I had my first professional experience of high altitude training camps in September 1979: 35 days at 4000m in the Tlamacas refuge, on Popocatepetl volcano, Mexico. 
Ten high-level athletes (8 runners and 2 walkers) participated in the expedition, among them a future Olympic champion and a 2-time winner of the New York Marathon. 
I joined them as doctor and as manager of the testing procedures with my colleague, Dr. Ziglio. 
I was also attending the camp as an amateur athlete myself, along with the technical manager, Giampaolo Lenzi, as we both engaged in the daily workouts of moderate intensity. 

The surprising success achieved in the ‘70s by Finnish athletes (Vaatainen, Viren, Vasala, etc..) had lit the interest of Federations’ experts on the effects of increases in the transport of oxygen (i.e. Hb) on athletic performance. 

The Italian Athletics Federation (FIDAL) chose an extreme logistics solution in the belief that the higher the altitude, the greater the effects on the production of red blood cells and thus performance. 
In addition, some of the athletes would be able to compete in the Universiade in Mexico City, which took place during the period of the camp. 

Eventually the results were not at all as expected. 

The Tlamacas refuge was newly built, rather comfortable, but still a mountain retreat, with dorm rooms and shared facilities, definitely not suitable for such long stays. 
Proper nutrition and the safety of food and drinks were a problem. 
But the greatest difficulty was the organization of training sessions: at that altitude the only possible efforts were jogging or walking uphill on the slopes of the volcano, just as the strong Mexican walkers used to do back then, 3 times a week. 

For running sessions, we needed to drive down (1h of twisting roads in a minivan) to Amecameca, a small village at 2600m above sea level: and even for this, two weeks were necessary to adapt to the altitude before we could carry out discrete intensity efforts. 
Mexico City was at a slightly lower altitude (2200m) but required more than 2 hours of travel: we went there once a week, for the execution of the "Conconi test" on track. 
It was not possible to descend to lower altitudes. 

Three of the athletes, after 2 weeks of training camp, competed in the 5000 and 10000 meters at the Universiade Games with disastrous results, doubled by European rivals arrived at altitude a few days before the event. 

Back in Italy, some got rather good results in national and international competitions, but others performed negatively or passed through a period of psycho-physical crisis. 
Hb concentrations did not show any significant increase. 
The manager and I were the only ones who had obvious benefits in terms of performance, by running at moderate intensity: after the camp, our anaerobic threshold rose by 8% and 12% respectively, with increases in Hb of 1.5 g and 2.0% . Even our race performance improved significantly. 
Despite the less-than-exciting results of the Mexican experience, I became convinced that training at altitude, with appropriate and necessary measures, could be very useful in the preparation of athletes and in subsequent years I began to develop gradually more effective protocols. 

In the '80s I attended numerous altitude training camps, especially with Francesco Moser while preparing for his Hour Record attempts: in Mexico and Colombia (Bogota). 
In all cases the altitude of training was between 2200m and 3000m and it was not possible to ride at lower elevations. 
This limited the intensity of the efforts and made the recovery from workloads more difficult, despite the attention paid to nutrition (adequate protein and iron intake) and rest. 

The main problem which manifested itself in the first 8-12 days was the failure of heart rate response to medium-high intensity: despite the efforts of the athlete, the HR did not rise above 140-150 beats and chronometric performances regressed (power meters did not exist back then). 

Although some difficulties in adaptation, thanks to the appropriate insertion of rest days, the results of the training camp were generally positive nonetheless. 

In the ‘90s I reinforced my conviction about the benefits of altitude in the preparation of athletes and cyclists in particular: if properly managed, the hypoxic stimulus, present both at rest and during exercise, induced improvements that went beyond the simple increase in hemoglobin mass. 
An increase in the efficiency of pulmonary gas exchange, myoglobin and mitochondria were probably playing a role too: I cannot quantify to what extent, but the end result was obvious. 

I remember the training camp with Tony Rominger in Vail (Colorado) in 1993, in preparation for the TdF of that year: we received a visit from a Swiss journalist, Matthias Erne, who expressed his surprise at the fact that Tony prepared the Tour at altitude, in the heyday of EPO. "Natürlich wird gedopt, es interessiert mich nicht aber, was andere machen" was my answer and also the title of the long interview. 

Rominger managed to finish that TdF in second place, his best result ever, rivaling Indurain despite a lot of bad luck in the first week of the race. 
But even Vail was not the ideal training solution for cycling: wide and not steep enough roads and, once again, going below 2000m of elevation required long trips. 
Furthermore, just as in Mexico and Colombia, the issue of a radically different time zone added problems of adjustment, both at the time of arrival and return to Europe. 

Finally in 1999 I was able to find the ideal place for training camp at altitude in Europe, especially in winter and spring, for high-level cyclists: the Teide volcano in Tenerife. 

Hotel Parador is located at an altitude of 2100m, in an area devoid of vegetation, within an archaic crater (2 million years old), a huge basin of about 30 km in diameter inside of which there is a slightly hilly road 35 km long, placed between 2000m and 2300m above sea level. 
The area is accessible from 5 different directions, with 30-40km climbs that rise from the sea, with variable slopes; on the island there are also numerous other shorter and steeper climbs at lower altitudes. 
There are hilly courses at 300-600m above sea level. 

Over the past 10 years I have organized dozens of training camps on Mount Teide and the results were almost always very good. 

I compared the improvements in Anaerobic Threshold (measured at 600 m of elevation) at the end of a camp at altitude with those at the end of a camp of the same duration (2 weeks) at sea level, in the same periods of year (January-February): athletes who had trained at high altitude improved on average by 16.2%, while for those who trained at sea level the average improvement was 7.9%. 

After more than 30 years of experience in altitude training, I think I have identified the evaluation criteria of an ideal training camp: 

- the elevation of sojourn must be between 2200 and 2600m above sea level: heights lower than 2000m do not constitute a significant hypoxic stimulus, while heights of over 2700m do not allow adequate recovery in the hours after training 
- there should courses that allow training at lower altitudes 
- gradients and length of climbs must be adequate to the level of the cyclists
- the duration of the camp must be between 12 and 18 days: shorter periods are not effective, whereas longer sojourns are poorly tolerated psychologically by athletes 
- logistics accommodation must be sufficiently comfortable to allow flexible hours for meals and a proper nutrition for athletes, as well as rooms dedicated to massage and storage of bicycles and equipment.