“When you’re up around threshold, or really, sort of, intense effort. You want the maximum amount of air you can basically get. And if that’s through your mouth and your nose, that’s going to be the absolute best. If you’ve ever ridden with a cold, you’ll know what it’s like to try and do an effort with your nose blocked. And, it’s a horrible feeling. You feel like you’re suffocating.
So, especially when you’re going hard, you want that maximum airflow and you’re going to breathing through your nose as well as your mouth.” – Chris Froome