They are more vulnerable to pesticide exposure because their organs and body systems are not fully developed and, in relation to body weight, they eat and drink more than adults. (westonaprice.org)
In relation to his body size, he also has small, thin arms and no legs (with just his feet). (mariowiki.com)
Besides a more defined back, you'll also gain arm and core power and improve your strength in relation to your body mass (aka relative strength). (dailyburn.com)