Using 360˚ Videos for Teaching Volleyball Skills to Primary School Students

Rhodes, Abstract The study presents the results from a pilot project in which 360˚ videos were utilized for teaching students basic volleyball skills. The target group was thirty-six, eleven-to-twelve years-old primary school students, divided into two groups: the first was taught conventionally and the second using apps in which 360˚ videos were embedded. The project lasted for six two-teaching-hour sessions (three for each method), and data were collected using observation sheets and a questionnaire for recording students’ views regarding their experience. The data analysis confirmed that, compared with conventional teaching, 360˚ videos allowed students to perform better the skills that were examined. The participating students also thought that by viewing 360˚ videos they were more motivated to learn and that their experience was an enjoyable one. On the other hand, students did not consider the 360˚ videos as being useful in their learning. Given the lack of research in this field, the findings provide an initial indication of 360˚ videos’ potential in Physical Education. Then again, the results also point to the need of finding more innovative methods for integrating 360˚ videos in everyday teaching.


Introduction
Physical Education (PE) is a learning subject that differs significantly from all others, as its main objective is the engagement of students in physical activities. In its current form, it focuses on team sports rather than in activities related to the outdated philosophy of Swedish/pedagogical gymnastics. That is because students' participation in team sports allows them to become physically fit and to develop their motor and social skills (Kelly & Melograno, 2014). What is more, the teaching of movement coordination and motor skills, contributes to the improvement of students' reflexes, helps to avoid injuries, and creates incentives for further involvement in sports (Šimonek, 2014). The role of PE teachers is quite complex, as they are called to carefully design and organize their courses in order to achieve the effective transmission of knowledge/skills and create a pleasant climate that motivates students to participate in the activities, even the ones of increased weight, integration problems, and low self-esteem (Greek Ministry of Education, 2016). The process of learning sports related motor skills and techniques has been the subject of numerous studies; many, often conflicting, opinions and theories were tested and eventually adopted or disapproved according to their results. What is widely accepted, however, is that it is not enough for a PE teacher to simply give some instructions for performing  Fun and motivation contribute to the effectiveness of 360 o videos.
In the past decades, ICTs were introduced in all levels of education and across almost all learning subjects, including PE. However, the introduction of ICT tools in PE is not an easy task. The most common problem is the lack of infrastructure, which hinders or even prohibits the use of ICTs in this subject (Yaman, 2008). Then again, videos are quite commonly used in the context of PE with positive results (Weir & Connor, 2009). Their contribution to the educational process is found both during the teaching and evaluation phases. During teaching they are mainly used for demonstrating, for example, a movement, in order to enable students to understand its mechanics. During the evaluation, they provide an opportunity for PE teachers to document the improvement of students' skills (Mohnsen & Thompson, 1997). In recent years, videos have evolved; surpassing the limitation of the single point and limited field of view. The technology of 360 o videos (also known as spherical videos), by using special cameras, allows the recording of images from a whole sphere. Users are then able to view these videos on their PCs, smartphones, or using head-mounted displays (HMDs). What is of interest, in the last two cases, is that when users move their smartphones or heads, a different area of the current scene is displayed. Thus, 360 o videos offer an unparalleled viewing experience, immersing users in the environment they present (Higuera-Trujillo et al., 2019;Slater et al., 2016).
Research has demonstrated that 360 o videos had a positive impact on learning, motivation, and enjoyment while learning (Lee et al., 2017). On the other hand, their educational potential is still largely unexplored, as relevant studies in the field of PE are sparse. Given this lack of research, a pilot study was carried out having as its main objective to examine whether 360 o videos can produce better results, in terms of improving sport-related skills, compared to conventional teaching. It was also considered important to examine students' views on the use of 360 o videos in relation to their motivation, enjoyment, and whether they thought that 360 o videos can facilitate their learning. Details for the project and its outcomes are presented in the coming sections.

