We all have seen children who can run and play for hours and hours continuously, taking only short rests. Children’s muscles are not just fatigue-resistant but recover quickly from high-intensity exercises, even faster than well-trained and experienced adult endurance athletes. Researchers from the Université Clermont Auvergne justifies the fact through their study.

Dr. Sébastien Ratel, Associate Professor in Exercise Physiology who completed this study at the Université Clermont Auvergne, France, co-author of Anthony Blazevich and Professor in Biomechanics at Edith Cowan University of Australia, said: “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.

Repeated experiments on the fact have shown that the muscles of children seem to fatigue more slowly than adults. Dr. Sébastien Ratel further added, “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.”

These outcomes are a contradiction to our popular beliefs and what science would predict. Like, just to justify, children possess shorter limbs, so they have to take comparably more steps and should therefore theoretically use more energy. Children are also less skilled at making the use of tendon energy return systems. That is, they store very less energy in their tendons so they can’t further reuse this energy to propel themselves during physical movements.

This research could help enhance the athletic potential in children as well as improve our fundamental understanding of how our bodies develop from childhood to adulthood, including how these processes contribute to the increased risks of diseases such as diabetes.

This is how the study went. The researchers examined three groups – 8-12 year old boys, endurance athletes and untrained adults to perform cycling tasks. The boys and untrained adults were not participants in the regular vigorous physical activities. In contrast, the middle group, the endurance athletes, were the national-level competitors at triathlons or long-distance running and cycling.

All the groups were assessed for the body’s two different ways of producing the required energy. First, being the aerobic uses oxygen from the blood. The second, anaerobic, doesn’t consume oxygen and produces acidosis and lactate (not to be confused by the incorrect term, lactic acid), which may cause muscle fatigue. The participants’ oxygen levels, heart-rate, and lactate-removal rates were checked after the cycling tasks to see the pace with which they recovered.

They used this information to determine whether the first group, i.e. children used their aerobic or anaerobic metabolisms when their bodies required fuels to exert during physical exercise. In all the cycling tasks, the children group outperformed the untrained adults.

One possible reason for the remarkable muscular endurance of children could be their different use of energy pathways. “We found the children accessed more of their aerobic metabolism and were, therefore, less tired during the high-intensity physical activities,” says Dr. Sébastien Ratel.

The Research head further added, “They also recovered very quickly, even faster than the well-trained adult endurance athletes as shown by their faster heart-rate recovery and capability to remove blood lactate. This may justify why children seem to have the ability to keep playing and playing nonstop, long after adults have become exhausted.”

Dr. Sébastien Ratel and Blazevich explain the significance of these findings. “Many parents ask about the best way to enhance their child’s athletic potential. Our study states that muscle endurance is often very good in children, so it would be better to focus on some other areas of fitness such as their sports technique, sprint speed or muscular strength. This might help to optimize physical training for children so that they perform better and enjoy sports more.”

The authors hope their research could help scientists better understand how the human body develops with age, and the role this plays in the risk of diseases like diabetes. The latest stats published in 2017 show that an estimated 30.3 million people in the United States have a chronic disease.

It could be the fact that the decrease in muscle aerobic capacity between childhood and early adulthood is a key factor that allows metabolic diseases to take hold.

It will be interesting in the future to find the link between muscle maturation and disease and see whether the maintenance of our childhood muscles through high-intensity exercise training might be the best medicine to prevent disease.

Ratel continues, “With the rise in diseases and problems related to physical inactivity, it is helpful to understand the bodily changes with growth that might contribute to the risk of diseases. Our research shows that aerobic fitness, at least at the muscular level, decreases significantly as children move into adulthood, which is around the time diseases such as diabetes develop.

On top of this, the data collected during recovery from the exercise also revealed startling results. The pace at which oxygen use declined after the exercise was the same in the children group and athletes. The rates at which heart rate returned to its normal and lactate (a compound associated with muscle fatigue) declined from the blood were even faster in the children, and again even much faster than in untrained adults.

“This would be interesting in future research to judge whether the muscular changes we have seen are directly related to disease risk. At least, our findings might provide inspiration for practitioners to maintain muscle fitness as children grow. It seems that being a young child might be healthy for us.”

Paul Hough, sport and exercise scientist at St Mary’s University, London, said that while the findings are interesting there could be a misconception that children are more fit than adults and athletes. “We have to keep in mind the adults and athletes are generating higher absolute power outputs,” he argued.

He further added: “I would suggest that diet and daily physical activities play a more crucial role in chronic diseases than changes in fatigue recovery profile.”

Whatever it be, at least we now have some idea as to why children can play, and play, when we adults need frequent breaks.


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