Monday May 21, 2018 Q&A

Children’s muscles tire less quickly than adults’ because:


1 children’s muscles generate less of an effort

2 children have a lower body mass

3 children’s muscle fibers show greater endurance

Correct answer: 3. Children’s muscle fibers, unlike those of adults, are geared for endurance.

Children can play all day long with barely a rest. But where do they get their energy? It turns out their amazing endurance may have something to do with their muscle structure. Human muscles are made up of different types of fibers, and children have more Type I – or slow-twitch – fibers than adults do. This may be why their muscles don’t tire out as fast.

Metabolic pathways

The human body has two types of pathways for delivering energy to our muscles: aerobic (with oxygen) and anaerobic (without oxygen). Your body is able to produce a large amount of anaerobic energy very quickly, but you will tire out fast. That’s the system at work when someone sprints, for example. With aerobic energy, your body produces less energy but has much greater endurance – which is more useful for a marathon.

It has now been shown that children draw more on their aerobic pathways than adults do. This means that their bodies produce less anaerobic energy, which is the source of muscle fatigue.

Athletic muscles

A recent study compared fatigue rates and recovery between young boys and both trained and untrained adults (Birat A. et al. 2018). The researchers demonstrated that not only did the children outperform most adults, but that they were on par with endurance athletes.

Following exercise, the children and athletes recovered more quickly than the untrained adults, as measured by heart rate levels and the elimination of lactate – a substance linked to muscle fatigue –from the blood.

These findings show that children’s muscles bounced back faster from high-intensity exercise. They may also help explain why children are able to keep on going long after most adults throw in the towel.

Training intelligently

According to the researchers, the aerobic capacity of children’s muscles declines when children hit puberty. This is why teenagers and adults need to work on their endurance. Until puberty hits, however, physical activities for children should focus on speed, motor skills and muscle development.

(Photo credits: iStock)

For more information:

Are Prepubertal Children Metabolically Comparable to Well-Trained Adult Endurance Athletes? Ratel, S. & Blazevich, A.J. (2017) Sports Med 47: 1477. doi:10.1007/s40279-016-0671-1

Metabolic and Fatigue Profiles are Comparable between Prepubertal Children and Well-Trained Adult Endurance Athletes. Birat, A., Bourdier, P., Piponnier, E., Blazevich, A. J., Maciejewski, H., Duche, P., & Ratel, S. (2018). Frontiers in Physiology9, 387. doi:10.3389/fphys.2018.00387

Yes, your kids can run all day – they’ve got muscles like endurance athletes, Ratel S. and Blazevich A., 24.04.18, The Conversation.

Pourquoi les enfants sont infatigables ? La science répond, Boches J., 14.05.18, Topsanté.