This training minigame can be played at the gym in the morning by selecting the weight bench once Kevin has been convinced Kevin to spot the main character. To do so, talk to Kevin in the school cafeteria, he requests the main character to find him a replacement for his duty. Meet Erik who agrees if you bring him a new video game.
Tap the screen or press Space as fast as possible until you fill the bar on the left side of the screen. You succeed if you fill the bar completely before the gauge reaches the top. It will climb faster in higher difficulties.
Successful completion provides +1 to strength.