At the bike camps in Colorado where I'm an instructor, many campers fly in from sea level and the next day they're laboring up Tennessee Pass at 10,000 feet, gasping like beached fish.
That's when I ride alongside and explain how to get the most out of every breath. This approach, called "switchside breathing," produces almost miraculous increases in climbing speed and comfort and it's easy to learn.
I picked it up from Ian Jackson, author of the book BreathPlay, when we used to go snowshoe running around Aspen. Then I started using it on the bike. No one is quite sure why switchside breathing helps. When I was a mountain runner, I noticed that a runner's injuries would often be on the same side.
For example, his right knee, ankle and hamstring all hurt. And the injuries often coincided with his dominant breathing side. But when we taught him how to switchside breathe, the injuries went away. Apparently, if you always breathe on one side, you may subconsciously exert more force on that side. Switchside breathing balances out the effort of the legs and makes climbing easier. Give it a try!
Start by practicing correct athletic breathing off the bike. Lie on your back on the floor with a book on your stomach. Breathe in slowly and fully, expanding your diaphragm, not your chest. The book should move toward the ceiling. Then exhale steadily so it moves down toward the floor.
Most people think they should expand their chests, as a drill sergeant does. But if you look at side view photos of professional riders, they almost look fat. Their diaphragms are expanded like bullfrogs in full voice. It may look funny but it leaves more room for air to get into the lungs.
Be a switch-hitter
Now try it on the bike. Most riders exhale, every time, on the same side of the pedal stroke. If you're right handed, you probably breathe out when the right pedal starts the downstroke. You can check by climbing a flight of stairs and paying attention to your pattern of in-and-out breaths. Once you get a rhythm going, I bet you exhale each time the same foot hits a step.
The easiest way to break out of this pattern of same-side breathing is simply to take an extra-long out-breath every five to 10 pedal strokes. That will automatically switch your out-breath to the other down-stroke. Try it a couple of times on long climbs and it will become second nature. You can even practice off the bike by climbing stairs in a tall building. While stair climbing, the footstrike is slower and more pronounced than in cycling, so it's easier to coordinate with breathing.
Exhale with vigor
Finally, emphasize the out-breath. If you force air out of your mouth, you won't even need to think about breathing in. It will happen automatically. Some riders make a guttural sound as they breathe out, like weight lifters. Ex-pro Davis Phinney jokes about us sounding like a pen full of pigs when we climb, but it works.