Many facets of human existence have been altered by digital technology and sports, including football. Football training and coaching are crucial to developing player skills and success in the sport. Drills, physical exercises, and tactical discussions are common components of traditional training techniques. However, there is significant interest in introducing virtual reality (VR) technology into football training and instruction to transform the sport. VR provides an immersive and engaging experience that allows players to train in realistic game settings, evaluate their performance, and receive instant feedback. A constructed Virtual Environ-ment (VE) allows participants to interact with 3D computer-produced models in real-time while using their natural senses and talents [1].

In football training, player activities in a sporting environment are usually time-limited, one-of-a-kind, complicated and rely on visual clues gathered from their surroundings [2, 3]. Players' performance is determined by their perception as well as their ability to predict and execute skills under time restrictions [2]. As sport is perceptually demanding, visual-perceptual and visual-motor abilities are frequently emphasized in training programs [4]. Coaches and players desire to enhance these skill sets for competitive performance and to do so, they are embracing new technology to gain an advantage through improved training procedures [5].

Before VR technology was widely used, video-based training (VBT) was a kind of practice in which videos were used to offer stimuli that required participants to make perceptual and cognitive judgments [6, 7]. Approaches included viewing and simulating video sequences of matches [8, 9], obstructing action sequences, and providing participants with feedback on the correctness of test outcomes [10, 11]. VBT allowed learners to practice skills without performing them [12]. It expedited the development of perception-cognitive abilities, especially in sports like football, that call for continuous engagement [13]. Match broadcast video was commonly used in VBT, but it was often criticized for its lack of fidelity [14]. VR was used in training to ensure that training activities represented real scenarios [13, 15]. By enhancing the visual correlation of video simulations, VR improved viewers' immersion [16]. VR has also been recognized as a new VBT technique [17].

Simulations are often computer-based. Using a software-generated model to support managerial and engineering decisions, as well as for training reasons, the models are both visible and interactive. Simulation approaches enhance learning and experimentation. In the conventional understanding, VR is to have a high immersion experience, but currently, it is difficult to widely popularize it with high immersion and high interaction experience in the field of training. Simulation technology has a wider scope and can be widely developed in the field of training; for example, screen-based simulation training is often used in training football and perception-cognitive and decision-making; therefore, we did not choose VR as a theme.

Simulations are inherently ‘virtual’; the objects being simulated are mostly software-generated artefacts. However, we observed a tendency in many published papers to add a ‘virtual’ label to simulations that are clearly already virtual. It was further discovered that some authors recently tried to distinguish between simulations using real objects, for example, games using real players in test scenarios, and supposedly ‘pure’ simulations using entirely synthesized objects, which were labelled ‘Virtual Simulations’. However, simulations using computer modelling to simulate scenarios for multiple purposes have been used for decades and have, logically, considered these simulations to be virtual, without the need for any unnecessary term elevation. Thus, we have followed traditional use and eschewed the addition of ‘virtual’ throughout the paper and simply referred to ‘simulations’.

Simulations have four types [18], which are as follows:

1) Telesimulation: A technique for delivering instruction, training, or evaluation to students at a distant place using telecommunication and simulation resources [19].

2) Cave Automatic Virtual Environment (CAVE) (Immersive): A cube wall construction with projected graphics allows a person to stand inside it to experience an immersive virtual environment. Participants may use special goggles within the CAVE to simulate depth with stereoscopy [20].

3) Extended Reality (Immersive) (XR): A synthesis of all realities, including Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR), XR creates technology-mediated experiences made possible using a wide range of hardware and software, including sensory interfaces, applications, and infrastructures. XR is referred to as immersive video material, improved media experiences, and interactive and multidimensional human encounters [21] (XRSI.org, X Reality Safety Intelligence).

4) Screen-Based Simulation (Non-Immersive): It is an interactive simulation in which the user interacts with the interface via a keyboard, mouse, joystick, or other input device. It is a simulation that is shown on a computer screen with graphical pictures and text, akin to a popular gaming format.

