I have excercise enduced asthma. So this is a big concern.

I think one thing to remember is in the colder temperatures you should not push yourself as hard as you would in more "enjoyable" temps. Your body is working much harder to maintain its temperature and provide energy to your muscles for your activity.

I too use a belaclava. I have 2 differnet types. One is fleece the other is nitted. The nitted breathes much better than the fleece. But also lets a bit more air pass through.