Role of Cultural Tendency and Involvement in Heritage Tourism Experience: Developing a Cultural Tourism Tendency–Involvement–Experience (TIE) Model

: Tourists’ attitudes, especially when searching with a cultural tendency, can inﬂuence the tourism experience in cultural heritage tourism. Based on the cultural contact theory and tourist involvement theory, we try to reveal the tie or the relationship between local culture and tourism. Here, we deﬁne cultural tendency as the extent to which tourists positively intend to learn about the culture of the destination. Then, we examined the roles of cultural tendency, involvement, tourist experience, and satisfaction in heritage tourism and proposed a tendency–involvement–experience (TIE) model. Using a questionnaire with tourists in Mogao Caves, a world heritage site, we found that cultural tendency through involvement enhanced tourism experience and satisfaction. Moreover, the tendency of different cultures had various effects on tourists’ experiences. Prior knowledge did not play a moderating role on the relationship among cultural tendency and involvement. The ﬁndings underscore the importance of cultural tendency in creating experiences, and heritage tourism must address tourists’ preferences for a better experience. J.Z. methodology, L.X.; L.X. and Z.N.; analysis, L.X. and Z.N.; investigation, L.X.; L.X.; data Z.N.; writing—original L.X.; and J.Z.;


Introduction
Heritage tourism has become popular, with more tourists looking for a meaningful relationship with the past [1]. At the core of heritage tourism are tourists' perceptions of heritage sites [2]. Therefore, quality in heritage tourism is mainly approached from the tourists' experience perspective [3]. Tourists' behaviors and experience can also guide heritage conservation and development [4]. Over the decades, studies on heritage tourism have provided diverse and highly segmented studies on different topics including heritage tourists [5], heritage experience [6], and experience stages of heritage tourism [7]. Recently, many studies have discussed that the inner factors and co-creation of tourists can largely influence heritage experience [8][9][10] and heritage protection [11]. This confirms the impact of tourist initiatives on tourism experience and heritage management. Heritage includes a synthesis of connotations containing multiple cultural values [12], and the tourist tendency for different cultures can affect the tourism experience [13]. However, there is limited research on the multifaceted cultural connotations of heritage from the perspective of tourists' experiences. In addition, balancing the development and conservation of heritage is a perpetual hot topic [14]. Therefore, identifying the tourists' tendency in heritage culture and conducting targeted tourism development can balance heritage conservation and development.
The Mogao Caves in China were listed as a World Heritage Site in 1987, attracting many domestic and international tourists. However, the space inside the caves was small, and the fresco material was fragile. An excessive number of visitors disturbed the stable environment of the caves and caused damage [15]. The Mogao Caves have developed responses, including establishing a reservation system for peak season visits, rotating cave openings, and a digital exhibition center [16]. However, these solutions focused only on the supply-side perspective, ignoring tourists' cultural tendency and needs. Therefore, a demand-side perspective considering the preference and experience of tourists was required to achieve selective tourism development.
Therefore, this study aimed to develop an original tendency-involvement-experience (TIE) model to examine the relationship between cultural tendency, involvement, tourist experience, and satisfaction in heritage tourism. In addition, the study investigated the moderating effect of subjective knowledge on the relationship between tendency and involvement and tendency and tourists' experiences. We investigated the influence of tourists' cultural tendency on tourists' experiences in heritage tourism. We believe that this study could help provide guidelines on increasing tourists' experiences and balancing conservation and development by identifying tourists' cultural tendency, which would help build competitive advantage and achieve sustainable development of cultural destinations.
This article is structured as follows. First, literature reviews of cultural tendency, involvement, experience, and satisfaction are presented, and the TIE model is proposed based on the relationship among variables. Secondly, a short portrait of Dunhuang Mogao Caves and the research methods are provided. Thirdly, the results are presented including sample characteristics and tests of the measurement model and structural model, followed by the discussion. Finally, the significance of the TIE model is highlighted and some directions for future research are suggested in the conclusion.

