Unquestionably, acclimatization to altitude improves performance at high levels but can altitude training improve an athlete's performance at sea-level?
The research is inconclusive. In theory, some adaptations that take place during prolonged exposure to the hypoxic conditions at 1500 m (4921 ft) or more above sea-level, should improve VO2 max and endurance performance at sea-level. Recall from the acclimatization to altitude article, that staying for a period of time at altitude increases the blood's oxygen carrying capacity.
However, maximal cardiac output is also decreased with exposure to altitude. Along with dehydration and a loss of lean muscle mass these detrimental effects may explain why living and training at altitude does not improve VO2 max or endurance performance on a return to sea-level (1).
Those few studies that have shown altitude training to have an ergogenic effect on sea-level performance are easy to criticize (2). Subjects have not usually reached a training peak so it becomes difficult to determine whether increases in aerobic power and / or endurance performance are the result of the adaptations to altitude or intensive training.
The major problem athletes living at altitude face is a significant reduction in training intensity. At 4000 m (13,122 ft) athletes can only exercise at 40% of their sea-level VO2 max compared to 80% at sea-level for example. Breathing hypoxic gases significantly reduces power output (3) and this could lead to substantial detraining negating any of the ergogenic effects associated with acclimatization.
Is it possible to induce the positive changes associated with altitude acclimatization without the associated negative effects? One banned and potentially dangerous tactic is blood doping and erythropoietin injections, which increase the blood's oxygen carrying capacity.
In an attempt to curb the detraining effect of reduced exercise intensity at altitude, Levine and Stray-Gundersen (4) studied the effect of living high and training low on endurance performance. A group of 39 middle-distance runners were split into three altitude training groups - a "live high - train low" group, a "live high - train high" group and a "live low - train low" control group.
Unlike the control group, both "live high" groups increased their VO2 max on a return to sea-level by 5%. This was in direct proportion to the increase in red cell mass volume. However, only the "live high - train low" group improved their endurance performance as measured by a 5km time trial. Velocity at VO2 max and maximal steady state also improved in this group helping to shave an average of 13.4 seconds off their time.
The same researchers carried out a further altitude training study on elite male and female runners and found similar performance enhancing effects of living high and training low (5). The athletes' 3km time was measured before and after a period of 27 days living at altitude (2500m, 8200ft) interspersed with training sessions at sea-level. VO2 max increased an average of 3.2% and performance by an average of 1.1%. While this may seem like a negligible improvement, 1.1% at an elite level translates into a significant performance advantage.
Further altitude training studies, both at real altitude and simulated altitude, have shown that living high and training low can improve running economy (6), 800m, 1500m 3km performance (7), 400m performance (8,9), submaximal cycling performance (10) and muscle buffer capacity (10).
These favorable results have stimulated interest in how athletes can "live high - train low" without having to actually move to high elevations. Several methods exist for artificially re-creating the hypoxic environment at altitude. These include hypobaric chambers, increasing the air's nitrogen content and altitude sleeping tents.
Sleeping tents are likely to be the most affordable and accessible option and don't seem to disrupt normal sleep quality (11,12). However, more research is needed to confirm whether these apartments do indeed improve performance (13).