Why exercising with air conditioning on is a very bad Idea?

During cold temperatures muscles become rigid and stiff. A sudden movement can result in muscle damage or injury if warming up wasn't done properly.

In cold temperature the body warms up slowly thus extra energy and time are needed to get the body to warm up.

The body cools down fast in cold temperatures. While this can help the body maintain its ideal temperature it can also result in a reduced performance as the body goes back to the pre-warming up state.

When a person sweats toxins and harmful materials leave his body. Exercising with Air conditioner on results in less sweating and as a result less toxins leave the body.

A very cold temperature can make a person feel sleepy and make it harder for him to warm up. When the body gets cold it reduces the activity level to help preserve energy.

A low temperature can make a person less active and sleepy. While a very hot temperature can affect performance in a bad way a cold temperature might prevent a person from exercising well.

Exercising in hot weather increases heart rate. When the heart rate increases the person becomes more active. Some Pre-workouts make people more active by increasing the heart rate. An effect that can be naturally achieved by turning off the air conditioner. (See Why Some People Never Exercise?)

When the temperature gets high the blood pressure is lowered. The opposite happens when the temperature is lowered.

Sweating gives a psychological feeling of satisfaction. While more sweat doesn't necessary mean that more calories are burned still sweating can psychologically make a person think that he exercised well. (See How to strengthen your core muscles?)

If a person came from a hot area to a place where the air conditioner is adjusted to a cold temperature then the sudden drop in temperature might signal that body that sleeping time has came making the person less active. This is why a warm bath helps people sleep.