Bibliometric analysis and visualization of online education in sports

Abstract The study focuses on how online education is used in the sphere of sports from 2001 to 2022. Especially in the era of COVID-19 popularity, the deepening cross-fertilization between the field of sports and other fields, coupled with the fact that scholars have not yet analyzed and organized the areas in which online education is combined with sports, and what opportunities there will be for the development of online education in the field of sports. In this article, it summarizes the past two decades of research with bibliometric and scientometric research methods, quantitatively exploring the development paths, research hotspots, and evolutionary trends in the field under the online medium, and systematically integrates the field through knowledge mapping to suggest and indicate the development process for the combination of the sports field and online education. The information of authors, keywords, and the number of national publications are used to determine that online education will continue to be studied in the field of sports with high explosive keywords such as children, online education, and COVID-19. This will provide suggestions and directions for the development of the sports field and online education.


PUBLIC INTEREST STATEMENT
In the previous 20 years, particularly during the Covid-19 period, online education has achieved its pinnacle in numerous sectors, and the sports field need not be an exception. Online education in sports has become a method of delivery. The scientific validity of Pierce's Law and Pavlov's Law is further confirmed in this regard by a systematic review of the research hotspots and future trends of online sports education in recent years, as well as by an analysis of keywords, authors, countries, timeline graphs, and outbreak words in the industry.

Introduction
Online education, also called e-learning, blended learning, and online education are all used interchangeably and have numerous replacement concepts (Sun & Chen, 2016), it is a way of learning knowledge in a network through the form of the internet. Whereas its use only began in 1995, it has also taken a long time to evolve from its humble beginnings as a learning management system to what is now known as Blackboard (Bates, 2014). For such a long time, through a study of two decades of definitions of online education between 1988 and 2018 found that the main elements in the definition of online learning were technology, time, and synonyms (Singh & Thurman, 2019). This is because, with the development of online education, learners can choose the content of online courses and find it on their computers according to their needs (Saul Carliner, 2004) and also found that this online education model has many advantages over face-to-face classes, such as Enriched course materials, an intimate community of learners contributes to the development of lifelong learning (Kassop, 2003), which is one of the reasons why online education is growing rapidly. In addition, it was found through experiments that participants who use online education generally have high satisfaction levels (Kim & Bonk, 2006). In summary, once we are familiar with the scope and efficacy of online education and its interdisciplinary emergence in the field of physical education, we will demonstrate the extent to which online education is being used in the field of physical education and the hot research trends in the future.
Under the influence of COVID-19, the face-to-face classroom model has been challenged by the times and has ushered in a period of high-frequency use of online education, and countries around the world are constantly exploring the social value of online education and are beginning to delve into research and development of new features (Zhou et al., 2020). In particular, online education in the field of physical education has been used from the beginning of using mainly MOOCs to train physical education (PE) teachers (Conole, 2013), meeting the development of PE teachers while testing the effects through experiments (Griffiths et al., 2022). The development went through from the main initial use for training and managing teachers, to the later use in PE classrooms with a combined offline-online PE education model for classes (Wang, 2021), and finally the use of virtual online classes to enable students to perform a synchronized exercise (Isikgoz, 2021), etc. All of this shows the high level of engagement with online education in sports. However, the difficulties of online education in the field of sport are different from other fields in that it does not simply impart theory, but also physical activity supervision and monitoring, so new functions arise for online education to drive students' physical activity.
Starting from 2005, the online education function has been upgraded today, combined with the development of the advanced technology of the times and the expansion of the combination of programs, and has gradually risen in status and is used more frequently, even starting to replace distance education and face-to-face courses (Hiltz & Turoff, 2005), and online courses have become diverse and gamified (ANDERSON, Craig & BUSHMAN, Brad, 2001;Betz & Betz, 1996J.A, 1996, collaborative (Kop & Hill, 2008), and ALN has even found advantages over face-to-face courses (Hiltz & Turoff, 2005). With so many advantages, if we take advantage of them and apply them to the field of physical education, can we create a new model of physical education? It is worth considering whether new values in the field of physical education can also be developed.
In this paper, we will focus on online education in the field of physical education, mining data for twenty years from 2001 to 2022, systematically integrating the field through knowledge mapping, providing suggestions, and indicating the direction of development in the process of physical education and online education, and making constructive recommendations.

