There is some evidence that athletes who live at altitude and train at sea level can boost their endurance performance. But does simulated altitude achieve the same result? That’s the question a group of researchers from New Zealand set out to answer with a study of runners sleeping in ‘hypoxic tents’.

The study involved 20 competitive male and female runners, of whom half slept in hypoxic tents for four weeks while continuing with their normal training. The other ten runners slept and trained as normal.

Hypoxic tents simulate the effects of altitude by reducing the oxygen concentration in the air flushed through the tent. In this case they were designed to simulate an altitude of 2,500-3,500m, with gradual adjustment of the gas mixture as the runners became ‘acclimatised’.

All the athletes completed performance tests on a treadmill four weeks and one week before the study started and at weeks 1, 5 and 9 afterwards. Additionally, those in the altitude group performed a run to exhaustion in each testing week.

One week after exposure to the simulated altitude, the lactate threshold speed – the speed at which lactate begins to accumulate in the blood – of the altitude group increased by 1.2% by comparison with the control group, suggesting an improvement in endurance capacity.

However, the groups were not completely evenly matched, with slightly better runners in the altitude group. And when this difference was allowed for, the apparent effects of altitude disappeared. Performance did not change at weeks 5 or 9.

The runners in the altitude group improved their time to exhaustion over the study period by an amount equivalent to about 2% in a time trial. But since there was no control group for this part of the study it was impossible to say how much of this improvement was due to altitude exposure.

The researchers conclude that: ‘simulated altitude exposure using tents may not provide the necessary stimulus for sea-level performance improvements’.

J Sci Med Sport 2005; 8(4):451-457