There have been many reviews on simulation technology-assisted sports training in recent years. Yunchao, Mengyao, and Xingman (2023) systematically reviewed 10 papers published until December, 2022. They systematically reviewed simulation technology used in sports decision training and found that it simulated sports decision-making activities as well as used in assessing and analyzing player decision-making abilities [22]. Further studies demonstrated how useful virtual reality was as a tool for evaluating decision-making. Farley, Spencer, and Baudinet (2019), in their review, noted that VR technology was becoming increasingly used in competitive sports, with an obvious impact on gathering numerous physiological elements, recognizing and strengthening sensorimotor skills, immersing players in competition settings, where response speed was essential, and enhancing skill development [23]. As a result, technological improvements and approaches will have a continuing impact on how coaches focus on building capacities that contribute to the performance of athletes in all sports. Putranto et al. (2023) analyzed 30 papers on the implementation of VR technology for sports education and noted that although VR was used to improve individual athlete performance, it worked better as a valuable tool for coaches and teams to design strategies or tactics; they recommended re-evaluating the design of the head-mounted displays to construct head-mounted displays that are lighter in weight, more comfortable, and provide users with broader motor access. They have the potential to increase the use of VR technology in sports teaching and training [24].

Neumann et al. (2018) found that a VR-based system for training and participation has several advantages, including allowing athletes to train regardless of weather conditions, providing an opportunity to compete with others in a different geographic area, and allowing precise and repeatable control over the characteristics of the virtual environment [25]. Miles et al. (2012) studied virtual environments (VE) for training in ball sports and concluded that improving motor control abilities in ball sports was effective. Anticipation and decision-making abilities could also be trained in a VE, and the task's intensity could be gradually raised. They believed that this field would expand rapidly, with more examples emerging from research laboratories and being adopted by professional sports organizations [1]. Thatcher et al. (2020) observed that VR exposed players to components of play that they would not be able to practice easily in a real-world situation, bridging skill gaps and speeding up player improvement. Moreover, academy players could use VR to build and assess decision-making skills. An emerging topic for the study was the potential for VR applications in rehabilitation and recovery [26].

Zhao et al. (2022) discussed 10 papers on video-based training (VBT) on anticipation and decision-making in football players. Their summary supported the idea that VBT helped football players by increasing their ability to anticipate and make decisions [27]. They suggested that virtual video and 360 VR were more reliable representations of players' real on-field performance. They further suggested that future studies should consider factors, including weariness, anxiety and off-field noise, that might affect match activity. By including these potential variables that might impact match performance, the realism of a simulated task was assured. Finally, when using VBT, they noted that it was essential to take into account how the training would be applied to on-court performance.

Simulation technologies cover many categories, and there are many studies on simulation technology in sports training, including football. At present, there is no systematic review of the application of simulation technology in football training. Thus, this review presents a critical overview of simulation technology for football training, focusing on the characteristics of simulation technology, experimental process, benefits and challenges of simulation technology. The following research questions guided this review:

1) What were the characteristics of simulation tech-nology?

2) What were the experimental processes?

3) What were the benefits and challenges of simulation technology in football training?

We used the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology for this review [28]. We searched the following electronic databases: Web of Science, SPORTDiscus, Google Scholar, and Scopus. Our search strategy combined topic, abstract, and keywords. Boolean operations were used for the majority of online searches. The main process for finding appropriate articles follows with some operators adjusted to fit database search expressions:

(“Video-based” OR VR OR Virtual OR Simulation OR Simulator OR “Screen-based” OR Immersive OR CAVE OR 360 OR 3D)

AND

(Football OR Soccer)

AND

(Training OR Coaching OR Teaching OR Playing OR Learning OR Train OR Coach OR Teach OR Play OR Learn OR trainer OR Instructor OR Teacher OR Player OR Learner).

The search language was constrained to research articles in English published between January, 2014 to July, 2023. We analyzed the articles for exclusion or inclusion in two steps: based on the title and abstract and then based on the full article.