Data sources
In this study, WOS (Web of science core collection) was selected as the data resource. Web of science is accepted by many researchers as the most authoritative and certified database for data documentation, and is considered the most suitable database for bibliometric analysis (Ding & Yang, 2020). To ensure that the search data were comprehensive and accurate, the indexes were selected as SCI-EXPANDED, and SSCI, and to consider the combination of "online education" and "sports" the search strategy for this paper was finally determined as TS = (("Online Education" AND "Sports"). Education" AND "Sports") OR ("Online" AND "physical education ")OR ("e-learning" AND "Sports")), spanning the period from May 2001 to May 2022, with a search deadline of 1 May 2022, See Figure 1 for details of the data cleaning process.
Through data collection, 229 papers from 720 authors from 361 institutions in 40 countries, published in 84 journals, were used for this study, applying 8701 citations from 4252 journals. 49 of the 4252 journals were cited more than 20 times.
The status of online education in the sports sector can be seen in detail in Figure 2. From the overall situation, there is an upward trend, especially after 2019, the number of publications has shown a rapid growth phase, with more than 40 publications in 2020 and 2021, which indicates that more and more scholars have started to pay attention to this field in the last two years, and online education has become a new focus of attention in the field of sports.
Bibliometrics first emerged in 1969 (Pritchard, 1969) and quickly developed into  a separate discipline widely used in the field of documentary analysis (Diem & Wolter, 2013). The bibliometric analysis provides a quantitative method for reviewing and surveying the extant literature in each field (Mayr & Scharnhorst, 2015), during which detailed information such as authors, keywords, journals, countries, institutions, references, etc. can be obtained. Thus, the development of a field can be accessed through bibliometric analysis (Abramo et al., 2011) based on modern computer technology, graphical and visual results can complement literature analysis.
Two software programs, CiteSpace and VOSviewer, are used for knowledge mapping. The two software complement each other like a tiger. Firstly, CiteSpace is based on a set-theoretic approach to data normalization for similarity measurement of knowledge units, and similarity algorithms are used to obtain time zone and timeline views within time slices so that the evolution of knowledge in the literature and the historical span of literature in a certain cluster can be clearly outlined on the timeline to understand. This allows for a clear overview of the evolution of knowledge and the historical span of documents in a cluster on a timeline, and an understanding of the development process and trends in the field (Chen, 2006). Secondly, VOSviewer adopts a probabilistic-based data normalization approach and provides various visualization views in the areas of keywords, co-organizations, co-authors, etc., including Network Visualization, Overlay Visualization, and Density Visualization, with the outstanding features of easy mapping and beautiful images (Van Eck & Waltman, 2010). With the interplay of the two software packages, it is possible to get a clearer picture of the evolution and clustering of a domain.

A bibliometric analysis of the author
We begin with an analysis of the authors of literature, which gives an idea of the current leaders in the field and some of the core findings. The scholar Price (1963) states that half of the papers on the same subject are authored by a group of scholars with a high level of productivity and that the number of these authors in the set is approximately equal to the square root of all authors (Price, 1963), with the following formula: Where n(x) represents the number of authors who have authored x papers, I = n max is the number of authors of the most productive papers in the field, which can be calculated using VOSviewer as n max = 19, N is the total number of authors, and m is the minimum number of publications by core authors. According to Price's Law, the minimum number of articles published in a field is ≈3.1, so authors who have published more than 3 articles are classified as the core authors in the field, and the top authors have published a maximum of I = 19 articles, m = 3, m + 1 = 4. This meets Price's criterion of half (50%). Bringing the values into Price's Law's formula is largely consistent. Therefore, it can be assumed that there is a stable group of collaborators in this area of online learning and physical education. Table 1 shows the top 10 authors with more than 5 publications.
The most cited author is Gaudreault, with 5 articles and 20.2 citations per article. Author Richards' paper is mostly the elaboration on physical education teachers at its core, while the most cited author, Gaudreault, has collaborated with Richards several times in his research and both are part of the same institution, This is true not only in terms of the educational assessment of physical education teachers but also in terms of job satisfaction (R Richards et al., 2019), and other external factors on physical education teachers (Washburn et al., 2020) explored in depth all the factors that would socially professionalize (Graber et al., 2019) the teacher as the dominant person on the physical education classroom (K. A. R. Richards et al., 2018), both conducting qualitative and quantitative literature studies.

