Doctors can use technology to evaluate preexisting health conditions so one does not push themselves too far. Technology can help monitor your heart rate, blood pressure, fat percentage, etc. This can give a base to know what to know where/ how much you improved when you look back. Technology can also be your own equipment like a treadmill which makes you more fit.
Condoms
vaccines
controlled rooms of sick/affected people
Answer:
Ping pong, or table tennis, is played on a 5' by 9' surface.