why when we climb mountain we breath difficulty???

The air is thinner in higher elevations.

depends. are u pregnant?

lol just kidding, idk maybe youre juust..tired?!?

As you get higher, the air is thinner and colder.

Because the higher you climb the less oxygen there is, but your body still needs the same amount of oxygen as it did at normal altitudes, so you naturally breath harder to try to get that lost oxygen. This is why mountain climbers use oxygen bottles to breathe from at high altitudes, otherwise they will suffer from a condition called hypoxia and eventually pass out and could die.

It is a combination of the exercise (lifting your body weight), exertion (depending how much gear you are carrying) and elevation (if you are at higher elevations). Not all climbing is at high altitude, but just the change in altitude from sea level to the height of one day is climbing, even if it is only 2,000 ft, can make a big difference.

Good Luck

Climbing is hard work so ya it would be hard to breath just like if u were to run a couple of miles u would start to get out of breath. Its the same thing. But with climbing u can also add elevation. The air is thinner & u have to take more breaths to bring the same amount of oxygen in to ur body that u would one breath at sea level. So this combination can in return make it hard to breath while climbing. l would suggest doing some cardio work out to help train ur lungs & give u endurance & stamina. u can also just be in high altitudes more this will acclimate ur body to the high elevation.

when humans climb the oxygen in the air starts to lessen
If you are over 11,00ft you might get (AMS) Acute Mountain Sickness, If AMS gets worse it may turn into Edema which cause a part of the body to fill with liquid (pulmonary- lungs) (Cerebral- Brain)
to prevent this you can acclimatize (stage the climb into sections) which multiplies the red blood cells in the body to make it easier to climb