Heritage Tourism
Heritage is the product of historical legacy, filtered through social value systems [17]. It includes architecture, art, scenic attractions, artifacts, and contemporary lifestyles that reflect history [18]. Heritage is of economic, social, political, and scientific importance. With the development of cultural tourism, tourists have become intensely interested in cultural heritage and its cultural values [19]. Heritage tourism has gradually come into the perspective of tourism research and is usually defined in terms of supply and demand. The supply perspective, centered on what we have inherited, can mean anything from historic buildings to artworks to beautiful scenery [20]. From the demand perspective, the primary motivation lies in the heritage-related characteristics of a place according to tourists' perceptions of heritage and willingness to engage in a personal "heritage experience" [21]. Extensive scholarly research has been conducted on heritage tourism, including on the characteristics and values of heritage sites, heritage tourists, heritage site communities, government, media, other stakeholders, and tourism activities in heritage sites. In addition, scholars have researched various heritage sites, such as cultural and natural heritage [22], agricultural heritage [23], intangible cultural heritage [24], industrial heritage [25], and ancient villages, towns, and cities [26]. As such, heritage includes a synthesis of connotations containing multiple cultural values; however, there is limited research on the multifaceted cultural connotations of heritage from the perspective of tourists' experiences. The subdivision of the multidimensional cultural connotations of heritage requires investigation. This study enriches the study of multicultural heritage experience by segmenting heritage cultures and investigating the cultural tendency of tourists.

Cultural Tendency as Tourists' Intention to Search for Cultural Experience
In cultural tourism research, cultural contact is often used to measure tourists' tendency toward the culture of a cultural destination [27]. Cultural contact is a general term used by archaeologists to refer to groups of people coming into or staying in contact with another culture for days, years, decades, centuries, or even millennia. [28]. Cultural contact is a long term, direct exchange between members of societies with different identities [29]. In the tourism literature, cultural contact measures the purpose and depth of experience tourists seek when traveling to experience a different culture [26]. In addition, it includes the predisposition of tourists to interact with external cultures and the desire to control that interaction [29]. Carefully considering the original cultural contact scale [30], we found that the scale contains four dimensions: cultural tendency, depth of contact, involvement, and overall level of contact (Table 1). In addition, tendency and involvement can measure tourists' attitudes and behaviors at different stages, and these can be treated as independent variables. Since our study breaks down the stages of tourism and explores how tourists' attitudes at each stage affect their behavior at the next stage, our study only explores the influence of tourists' cultural tendency on the tourism experience, so only the tendency part of the cultural contact scale is selected. Cultural tendency in this present study is the extent to which tourists positively learn about the culture of the destination. According to previous research on cultural tourism, cultural tendency influences tourists' specific behaviors at cultural tourism sites. For example, it influences the level of desire for authentic experiences and the degree of tourists' involvement in the tourism process [31], impacts tourism experience, helps tourists form cultural memories of the destination, and generates place attachments [30,32]. Moreover, an in-depth understanding of the destination culture and active participation in the lives of local people can make the experience more authentic and memorable for tourists [33]. The visitable historical culture produced and constructed in heritage tourism destinations is an essential cultural type that tourists are exposed to. Multiple dimensions of culture exist for each heritage tourism site, while tourists have different levels of multicultural tendency. However, current research exploring multicultural tendency is limited and requires classification. Hypothesis 1a (H1a). Cultural tendency toward historical legends positively and significantly influences involvement.
Hypothesis 1c (H1c). Cultural tendency toward cave art positively and significantly influences involvement.

Involvement in Heritage Tourism
Although the cultural contact scale contains the involvement dimension, involvement is a multidimensional variable with independent scales. It can also successfully represent the level of immersion of tourists during the tour [34] (p. 245). Therefore, in this current study, involvement is selected to measure the tourists' status during their visit. Involvement theory was derived from the psychological self-involvement theory and social judgment theory [35]. Involvement was introduced into the field of leisure and tourism research by Selin and Howard [36] in the late 1980s. Havitz and Dimanche [37] defined leisure involvement as "a potential state of motivation, activation, or interest in a recreational activity or related product" (p. 197). Leisure involvement is stimulated by a specific stimulus or situation. Tourist involvement was defined as "a psychological state of motivation, activation, or interest in an individual triggered by a recreational activity, a tourist destination, and its associated tourism product" [34] (p. 245). The theory of involvement in tourism research is divided into two categories: consciousness, indicating the evocation of a tourist's perception of or interest in the tourism activity or related products during the tourism activity, and the degree of engagement in individual action, meaning the time and effort that the tourist devotes to the tourism activity [38]. Involvement is influenced by personal traits, stimuli, and situations [39] and impacts tourists' awareness and behaviors. Tourist involvement can significantly influence tourist experience, image perception, satisfaction, and loyalty [40][41][42]. High-quality tourism experiences are not only influenced by tourism suppliers' products and services but are also the result of tourists' participation and co-creation [43]. Particularly in heritage tourism, the tourist experience is influenced by the tourist's cultural contact when entering a heritage-based historical situation. It is subject to tourists' involvement in the tourism scene. A higher level of involvement allows for a more immersive and authentic experience for tourists. Previous studies on involvement and tourism experience are extensive and include a variety of tourism types. Cevdet et al. [44] explored the relationship between involvement, experience quality, satisfaction, and willingness to recommend for Istanbul's cultural tourism and found that involvement had a significant positive correlation with experience. Shafaei [45] found that tourists' involvement in a cross-cultural environment was conducive to helping travelers form clear and positive destination perceptions and enhance their cultural tourism experience.