Physical education
The modern way of living has led to obesity problems, reduced physical activity, and bad eating habits. As a result, the need for quality training and exercise from an early age is imperative (Basoglu, 2018). PE can be part of the solution (SHAPE America, 2013). Its main objective, at all levels of education, is the development of students' motor skills and, through them, the cultivation of their physical abilities and the strengthening of their health (National Association of Sport and Physical Education, 1992). The above is achieved when students are able to perform a variety of motor skills, regularly participate in physical activities while being aware of their importance, and have a good overall physical condition (Metzler, 2017). PE is not only a set of motor exercises or physical games but, in a broader sense, it also involves the study of health issues and techniques that improve one's life. Through the teaching of PE and its various aspects, students are given the opportunity to promote and develop their critical thinking. Not only that, but students who are actively involved in physical activities perform better in school tests, in subjects such as mathematics, language, and the study of the environment (Azevedo, 2019;Brusseau & Hannon, 2015;Conyers & Wilson, 2015). This led to the introduction of the term "kinetic literacy", which describes the motivation, self-confidence, motor dexterity, knowledge, and the embracing of values related to lifelong physical exercise (International Physical Literacy Association, 2017). Therefore, students need to realize the benefits of PE (Singh, 2020).
Quite logically, one might ask what can be considered as effective teaching models in PE. Should the emphasis be on physical exercises or on the fun/enjoyment caused by physical activities? Although there is no easy answer to this question, as there are conflicting opinions, it appears that two major approaches exist. PE in the form of "fun activities" offers stronger incentives for participation (Prochaska et al., 2003;Werle et al., 2015), as they create a more attractive environment for learning (Garn & Cothran, 2006). On the other hand, PE in the form of "training/exercises", because it is a more demanding and intense procedure, can result not only in the development of physical/motor skills but also in the improvement of self-confidence, which, eventually, allows students to adopt a healthier lifestyle and become physically active individuals throughout their lives (Ferkel et al., 2017).
Nevertheless, the most important priority of both approaches is students to acquire motor skills that are considered important. Systematic training provides the necessary knowledge and confidence, so as students to actively participate in various physical activities and sports (Rink & Hall, 2008). Previous studies have demonstrated that confidence is positively linked to student's inherent motivation. When they come to believe that their skills can be successfully performed at any time and, if necessary, new skills can be acquired, students build their self-esteem and confidence (Rink & Hall, 2008). In turn, as long as students feel that they are capable of performing an activity, they are encouraged and enjoy their participation in PE (Goudas et al., 2000;Whitehead & Corbin, 1991). Mosston and Ashworth (2002) described a total of eleven PE teaching methods (i.e., commands, practice, reciprocal, self-check, inclusion, guided discovery, convergent discovery, divergent production, individually designed program, learner initiated, and self-teaching). Out of them, it seems that the dominant method and the most popular among PE teachers is that of commands (Kulinna & Cothran, 2003). In short, it is the PE teachers who make all the decisions about how to conduct the course. As far as a skill or an exercise is concerned, they divide it into smaller parts and demonstrate it. Following that, students are asked to perform the skill and PE teachers provide feedback on whether the skill/exercise was accurately performed or not. Also, a quite popular method is that of practice. As its name implies, students are divided into small groups and practice the given skill.
Coming to team sports, football and basketball are the ones most commonly taught in Greek schools; volleyball and handball are less frequently taught. Active participation in these sports is of paramount importance for learning the skills related to them. That is because the degree of participation determines the extent a skill is practiced but also has an effect on the desire of students to continue participating. As in all physical activities, modeling and visualization of a move/skill related to a sport, through kinetic representations, is vital. That is because it allows learners to decode the pattern of the move, facilitating the learning of the given motor skill (Zetou et al., 2002). In addition, feedback (in the form of oral comments from the PE teachers) when learning sports-related skills is also important. It is no surprise that from very early on, PE teachers are trained on how to provide this feedback (Cloes & Premuzak, 1995), with the emphasis being on the quality, but also in the form this feedback has to have. Positive feedback is often associated with the strengthening of students' inherent motivation, which ultimately leads to the strengthening of their resolution to perform better (Mouratidis et al., 2008).
The teaching of PE is not without problems, with the most important one being students' participation. Research has highlighted the inextricably linked relationship between a positive teaching climate, motivation, metacognition, and students' participation in sports (Papaioannou et al., 2006). Regrettably, this problem becomes even more prominent as students grow up and pass from one educational level to another, resulting in a lower desire and motivation to participate (Van Wersch et al., 1992). Moreover, in the early stages of learning a skill, additional obstacles are encountered, that render difficult the process of mastering it. Such obstacles are the need to monitor a moving object (e.g., a ball), the need to (quickly) select the corresponding motor skill to be applied, and the correct synchronization of more than one moves (Zetou et al., 2002). Quite often, students' attention is directed to these factors, disproportionally increasing the effort they have to put in performing and/or learning the skill, or resulting in the incomplete/incorrect learning of it. Videos are probably the most important tool PE teachers use in their task of modeling/visualizing a skill or move. As already stated in the Introduction, videos are used in both the teaching and assessment stages. Studies have reported not only positive learning outcomes but also a positive impact on students' motivation (e.g., Palao et al., 2015;Robinson, 2011;Weir & Connor, 2009). In addition, together with oral feedback, videos helped to reduce the amount of practice needed for learning a skill/move (Palao et al., 2015).

