1. Introduction
Padel has gone from being a minority sport to being one of the most practiced sports in the world, as it is played in more than 40 countries. This growth has led to an increase in men’s, women’s, team, senior, and junior championships. Likewise, the number of sports facilities, federated clubs, sponsors, or licenses around the world has increased [
1]. Specifically, the most established professional men’s and women’s circuit in the world is the World Padel Tour (WPT), a competition that is based in Spain, but which organizes tournaments in different countries each season.
Interest in this sport has also been seen in the increase in scientific publications. There are many areas in which studies have been carried out on padel in recent years—educational [
2], anthropometric [
3,
4], physiological [
5,
6], psychological [
7,
8], etc.
Specifically, there is special interest in the analysis of performance indicators in padel. Studies have been conducted to describe the competition [
9], the technical–tactical actions that may be more effective [
10,
11,
12], physical condition [
13,
14], movements [
15,
16], biomechanics [
17,
18], or the discovery of game indicators [
19,
20,
21]. In addition, various investigations in padel have studied the differences that exist between winning and losing pairs [
21,
22,
23,
24] or between women’s and men’s padel [
12,
25,
26].
Research related to the analysis of performance in padel has concluded that there are two basic playing areas. The net area, which is the one in which the pair plays in positions close to the net, and the background area, which is the one in which the pair plays at the back of the court [
27]. In both of these zones, offensive and defensive shots could be played. However, pairs that win games in padel perform more attack actions (near the net) in 85% of the points, spend more time in the net area, and hit fewer shots from the back of the court during the game [
21,
22,
23]. In addition, these studies show that about 80% of the winners are obtained from near the net. Thus, there is a relationship between scoring points and occupying areas close to the net. While the objective of the pair of players who are in the background zone is to fight to achieve the net position, the objective of the players who are in the net zone is to fight to preserve it [
23].
Various studies have shown that the lob is the most used technical–tactical action by men and women padel pairs from the background position to achieve the net position. However, the point does not end, thus allowing continuity in the game and giving rise to more exchanges of position between pairs during the same point [
11,
28,
29]. To obtain these results, the researchers used ad hoc tools, based on observational methodology, which allow the notational recording of the game actions studied. However, no designed and validated observational tool has been found aimed at studying the shots used by padel partners to achieve the offensive position, despite the fact that there are several observational tools that have been designed and validated aimed at the study of padel based on the analysis of the quantitative and qualitative judgment of a group of experts [
30,
31,
32].
After a review of the scientific literature, the non-existence of a validated instrument that analyzes the shots used by padel pairs to achieve the net position or reach the net was confirmed. Therefore, the objective of this research was to design and validate an observation instrument to ascertain the characteristics of the different strokes that padel pairs use to reach the net and their consequences in subsequent shots.
3. Results
Table 4 shows the results obtained using Aiken’s V coefficient and their confidence intervals regarding adequacy.
It was observed that variables 8 (key point), 9 (streak), 15 (order of the rally), and 16 (rally) did not exceed the critical value for Aiken’s V with respect to the adequacy that was established at 0.90, and therefore these variables were eliminated from the record sheet.
Table 5 shows the results obtained after calculating Aiken’s V coefficient and its confidence intervals regarding the wording.
The experts stated that the variables 2 (player), 5 (partial result of the game), 8 (key point), 9 (streak), 11 (type of shot), 13 (action of the rival pair), 14 (action in the net zone), 15 (order of the rally), and 16 (rally), should be revised. None of them exceeded the critical value for Aiken’s V with respect to the wording, and therefore, special treatment was necessary with these variables to improve them.
Table 6 shows, by way of example, the qualitative assessments provided by the experts and the actions that were carried out accordingly.
Once all the changes and consequential corrections of the quantitative (Aiken’s V) and qualitative (contributions) assessment of the experts had been made, the tool was validated and is presented in
Appendix A.
Finally,
Table 7 shows the values for the reliability of the tool through Cronbach’s α coefficient, before and after eliminating the variables that obtained a value lower than 0.90 in Aiken’s V coefficient with respect to adequacy. After eliminating the 4 variables (key point, streak, order of the rally, and rally) suggested by the experts, Cronbach’s α coefficient improved.
4. Discussion
To carry out research that analyzes performance indicators through observational methodology, it is necessary to have validated tools. The objective of this research was to design and validate an observation tool to analyze the characteristics of the different strokes that padel pairs use to reach the net and their consequences in subsequent shots. Thus, an instrument was created—the NAPOA, made up of 12 variables, which allows us to analyze these game situations that constantly occur in padel. Despite the fact that these game situations have been the object of study of various investigations [
11,
28,
29] in different game contexts (amateur padel, professional women’s padel, or professional men’s padel), an instrument that analyzes them in a specific way, built from the analysis of the quantitative and qualitative judgment of a group of experts, has not been established so far. This is surprising, since there are several observational tools that have been designed and validated aimed at the analysis of the game in padel [
30,
31,
32].