The basic information of 18 eligible articles, including publication period, characteristics of simulation technology tools, research process (including research design, experimental subjects, and research results), as well as the benefits and challenges of simulation technology for football teaching, are summarized in Tables 1 to 3. From the perspective of time, although nearly 10 years of papers were searched in this review, the research in this field was concentrated in 2020-2023, with 16 relevant studies since 2020 and only two relevant studies before 2020, which showed that research in this field witnessed strong expansion in the last three years.

Among the 18 selected articles, simulation technology was applied to football training. The purpose of these articles was to conduct virtual training for participants through simulation technology or use simulation technology as a test platform to measure the ability of athletes in some aspects. Most of these articles first designed simulation tools and then conducted empirical research to diagnose and investigate the effect of simulation tools applied to football training. The focus of this systematic review was to study the empirical research process of the selected articles. These 18 articles all included quantitative analysis, and most were completed in a short period of time on a small scale. The participants were mainly professional or semi-professional football players.

It should be noted that the empirical evidence presented in this section is not exhaustive. Despite the fact that we searched the most well-known academic sites for keywords related to simulation technology in football training, the searching and screening processes might have been biased. Other journals and databases may have research works that are relevant. However, our research has been sufficient to comprehend the current research status and challenges associated with the application of simulation technology to football training, and we may provide helpful ideas for future research directions.

From the classification of simulation tools (Table 1), of the included studies, nine used Head-Mounted Display (HMD), two used CAVE, and seven used screen-based simulation.

From the description of simulation tools, of the nine studies using HMDs, eight studies used head-mounted displays (HMD), and one used stereoscopic glasses. HMD is a display device that is worn on the head or as part of a helmet and has a small display optic in front of one or both eyes [29]. Fig. (2) presents a VR training platform for football. Two studies used CAVE, CAVE is an immersive virtual reality environment where projectors are directed to between three and six of the walls of a room-sized cube (Fig. 3). For the 360° simulator, seven studies used screen-based simulation; the training content was developed after collecting real football match situations by computer, and the training or testing used a computer screen or video screen.

Fig. (1). PRISMA four steps selection.

Fig. (2). VR training platform for football. Available online under the under the terms of the Creative Commons Attribution License (CC BY) [30].

Fig. (3). 360° simulator. Available online under the Creative Commons Attribution-Non Commercial-NoDerivatives CC-BY-4.0 License [31].

From the interactive characteristics of simulation tools, of the 9 studies using HMDs, virtual reality headsets are HMDs combined with inertial measurement unit (IMU), so the tracking motion capture system is used for real-time feedback on user participation to achieve interaction. Of the 2 studies using CAVE, one of the studies used a tracking motion capture system [31] and another study interacted with the screen via a hand controller [32]. Of the 7 studies that used screen-based simulation, participants of four studies interacted directly with the screen via sensors (including mouse, tap on the screen, handheld response devices or gamepads) and participants of three interacted orally or in writing.

From the functions of simulation tools, seven studies used the tools for training or assessing player’s basic football skills, including training heading [33] [34], measuring reaction speed [35] or executive functions [30], evaluating movement variability [36], and assessing skill levels [37] and goalkeeper [38]. Ten studies used the tools for training or assessing player’s perceptual cognition and decision-making, including training and assessing perceptual-cognitive skills [31, 32, 39-42] or training or assessing decision-making skills [8, 43-45]. There was also a very special study that used football PES (2021) as a tool to develop players’ tactical thinking [46].

A summary of the experimental process is given in Table 2. All studies were true experimental and quantitative research. Most of the studies used tests to measure the results, a few studies used a combination of tests and questionnaires, and only one study used a questionnaire. A representative study compared experimental and control groups, by pre-test and post-test, to measure heading performance [34]. A representative study analyzed the difference in cognitive ability of different age groups after training intervention [31], and a representative study tested the response of participants to the different intensities of the intervention stimulus [41].

