The other day with a rested body Zack managed to run the 4 km, but he was exhausted after running and ran slower than before, yet Jake didn't interfere as long as Zack could.
As it was, it would take a few more weeks for Zack to move on to 6 km training, when Zack's fitness improves faster and he can complete 42 km.
So next month Zack would improve much faster if he didn't give up on training, it also served to show Jake the difference between him and another of his age, at 14 Jake could easily run that distance with the speed that Zack was running.
And because Zack was supposed to have more than 14 on average statistics and had the advantage of being adult and having developed body that Jake did not have as a child, yet it was obvious what Jake could do better than others thanks to the system.
