increase their energy. We live in a world with caffeine, energy drinks and, well, food in general. But not all means of increasing energy require you to put something in your mouth. Other people can increase our available energy too.

It’s different of course. A sugary drink adds to your individual energy. With other people, you pool your energy together so that collectively you have more. A group of five can throw much more energy at a woolly mammoth hunt than a sole individual. Because of the pooled energy, it’s less important for you as an individual to hang on to your reserves. Too exhausted to fend off that tiger? No matter, so long as someone else in your group still has strength to throw a spear.

Since other people can pick up the slack, it would make sense if perceiving yourself to be in a supportive social group would loosen the body’s grip on your energy supplies. The body would allow you to spend more energy before flooding you with feelings of fatigue. (This could be the case even if you are not, in fact, in a supportive group. Just like how believing you’ve ingested a performance aid can decrease fatigue, even when it’s fake).

There are already some studies consistent with this idea. When given “cues” of social bonding, like photographs of loved ones, performance increases and reported fatigue decreases. Emma shares that this has been recorded for running trials and hand-grip tasks . But, she says, there is still more work to be done to show that this response to social cues is really because those cues signal extra energy resources.

Most researchers approach sociality in exercise in terms of competition. Emma and her team are bucking the trend by focusing on cooperation. If they’re right, then the home side advantage – the power of the “12th man” – is not just sporting superstition, it’s good science.

Keep up with the Social Body Lab and their research at https://socialbodylab.web.ox.ac.uk/

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