Originally Posted by w126

What do mean by can't breathe properly?

Short of breath, wheezing, painful to inhale cold air?

I don't like to diagnose probs on the internet, but this is pretty specific.

Try warming up inside for 5 minutes before heading outside. Jumping jacks, skipping rope, or push ups to increase your body temp.

It sounds like you might be sensitive the cold air, so breathing through both nose and mouth should ensure enough oxygen for exercise as well as warmer air temperature. Nose breathing has a greater air-warming effect (actually that's still up in the air), but it's difficult to get enough air through your nose alone to sustain rapid breathing. Also, keep yourself hydrated, just as you would if it were a warm day.