The placebo effect of mountain air
High-altitude training is supposed to keep endurance athletes in top form. But controlled comparisons have failed to find any impact. By Florian Fisch
(From "Horizons" no. 113 June 2017)
When the elite athletes Nicola Spirig and Nino Schurter landed in Rio de Janeiro in August 2016, they had already undergone altitude training. This entailed spending several weeks above St. Moritz, but training every day down in the valley. They have to organise their preparations exactly so that their competition falls in a time window of 14 to 25 days later. In recompense for their efforts, they hoped to achieve an increase in performance – perhaps just enough to secure them an Olympic medal.
Elite athletes full of haemoglobin
The Danish physiologist Carsten Lundby came to the University of Zurich in 2010 to find out the impact of altitude training. The scientific literature writes mostly about a higher concentration of the red blood component haemoglobin, which transports oxygen. In order to compensate for the lack of oxygen at high altitude, the body increases its production of haemoglobin. The then school of thought was that this excess capacity improves performance when the athlete is back in normal air pressure.
After several tests, Lundby changed his mind. He is now convinced that this training method achieves nothing. When his research group tested the blood of athletes after their altitude training, they were unable to find any difference. He suspects that the athletes are already so full of haemoglobin that their altitude training simply has no effect.
But Lundby wanted to have more precise information. "We organised a study that was double-blind and placebo-controlled, just like a drug trial". For half of the test subjects, he artificially lowered the oxygen concentration in their bedrooms so that it corresponded to an altitude of 3,000 metres above sea level. Neither the researchers nor the athletes knew to which test group they belonged – i.e. who was subjected to 'altitude training' and who wasn't. Lundby has meanwhile completed a total of six controlled studies with between 15 and 19 cyclists and cross-country skiers each time. His conclusion is this: "It's all a placebo. If the athletes didn't know to which group they belonged, we found no effect at all". It is only effective at unrealistic altitudes. In his overview of the literature, Lundby advises elite athletes to give up this expensive form of training. He now teaches at the University of Copenhagen.
Better blood supply to the muscles
Lundby's conclusions are disputed, however. Jon Wehrlin, the head of the Sports Physiology (endurance) Section at the Swiss Federal Institute of Sport in Magglingen in the canton of Bern, offers a more qualified opinion: "Many of the studies we have observed made methodological mistakes in their training". Some of them, he reports, had not waited for the right time window, or had simulated an altitude that was too low. So in his opinion, it isn't surprising that there was no perceivable improvement in performance. After many years of experience, he says, he is sure that the positive effects can be very individual. Furthermore, it is not possible to prevent athletes from knowing to which test group they belong. "For 15 years it's been evident that altitude training can have a positive effect on performance in endurance sports".
This is also confirmed by Grégoire Millet, a professor of physiology at the University of Lausanne. Altitude training has been carried out since the 1960s and has been called into question before, he says. In an ideal case, however, performance can improve by up to three percent.
Millet and Lundby published an overview of the literature in 2012 in which they defined standards for more rigorous controls in studies. After that, they went their separate ways. Millet developed 'repeated sprint training' using reduced oxygen in order to delay the onset of muscle fatigue under maximum stress. He carried out several studies and was able to prove that this indeed improved the blood flow to the muscles. Even when it comes to other methods, Millet believes that the literature clearly indicates the efficacy of altitude training. "Since 1997, over 70 articles have been published on the most popular variant – 'live high, train low' – of which only two write of a placebo effect".
Peter Bärtsch is a doctor and a former director of the Department of Sports Medicine at the University of Heidelberg. He is also a co-author of the literature review that defines the standards for the field. But he affirms the high quality of Lundby's study. "I would continue to recommend athletes to 'live high and train low', though it remains unclear whether the effect is physiological or psychological".
Florian Fisch is a science editor at the SNSF.
C. Lundby, P. Robach: Does altitude training increase exercise performance in elite athletes? Experimental Physiology (2016)F. Brocherie et al.: Effects of Repeated-Sprint Training in Hypoxia on Sea-Level Performance: A Meta-Analysis. Sports Medicine (2017)