Although each child develops uniquely based on their individual genes and environment, young children should not be viewed as miniature adults, neither from a cognitive or physiological standpoint.  From a cognitive perspective, the frontal lobe of the brain is less developed in growing children.  This area is responsible for reasoning and objective thinking.  Young children are much more emotional thinkers than their adult counterparts.  From a physiological standpoint, the heart is not yet fully developed (the greatest increase in heart volume occurs at approximately eleven years of age for girls, and approximately fourteen years of age for boys) and many lack the requisite enzyme glycogen phosphofructokinase to produce energy anaerobically (think of glycogen as gasoline.  In order for the car to work it must use, or break down gasoline.), coupled with the fact that there is a less amount of stored glycogen in the liver and muscle due to size.  Finally, anabolic hormones such as testosterone don’t start making large jumps until puberty.