By summarizing the age and gender of participants in the 18 studies, we found that most of the subjects were young players, and no studies compared the performance of males and females. The youngest group was 12-13 years old football players [33].

Comparing the experience levels of the participants with the key findings of the study, we found that in the studies on training or assessing perception-cognitive and decision-making, the experience level of the participants was generally above the professional or semi-professional level, but in the studies of training or assessing motor skills of football, the participants were mostly amateur players.

From the key findings of the studies, we found that simulation technology significantly improved performance. A screen-based simulation was found to be beneficial in improving decision-making skills [41, 45], and the more advanced the athletes were, the better their decision-making skills [8, 44], and this ability improved with age. This made the tool of evaluating the decision-making skills of athletes a reference method for coaches to select talented players [43]. While HMD was more beneficial in enhancing the motor skills of football players, for example, VR training for goalkeepers improved their virtual goalkeeping abilities for a brief period of time [35]. VR training system gave feedback on the skill of the goalkeeper [38], and an experimental group significantly improved their heading performance [34]. Therefore, a VR application can be used as an alternative training for football-specific heading skills [33].

There were two CAVE articles considered in this review, and although the sample size was small, both of them demonstrated the perception-cognition effect of simulation technology in CAVE on football players. The CAVE test can be used for talent identification and the general assessment of cognitive abilities [31]. These results emphasized the importance of perceptual-cognitive skills for talent development and provided information for research and practice in perceptual-cognitive diagnostics in youth soccer [32].

From the key findings, it was also found that, in some studies, participants were surveyed about their emotions and motivation in training. VR training significantly improved perspectives of confidence in general heading ability and raised perceptions of self-efficacy [34]. Gamification had a significant favorable impact on the establishment of interest and motivation to play football [46].

By summarizing the benefits of simulation technology (Table 3), we found the following benefits for the players: it provided immersive training in a fully virtual environment with no time and space constraints and low training risk [30, 34, 46], it allowed injured players to maintain a level of perceptual-cognitive skill [37], and it was easy to use through a computer [8]. Following are the benefits for coaches: it provides an additional instrument for player scouting and development improvement, promoting talent discovery and selection in football [31, 43]. Moreover, it was a supplement to regular football training [45].

By summarizing the challenges of simulation technology, we found that the long-term effects of training were not clear [40, 45]. The current results were not replicated in a verified real-world environment, as they did not reflect the real training and competitive environment [32, 35]. During body rotation or movement, participants worried that the hardware (cable) affected them [39]. It did not accurately reproduce a first-person perspective [42]. Moreover, there was a lack of theoretical and empirical justification for the included training tasks [30].

We summarized the following perspectives on the application of simulation technology in football training. The most significant benefits are its ability to generate realistic game scenarios and replicate match conditions, training, and testing in this virtual environment, which brings new training methods to coaches and athletes as a supplement to traditional training. The current studies reported that it allows players to work on specific technical skills in a focused and repetitive manner, and the instant feedback provided by the simulation software allows players to discover areas for improvement and make adjustments that are needed to improve their abilities. Injury prevention and rehabilitation can also benefit from simulation technology. Players can simulate game movements and practice techniques using VR headset displays and motion-capture systems without putting undue strain on their bodies, creating a safer training environment and lowering the risk of injury. Furthermore, simulation technology created scenarios that challenged players to analyze game dynamics, anticipate opponents' moves, and make appropriate decisions. This helps enhance the players' tactical acumen and ability to adapt to different game situations, which challenges their mental abilities, such as perception, attention, and memory, ultimately improving their ability to process information and make quick decisions on the field. Finally, the interactive nature of simulation technology can increase engagement and motivation among football players and the realistic visuals and game-like experience of simulation training can make training sessions more enjoyable and engaging, leading to improved focus and effort from the players.