For the validation of an instrument to be satisfactory, a series of guidelines must be met [
36,
58], which will be developed throughout this discussion: (i) the selection criteria of experts; (ii) the number of experts that comprise the panel; (iii) the procedure used by the experts to assess the validity of content; (iv) the statistical or quantitative procedures to evaluate the experts’ scores; and (v) the selection criteria used to determine whether the items are kept, modified, or eliminated from the final proposal to be included in the instrument.
The selection criteria for the experts were custom-defined for the present investigation. Except for one who is in the process, all the experts are Ph.D.s, thus guaranteeing their scientific training. Likewise, all the experts have taught at university and are authors of scientific publications where the object of study is the analysis of the game in padel. Moreover, except for one, all the experts have the federative qualification and have worked as a padel coach or that of another racket sport, guaranteeing their experience. Other investigations, aimed at the validation of tools, have used selection criteria similar to those described. That is, they have used Ph.D.s [
31,
53,
59], experts with scientific publications related to the topic to be analyzed [
52,
53], and experts who have federal qualifications and have served as coaches [
30,
31]. In addition, the rule that experts must meet 80% or more of the inclusion criteria to be part of the sample has been used by other investigations on this topic [
31,
52]. Therefore, the quality of the experts participating in the study is guaranteed, as are their quantitative and qualitative assessments.
In the sports field, ten or more subjects offer an acceptable estimate for the content validity of a validation instrument [
59,
60,
61]. The sample of this study is made up of eleven experts, so this requirement has been exceeded. Thus, the contributions of our experts are sufficient in terms of numbers for the validation of this observation tool.
The experts made a quantitative assessment of each of the variables in the NAPOA instrument. This assessment awarded scores from 1 to 10 for the drafting and adequacy of the items, as carried out in other studies [
31,
52], and the procedure that was used to quantitatively analyze the content validity of the tool has been used in other investigations [
31,
62,
63,
64]. This procedure uses the cut-off point to eliminate a variable at 95% confidence. Thus, four of the sixteen variables were eliminated (key point, streak, order of rally, and rally), since they obtained values lower than 0.90 in Aiken’s V for adequacy. The experts considered that these variables should not be part of the tool. On the other hand, when the values were between 95% and 99% of confidence, the variables were improved. Specifically, the variables player, partial result of the game, type of shot, action of the rival pair, and action at the net were modified. The comments made by the experts were taken into account for their modification, since they carried out a qualitative assessment of the variables, which was essential for the final development of the tool [
36,
65]. The degree of openness per player on the right side and player on the left side was changed in the player variable. In the partial result of the game, the categories of the opening range advantage-40 and 40-advantage should be omitted when the instrument is used for the analysis of World Padel Tour matches. The ranges of the variables type of shot (lob, passing, and chiquita), action of the rival pair (winner, error, and continuity) and action in the net zone (winner, error, continuity, and no action) were modified. Finally, an item was considered to be correct when it had a value greater than 99% confidence [
52,
53], in other words, when Aiken’s V was 1.00. Thus, a new proposal of the validated tool was built, which was made up of 12 items, both situational—defining the state of play, and specific—analyzing the stokes that padel pairs use to reach the offensive position and their consequences in both subsequent shots (
Appendix A).
Various studies aimed at the validation of observational tools use the same procedure that was used in this research to obtain reliability [
31,
63,
66,
67]. The tools in these investigations, like the instrument in this study, reach optimal reliability values, since they all obtain values higher than those that the experts mark as a reference [
56,
57]. In addition, it is novel to calculate said reliability once the variables that reached values lower than 0.90 in Aiken’s V coefficient in adequacy had been eliminated, since its value improved considerably, from 0.84 to 0.89 in Cronbach’s α coefficient. Thus, NAPOA has sufficient internal consistency, that is, the variables measure the constructs of the characteristics of the strokes used by padel pairs to achieve the net and their consequences consistently.
5. Conclusions
The tool designed in this study is valid. Although a very high cut-off point was determined due to the number of variables and experts, all the variables that make up the final tool (
Appendix A) present an appropriate value in Aiken’s V coefficient with respect to adequacy. In addition, the wording of the variables that presented a value between 0.90 > 1.00 in Aiken’s V coefficient was modified according to the qualitative evaluations of the experts.
NAPOA is a reliable tool, since the value obtained in Cronbach’s α coefficient is very high and the variables of the instrument consistently measure the characteristics of the strokes that the padel pairs use to reach the net and their consequences in the two strokes.
This instrument is valuable and very useful for other researchers who face the possibility of carrying out this type of study. In addition, it is important to use validated and reliable observation tools to analyze the analysis of the game in padel.
This tool makes it possible to ascertain the characteristics of the strokes used by the padel pairs to reach the net and their consequence in the two subsequent shots. It would be convenient to use this tool for future scientific studies in all kinds of contexts, that is, in different padel sports categories and in both men’s and women’s matches. It would be of great help for padel players to know which shot is the most suitable or effective to achieve the offensive position, its characteristics, and what the consequences would be. Likewise, this information is vital for padel coaches, and for the development of training tasks and game strategies.