Hypoxic, Hypobaric Training; Altitude Training in Swimming: Does it Actually Help?

Older reports and experiences

Many athletes consider high-altitude training as a means to improve their endurance. High-altitude training became known in 1968, when athletes had to prepare for the Olympic Games in Mexico City. Later, it was seen as a method to improve endurance in all endurance-dominated sports, including swimming. Today, experts agree that high-altitude training is necessary to prepare for competitions at high altitudes. However, it is debated if high-altitude training helps when returning to low altitudes (see below, recent findings).

At high altitude, the oxygen's partial pressure decreases in the air and in the body, provoking a higher respiratory rate und the synthesis of erythrocytes (erythropoiesis), leading to a better oxygen supply in tissues. The increased respiratory rate also strengthens the respiratory muscles.

According to sports physicians, the acclimatisation improves performance very much, as long as the athlete stays up in the mountains, i.e. above about 2,500 metres. It is assumed that three weeks of high-altitude training are necessary to fully adapt to the low-oxygen environment. The increased haemoglobin and haematocrit values observed during the first couple of days at high altitude are due to a reduced blood plasma volume.

A reduced plasma volume can have a negative effect on performance after returning to low altitudes, because the blood becomes more viscous. The same can happen having increased erythrocyte counts, which also reduces the blood's viscosity. This is why increased haematocrit values entail a temporary safety ban when detected in an athlete.

Sports physicians emphasise that the adaptation and the changes can vary a lot between individuals. The performance-enhancing effects observed earlier are believed to be due to a higher quality of the training, and an incentive training environment in the high altitude camps.

Those who want to profit from thin air can do this by sleeping in a high-altitude tent, which is markedly less expensive than a high-altitude camp.

The tent allows you to lower the air pressure, for example as low as at 4000 metres (13,000 ft). In this example, the oxygen partial pressure is lowered by approximately 40%. Keep in mind that haematocrit values above 50% can become detrimental to your health (thrombosis).

Recent findings

• Research presented by University of Lausanne's Virgile Lecoultre and colleqgues corroborates the findings that hypoxic training has no benefits for performance at low altitude. Lecoultre and colleagues found that glucose and insulin blood levels are elevated in subjects training at high altitude, a condition that may be detrimental. It is recommended that overweight athletes and diabetics should not exercise strenously at high altitude [Abstract in English].
• A working group led by Ferran A Rodríguez (University of Texas, [Abstract in English]) arrived at results that were not quite so negative. The findings can be summarised as follows: A four-week simulated high-altitude breathing protocol failed to improve overall time-trial performance or aerobic capacity in a mixed group of trained runners and swimmers. However, when analyzed on their own, the swimmers who used the altitude protocol saw notable boosts in their aerobic fitness (VO2 max) and endurance thresholds after a pre-competition training taper. Ultimately, while this specific "dose" of altitude exposure didn't work for everyone, it suggests tailored high-altitude breathing might still offer hidden benefits for swimmers preparing for a race.