360 o videos
As mentioned in a preceding section, 360° videos are recorded using cameras able to capture images from a 360 o field of view (from a whole sphere to be exact), instead of the conventional limited angle of coverage of regular videos; thus, 360° videos offer a view that is perceptually similar to what individuals can see, in real life, by turning their heads in every direction (Pham et al., 2018). Video editing does not differ from the procedures followed with regular videos. While 360 o videos can be viewed at any device and by using any software capable of playing regular videos, it is preferable to use a smartphone or, even better, an HMD. That is because the gyroscopes in these devices allow users to simply move their smartphones or their heads in order to display a different part of the scene. As a consequence, users are immersed in an environment that is not that different from reality, resulting in a high degree of engagement with what they see (Hebbel-Seeger, 2017). Interactive hotspots can be added that allow the transition to other (360°) videos or the display/playback of multimedia elements (e.g., web pages, images, sounds, music, and text) (Argyriou et al., 2016;Kallioniemi et al., 2018). 360 o videos have found their way in diverse scientific/professional fields. For example, they are used for virtual guided tours (Garzotto et al., 2018;Hakulinen et al., 2017), for demonstrating medical procedures (e.g., a surgery) (Guervós et al., 2019), and, as expected, in education (Lee et al., 2017;Queiroz et al., 2018). As far as the latter is concerned, 360° videos are applied in a rather impressive range of subjects and disciplines such as history (Rasheed et al., 2015), astronomy (Rupp et al., 2016), foreign language learning (Huang et al., 2019), medical training (Yoganathan et al., 2018), chemistry and lab training (Clemons et al., 2019), and physics (Wu et al., 2019). Besides the positive impact on knowledge (e.g., Berns et al., 2018;Chang et al., 2019) and skills (e.g., Parmaxi et al., 2018), researchers have reported increased knowledge retention , motivation and enjoyment while learning Huang et al., 2019;Rasheed et al., 2015), and raised awareness of important issues (e.g., social, political, and environmental) (Elmezeny et al., 2018).
The keys for understanding the educational potential of 360 o videos are immersion and the realistic experiences they provide; after viewing them students, as well as any other user, are left with the impression that they were "in" the environment presented in the video (Narciso et al. , 2019). Moreover, because students have the opportunity to observe details that can be passed unseen in regular videos and to choose the perspective from which to observe and interact with the content, they are able to experiment without being afraid to fail (Hussein & Nätterdal, 2015). As a result, teaching, in the eyes of students, becomes a meaningful process, while, at the same time, they are provided with the incentives to participate in the course (Lee et al., 2017).
Teachers' attitude regarding the introduction of 360 o videos in their courses is also positive (Geng et al., 2019;Stojšić et al., 2019).
On the negative side, a common problem is what is called "simulator sickness." Users often feel discomfort, vertigo, nausea, and dizziness, because their bodies (which are static) and their eyes (which view moving images) provide conflicting information to their brains (Lawson, 2014). This situation, although a temporary one, severely impairs their cognitive abilities and negatively affects the learning outcomes (Rupp et al., 2019). An additional problem is the weight of some HMDs, which can cause discomfort and/or fatigue (Broeck et al., 2017). Other issues mentioned in the literature are the instability of the video and lagging (it takes a few milliseconds between the turning of the head and the display of the corresponding part of the scene) (Martín-Gutiérrez et al., 2017). Students are sometimes distracted by the novelty of the experience (Rupp et al., 2016) and do not pay attention to what they are supposed to learn (Karageorgakis & Nisiforou, 2018).
Research regarding the use of 360 o videos in PE and in sports is rather limited; therefore, the results of the relevant studies have to be viewed with some caution. They were used for PE teachers' training (Roche & Gal-Petitfaux, 2017), with the authors concluding that the participants considered them effective tools for monitoring students' performance. In another study regarding the usefulness of this tool in sports journalism (Delmazo, 2018), they proved to effectively convey to viewers the intensity of the effort of para-Olympics basketball players. In a number of studies in which 360 o videos were used for improving athletes' decision-making skills in team sports, such as basketball (e.g., Pagé et al., 2019;Panchuk et al., 2018) and football (e.g., Kittel et al., 2020), the results were mixed. On one hand, participants enjoyed the experience and had a positive attitude towards their use. On the other hand, the results in terms of acquisition of skills were not that different from the ones that were achieved from the use of a virtual reality application (Pagé et al., 2019) or conventional training (Panchuk et al., 2018). The results were similar in the study of Kittel et al. (2020) but the authors noted that the retention of skills over time was better with the use of 360 o videos.

