# Analysis of Penalty Kick Performance in the Spanish Football League: A Longitudinal Study
## 4 Discussion  
The aim of this research was to detect patterns of penalty kick effectiveness in the Spanish league through a longitudinal study of eight seasons. The effectiveness rate of La Liga players between the 2012/2013 and 2019/2020 seasons (76.9%) was similar to that described in previous research in men's professional football leagues [1, 26, 27, 28, 29, 6, 5, 26]. The success rate of the studies mentioned (70-85%) may be due to the specific training that players undergo to execute this free kick, although it may also be due to the nature of the action itself, in which the goalkeeper is at a clear disadvantage compared to the kicker [5]. Significant differences were found in the relationship between the season and effectiveness. Since the 2018/2019 season, an increase in the percentage of successful penalty kicks has been observed, likely due to the implementation of VAR [30]. This technology has allowed for the confirmation that several saved penalties were invalid because the goalkeeper had moved off the line before the player made contact with the ball, a phenomenon previously identified in the literature [11], but which could not be verified with such precision without the use of VAR. Figure 5: Effectiveness in critical moments during the match (direction-goal and direction-laterality). This research confirms, as in other similar studies, that most of the penalties are awarded in the last 30 min of the match [1; 4; 5; 11]. Penalty kick success oscillated in similar values throughout the different 15 min periods studied (approximately over 78%), with a slight decrease between minutes 61 and 75 (71.2%), returning to around 78% in the final minutes of the match. This contrasts with one of the investigations analysing this element of the game, in which a decrease was observed as the final period of the match began [8]. The increase in fatigue (both physical and psychological) and the associated loss of concentration do not appear to be variables that influence the success of the penalty kick. On the contrary, this could be one of the reasons why teams commit more fouis inside the penalty area and, consequently, more penalties are taken [5; 15; 31; 32]. The result of the match at the time of the shot had no consequences, a priori, on the success rate. Thus, the values here ranged from 77.6% in the case of a tie to 76.3% with a favourable score and 76.4% with an unfavourable score, similar to those of other studies consulted [1]. According to some studies [5], the advantageous situation of the kicker or the ability of specialist kickers to withstand moments of pressure could be one of the explanations. But if we look closely at Figure 5, lower effectiveness rates can be observed if we consider only critical moments of the match (69% in a tie situation between minutes 61 and 75; 68% when losing by one goal between minutes 61 and 75; 72% in a tie situation between minutes 76 and 90+; 68% when losing by one goal between minutes 61 and 75). This indicates that the analysis of the data should not only consider the overall score (winning, losing or tying), but also the moment of the match and the specific result. It is possible that players experience increased pressure during critical moments of a match, which could explain why higher success rates are not achieved compared to those reported in previous studies where this variable was not considered [5; 7]. In other research [7], the success rate was higher with respect to the score depending on the league studied (English league, higher rate when losing; Spanish and Italian leagues, tying, and German league, winning). This corroborates the idea that this aspect needs to be studied further from more specific perspectives. Previous studies have shown that the player's footedness has no influence on the success rate of penalty kicks [1; 5]. This study corroborates previous studies, with no significant differences in effectiveness between right-footed and left-footed players (77.3% vs. 75.9%).