Ever wonder why children can run around all day and not get tired? According to research published today in Frontiers in Physiology, children have fatigue-resistant muscles and the ability to recover quickly from high-intensity exercise.
"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. 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," explain co-authors Sebastien Ratel, associate professor in exercise physiology at the Université Clermont Auvergne, and Anthony Blazevich, professor in biomechanics at Edith Cowan University.
Previous research has shown that children do not tire as quickly as untrained adults during physical tasks. Ratel and Blazevich believed the energy profiles of children could be comparable to endurance athletes and set out to prove it.
The researchers asked three different groups—8-12 year-old boys and adults of two different fitness levels—to perform cycling tasks. The boys and untrained adults were not participants in regular vigorous physical activity. In contrast the last group, the endurance athletes, were national-level competitors at triathlons or long-distance running and cycling.
The participants' heart-rate, oxygen levels, and lactate-removal rates were checked after the cycling tasks to see how quickly they recovered. In all tests, the children outperformed the untrained adults. "We found the children used more of their aerobic metabolism and were therefore less tired during the high-intensity physical activities," says Ratel. "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."
"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,” Ratel explains. “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.
"It will be interesting in future research to determine whether the muscular changes we have observed are directly related to disease risk. At least, our results might provide motivation for practitioners to maintain muscle fitness as children grow up."