Heritage Tourism Experience
The "experience economy" is becoming one of the core social services. Consumers are increasingly seeking the best experience when participating in social and business activities [46]. With the development of mass and personalized tourism, tourists' requirements for experience are gradually increasing. Tourism experience refers to the experience of the travel environment and processes through sensory organs, tactile organs, and thinking activities [47]. People's main desire for tourism is to experience various natural and human elements at tourist destinations to gain knowledge, aesthetics, curiosity, adventure, novelty, intimacy, satisfaction, and other experiences that are different from daily life [48]. Cultural tourism is the process of leaving one's living environment to observe and experience a foreign place or heterogeneous culture and satisfy the impulse of cultural intervention or participation, triggered by people's knowledge and longing for a heterogeneous foreign culture [49]. Heritage tourism has become an increasingly popular choice for tourists, and more tourists are looking for connections and meaningful experiences with the past [41]. Cultural heritage tourists' primary motivation is to get away from their usual culture and learn and experience the cultural connotations embedded in the heritage [19]. Many studies on tourism experiences are based on Pine and Gilmore [46], who identified the dimensions of the quality of the client experience as recreational, escapist, aesthetic, and educational [46]. On this basis, scholars have subdivided tourism experiences into ordinary, high-quality, extraordinary, and memorable [42]. Tourism experiences have been widely used in studies in various contexts, including rural tourism [50], culinary tourism [51], and cultural tourism [52]. Richards et al. [52] proposed that cultural experience contains four main dimensions: cognitive, intentional, emotional, and novelty. Lee and Smith [53], based on the characteristics of historical sites and museums, suggested that heritage tourism experience includes five dimensions: entertainment, exploration of cultural identity, education, relationship development, and escapism.
Satisfaction is the difference between consumers' expectations and perceived performance [54]. Satisfaction is a cognitive process that culminates in an affective state that is influenced by the product and consumer experience [55]. In tourism research, satisfaction is a cognitive and affective state obtained from the tourism experience [56] and a tool used to assess the tourist experience. Tourist satisfaction significantly impacts tourists' travel decisions, tourism consumption, loyalty, and post-tour behavioral intentions [57]. Chen and Chen [58] proposed that tourism satisfaction is a combination of tourists' expectations during the tour and their post-tour experiences. Satisfaction is increased if the tourism experience meets the tourist's pre-tour expectations. Many studies have discussed the relationship between tourism experience and satisfaction, noting that tourism experience subtypes have an impact on tourism satisfaction, including cruise tourism [59], cultural tourism [60], and adventure tourism [61].

The Moderating Effect of Prior Knowledge
Consumers' existing product knowledge and the ability to evaluate it helps to determine the attributes and benefits of the product, which shapes consumers' attitudes and behavior toward the product [62]. Prior knowledge could be defined as destination-specific information stored in personal memory [63]. In heritage tourism, prior knowledge is one of the decisive factors that determine the depth of tourists' cultural consumption in cultural heritage tourism attractions [64]. Previous studies have discussed the interaction between prior knowledge and involvement. If tourists are highly involved in tourism activities, they know more about them, accordingly, and more prior knowledge could allow them to become more deeply involved [65]. For tourists, the more prior knowledge they have, the more likely they are to want to learn about the culture at their destination. Thus, it could be assumed that tourists with different levels of prior knowledge differ in their relationship between cultural tendency and involvement. The following hypotheses are proposed based on the relationship between prior knowledge, cultural tendency, and involvement.
Hypothesis 5a (H5a). Prior knowledge of historical legends could moderate the relationship between cultural tendency toward historical legends and involvement.
Hypothesis 5b (H5b). Prior knowledge of Buddhist culture could moderate the relationship between cultural tendency toward Buddhist culture and involvement.
Hypothesis 5c (H5c). Prior knowledge of cave art could moderate the relationship between cultural tendency toward cave art and involvement.
In summary, this study proposes a tendency-involvement-experience Model (TIE). The conceptual framework is presented in Figure 1.

