As a youngster my Son always lagged behind, we were constaantly stopping and waiting for him to catch up...Until one day, on our 2nd hike to the Hike Inn in Ga. he inquired as to how long it had taken us to do the 5-6 miles last time we were there. A little over 2 hours I replied. Can we do it in less then  2 hours. I am sure we can...From then on (he was probably 9 at the time) he has been the leader on most of our hikes (he is now 14) and 'competes' w/his older 17 old sister on every hike. It has gotten to the point where his not so young Dad (I'm 57) has to work to keep up. My point is, I guess, is you never know what may serve as motivation, but since both of my kids are quite comptetitive athletes, that is what has worked for them. Just keep getting them out there, having a goal like a swimming hole or waterfall, etc. has always seemed to be a big help as well.

Many states where we live also have 'passports' which are good motivator, we have done the letterboxing which is a presursor to Geocaching, I like it better because you use clues and maybe a map, not electronics which we are trying to escape. And, we participate in our states 100 mile challenge, where you can also earn stamps and other cool swag....for free.