Ever look at kids playing and wonder how they seem to never get tired? Well, the muscular efficiency of prepubescent children and adolescents is comparable or even superior to that of well-trained athletes. The demonstration of this physiological characteristic of children – which explains their tirelessness and excellent capacity for recovery after intense efforts – is the result of a study conducted by researchers at the Clermont Auvergne University in Clermont-Ferrand, France, published in “Frontiers in Physiology”. 

Children have limited cardiovascular capacity, generally they tend to adopt less efficient motor patterns and to cover a certain distance they have to perform a greater number of movements. One could expect that in many types of activities they get tired long before adults, but experience shows that it is not at all like that.

The secret of the indefatigability of children

Sébastien Ratel and colleagues evaluated the mechanisms of energy production and recovery of forces during and after intense cycling activities in three different groups of subjects. The first group included boys between 8 and 12 years, the second young adults not used to intensive physical activity and the third young athletes dedicated to endurance sports, such as triathlon, long distance running or cycling.

For each participant, the heart rate, blood oxygen levels and lactate removal rate were checked, a waste product of the anaerobic muscle metabolism that replaces the aerobic one when it is necessary to develop more energy than can be produced thanks to the oxygen present in the blood. Lactate accumulation in the muscles is what causes muscle fatigue. 

Children Playing on Inflatable Castle“We found that the children used more aerobic metabolism and were therefore less tired during high intensity physical activities,” said Ratel.” They also recovered very quickly, even faster than the trained athletes, as is shown by lower heart rate recovery time and greater efficiency in the removal of lactate. ” 

The discovery – the authors note – can help on the one hand to better develop the athletic potential in children. Since their muscular resistance is often very good, it could be more useful to focus on other aspects such as sports technique, speed or muscle strength. But on the other hand it can also help to understand the physiological changes that, with the growth, can contribute to the risk of diseases, such as diabetes, that are linked to physical inactivity.