Tennis Academy Training Center
From the Super Mario Wiki
Mario Tennis: Power Tour
In Mario Tennis: Power Tour for the Game Boy Advance, when the player first walks in and goes to their left, they will come across and miniature relaxing center with two people. One of them, is in front of a mirror flexing muscles. If they exit this room, they will come across three doors. The one on the left is the Wall Practice Room, the one in the center is the Tennis Machine Room, and the one on the right is the PS Training Area. The PS Training Area has minigames that can help Clay or Ace upgrade their Power Shot. Across the door from the PS Training Area, there are treadmills, but they are not in use anymore.
Minigames in Mario Tennis: Power Tour