The stadium where the team plays as a local, “Universitario stadium” is located at an altitude of 525 m and its training center is at 370 m. When the team is visitor, arrives at the venue 24 hours before.

Numerical variables were reported as means (± SD) The distribution of the numerical variables was assessed using the Kolmogorov-Smirnov normality test.

In the bivariate analysis, Student's t-test was used to compare two quantitative variables with a parametric distribution. For the comparison of numerical variables in three or more groups, the ANOVA or Kruskal-Wallis test was used according to the distribution of the variable. The comparison of qualitative variables between groups was made with the Chi-square test. A p-value of less than 0.05 was considered significant. The statistical analysis was performed with SPSS Statistics version 24. The effect size was calculated using the partial eta squared (small: 0.01, moderate: 0.06, large: 0.14).

In the global performance of the team at “Near sea level” a distance of 9854.77 ± 835.98 m was covered at a mean speed of 6.26 ± 0.52 km/h and a total of 19.20 ± 7.55 sprints with a time of 5.30 ± 2.44 min between each. At “Low Altitude” the team had a displacement of 10102.39 ± 1930.45 m, a mean speed of 6.40 ± 0.57 km/h, 20.48 ±7.88 sprints and 5.06 ±2.49 minutes between each.

At “Moderate Altitude” a distance of 9878.46 ± 835.95 m was covered at a mean speed of 6.22 ± 0.54 km/h and a total of 19.37 ± 7.39 sprints with a time of 5.38 ± 2.41 min between each sprint (Table 2).

We compare the performance in “Near sea level” and “Moderate altitude” against the parameters for “Low altitude”. There was a decrease of 2.45% in the total distance covered in “Near sea Level” and of 2.22% in “Moderate Altitude. Mean speed decreased 2.19% in “Near sea Level” and 2.81% in “Moderate Altitude”. It decreased in the number of sprints by 6.25 %% “Near sea Level” and by 5.42% in “Moderate Altitude”, with an increase of 4.47% in the time between sprints in “Near sea Level” and 6.32% in “Moderate Altitude”.

No statistical differences were found between altitude and the total distance covered (p=0.165; ES 0.004) A significant difference was observed in the mean speed at “Low Altitude” (p=0.000; ES 0.20). No relationship was found between altitude and the total number of sprints (p= 0.115; ES 0.005) and the time between sprints (p=0.237; ES 0.003).

Defenders covered a distance of 9577.44 ± 578.55 m at “Near sea level”, 9820.01 ± 2611.38 m at “Low Altitude” and 9577.44 ± 699.22 m at “Moderate Altitude”. Midfielders covered a distance of 10501.25 ± 701.50 m at “Near sea level”, 10676.89 ± 931.14 at “Low Altitude” and 10470.09 ± 705.41 at “Moderate Altitude”. Forwards covered a distance “Near sea level” of 9529.31 ± 964.56 m, at “Low Altitude” 9750.52 ± 931.14 m and at “Moderate Altitude” 9530.95 ± 787.56 m.

In the total distance covered according to the position of the players, we observed in the defenders a decrease of 2.84% in “Near sea level” and of 9.40% in “Moderate Altitude”. In midfielders it decreased by 1.65% and 1.94% in “Near sea level” and “Moderate Altitude” respectively. Forwards decreased by 2.27% in “Near sea level” and 2.25% in “Moderate Altitude”.

No relationship was found between level of altitude and total distance covered in defenders (p= 0.561; ES 0.003), midfielders (p= 0.064; ES 0.017) and forwards (p= 0.342; ES 0.013) (Table 3).

Mean speed of the defenders was 6.06 ± 0.36 km/h “Near sea level”, 6.16 ± 0.37 km/h at “Low Altitude” and 6.03 ± 0.41 km/h at “Moderate Altitude”. Midfielders had a mean speed of 6.66 ± 0.36 km/h “Near sea level”, 6.80 ± 0.40 km/h at “Low Altitude” and 6.61 ± 0.47 km/h at “Moderate Altitude” while forwards had a mean speed of 6.07 ± 0.62 km/h “Near sea level”, 6.23 ± 0.53 km/h at “Low Altitude” and 5.99 ± 0.53 km/h at “Moderate Altitude”.

The mean speed of the defenders decreased by 1.62% in “Near sea level” and 2.11% in “Moderate altitude”. The mean speed of midfielders decreased by 2.06% in “Near sea level” and 2.97% in Moderate Altitude”. Forwards also decreased by 2.57% on “Near sea level” and 3.85% on “Moderate Altitude”.

