When the 'Iron Curtain' came crashing down and Western journalists took their first detailed look at East-German athletic facilities, they discovered a unique bunker buried in the earth near Berlin. Although the fortified structure did not contain the much sought-after remains of Adolf Hitler and Eva Braun, it did hold a unique laboratory full of exercise cycles, on which top East German cyclists had pedalled away while breathing in low-oxygen air.

By carrying out punishing training while taking in paltry amounts of oxygen, the athletes presumably had stimulated their leg muscles to use the precious gas more efficiently. In effect, the bunker allowed East-German athletes to train at high altitude while they were underground. The belief was that such stressful exertions would eventually lead to greater performances.

To athletes and coaches who favour altitude training, the low-oxygen bunker seemed like a great idea, but some scientists were sceptical about the underground vault's actual worth. In fact, many of them maintained that the reduced-oxygen air might have hurt - not helped - the East-German cyclists' performances. As the sceptics wisely pointed out, sparse amounts of oxygen actually diminish a cyclist's ability to pedal at high speeds. For example, a sea-level athlete who ascends to an altitude of 2500 metres will often cycle about 10 per cent more slowly than usual during training. That's a real negative, since tortoise-like training is definitely not the way to become a more powerful performer.

For that reason, many researchers have advocated the exact opposite of altitude workouts - training below sea level or in some kind of high-oxygen atmosphere ('hyperoxic' training). In a surplus-oxygen environment, the extra oxygen should pass quickly from the lungs into the blood and then bubble through the bloodstream to the muscles. In the best-case scenario, the muscles would happily use the added oxygen to create more energy aerobically, and an athlete could carry out faster-than-usual training. Over a period of several weeks, this upswing in workout intensity would produce augmented physiological adaptations and an increased ability to cope with high speeds during races.

To determine whether hyperoxic workouts really work in this positive way, scientists at the University of New Mexico recently studied five experienced cyclists during regular and hyperoxic training. Initially, the athletes trained in a very basic way: they spent about two-fifths of each workout at a modest training intensity of 50 per cent of their maximal work load (maximal work load was simply the highest work rate - in watts - which the cyclists could sustain for at least 30 seconds). Heart rates probably reached 50-60 per cent of maximal during these light efforts.

During the remainder of each workout, the athletes trained at a fairly difficult intensity of 85 per cent of maximal work load, which led to heart rates of around 90-95 per cent of maximal. The cyclists continued training in this manner for several weeks until their performances finally reached a plateau, beyond which no further improvements in endurance were attained. Depending on the athlete, it took from seven to 35 weeks to reach this plateau.

After reaching this levelling-off in performance capacity, the athletes tried to step up their workout quality by alternating three-minute work intervals at 95 per cent of maximal work load (in place of the previous 85 per cent) with two-minute recovery intervals at 50 per cent of maximum. However, the 95-per cent intensity was so tough that it was impossible for the cyclists to complete a 40-minute workout.. In.fact, the best they could do was to cycle for a total of about 10 minutes - or just two work intervals and two recoveries!

To make it possible for the cyclists to complete a full workout at the seemingly unattainable 95-per cent intensity, the scientists allowed the athletes to breathe a rich air mixture containing 70-per cent oxygen as they exercised (the oxygen concentration of 'normal' air is 21 per cent - unless you live in New York, London, or Los Angeles, where it's a bit more elusive). With the added oxygen, the cyclists were able to complete the higher-intensity, 40-minute workouts (eight work intervals and eight recoveries), and they carried out four of these workouts per week for a grand total of six weeks.

The six weeks of hyperoxic work improved the athletes' performances considerably. Their endurance while pedalling at 85 per cent of maximal workload (90-95 per cent of maximal heart rate) increased by 32 per cent (!), and heart rate during high-intensity cycling declined by around five beats per minute, a change which would make tough pedalling velocities feel easier. Since the athletes had plateaued just before the hyperoxic work began, it's likely that the high-oxygen training was responsible for these two major advances. Importantly, the athletes achieved their gains without having to spend more time training; they trained with the same frequency and duration which they had used before the six-week, hyperoxic-training period. The only change was the raising of interval intensity from 85 to 95 per cent of maximal, an increase made possible by the supplemental oxygen.

How did the hyperoxic training actually improve the cyclists physiologically? The New Mexico scientists speculated that the loftier training may have gradually boosted the athletes' blood volumes. A spike in blood volume is one of the key adaptations to endurance training, and intensity - not the number of workouts per week or the duration of each workout - is the most potent elevator of blood plasma. That's because high-intensity workouts stimulate the kidneys to hold on to more plasma, thus thwarting the kidneys' perverse desire to literally urinate away fitness. The increased quantity of blood permits more of it to reach athletes' muscles during exercise. More blood means the muscles get more oxygen, and that means greater energy production and higher performances.

In addition to increasing blood volume, the hyperoxic training may have also strengthened the athletes' hearts. This increased cardiac power, like the hike in blood volume, would mean that more blood could bathe the muscles during exercise.

The bottom line is that breathing in more oxygen during workouts delivers more oxygen to your muscles and permits you to work at higher intensities. These higher intensities then produce fairly dramatic improvements in your overall fitness. Obviously, it's just a matter of time before some entrepreneurial exercise-cycle company begins to equip its bicycles with oxygen tanks, plastic hoses, and mouthpieces. With an oxygen pipeline attached to your bike, you'll be able to breathe in more of the life-giving gas as you exercise, and you'll reach extraordinary new performance heights.

It's likely that the East German strategy of training with low oxygen pressures was actually a mistake that led to lower overall training quality. The East Germans would have been better off working out with surplus oxygen, and their many successes were probably due to 'other factors'. Similarly, the U.S. Olympic Committee should take note of the New Mexico research. Instead of encouraging many of their athletes to train at the Olympic Center in Colorado Springs (altitude = 6000 feet), the committee would be wise to ask athletes to come down to earth and strap on oxygen bottles for at least some of their workouts.

Hyperoxic Training Increases Work Capacity After Maximal Training at Moderate Altitude, 'Chest, vol. 104(6), pp. 1759-1762, December 1993