Method
As we presented in the preceding sections, although research on the educational uses of 360 o videos is still at its early stages, the literature suggested that they constitute an interesting alternative teaching tool, applicable in a wide range of settings and disciplines. Having the above in mind, we decided to implement a pilot project in order to examine their impact on the teaching of skills related to PE. Out of the various sports, we selected volleyball, as it is among the ones that are not systematically taught (at least in Greece). As we were interested in comparing the results from the use of 360 o videos with conventional teaching, we followed a two conditions/treatments between-subjects design, meaning that we had two groups of students who were taught the same subjects using two teaching tools/methods (conventional teaching-control group and 360 o videosexperimental group). We set the following research hypotheses: H1. Compared with conventional teaching, 360 o videos are more effective in teaching primary school students skills related to volleyball.
H2a-e. Compared with conventional teaching, primary school students consider 360 o videos as being more (a) useful, (b) motivating, and (c) a more enjoyable experience.

Sample and duration
Given that in Greece's primary schools volleyball is usually taught at the last grades, we decided the participants to be eleven-to-twelve years-old students. We communicated with several public primary schools located in Komotini, Greece and we asked their PE teachers to provide some data for their students, which would help us to form an ordinary and typical sample (Creswell & Creswell, 2017). As a result, we selected two classes, each having twenty students (twenty-one boys and nineteen girls), who: (i) had never before been formally taught skills related to volleyball, (ii) had no prior experience in using HMDs, and (iii) the boys to girls ratio was close to the national ratio. To ensure compliance with the ethical standards and research guidelines, we applied for and we were granted a research approval from the University's ethical committee. Also, we asked for students' parents written consent, following a briefing regarding the study's objectives and methods. The duration of the project was six two-teaching-hour sessions (three for each tool).

