While learning to control himself and his rope the student will raise the limits of his agility, strength, and endurance. Agility will enable him to use more efficiently the strength he builds. The actual exercise will ease his acclimatization to high altitude. When his muscles and vital organs are in tone, and he has finally become smart enough to hoard his fund of energy, spending it only when necessary, he will have endurance. It is endurance that gets mountaineers up big mountains, endurance so distinct from the flash energy used in downhill racing or football that it has been said that the ideal age for those who would attempt to climb Mount Everest is 25 to 35. Younger men spurt too much.