To climb at high altitudes, climbers must carry proper equipment like stoves, sleeping gear, first aid supplies and food, wear synthetic underwear, fleece layers and waterproof jackets and pants, and use heavy duty boots and helmets for protection. The body naturally adapts to less oxygen at altitudes over weeks or months by producing more red blood cells and water to transport oxygen efficiently, while respiratory and digestive systems are affected with decreased oxygen causing faster breathing and more blood flow to vital organs.