Materials
The development of the project's materials was a multi-stage process that lasted several weeks. The first step was to select which volleyball skills to teach. We decided to avoid teaching rules and tactics or to try to improve students' general physical skills; we deemed that it would be better to focus on basic moves that are relatively easy to quantify how well they are executed. By doing so, it would be easier for us to measure the interventions' outcomes. Consequently, we selected the setting, passing, and underhand serving as the project's subject matter. The next step was to search for suitable, ready-made, and freely available multimedia material. While we were able to find some regular videos, photos, and figures, we did not find any 360 o videos relevant to the project. Therefore, for each of the three moves, we recorded several video-clips, using fairly cheap 360 o cameras. We have to note that we recruited professional volleyball players to demonstrate the moves, so as to ensure that each was perfectly executed and also because literature suggested that this contributed to the better understanding of sport-related skills (Magill & Schoenfelder-Zohdi, 1996;McCullagh & Caird, 1990;Zetou et al., 2002). Not only that, but we recorded each move from three different angles (Figure 1). By doing so, together with the fact that, by default, in 360 o videos, it is possible to zoom in and out, the viewer would be able to observe each move in much greater detail than in a regular video. The next step was to edit the recorded video clips, add voiceovers and subtitles. Following that, the videos were imported to 3D Vista Virtual Tour (https://www.3dvista.com/), for adding multimedia, as well as interactive features, and for the development of apps that could run on smartphones. This relatively easy-to-use software allows the development of apps which are, essentially, virtual guided tours. Hotspots were added allowing the transition between different scenes and the display of images, texts, and regular videos, which provided additional information for the move that was demonstrated (Figure 2). Out of the available methods to trigger these hotspots, we selected the "gaze" technique. In essence, for triggering an event, this technique requires users to focus on a certain area/hotspot and hold their position for about two seconds. Three apps were developed using this software, one for each move. Five sixth-grade students (who did not participate in the study) used the apps. On the basis of their comments, we re-edited some parts of the apps.

Figure 2. Screenshots from the development of the apps
For viewing the 360 o videos/running the apps, the participants used their smartphones together with HMDs similar to Google Cardboard (which we provided to them). Google Cardboard is a low-cost system made out of cardboard or plastic with just two lenses and a compartment in which a smartphone is inserted. While they are not actual HMDs, as they do not have any electronics, Google Cardboard and its clones provided access to 360 o videos and virtual reality applications to millions of users (Martín-Gutiérrez et al., 2017).

Instruments
For collecting data, we used an observation protocol. For that matter, each of the three volleyball moves/skills included in our study was broken into smaller easy to observe segments (Table 1). Two individuals acted as raters (a teacher and a researcher), simultaneously collecting observational data (i.e., whether each segment of the volleyball move/skill under examination was executed correctly). We trained them both in two sessions prior to the beginning of the project, by asking them to observe ten students (who did not participate in the study), who repeated each move for five times. We assessed the consistency among the raters using Cohen's kappa coefficient and we found it to be very good [κ = .89, p < .001, 95% CI (.87, .91)] (Landis & Koch, 1977). During the implementation of the project, the participants were observed twice for each move/skill, once prior to the intervention and once right after it. In both cases, they were asked to repeat each move five times. The raters added a point when all the segments of a move were executed correctly; otherwise, no points were added to the participant's scores. For examining H2a-c, we used a questionnaire that was based on a validated modular scale designed for examining digital educational applications (Fokides et al., 2019). We selected three of its factors, which corresponded to H2a-c, namely, fun/enjoyment (six items), subjective usefulness (six items), and motivation (three items). In this scale, all items are presented on a fivepoint Likert-type scale (ranging from 1 = strongly disagree to 5 = strongly agree). We administered this questionnaire to both groups at the end of all interventions.

