Is it ever too cold to exercise? During those cold winter months, it sometimes seems too chilly to run or jog. What if your lungs freeze?

Well actually, your body is designed so that by the time air reaches your lungs, it's been warmed up and moisturized by your nasal passages, throat, and trachea.

Besides, the blood supply in your lungs is so well developed that there's virtually no way they can freeze--the circulating blood keeps them nice and toasty.

It hurts to breathe because when the air is frigid, it doesn't warm up sufficiently before it reaches the airways leading to your lungs, and so it shocks the surrounding muscles and causes them to contract. This, in turn, causes your bronchial tubes to contract too, which results in that tight, prickly feeling.

Unless you suffer from asthma, breathing in cold air won't hurt you--and you'd have to worry about frostbite to your fingers and toes long before worrying about your tongue freezing.