A bibliometric analysis of the journal
The type of journal to which the literature belongs is analyzed the number of articles carried. This is verified using Bradford's Law while examining the literature score. Bradford's law suggests that the distribution of the number of scientific and technical specialties in the corresponding journals in which they are published is highly asymmetrical or skewed concerning the number of specialties in their corresponding journals in what appears to be a haphazard collection of literature. Each zone  contains an equal number of papers, at which point the number of core journals and their successor journals is related in a 1: a: a 2 of relationship.
The search revealed that the main journals with more than 15 articles were Journal of Teaching in Physical Education, Physical Education and Sport Pedagogy, European Physical Education Review, and the first three journals are all core journals in the field of physical education and are of high quality in Table 2 . There are 18 articles in Physical Education and Sport Pedagogy have an average citation of 10.3, which indicates that the quality of this journal is relatively high compared to the other journals and that it has a strong focus on the application of online education in the field of sport. The Journal of School Health, although in 9th place, has an average citation of 28.2. Physical education is mostly conducted in schools, so the quality of the journal is also relatively high.
In the area of online learning and physical education combined, the results of the division of the journals into regions based on the number of articles are shown in the table, where the number of papers in the three regions is roughly the same and the ratio of journals is close to 1:4:16 (1:4:42) indicating that the distribution of research papers in journals in this area is consistent with Bradford's Law formula, see Table 3.

A bibliometric analysis of the country
To understand which countries have made outstanding contributions to the field of online education and sport, we analyzed data from all 40 countries using VOSviewer and found that the top 5 countries are represented in Table 4. Among them, US academics are the highest contributors to the field, ranking first with 96 publications and the highest number of citations at 1408, with an average citation count of 14.7. The next most-cited country is England, with 21 papers cited 178 times and an average citation of 8.5.

Keyword co-occurrence analysis
Keywords are the main core words of the article. Through keyword analysis, we can discover the research hotspots in the field and predict the future research trends. We used VOSviewer to draw a keyword co-occurrence network view of 229 articles and selected 68 keywords with a frequency greater than 5 for visual analysis, as shown in Figure 3. In the figure, the larger the dot represents the more occurrences and the more representative of the hotspots in the field, and the nodes are connected to represent the strength of association, and the more lines represent the more occurrences of two keywords in the same article. The different colors represent different clusters, i.e., topics of research, and the time of appearance is represented from blue to yellow.
Then, we selected the high-frequency keywords with a frequency greater than 6 according to Price Law as shown in Table 5. Since there were too many keywords, we only selected the 20 keywords with the highest number of occurrences. Through Figure 3 and Table 5 we can see that Physical Education, Children, Physical Activity, Adolescents, Teachers, Education, COVID-19, etc. are the representative high-frequency keywords in this field at present. Physical Education is the greatest section of the circle and the center of the entire graph, according to Figure 3 and Table 5, and it also makes up the majority of the circle in terms of appearances (54), making it the most important component of the graph; followed by Children with the greatest number of appearances, with 30 appearances. This also represents that in this 2018 scholars are paying more and more attention to children's physical education, which also points to the direction of our sports development afterward. On-Line education and E-Learning are both used as a way of online education, only called differently; And because of the sudden appearance of the keyword COVID-19 in 2020, and so on It can be seen that under its influence online education in physical education has become a new hot spot, and it can provide sports services for young children remotely to avoid the influence of COVID-19, so in the future, online physical education on the Internet has a very high research value and research potential.
From Figure 4 the keyword Teacher has the highest outbreak index reaching 3.46 and starting in 2017 and ending in 2019. The emergence of online education also provides a new platform for physical education teachers, teacher formation and teacher quality (Hanushek & Rivkin, 2006), and teacher behavior (Brophy & Brophy, 1979) can have a significant impact on students, and various educational issues need to be addressed by teachers. So, we see that about burnout's study on teachers' burnout also had a high outbreak of 2.34, which lasted from the 2018 outbreak to 2020.  The emergence of online education has also provided a new development platform for the preparation and development of physical education teachers through the platform (Boswell & Yoon,2015) to improve the cross-disciplinary learning and diversity development of physical education teachers.
In the development of diversity, the emphasis on health promotion and wellness activities in school activities is accompanied by the awareness that unintentional injuries can occur in physical education. Therefore, this requires teachers and students to avoid sports injuries as much as possible (Cale et al., 2016). Teacher professional development (PD) as a sustainable process, the improvement of teacher quality is inevitably accompanied by an improvement in the quality of student learning (Armour et al., 2017). The same applies to physical education teachers, so along with the expansion of online platforms, physical education teachers have evolved as well.