Procedure
Prior to the beginning of the project, in order to avoid technical problems and/or usability issues, we took a series of measures. First, we demonstrated to students participating in the experimental group how to use their smartphones together with the Google cardboard compatible HMDs. Following that, we installed an app on their smartphones. Although it was not relevant to the project, its structure and interactive features were similar to the ones developed for the project. Next, students were allowed to practice for about an hour and a half, for familiarizing themselves on how to handle the equipment, as well as on how to navigate and use the app. At the end of the familiarization period, we checked whether they were competent enough in using both the HMDs and the app. Each of the project's apps was installed on students' smartphones right before the corresponding intervention. For example, the app demonstrating the underhand serving was the last one to be installed, given that this move/skill was demonstrated during the third and final session.
At the beginning of each session, the participants (regardless of the group they belonged to), were individually asked to perform five times the move/skill that was the session's subject. For example, they were asked to perform a pass, the way they thought it should be done. While doing so, the raters observed them, following the protocol we presented in the preceding section. The reason for this was to collect data regarding the initial students' skills for the given move. Next, depending on the group, the students either used the app or the PE teacher explained and demonstrated the move. In any case, students were allowed to use the apps for three times, which were considered enough for grasping the basics of the move. The same applied for the control group; the PE teacher explained/demonstrated the move three times. Following that, students were asked to perform, once again, for five times the move that was presented to them. At the same time, the raters observed whether the move was correctly performed, as they did at the beginning of the session.

Results
Although forty students were enrolled in the project, we had to exclude four of them because they were absent in one or more sessions. We averaged the score of each student in each move and we imputed the resulting data into SPSS 26 for further analysis. Table 2 presents descriptive statistics for each move/skill. After checking that the data were suitable for one-way ANOVA testing (we found no violations of the assumptions), we conducted a series of these tests for determining whether there were differences between the experimental and the control group. The results demonstrated that there were no differences in the pre-intervention observation sheets (p = .106, .421, and .106 respectively) (Table 3). This means that any differences we were to find in the post-intervention observation sheets could be attributed to the different method/tool we used. Indeed, we found statistically significant differences in all the post-intervention observation sheets (p = .002, <.001, and .008 respectively), indicating that the students in 360 o videos group had better results in the three moves/skills we examined. Thus, we can confirm H1. We checked the questionnaire's overall internal consistency, as well as the reliability of the three factors, using Cronbach's alpha. In all cases, we found α to be very good, as it was well above the recommended value of .70 (DeVellis, 2003) (ranging from α = .785 to .811 for the factors and αoverlall = .804). We present descriptive statistics for the factors included in the questionnaire in Table 4. For analyzing the data, we followed the same procedure as in the observation sheets. We found no statistically significant differences subjective usefulness (p = .800) ( Table 5). On the other hand, we found a statistically significant differences in fun/enjoyment (p = .002) and motivation (p = .003), indicating that students in the 360 o videos group had more fun and were more motivated to learn than in the control group. Given the above, we have to reject H2a, while we can confirm H2b and H2c.

