KC...am a climber and we don't call breathing deep while climbing a "rest step". We call it: getting more oxygen for the task.

A rest step is the actual motion of slowly moving forward, pausing and giving the muscles a short period of time to regulate the lactase in the cells allowing the bones to support more of your weight conserving energy.

Breathing at altitude or sports for that matter is about having a better blood oxygen concentration. Better physical conditioning AND acclimitization are the most important. Individual physiology and capacity are secondary, but also important. Some people adapt better than others in mountain enviroments even if they are not as good of "shape".

Acclimitization "begins" in the matter of hours. Frequent trips to altitude gives your body the cues to acclimitize more quickly than most of those that get out of their vehicle at 6 or 7,000' from starting out at sea level once a year or so.

Don't ask me about my military service or heroic acts...most of it is untrue.

Pronoun: Yes, SIR !