All your players have a stamina stat. This determines how many shots they can hit until they get exhausted in matches. When a player gets near exhaustion, the heart by their health meter in the scorer will start to beat. Initially this is just a warning.
The first line in the health meter shows when you have entered Low Health. When in this state, power will start to reduce on shots and movement around the table will become slower.
If the next line in the health meter is reached, you have entered Critical Health. The screen will start to pulse red. In this state, you must hit perfect shots otherwise you'll start to mishit the returns. Movement is further limited around the table, making incoming fast shots much harder to return.
👍 TOP TIP
Health recovers during serves so wait when serving to replenish. However, this will also replenish your opponent's health (if also low) and you risk running out of time to serve.