There was an interesting article in the
Journal of Applied Physiology last month. They studied Armstrong over a 7-year period. During this time, his muscle efficiency increased 8%. Since he also reduced his bodyfat and therefore weight during this period, his power/weight efficiency increased 18% (power/weight is critical for climbing).
The also looked at the amount of lactic acid he produced at exhaustion, 6.5 mM. Every other professional cyclist they tested, including some of his teammates, had levels of 9–14 mM.
Oh, and in the middle of all this he had brain surgery and chemotherapy for cancer.