###### Abstract  
The objectives of this study are: (1) to compare match load demands through load indicators between starters and substitutes, and (2) analyze the degree of correlation in the variables analyzed in this investigation. Twenty-two semi-professional soccer players were analyzed during a full season's 38 official matches. Participants were assigned to two different groups according to their participation in the game: (a) starting-up players (\(\geq\)90 min played) vs. substitute players (\(\geq\)45 min played in the second half). Statistical analysis was performed by using Mann-Whitney U test to conduct pairwise comparison and Spearman correlation to demands correlation in each group. Significant differences in both absolute and relative variables in player load (P, \(p<0.01\); \(p<0.01\)), metabolic power (MP, \(p<0.01\); \(p=0.15\)), equivalent distance index (EDI, \(p=0.87\); \(p<0.01\)), dynamic stress load (DSI, \(p<0.01\); \(p=0.977\)), energy expenditure (EE, \(p<0.01\); \(p<0.01\)), high metabolic load events (HMLE, \(p<0.01\); \(p<0.01\)), and high metabolic load distance (HMLD, \(p<0.01\); \(p=0.09\)). Overall, high direct correlations in the starting-up group in absolute and relative demands of PL, PM, HMLD, EE, and DSL were found, as well as high inverse correlation in the substitute group in all variables, excluding DSL and HMLD. In conclusion, the absolute differences found suggested a different training load management during training sessions. applied sciences; football; load; technology; global positioning system +
Footnote †: These authors contributed equally to this work. gyroscopes, and magnetometers are commonly used to measure the activity profiles of athletes in team sports [8]. Recently, FIFA has amended its policy to allow the use of Electronic Performance Tracking Systems (EPTS) as tracking devices in official matches [9]. This modification means that the use of microtechnology to quantify the movement of the player during matches is not reduced to only friendly matches [10] and can be used in real competition situations. Commonly, variables such as distance covered or activity time at different speeds have been used for the quantification of football demands [11], the profile of these requirements being analyzed in competitions such as English Premier League [12], Italian Serie A [13], Spanish La Liga [14], French Ligue 1 [15], German Bundesliga [16], and also in the European Champions League [17; 18] and in International Championships [19]. Subsequently, the indexes based on triaxial acceleration and metabolic cost have been progressively introduced [20; 21], the second being controversial despite published research [22]. The analysis of this information has tended to be more complex because the technologies use different algorithms and time duration to classify the actions and this limits the comparability between the studies [23]. The different investigations which have analyzed the load in football have shown that there seems to be a decrease in the physical performance of the players in three different moments of the matches [13]: (1) after short periods of intense activity in both halves; (2) in the initial phase of the second half; and (3) towards the end of the game. This loss of performance has been associated with the physiological fatigue of the players [13; 24], since the physical activity carried out by the players in the first half and in the second half has been analyzed [12; 17; 25]. In order to minimize the effects of fatigue, coaches can introduce substitute players to replace injured or underperforming players, in addition to making tactical changes [18]. The decrease in physical activity during official matches occurs not only due to physiological fatigue, but also to situational variables such as the half-time score [26], the level of the opponent [26], and the location of the match [27], which also have an influence on performance.