Physically active children cope better with stress

Adults complaining about stress in their lives are frequently advised to exercise. Now, a team of researchers led by the University of Basel wanted to find out if this applies to children as well. Could physical exercise help kids manage the pressures to achieve in school? 

A series of experiments devised to assess the effect of physical activity on children’s stress levels led to a positive answer, suggesting that school children cope better with stress if they get plenty of daily exercise.

How the research was conducted 

The scientists enrolled 110 children aged 10 to 13 and asked them to wear a sensor tracking their daily movements during a week. 

Afterwards, they brought the participants into the lab twice to complete both a stressful and a non-stressful control task (an experiment known as the Trier Social Stress Test for Children). 

Stressful task

In the stressful task, children were asked to read a story with an ambiguous ending. After reading, they were given a brief five-minute window to prepare, after which they were asked to present a possible continuation of the story to a panel. 

The participants were not aware that the preparation period was deliberately set to be insufficient. Within roughly a minute, most of them ran out of notes, forcing them to improvise for the remaining time. 

Arithmetic challenge 

This was followed by a seemingly straightforward arithmetic challenge, where they had to consistently subtract a specific value from a high three-digit number for five minutes. If they made mistakes, they had to begin the task anew, which added to the stress. 

Control task 

In a separate session, designed as a control task, the children read another story. However, this time, they engaged in a casual discussion about it with a researcher, devoid of any performance pressure. Throughout both sessions, researchers collected saliva samples at regular intervals to assess cortisol levels.

“We wanted to determine whether physical activity makes children more resilient under laboratory-controlled circumstances,” explained senior author Sebastian Ludyga, an expert in Sport, Exercise, and Health at Basel.

What the researchers discovered 

The experiments revealed that participants who engaged in more than an hour of exercise per day – as the World Health Organization (WHO) recommends – produced less cortisol in the stressful task than the children who were less active. 

“Regularly active children seem to have a reduced physiological stress reaction in general,” said lead author Manuel Hanke, a postdoctoral fellow in Physiology, Neurology, and Sport Psychology at Basel.

The scientists were surprised to find that even in the control task, which involved an unfamiliar situation, thus making it still somewhat unsettling to the participants, there was a significant difference in cortisol levels between more and less active children (although overall cortisol levels were lower than in the stress task).

Possible explanation 

According to the researchers, a possible explanation of these findings is that cortisol levels also increase during exercise. 

“When children regularly run, swim, climb, etc., the brain learns to associate a rise in cortisol with something positive. The body’s reaction always has a cognitive component as well: this positive association helps to prevent the concentration of cortisol from rising to too high a level in exam situations as well,” Ludyga explained.

Cognitive effects of stress 

In addition to analyzing saliva samples, the researchers monitored the participants’ cognitive responses to stress by capturing their brain activity using an electroencephalogram (EEG). The group is gearing up to delve into these findings next. 

“Stress can interfere with thinking. Some of us are familiar with this in its most extreme form – a blackout,” Hanke said. Thus, the researchers’ next objective is to determine whether physical activity might also have a significant influence on these cognitive effects of stress.

The study is published in the Journal of Science and Medicine in Sport.

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