Study Area
Tourists visiting the Mogao Caves in Dunhuang, China were surveyed to test the proposed conceptual model. Dunhuang is located in the northwestern Gansu Province and is a vital node city on the Silk Road. Historically, Dunhuang was an important hub where East and West met, and people from different countries and nationalities converged.  Known for their painted sculptures and murals, the Mogao Caves showcase Buddhist art that has lasted for millennia [66] and are a typical multicultural heritage site. The history of the Mogao Caves through generations reflects the history of Dunhuang and the ancient Silk Road, creating a unique Western history and giving rise to legends. Dunhuang was one of the first areas in China to which Buddhism spread and the first stop for Buddhism in the Central Plains. The Mogao Caves contain a wealth of Buddhist heritage that documents the spread, exchange, and integration of Buddhist culture in China [67]. In addition, the Mogao Caves are known for their architecture, painted sculptures, and murals. The composition of cave art is of great artistic and aesthetic value in terms of subject matter, formal techniques, and style (Figure 3). Previous tourism studies have not systematically categorized Mogao Cave heritage and culture. Therefore, based on relevant studies on the Mogao Caves [67], this study divided Mogao Cave culture into three categories by visitor orientation: historical legends, Buddhist culture, and cave art ( Table 2).

Research Methods
Structural equations were analyzed using the structural analysis of covariance based on the method of greater likelihood and analysis of variance based on the partial least squares method. As the variable data in this study did not follow a normal distribution and there was no mature theoretical model to support it, the model was an exploratory study. The partial least squares (PLS) method does not have strict requirements for the normality of variable data [68]. It is applicable in exploratory and descriptive studies [69]. This study used SmartPLS 2.0 to explore the relationship between cultural tendency, involvement, and tourism experience.
The questionnaire contained the cultural tendency scale, the involvement scale, the tourism experience scale, the tourism satisfaction scale, and the demographic characteristics of the participants ( Table 3). Most of the above scales are from the previous literature, and many empirical results show their high reliability. Since cultural tendency is a partial dimension of cultural contact, related items were selected as the scale of tendency. Based on the introduction and classification of Mogao Caves cited above, cultural contacts are divided into three parts: historical legend, Buddhist culture, and cave art. The questionnaire used a 5-point Likert scale (1 = strongly disagree, 2 = disagree, 3 = neutral, 4 = agree, and 5 = strongly agree). The questionnaire was distributed to visitors at the Mogao Caves using the convenience sampling method from 21-25 August 2019. The surveyed samples were tourists who had just visited Mogao Caves and were ready to leave. Three postgraduate students who had taken a course in research methods and had experience in data collection helped collect data. In the process of the face-to-face survey, the research assistants dealt with requests for clarification and answered any questions from tourists. Finally, a total of 600 questionnaires were distributed, and 537 questionnaires were completed and returned. Excluding the surveys with invalid data or multiple missing data, 406 valid questionnaires were obtained for further analysis.

Sample Descriptive Statistics
A descriptive statistical analysis of the sample (Table 4) demonstrated that the gender ratio among the respondents was relatively balanced, with a predominance of young and middle-aged people. As the survey was conducted during summer vacation, which is the peak time for teachers and students to travel, students and professional/clerical technicians were predominant, and the majority of participants had a bachelor's degree or higher. As a cultural tourism destination, Dunhuang attracts a higher number of tourists with higher levels of education. This demographic profile is consistent with the segmented visitor profile of the Mogao Caves.

