Effect of altitude on physiological performance: a statistical analysis using results of international football games

Dear Editor

In BMJ 2007; 335: 1278-1281, it was published an interesting article
regarding the effect of altitude on physiological performance using scores
of international football games (1). In his conclusions the author
indicates that altitude provides a significant advantage for high altitude
teams when playing international football games at both low and high
altitudes. The author also refers that the International Football
Association (FIFA) Sport Medicine Commission recommends that football
matches above 3000 m should be played only after an acclimatization period
of 10 days because of the acute effect of altitude on performance (1).

This is not strictly true. In fact, in 1998 I published a book on
football and acclimatization to high altitude based on our participation
in the process of acclimatization of the Peruvian National Football team
for the eliminatory round competition of the World Football Cup (France,
1998). In one chapter (2), we analyzed results and scores of international
football games played by the Bolivian National Football team between 1950
and 1993 against other Latin American or European teams. According to this
study, 0% of the lowland teams won a game if they play the same day of
their arrival. However, lowland teams won 40%, 60% and 50% of the games
after 1, 2 or 3 days of acclimatization, respectively. In a logistic
regression analysis including as independent variables days of
acclimatization, kind of game (competition vs. friendly) and previous
experience at high altitudes in the same year, the only variable
associated to the probability of winning a football game was days of
acclimatization. The percentage of home wins was 82% when visitors play
the same day of their arrival to high altitude whereas this percentage was
reduced to 40-50% if visitors were acclimatized from 1-3 days. This is
less than the 53.7% of home wins described by McSharry (1) for two teams
from the same altitude. This suggests that it is not necessary to wait 10
days to be able to win a game at high altitude and that the probability of
the Bolivian National team of winning a football game was lower than the
average for South American football teams. I have also assessed the number
of goals scored and conceded. At 3600 m, the Bolivian National team has a
ratio of 3.83 goals scored/goals conceded. This value was reduced to 1.02,
1, and 1.2 after 1, 2 or 3 days of acclimatization of the opponent team.

In 1996 a plan for acclimatization to high altitude was performed to
the Peruvian National Football team. Thirty five percent of the players of
the Peruvian National team developed acute mountain sickness (AMS) within
6 hours after arrival to Cuzco (3400 m). The study demonstrated that
occurrence of AMS did not predict a low performance in physical activity
at high altitude (3).

Data suggest that at least with one day of acclimatization the
probability of winning at altitude was similar to any other away games,
and that AMS was not related to performance during the game if players
have been acclimatized at least by one day. In our experience, the
conclusion that altitude provides a significant advantage for high
altitude teams when playing football games from low altitudes (1) is not
consistent at all. For instance, people from high altitudes who descend
to sea level have a blood volume and red cell mass that are excessive for
their new environment and a process of neocytolysis is observed (4). This
results in a rapid decrease in hemoglobin concentration. At sea level,
reticulocyte production continues unchanged in the first few days not
decreasing until day 8 in response to ongoing erythropoietin suppression.
Decrease in red cell mass as reticulocyte production remains normal
provides conclusive evidence of a hemolytic process. In turn this may
affect athletic performance. In Peru, since 1961 the National Football Cup
includes teams from sea level and those from 2000 to 4340 m. It is a well
known fact that the chances of a high altitude team at low altitude are in
general much lower.

Mc Sharry´s article should include days of acclimatization in his
statistical analysis to demonstrate that at high altitude is much worse to
play the same day of arrival but it is not necessary to wait 10 days to
play a football game.

Gustavo F. Gonzales. D.Sc; M.D
Specialist in Endocrinology

Instituto de Investigaciones de la Altura (High Altitude Research
Institute) and Faculty of Sciences and Philosophy. Universidad Peruana
Cayetano Heredia, 430 Av. Honorio Delgado, Lima 31, Peru.
ggr@upch.edu.pe

References

1. McSharry PE. Effect of altitude on physiological performance: a
statistical analysis using results of international football games. BMJ
2007; 335: 1278-1281.

2. Gonzales GF, Villena A. Football and altitude: The eliminatories of the
world cups [in Spanish]. In Football and acclimatization to altitude.
Universidad Peruana Cayetano Heredia: Lima. 1998:99-112.

3. Gonzales GF, Villena A, Aparicio R. Acute Mountain Sickness: Is
there a lag period before symptoms?. American Journal of Human Biology.
1998;10: 669-677.

4. Rice L, Ruiz W, Driscoll T, Whitley CE, Tapia R, Hachey DL,
Gonzales GF, Alfrey CP. Neocytolysis on descent from altitude: A newly
recognized mechanism for the control of red cell mass. Annals of Internal
Medicine. 2001; 134: 652-656.

Competing interests:
None declared

Excellent study and greatly appreciated. The next step for this USA
fan is for FIFA to lower the altitude limit to 2000m (Azteca Stadium in
Mexico City is at approx 2250m).

Competing interests:
USA fan