By completing achievements or goals, by winning in Tennis Live Arena or simply by collecting your daily bonus, you will earn some free packs. There are 3 types of packs:
1/ Action points packs (to launch new training sessions)
2/ Physical packs to refill your player's physical shape bar
3/ Mental packs to refill your player's shape bar.
You can also buying bundles into the shop to get lots of these packs at a special price!