Using the Seven Summits as an example, two stand out for the skills they require, altitude notwithstanding: Everest, for climbing through the Khumbu Icefall, and Carstensz Pyramid, for mid-5th-class rock climbing.

On Everest’s Nepal side, the Khumbu Icefall is glacial ice, not comparable to ice climbing in places like Ouray, Colorado. The terrain varies from almost flat to steep, with short climbs where ladders are often, but not always, used. Any ice-climbing experience will help you move through these sections confidently. The primary danger comes from ice falling off Everest’s West Shoulder, seracs collapsing, or the ice structure itself collapsing, as happened in 2014 when the upper section collapsed and killed 16 Sherpas.

On the Tibet side, the concerns are weather and rock. It is colder, windier and dustier, with wind chills near -40°C/-40°F. There is more exposed rock, especially at the three Steps, where you will scrape crampons against smooth rock at extreme altitude, so your lower body and core need to be at full strength.

The 300-foot (100 m) headwall between Carstensz Pyramid’s base camp and the ridge requires mid-5th-class rock climbing. There is a fixed rope you can clip a jumar to, but mostly you will be climbing with your hands and feet, so solid rock-climbing experience is essential.

You can hire porters on some climbs, such as Aconcagua, and you will have strong Sherpa support on Everest, but you carry your own gear on most other peaks. On Denali you climb roped to others with crampons, a jumar and a rappel device, and you’ll split around 120 pounds between your pack and sled.

Two simple techniques make a big difference on every one of these climbs: see The Rest Step and Pressure Breathing. For a ladder of climbs to build these skills, see The Climbing Progression.