healthHealth and Medicine

There’s A Scientific Explanation As To Why Kids Never Seem To Tire


Researchers say their results might provide motivation for parents to maintain muscle fitness as their children grow up. Monkey Business Images/Shutterstock

Being a parent is a tough job. It’s been shown to be more rewarding – and more exhausting – than paid work. Parent burnout is a very real thing, and now it is easy to see why. Children are as fit as and recover faster than endurance athletes, according to a new study published in Frontiers in Physiology

It builds on earlier research that explored whether children tire as quickly as adult athletes when it comes to high-intensity exercise. The study found that children’s muscles have a greater resistance to fatigue, which allows them to recover faster than national-level triathlon athletes, long-distance runners, and cycling competitors.


"During many physical tasks, children might tire earlier than adults because they have limited cardiovascular capability, tend to adopt less-efficient movement patterns and need to take more steps to move a given distance," said the study authors. "Our research shows children have overcome some of these limitations through the development of fatigue-resistant muscles and the ability to recover very quickly from high-intensity exercise."

Researchers compared the energy output and recovery rates following cycling tasks in boys aged 8 to 10 years, untrained adults, and endurance athletes. By monitoring heart rates, oxygen levels, and lactate-removal levels after the tasks, they could see how quickly participants recovered using either aerobic (using oxygen from the blood) or anaerobic (doesn’t use oxygen and may cause muscle fatigue) metabolisms. Children outperformed adults in all of the tests.

"We found the children used more of their aerobic metabolism and were therefore less tired during the high-intensity physical activities," said study co-author Sébastien Ratel in a statement. "They also recovered very quickly – even faster than the well-trained adult endurance athletes – as demonstrated by their faster heart-rate recovery and ability to remove blood lactate."

But let’s set something straight: The study was small with just 37 participants (12 prepubertal boys, 12 untrained men, and 13 male endurance athletes). It also doesn’t address differences in female athletes and young girls.


Regardless, the authors say it could help parents develop their child’s athletic potential. Since muscle endurance is already built into kids, it might be better to focus on other areas of fitness such as technique, speed, or strength. It could also help improve our understanding of how the human body changes from childhood to adulthood, and how that transition may contribute and relate to the risk of diseases.  

"With the rise in diseases related to physical inactivity, it is helpful to understand the physiological changes with growth that might contribute to the risk of disease,” said Ratel. “Our research indicates that aerobic fitness, at least at the muscle level, decreases significantly as children move into adulthood – which is around the time increases in diseases such as diabetes occur.”


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