Keyword co-occurrence time zone mapping analysis
Keyword co-occurrence time zone mapping can help us better cluster and analyze the research status in recent years, and do not cut can recognize the inflection point of development and the frontier temporal pattern and observe the research heat in each time zone in detail. In order to create the keyword co-occurrence time zone mapping shown in Figure 5, set the node selection keywords through CiteSpace with a time slice length of 1 year. Each column has a corresponding time node indicating the first occurrence of the keyword, the size of the node indicates the number of occurrences, and the keyword is located on the horizontal line indicating the beginning and continuation of the time. The evolution and development of online education in sports can be divided into two stages by combining qualitative analysis: First, the combination of online education in sports from 2001 to 2008 was narrow, with only the most basic areas of physical education, Higher Education and Technology in sports. From 2009, there was an explosive blossoming of research, with keyword clusters such as children, students, teachers, physical fitness, and psychology all coming to the fore at this stage and becoming the mainstream of research, and online network teaching and learning became the main means, and attention began to be paid to the new physical education system under the influence of COVID-19. Multi-level and gradually deepening trend development.

Co-cited journal mapping analysis
It visualized a total of 40 co-cited journals by using VOSviewer software and setting the number of co-cited journals for the node to 24 as shown in Figure 6, which is roughly divided into three types, red clusters, green clusters, and blue clusters, with the top three cited journals being Journal of Teaching in Physical Education, Sport, Education and Society, and Research Quarterly for Exercise and Sport has a total of 360, 188 and 161 citations, respectively. Among the three clusters, the blue and green clusters are mostly in the field of educational technology, research papers with quantitative analysis in the review category, citing these journals mostly as empirical studies that provide themselves with theoretical support and technical support; the red part is mostly in public physical health, citing these journals mainly to illustrate the public health role of physical education and the health promotion function brought by the role of physical education itself.
The co-cited literature was further analyzed with VOSviewer, and the number of co-citations was set to 8, with a total of 27 co-citations, and the top 5 articles that were cited from 2001 to 2022 are shown in Table 6. and Table 7. From Table 8. and Table 9., it can be seen that most of the articles are old and retrospective empirical studies conducted for review.

Conclusion
Physical education as a system in social science is an important and active role in people's physical activity, physical exercise, and recreation, and is an important activity for a healthy body. This study analyzed the research related to online education in the field of sports in the past two decades by visual analysis software VOSviewer and CiteSpace, systematically reviewed the status of previous research, also verified the scientific validity of Pierce's law and Pavlov's law, made  a systematic analysis of core authors, countries, highly cited journals and highly cited literature and keyword clustering in this field. The following conclusions were obtained.
1: A collaborative group of authors in the field of online education and sports is gradually forming, and it is following Price's law, and several core scholars have been formed.
2: The main journals that publish in this field are the Journal of Teaching in Physical Education, Physical Education and Sport Pedagogy, and European Physical Education Review.
3: We found that there are more American scholars in this field, more than half of them, and the average number of citations is also more than American scholars, which have high recognition in this field.
4: In the clustering analysis of keywords, we also found that different implicit research themes were formed, such as teacher management, teacher development, children's physical education, physical education, etc. Teachers are in the dominant position in physical education classes, so the number of occurrences is also high. The rapid explosion of keywords such as COVID-19, Children, Online Teaching, etc. also indicates the prospect of future research.
5: The analysis of authors' co-citation also shows that the hotspots in the field are constantly replaced by iterations, and the chronology (circle size) of the highly cited keywords can further understand the iteration of the hotspots.