How many steps?

This week in third grade we are doing several lessons with pedometers. The children are trying numerous activities and learning how many steps each activity takes. The children also guessed how many steps they should be getting every day, and how many adult needs. Turns out children between the ages of 6-12 need approximately 12,000-15,000 steps every day to be at a healthy activity level. Adults need 10,000. Hmmmmm... the children wondered why adults need less. And how come it takes less steps to run if you are faster? And why don't I get many steps when I do crunches and push-ups? Lots of theories to discuss!