At the highest altitudes any kind of physical effort – even walking – can be difficult. Climbers often describe themselves moving so slowly as they approach the summit that they feel like an elderly person barely making it down a street. That’s the impact of altitude on extreme athletes. You can imagine what it would do to anyone who is out of shape. Exertion is also a factor than can aggravate or bring on altitude sickness. All the more reason to prepare, train, and acclimate before attempting a summit or other work at high altitude.