Discussion
The data analysis we presented in the preceding section confirmed our main research hypothesis, namely, that 360 o videos are more effective in teaching primary school students volleyball skills compared to conventional teaching. We can draw some interesting conclusions from our results, as we elaborate in the following paragraphs.
An interesting observation comes from students' scores in all the pre-intervention observation sheets. Depending on the skill that was tested and on average, they were able to correctly perform 1 up to 1.9 moves (out of five attempts per move) (see Table 2). Taking the results in the pre-intervention observation sheets as reference points, the results in the post-intervention observation sheets indicated a significant positive change, ranging from 70 up to 106% for conventional teaching and from 85 up to 144% for 360 o videos. Whether these outcomes, in relation to the effectiveness of 360 o videos, can be characterized as satisfactory, is a matter of debate. In fact, two opposing views can be supported. On one hand, some might argue that the positive effects of conventional teaching cannot pass unseen. Moreover, a skeptic might add that these results were achieved without using a "fancy" technology (such as 360 o videos), without investing valuable time for the development of the relevant apps, and without additional costs (for purchasing HMDs). Moreover, the improvement of motor skills depends heavily on the repetition of exercises and recurring training (Zahradník & Korvas, 2012). In this respect, conventional teaching is an effective method that hardly needs to be reformed. On the other hand, some might argue that even the slightest positive change in the outcomes of training of motor skills is important (which is even more important when athletes are involved). In a way, the above arguments reflect the ongoing -and still unresolved-debate on the educational value of almost all ICTs, which is beyond the scope of our study. Nevertheless, the fact that we noted statistically significant differences between conventional teaching and the use of 360 o videos, in favor of the latter and in all the three skills/moves we tested, allows us to support their integration into teaching.
Therefore, what we have to discuss is why the results of our study were in favor of 360 o videos. Generally speaking, the results confirm the findings of several other studies regarding the effectiveness of this technology in several learning domains (e.g., Berns et al., 2018;Chang et al., 2019;Parmaxi et al., 2018). Our findings are also in line with past research that stressed the importance of videos in PE, as they allowed the better visualization of skills/moves (e.g., Palao et al., 2015;Robinson, 2011;Weir & Connor, 2009;Zetou et al., 2002). Thus, we can argue that 360 o videos are also effective in visualizing PE related skills/moves. Quite interestingly, our findings contradict the ones of past research in which 360 o videos were used in the context of PE or sports (e.g., Kittel et al., 2020;Pagé et al., 2019;Panchuk et al., 2018). That is because these studies reported that 360 o videos produced similar outcomes with that of virtual reality applications or conventional training. Then again, we have to stress that it is rather hard to compare the results of our study with the above-mentioned studies, given that they focused on the improvement of decision-making capacities while we focused on the acquisition of skills. Although decision-making is an important perceptual process that determines the effective utilization of motor skills, however, it follows, methodologically, the learning of motor skills. Moreover, these studies had athletes as their target groups and not primary school students.
Yet, in line with previous studies (e.g., Chang et al., 2019;Huang et al., 2019;Lee et al., 2017), we found that students were more motivated to learn than in conventional teaching and had a more enjoyable learning experience. Consequently, motivation offers a plausible explanation for our results, as it directly (and positively) affects the learning outcomes in almost all teaching subjects (Fokides, 2017;Fokides & Atsikpasi, 2018). The same applies for enjoyment; it is as a rather common finding in most research regarding the educational uses of 360 o videos, positively correlated (together with motivation) with the learning outcomes (e.g., Chang et al., 2019;Huang et al., 2019;Rasheed et al., 2015).
Unfortunately, our research hypothesis that students will find 360 o videos as being useful tools in their learning of volleyball related skills was rejected. We set this hypothesis on the basis of past research which indicated that participants have a positive attitude towards the use of 360 o videos (e.g., Kittel et al., 2020;Panchuk et al., 2018). A plausible explanation for this outcome is that students' pre-existing learning stereotypes inhibited their acceptance of 360 o videos. Students are not trained using similar innovative educational means; therefore, the use of 360 o videos was viewed as a deviation from what they are familiar with, making them a bit reserved. Moreover, we think that this result has to be considered together with the teaching framework we selected. We deliberately applied the commonly used method of commands as a teaching style to both groups, in order to avoid a possible impact of the teaching method on the results. Then again, literature suggested that constructivist, student-centered teaching frameworks are better suited when 360 o videos are used (Fokides & Kefallinou, 2020). In this respect, the results related to the subjective usefulness of 360 o videos, might have been better, if we had allowed students to be more actively involved in the learning process by using a different method, for example, self-check or guided discovery (Mosston & Ashworth, 2002).

