Ok my 2 boys currently go out at 9/10 in the morning for 1hour (mountain walk )they are constantly running ,then the go out again for another hour at about 4ish (mountain walk again )and are running most of the time ,then they go out again at about 11/12 for 10/15mins just to do ther buisness .on the weekend i ride my bike down an old railway track which takes us about 2hrs and they are constantly running to keep up with me ..do you think this is enough exersize for 2 young boy's :thumbsup: they also have constant use off a small back yard .