Opening the window

Why are windows not opened during an ongoing course but only at the end of each course?

Our sports centers are equipped with suitable ventilation systems, ensuring sufficient fresh air supply during physical activities. Opening the windows during an ongoing course or training session, especially when combining sweating and drafts, could potentially pose a health risk. After each course or fitness training session, our premises are additionally ventilated with fresh air for at least 10 minutes through controlled window opening.