A boy in shorts doing a skateboard trick.
a boy engaged in a leisure activity
Skateboard trick is a leisure activity.
Skateboarding is something you can do for fun or a leisure activity. Doing a skateboard trick means you are skateboarding. Therefore if you are doing a skateboard trick, you are engaged in a leisure acitivity.
Sports are considered a leisure activity therefor if he is doing a skateboard trick he is engaging in a leisure activity.