Mean speed was significantly higher at “Low Altitude” in defenders (p= 0.005; ES 0.024) and midfielders (p=0.004; ES 0.034).This relationship was not found in forwards (p=0.53; ES 0.034).

Defenders had 17.19 ± 6.91 sprints at “Near sea level”, 17.05 ± 6.90 at “Low Altitude” and 16.34 ± 6.80 at “Moderate Altitude”. Midfielders had 22.28 ± ±7.85 sprints “Near sea level”, 24.41 ± 7.95 at “Low Altitude” and 22.75 ± 7.49 at “Moderate Altitude”. Forwards had 18.69 ± 7.19 sprints “Near sea level”, 22.06 ± 5.96 at “Low Altitude” and 20.54 ± 5.45 at “Moderate Altitude”.

Regarding the number of sprints performed, defenses increased in 0.82% in “Near sea level” and decreased by 4.16% in “Moderate Altitude”. Midfielders decreased 8.32% in “Near sea level” and 6.80% in “Moderate Altitude”. Forwards decreased 15.28% in “Near sea level” and 6.89% in Moderate altitude ”. No relationship was found between the number of sprints performed and the level of altitude in defenders (p=0.670; ES 0.002), midfielders (p=0.187; ES 0.011) and forwards (p=0.067; ES 0.032).

At “Near sea level” the time between sprints in defenders was 5.94 ± 2.78 minutes, 6.05 ±2.94 min at “Low Altitude” and 6.31 ± 2.79 at “Moderate Altitude”. In midfielders, this time was 4.43±1.51 minutes at Near sea level”, 4.09 ±1.66 min at “Low Altitude” and 4.42 ±1.66 at “Moderate Altitude”. Forwards had a time of 5.22 ± 2.53 minutes between sprints at “Near sea level”, 4.27 ±1.24 min at “Low Altitude” and 4.89 ±1.71 at “Moderate Altitude”.

The time between sprints in the defenders, decreased 1.82% in “Near sea level” and increased 4.30% in “Moderate Altitude”. Midfielders increased by 8.31% in “Near sea level” and 8.07% in “Moderate Altitude”. Forwards increased 22.25% in “Near sea level” and 14.52% in “Moderate Altitude”

No relationship was found between the time between each sprint performed by defenders (p=0.711; ES 0.002), midfielders (p=0.261; ES 0.008) and forwards (p=0.14; ES 0.050).

When comparing the performance against those rivals that live in “Near Sea Level”, we found a non-significant decrease of 5.68% in the “Number of sprints”. Compared with those teams that are at “Low Altitude”, we found a significant increase of .094% in average speed, a non-significant decrease of 6.15% in the number of sprints and a non-significant increase of 5.03% in the time between sprints. When comparing rivals living in "Moderate Altitude", a non-significant decrease of 15.59% in the number of sprints and a significant increase of 16.91% in the time between sprints was found.

Although at “Moderate Altitude” the percentage of victories decreased, the percentage of defeats increased; Fewer goals were scored, and more goals were received in matches held in “Moderate Altitude.” No correlation was found between the result and the number of goals scored and received at different altitudes (Table 4).

One of the ways in which the effects of altitude can be studied is through the total distance covered.20 No statistically significant differences were observed between the distances covered between the players at the different altitudes during the entire game or in each half of the game, this contrasts with the information obtained by Bohner,15 where statistically significant differences were observed when comparing the distance by average minute between a game played on a Near Sea Level playing field and another at moderate altitude, although in this study the total distance was not evaluated and that the games were played in a collegiate soccer league. In addition to this, the distances were measured through a GPS device on the players' arms where the margin of error of the devices was not reported, in contrast to the data obtained in the Mexican league through a camera system, tracking the exact position and distance that the players covered.

Also, we found a decrease of the 2.2% in the total distance covered in “Moderate Altitude” contrary to a significant decrease in the distance traveled reported by university soccer players, although in this study the absolute values or reduction percentages were not reported, so this conclusion was obtained from the graphics in the full text.15

Garvican found in his study a decrease of 9.1% of the total distance obtained on day 4 of training at an altitude of 1600, compared to the game at sea level, however, in this study, 3 periods of 25 minutes were played in the moderate altitude in contrast to the game at sea level which was a standard 2 halves 45-minute match.16 In our study, only those players who had played the two 45-minute halves were considered in different altitudes. This could explain the smaller difference between the distances covered at sea level and a higher altitude compared to Garvican´s study,16 where matches times were shorter at higher altitudes. Trewin et al.17 found a 4% decrease in performance in elite women's soccer players when the altitude increased, and Nasis18 who found a decrease of 3.1% in the total distance covered in 1200 m (Low altitude in our study). In this study decrease was of 2.5%. Nasis18 in her study hypothesizes that the decrease in the distance traveled may be due to the reduction of the Vo2 Max which results in a greater intensity of the exercise.