Measurement Model
Measurement models are generally evaluated using reliability and validity indicators. Reliability refers to the consistency, stability, and reliability of the measured variables. Validity refers to the extent to which the measurement results reflect the content of the study. In this study, the reliability and validity of the measurement model were examined using Smart PLS 2.0. The results are listed in Table 5. The reliability of the measurement model was determined using the Cronbach's alpha coefficient and combined reliability. Cronbach's alpha coefficients ranged from 0.783 to 0.875, which was higher than 0.7, indicating that all groups of observed variables reflected the characteristics of latent variables and were unique. The composite reliability (CR) values were greater than 0.8, indicating high internal consistency and reliability of the measurement model.
The validity of the measurement model was determined using the factor loading coefficient of each observed variable and the average extracted variance (AVE) of latent variables. Differential validity requires that the square root of the AVE value of each latent variable is greater than its correlation coefficient with other latent variables [75]. The standardized factor loadings of the measurement variables were greater than 0.6, indicating that the measurement model had strong convergent validity (Tables 5 and 6).
The AVE values of each latent variable were greater than 0.5, and their square roots were greater than the correlation coefficients between the variables, indicating good discriminant validity among the latent variables.

Structural Model
R 2 reflects the extent to which the exogenous latent variables explain the endogenous latent variables and tests the predictive effect of the structural model. The R 2 value of the endogenous latent variable of tourism involvement was 0.403. The value of tourism experience was 0.332, while the value of tourist satisfaction was 0.498, indicating that the structural model had a good fit.
The results of path analysis are presented in Table 7. Hypothesis H1a, H1b, H1c, H2a, H3, and H4 were confirmed, while the t-values of H2b and H2c were not significant. The tested structural model demonstrated that visitors' cultural tendency of the historical legends of the Mogao Caves, Buddhist culture, and cave art had a positive but decreasing effect on involvement. Involvement had a significant positive effect on tourist experience, and tourist experience had a significant positive effect on tourist satisfaction. In addition, cultural tendency of the historical legends had a significant positive effect on experience. Cultural contact with Buddhist culture and cave art did not have a significant effect on tourism experience.

Testing the Moderating Effect of Prior Knowledge
This study used the multiple group analysis method (MGA) to explore the moderating effect of prior knowledge. The variable prior knowledge was measured by three items: "How much did you know about the historical legends in Mogao cave prior to your trip?", "How much did you know about the Buddhist culture in Mogao cave prior to your trip?", and "How much did you know about the cave art in Mogao cave prior to your trip?" [74]. The participants were then divided into six groups according to the scores of the three items, in which the high group was higher than the average score and the low group was lower than the average score. The average scores of these three items were 2.82, 2.71, and 2.68. Based on the grouping result, we used the MGA method of SmartPLS (Bootstrapping 5000 times, others are the default) to explore whether different types of prior knowledge could moderate the relationship between cultural tendency and involvement. The sampling and MGA results are shown in Table 8. The MGA result shows that the path difference between groups was not significant. Hence, Hypothesis H5a, H5b, and H5c were not supported. In summary, whether tourists have prior knowledge did not significantly affect the relationship between cultural tendency and tourism involvement.

Discussion and Implications
This study reveals the tie or the relationship between culture and tourism by conducting an empirical analysis of the relationships between cultural tendency, involvement, and experience at a heritage tourism site. The findings confirm the relationships among cultural tendency, involvement and tourism experience, and validate the TIE model. Some new findings are also revealed that the type of culture influences the heritage tourism experience of tourists, and prior knowledge has no significant help for tourists to get involved in the destination. The findings of this study shed light on the importance of tourists' cultural tendency in heritage tourism. Moreover, an understanding of tourists' tendency toward different cultures in heritage tourism can also help heritage protection and management.

Theoretical Implications
Learning is often one of the main motivations in cultural heritage tourism [76]. Tourists' perceptions of culture are an important determinant of experience and satisfaction [52]. This study demonstrated that tendency in heritage culture, and desire to learn and interact with it increased tourists' involvement during the visit and positively influenced the heritage tourism experience and satisfaction. This is consistent with the results obtained from previous studies.
However, it is often difficult for tourists to develop comprehensive and in-depth knowledge of cultural heritage due to differences in traits, such as cultural education and personal interests [77]. There is a new finding that tourists' tendency toward different types of culture significantly influences their involvement. In this study, only cultural tendency of historical legends significantly influenced tourists' experiences. For cultural types that require cultural accumulation and aesthetic levels, it is difficult to significantly enhance the heritage tourism experience, even given a strong desire to interact, learn, and reach a high level of involvement. This finding enriches heritage tourism research by providing a multi-cultural perspective.
The MGA results show that tourists' cultural knowledge of different cultures cannot significantly moderate the relationship between cultural tendency and involvement, which is different from the results of previous studies. As this study focused on the immediate reactions and experiences of tourists immersed in the heritage tourism environment, even tourists with low cultural knowledge may have had a desire to learn about the culture, influencing their involvement during their visit. In addition, based on the theory of flow experience, tourists have a flow experience when their abilities and the challenges they face are matched [66]. Therefore, when the cultural competence of tourists is stronger than the cultural challenges of the destination, the impact of cultural tendency on tourists' involvement is diminished.

