Exercising while using an air conditioner or fan can actually be beneficial. In fact, it has been proven by a study conducted by researchers at George Mason University that exercise in a room cooled to about 22 degrees Celsius (72 degrees Fahrenheit) for 30 minutes can decrease heart rate and lower blood pressure significantly more than doing the same activity in a room where the temperature was kept at 25 degrees Celsius (77 degrees Fahrenheit). This indicates that when you are working out in a room cooled down to 22 degrees Celsius, your body will produce less heat and hence have less of an impact on your cardiovascular system. It also indicates that if you are planning to exercise indoors then air conditioning should not be turned off because the benefit outweighs any potential harm caused by overheating.