CONMEBOL Libertadores Cup: Altitude impact on goals and results in 16 years of soccer matches

Background: The CONMEBOL Libertadores Cup, is the continent’s most important international club tournament. Teams are exposed to different altitudes with short acclimatization periods. The present study describe the effect of altitude on the results and goals of soccer club teams matches between 2000 and 2015 in the CONMEBOL Libertadores Cup. Materials & Methods: All home and visiting matches from the group phase onwards and which have been played at the traditional team venue were taken into account, thus, 2039 games were analysed. The teams were classified into altitude categories according to the physiological impact and registered hometown altitude. Poisson´s generalized linear model was used to study the relationship between the altitude of both home and visiting teams and the number of goals scored for each team according to the altitude category. The probabilities that the home team winning, drawing, or losing the match were estimated using a regression model for ordinal variables and assuming a multinomial probability distribution with the logistic linkage. Factors as heat, temperature and general performance of the teams were not considered. Results: Local team scores more (2.62 goals) when the visiting team descends three altitude categories, followed by a descent of two altitude categories (2.01 goals) and an ascent of three altitude categories (1.89 goals). This is associated with an increase probability of winning for the local team, being 5.5 times more likely when the visiting team descends three altitude categories, 2.3 times more when it descends two categories, and 2.5 times more when it ascends three altitude categories. Conclusions: These findings suggest that the visiting team is more likely to lose a match when it has to descend two or three altitude categories and when it ascends three altitude categories.