Management Implications
Heritage tourism scenic areas should minimize the destruction of cultural heritage and enhance tourism experience during development. This study suggests that heritage tourism scenic area managers should selectively and hierarchically develop heritage resources by identifying tourists' tendency and interests. Site areas with high tourist interaction and learning desires should be given development priority. The interaction between tourists and historical and legendary culture at multicultural heritage tourism sites is conducive to enhancing the tourist experience. Therefore, heritage tourism development should continue to explore the myths, legends, and historical stories of heritage resources and interpret them while respecting their authenticity. The understanding of the multiple cultures and values of cultural heritage resources that are difficult for tourists to perceive can be aided through enhanced interpretation. Cultures such as religion and folklore can be presented in a storytelling and engaging fashion through performances and digital media displays. Elements of artworks that require a certain aesthetic level can be integrated into real life to achieve a deeper exploration of artistic values. Cultural and creative works could be created with heritage elements, and artistic intellectual property may be created for integrated marketing to disseminate heritage art values. For heritage resources that are extremely fragile and easily destroyed, tourists' cultural interests can be guided and diverted through marketing and other means to ease the pressure of heritage development and exhibition.
In addition, heritage sites should distinguish the cultural needs of various types of tourists for refined tourism development, which would improve the tourist experience and overall satisfaction of visitors.

Conclusions
The classic concept of cultural contact connoted the attitude or tendency of tourists to experience culture and the secondary effects after the experience. We extracted the tendency as an index of tourist intention toward cultural experience. This study examined the relationships among cultural tendency, involvement, tourist experience, and satisfaction with heritage tourism and proposed a TIE model. The heritage tourism cultures were divided into three types, historical legend, Buddhist culture, and cave art, to explore tourists' differentiated attitudes among different cultures. In addition, we examined the moderating effect of prior knowledge on the relationship between cultural tendency and involvement. The results demonstrate that the relationship between variables in the TIE model were all significant, except the cultural tendency of Buddhist culture and cave art on tourism experience, which revealed differences in the effects of different types of cultural tendency on tourism experience. Consistent with studies on heritage tourism, the results indicate that tourism experience positively influences satisfaction. Furthermore, this study confirms that prior knowledge did not significantly moderate the relationship between cultural tendency and involvement. Thus, this research provides a more comprehensive understanding of the tie between culture and tourism.
This study had some limitations. First, the data used to test the hypotheses were collected from a sample of tourists from China. As such, the findings could not be generalized to other cultural contexts or to other types of tourists. Future studies should consider the generalizability of international tourists. Second, this was a case study of the Mogao Caves, lacking spatial and temporal dynamics and requiring more empirical and theoretical research on different spatial and temporal scales. For example, future studies may consider using different types of cases to validate the TIE model. In this study, we focused on immediate experience. Future studies could explore the memorable tourism experience of tourists after their trips. Third, the classification of heritage culture was limited to the Mogao Caves; therefore, future research should refine universal criteria for classifying heritage culture from a macro perspective. In addition, this study used only quantitative research and lacked methods that reflect the subjective experiences of tourists. Correlations identified by SEM basically are statistical but not causal in nature. Future research should incorporate more qualitative methods and models for further exploration. For example, in-depth interviews and the hierarchy of effects (HOE) model would be useful to achieve a better understanding of the causal relations among cultural tendency, involvement, and experience in cultural tourism. Institutional Review Board Statement: Because of the observational nature of the study, and in the absence of any involvement of therapeutic medication, no formal approval of the Institutional Review Board of the local Ethics Committee was required. Nonetheless, all subjects were informed about the study and participation was fully on a voluntary basis. The study was conducted in accordance with the Helsinki Declaration.
Informed Consent Statement: Not applicable.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to the data being part of an ongoing study.

Conflicts of Interest:
The authors declare no conflict of interest.