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Football at high altitude

The questions raised by FIFA about playing football at high altitude provided an opportunity to review the knowledge on physical performance and preparation for athletic competition at high altitude. Thanks to the sponsoring of FIFA it was possible to invite leading researchers involved in the field and ask them to write a review article on a particular aspect of this topic. The content of these articles was presented and discussed during a meeting of experts in Zürich from October 25 to 27, 2007, in which FIFA officers, representatives of the Bolivian Football Association, and former professional football players also participated. Each presentation at the meeting was followed by an in depth discussion. The invited authors have revised their reviews accordingly under guidance of the editors of this special issue. Moreover, the discussions on the different aspects and topics resulted in a consensus statement related to the definition of altitude levels and a proposal for appropriate acclimatisation at different altitudes for training and/or playing football. The major focus of the meeting was on hypoxia, athletic performance, and playing football at altitude. Attention was also paid to the topic of hypobaria at altitude as it reduces air density, and in turn has an impact on the drag of the ball. Other aspects of high altitude performance such as temperature and humidity were not considered, as they will be the topic of other studies and expert meetings initiated by FIFA/F-MARC. The reviews presented in this issue are based on research that has been published in peer-reviewed scientific journals. The priority of literature cited, on which these reviews are based, has been weighted toward randomized controlled studies, whenever possible, and single or double blind design with sufficient statistical power. However, such studies are seldom available as regards elite athletes. Because studies on recreational athletes or untrained subjects may not be relevant for the elite athlete, studies on the latter group are important and are also of value, especially if the elite athletes have been followed over time. When various studies on the same subject provided contradictory results, study design and the population studied were scrutinized before making an overall final judgment on the findings. After the FIFA meeting, an article on football competitions at sea level and at various altitudes in South America was published in the British Medical Journal by McSharry (2007). The data presented were based on results from the National Team games over the last 104 years. McSharry’s mathematical modelling showed that the high altitude teams had an advantage from playing at low altitudes. This conclusion is contrary to what could be anticipated based on physiology and physics and questions were raised by experts of this meeting, which prompted the author to perform additional analysis using a nonlinear approach which led to opposite results at lower altitudes. This is further dealt with in the article by Gore et al. (2008) in this supplement. The World Anti-Doping Agency (WADA) had raised the question of whether the use of artificial hypoxia for improving performance should be banned, and thus, two scientists who have engaged themselves in the discussion of the related ethical issues were also invited to the meeting. They presented their individual views on the topic, which were extensively debated at the meeting. The polarization of thoughts on the subject became obvious during the discussion. The review presented in this issue reflects the opinion of the authors as well as some of the experts. The basis for an opposing view was that training in hypoxia merely activates a limited adaptive biological response to hypoxia, which should not be compared with e.g. injection of erythropoietin. Furthermore, prohibiting the use of artificial hypoxia would cause considerable inequality between those who have and those who have no access to moderate altitude. In addition to providing a thorough review of the literature regarding performance and training at altitude and in hypoxia, another achievement of this meeting is the agreement on a new classification of altitudes: