Bag of stones

I indulge in Sander's childish game by collecting stones in a bag and shlepping them up and over the hills.  
I don't understand those who jog with weights on their wrists and ankles.  It's a kind of throwback to imprisoned railroad workers and it only drags you down.
The bag weighs though and the thought strikes me that the stones I've picked up are very old and it will take centuries for more to form into throwable sizes. 
I've developed bowler's shoulder with my under arm but watch the boy thunder down the hill behind his rolling stone, knowing that for each of my mile I've done he has done two.