Being physically active has always been part of the human experience. We were designed to be physically active. We were not designed for organized sports, bodybuilding, or Olympic level competition. What we humans did best and most was walk. We are the great walkers. We are designed to walk almost anywhere, climb over downed tress, down hills, up mountainsides, and across grasslands. We also ran short sprints then stopped. We exerted ourselves then rested. We were very fit. No one was fat. We fasted much of the time.
If you watch children at play, you will see that they naturally follow this pattern. They need no coaching or adult supervision to play in the active way. They chase each other with gusto, the hide and seek, the crawl through the bushes, and walk through the woods. Children on the playground are the same. Our task is to facilitate this play, encourage it and interfere only to prevent harmful behavior not to interrupt its spontaneity.
Soccer, track, Lacrosse, volleyball, tennis, basketball, baseball are all sports that are fun, aerobic, do not often cause significant injuries. What is more, they do not cause closed head injuries. These are traditional sports that are offered broadly, expertly coached, and popular. They are appropriate for older girls and boys interested in these team and individual sports. There are adolescent versions offered at the middle and high school level and beyond.
Studies show that the strain of children’s play on bone does two vital things. First, it shapes the bone along the lines of force placed upon it by the exercise. This shaping force informs the bone where to grow in the best way to manage the strain placed upon it by the physical stress of the play. The play also directly affects the shape, form, and health of the muscles that overlie and attach to the bone. The sites of muscle attachment also shape the bone.
The second benefit exercise has on the growing skeleton is transmitted by the deformation of the calcium phosphate crystals that compose the mineralized bone. When a force is applied across the crystal, it is deformed slightly. In this way, the mechanical energy is stored in the crystal. When the pressure is released and the crystal returns to its normal form the mechanical energy is converted by the crystal into electrical energy through the piezoelectric effect. This results in the release of an electric impulse or an electron from the crystal. Since the bone crystals form a matrix surrounding aligned collagen fibers and multiple crystals are being strained and released in unison, there are multiple electrical impulses being generated simultaneously. This leads to a flow of electrons along the lines of force generated in the bone. This electrical stimulation results in more bone being deposited in these areas where it is needed to strengthen the skeleton.
Exercise stimulates the bones to grow stronger and to form more bone where it is needed most. Children and teens that are physically active, and eat a healthy diet rich in calcium, have good vitamin D levels, adequate protein, calories vitamins, and minerals have the best chance of reaching the peak bone mass potential.