Body Composition and Flexibility

These 2 areas help remind us that children are different from adults and each other. It may seem ridiculous to speak about body composition and flexibility in kids because we all know they are mostly made of Play-Doh. However, it is important to discuss the general changes in body tissues that occur during growth and the various effects these changes have on exercise and sports participation.

Girls and boys can play together until about the third grade. After this point, it is a good idea to start the transition of separating boys and girls in contact-type sports. This gives plenty of time for puberty to start and not have a 4’2″, 70-pound boy playing against a 5’9″, 130-pound girl. Remember, the average ages that puberty begins is much different for girls and boys. Even from early childhood, girls in general have more body fat than boys. That is just the way the cards are dealt. Differences in body fat stay throughout childhood and then increase in girls once they hit puberty. Boys have a more dramatic change in body composition because new levels of testosterone from puberty start to add muscle mass. Kids who are already overweight tend to remain overweight into adolescence and adulthood.

The changes in body composition are important because they may have an effect on sports participation and performance, especially in sports in which center of gravity and weight are important like gymnastics, diving, figure skating, and wrestling. Puberty is a time of multiple adjustments that can have an effect on your child’s participation in sports. Understanding the reality of the physical and chemical changes of puberty can enable you to support your active child during and through that period of development.

Children are also more flexible than adults. Who do you think was the model for Gumby? It had to be a child. But as usual, many good things must come to an end or just slow down. During the rapid growth of puberty, kids often become temporarily less flexible than they were prior to puberty. Let me paint a visual for you here.

Some children have a slow growth spurt, while others grow so fast they need a speeding ticket. Essentially, their bones are growing more quickly than their muscles and tendons can stretch to keep up. Most boys get more muscles and lose some body fat, but often lose flexibility.

Girls can also become tighter during the rapid growth of puberty if they cannot stretch to keep up with their growth. However, the increase in estrogen usually allows girls to maintain or improve their flexibility once they slow down their speed of growth. Having good flexibility may help some athletes self-select into certain sports such as swimming, diving, gymnastics, tennis, figure skating, wrestling, or martial arts. Understanding these changes in body composition and flexibility can prepare you for their potential effect as you watch your child exercise, train, or compete while going through puberty.

Author Paul R. Stricker, MD, FAAP
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