There has been some discussion about the use of simulation technology in football training in other studies. The VR platform has the potential to be used during the rehabilitation of injured football players who need to maintain a level of perceptual-cognitive skill while avoiding the physical stress experienced in real environments. VR has been shown to increase enjoyment, adherence to rehabilitation exercises, and confidence [47]. A VR digital gaming platform for teaching football skills might be useful during the rehabilitation of injured football players who need to keep their perceptual-cognitive skills while avoiding physical exercise [37]. Virtual technologies may be used to simulate real-life sporting environments, allowing players to play without worry of hurting themselves, recognize the details of each technical behavior, and examine their movements for miniature errors [48]. The advantage of using virtual reality to instruct sports skills is that it gives the user a sense of involvement and is an effective eye-hand coordination training solution that combines perception and action. VR offers an appealing option for a better understanding of the athlete perception-action process [49]. It allows players to practice decision-making in a controlled environment, which improves their under-standing of tactical situations and the ability to make quick and effective decisions on the field. It indicates that simulation technology can help football players develop tactical awareness and decision-making skills [27]. Sports video games can be an effective tool for motivating young individuals to engage in real-life sports and physical activity since they have a significant impact on cognitive engagement, affective engagement, behavioral engagement, and accessibility, all of which are strongly linked to real-life sports participation [50].

While simulation technology has been shown to be beneficial in football training, it is not without limitations and challenges. These elements must be taken into account to ensure effective implementation and maximize the potential impact.

Simulation technology allows players to practice technical aspects, such as heading, shooting, and tactics, but it cannot simulate the physical demands and challenges of real-world match scenarios. Football is a contact sport, in which players must show skills while under pressure from opposing players, making it difficult to fully simulate these aspects in a virtual setting. Even if players excel in simulated training, it is unclear how well those skills translate to real-world scenarios. Transferring skills learned in a controlled virtual environment to actual matches can be ineffective because it does not accurately reflect the real training and competitive environment [32]. Even without pressure from the opposing player, simulating the demonstration of a skill or decision while running or jumping is rare in existing research. Therefore, the practice in the virtual environment is not very helpful to professional athletes at present. This is a direction worth studying in the future, and the training environment that combines virtual and reality may better meet the training requirements.

It cannot accurately replicate complex decision-making processes. In order to succeed in football, players must quickly assess a variety of options and react to changing circumstances. Even though they can present some decision-making difficulties, simulations frequently lack the spontaneity and unpredictability of actual match scenarios. This restriction might make it more difficult for players to adjust to a real game’s dynamic nature. Additionally, it lacked practical application and failed to maintain the functional coupling between perception and action [41].

In terms of HMD, it is highly immersive VR. Due to the need for a lengthy cable trailing from the headset to transmit the visual data, HMDs have been claimed to disrupt a user's physical activities. Some are heavy and cumbersome, which may distract the user [51]. It was eventually overtaken by more user-friendly wireless VR headsets. Still, HMD users are unable to see their own hands, requiring the use of an avatar, which might lead to latency concerns [51]. Within such an environment, it is necessary to keep the athlete's constraints to a minimum and provide them the flexibility of movement they would enjoy in such situations. Despite all the advances in virtual reality technology, for example, the reduction of latency in devices, such as HMDs, symptoms of cybersickness can still recur in a wide range of people. As a result, using VR for sports analysis and skill acquisition has its limitations, just like any other training method, and some aspects must be perceived or implemented in a real-world environment.

In terms of screen-based simulation, since it focuses primarily on visual and cognitive processing, it might not accurately mimic the physical demands and muscle memory formation needed in real-match scenarios. The development of motor skills and real-time physical feedback are not adequately addressed by video analysis despite its potential value for tactical learning and understanding of game patterns. Due to the simulator's low immersion level, screen-based simulations may cause attention problems and a lack of first-person perspective [42].

Many studies report difficulties related to exposure time in immersive simulation environments. Although there were no problems caused by prolonged exposure to simulators reported in the studies we selected, this is an aspect worth explanation and consideration. To solve the difficulties related to exposure time in an immersive simulation environment, it is necessary to consider optimizing hardware, control of exposure time, training user adaptability, and individual differences. This can improve the usability and user experience of simulation technology in football training.