Implications for research and practice
The contribution of our study lies to the fact that it extends the -rather limitedliterature regarding the educational uses of 360 o videos given that we (i) examined the learning of sports-related skills with the help of this technology and (ii) contrasted the outcomes with that of conventional teaching and quantified their differences. The study's findings might have implications that could be of interest to researchers, software development experts, and educators. For example, we found that students did not consider 360 o videos as being useful tools for learning the skills we tried to teach them. While this finding was rather surprising, as we elaborated in a preceding section, one should probably consider how to avoid this issue. One way to attract the interest of students is by adding game-like features to the apps, a solution that is applicable to most ICT tools (Fokides et al., 2019). On the other hand, caution is advised. That is because there is always the chance the novelty of the experience 360 o videos offer, to overwhelm students, distracting them from the learning content (Rupp et al., 2016). The addition of game-like features might amplify this problem. Improving usability, in terms of user navigation and interaction with the apps, might also help. In our study, the hotspots were triggered by focusing on them. Hand tracking would have allowed a more natural interaction method (Miller & Bugnariu, 2016), although this would have required additional hardware (and costs).
There are also several issues that need to be tackled if we are to successfully introduce 360 o videos to PE. The first, and by far, the most important issue is the lack of relevant apps. Finding freely available 360 o videos or even recording your own is one thing, but there is a considerable distance between that and developing pedagogically and technically sound apps. Even though on the basis of the experience we gained in this study, we can support that it is not that hard to develop apps in which 360 o videos are embedded, it is questionable whether PE teachers have the expertise, the will, and the available time to do so. Therefore, we recommend education policymakers and administrators to take action with the objective of making available a large pool of ready-made apps to PE teachers. Certain ICT tools (including HMDs and 360 o videos), in order to be successfully integrated and properly used in everyday teaching, require time. It is rather unrealistic to use such tools in just one teaching-hour, considering that technical problems might arise, students have to become familiar with the tools, and the teaching framework has to be adjusted. Therefore, primary school's timetable and program of study have to be reformed and become more ICT friendly.

Limitations and future research
Although the results quite clearly demonstrated that 360 o videos have a positive impact on the acquisition of volleyball related skills, the study has certain limitations that bear mentioning. The sample size, although adequate for the statistical procedures we followed, could have been larger; a more diverse age range could have been included as well. Moreover, we focused on a handful of volleyball skills, covering just a fraction of PE related subjects. Quite logically, one might have reservations for the generalizability of our results. PE is not just about knowledge and skills; attitudes and behaviors are also important. Alas, we did not examine the impact of 360 o videos on the above. Then again, we have to stress that the study was highly exploratory in nature; 360 o videos are an emerging technology and research on their educational uses is still at its early stages. Nevertheless, the limitations we mentioned above can act as guidelines for future research endeavors. The opinions, experiences, and attitudes of PE teachers towards the use of 360 o videos during their teaching, are also interesting research subjects. The examination of a teaching method that will frame the use of 360 o videos in PE would be extremely useful. Finally, it would be interesting to contrast the impact of 360 o videos with that of other promising technologies (e.g., fully immersive virtual reality).

Conclusion
Nowadays, the importance of PE is emphasized, given that active participation in physical activities has become a necessity. This highlights the need of finding innovative methods that can effectively facilitate the acquisition of the relevant knowledge and skills, including the ones related to team sports. Videos are quite commonly used in training and PE. Given that (i) 360 o videos are the next step in the evolution of regular videos, (ii) they constitute an interesting alternative teaching tool, applicable in diverse teaching frameworks and domains, and (iii) research on their use in the context of PE is rather limited, we implemented a pilot project in order to examine whether they can be effective in the teaching of basic volleyball skills to primary school students, by comparing their impact with conventional teaching. Indeed, the results revealed that students who viewed 360 o videos performed better. Thus, it can be concluded that 360 o videos are, under certain circumstances, an effective tool in the context of PE. Their effectiveness can be attributed to the fact that they immerse users in a pleasant and motivating environment. While the study might prove useful to both PE teachers and researchers, there are unresolved issues in relation to the usability of 360 o videos, the features that have to be included in the apps utilizing them, and to the changes that have to be made in schools' program of study and timetable. In conclusion, the educational potential of 360 o videos and the added value they can offer to PE is still unexplored. Thus, there is room for many future studies in this field.