Do you know some swimmer or cyclist or xc-skiers born, living and training in altitude ?
Cyclists train in altitude for short periods of the season, and, how I had opportunity to explain several times, have a type of performance completely different from running.
The differences ?
1. During a season, for a cyclist there are from 50 to 80 days of competition. For an athlete, a max of 15-20, and for a marathon runner no more than 5-6 (including 2 marathons).
2. For runners, there are no competitions with many following stages every day (as Tour de France, Giro d'Italia, Vuelta de Espana, Tour de Suisse and many others). So, they don't need the same type of recovery a cyclist needs.
3. During a race of bikes, the speed is not even, but there are several accelerations, alternated with period of practical rest. At 40 km/h of speed, in group, a cyclist with good technique can stay comfortable at a level of 90-100 pulse heart per minute (such as a top athletes jogging at 10' per mile). When there is a mountain, or the cyclist tries to escape, there are accelerations so hard that the heart can reach max level, and the lactate can go around 15 mml or higher. So, a cyclist is physiologically more similar a specialist of 800m than a marathon runner.
4. During a marathon, also tactic, the level of effort is almost the same for all the duration of the race. This means we don't need very high aerobic power, but the ability to use a high percentage of it.
5. For increasing the speed if you are a cyclist, you need to be able to push a gear with 1-2 teeth more maintaining the same frequency, so the most important thing is TO INCREASE THE MUSCLE STRENGTH. For this reason, about doping, looking at some "aid" for enhancing the performances, GH and steroids are more important than EPO, that can be considered the base for being able to use more strength (look at the cocktail used by Armstrong).
6. For increasing the speed if you are a marathon runner, you don't need to increase your muscle strength, but your "strength endurance". This is more a enzymatic factor than a mechanical factor.
7. In some specific stage in the big Tours, a cyclist has a type of effort lasting 6-7 hours, where he can go 5-6 times from altitude of 200m / 600 feet to another of 2300m / 7000 feet. This provokes during the same race big jumps in the concentration of hgb and difference in hct.
Runners never have to face a similar problem.
8. A cyclist can eat during the race, because being sat his stomach doesn't have any "up and down" provoking reflux and acidity like happens running. A runner can only drink.
About swimmers, they never can reach the same level of heart beats we can reach running. This is due to the fact there is no gravity to win, the best technique is the ability in "sliding on the water", and lactate can be removed very quickly because of osmosis (the body is inside water). The demonstration of this is the possibility to compete at top level (sometimes to better WR, looking at Phelps and Locke) 3-4 times in 2 hours, meaning recovery is not a problem.
About xc-skiers, the best are from Norway, Finland and Sweden, and in those Countries there are no mountains....