These changes can be explained due to a lower oxygen pressure with increasing altitude with a decrease in ATP production, producing energy through the anaerobic pathway.

In addition to this, Nasis's study was carried out during the World Cup, where there were significant differences in the physical conditions between the teams where their players belong to elite teams in championships such as Europeans and where the geographical conditions of each country are different. There is evidence that players who play in high altitude conditions tend to have a shorter adaptation time when taken to places near sea level and then to high altitudes than those who have played exclusively near sea level, on average 7 days less.5 In Liga MX, teams are constantly traveling each week to play matches outside of their local stadiums, usually at higher altitudes.19–22 This could explain the smaller difference compared to previously reported studies.

It has been empirically assumed that decreasing air resistance would increase the speed of the players.6 However, there is a decrease in speed of 2.81% in the “Moderate Altitude” stages, in agreement with the observations made by Nassis et al.18 We hypothesize that the decrease in the availability of ambient oxygen, decreasing the mechanisms of ATP production through the mitochondrial pathway and the little time they have to adapt to rapid changes in altitude negatively impact the speed of the players.

Although the majority of the distance covered in football is at low speed,11,23 sprints are of major importance in soccer.10,24 The distance traveled at high speed distinguishes elite players from others11,16,25 and it is the most frequent action in goal situations in professional soccer, both for those who assist and those who score.3

Due to the decrease in air resistance at higher altitudes, the ability to perform a single sprint would be increased.7 Because there is a decrease in the hydrolysis of phosphocreatine11,23,27 and an increase in lactate concentration with increasing altitude.26

This may decrease the number of sprints performed as altitude increases, which is consistent with our findings6,27,28

We found a non-significant decrease of 6.25% in places near sea level and a non-significant decrease of 5.42% in “Moderate Altitude” stages. Similar changes were observed at “Low Altitude” stages with a 3.1% decrease as reported by Garvican.16

The similarity in the decrease in the percentages suggests that these may be caused by factors such as fatigue or weather conditions.19–22

Although a longer recovery time is seen between sprints at a higher altitude which can be explained by the increase in lactate due to the presence of the anaerobic pathway of ATP production could explain this phenomenon.8,26,28,29 A statistically significant difference was not observed,” Near Sea Level” there was a decrease of 4.47% and 6.32% at “Moderate Altitude”. Despite this, the authors of this work hypothesize that in stages higher than “Moderate Altitude”, the time between sprints may increase as a consequence of the adaptive physiological changes to the decrease in oxygen pressure in the environment, however, they may also be strongly influenced as a load of psychological stress due to playing in a foreign stadium, the tactical strategies used for the game or factors such as the weather.19–22

We did not find statistically significant differences in contrast to what was reported by McSharry7 and Faude,30 who reported a significant disadvantage when playing matches at "Low, Moderate, and “High Altitude”.

This non-significant decrease in the sport performance parameters at “Moderate Altitude”, can be explained by the decrease in the number of sprints and increase the time between sprints,31 and addition to the disadvantage of playing games as a visitor.32 In addition to that each week they travel to different stadiums, located at different altitudes, accompanied by the fact that these conditions are shared by all the teams in the “Liga MX”.

One of the weaknesses of our study was that the meteorological conditions were not considered. Considering that in Mexico there are drastic changes in temperature (winter matches have been held at less than 5°Celsius and summer matches have been held at 40 °) .Variables such as tactics, substitutions, age of the players and training methods were not considered.

No statistically significant differences were observed between the general performance of the soccer players of an Liga Mx team at sea level, Low Altitude”, and “Moderate Altitude”, as well as no better performance in variables such as speed and distance, covered. Contrary to what has been reported by other authors, altitude does not seem to be a decisive factor when evaluating the performance of the team, the researchers conclude that the altitude of the stadiums less than 3000 meters from sea level does not diminish the performance of the players. However, more prospective studies should be carried out that include factors such as weather conditions, the training method, and the playing styles of each team.