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I hadn't really considered the hunched over aspect. Somehow I can't picture anyone doing that UNLESS they are dead dog tired, then everything tends to droop. The advice I have given is to help you avoid that scenario.

In the mountaineering cadence I usually take the step upward, set it in place, take the breath and up I go. It is a very relaxing and methodical process.

With forced air breathing I have been doing it for many, many years and I'm not shy in employing it when needed. Be loud and proud. Usually 3 or 4 deep swooshing breaths will get you back on track. Get rid of that dead stale air in the bottom of your lungs. Once on a hike at Mt. Rainier I hit an incline I didn't feel like slowing down for and I forced air breathed for close to a mile and if anything I increased my speed upwards. Once in a while it's fun to "see what you've got" ;).