## 3 Results
### Patent Mapping  
To answer the first research question, patents were analyzed in terms of publishing trends, origin location, top assignees, International Patent Classification (IPC) and technology trends. Q1: How are patents that are related to virtual reality and digital human modeling for physical ergonomics assessment during the product design phase in industry characterized? In terms of patent publishing trends, Figure 2 shows an impressive growth in annual patent publication since 2016, with a significant increase in 2019. The upward trend slowed in 2020, with the probable explanation being the 18-month patent legal secrecy restriction. We omitted 2021 patents from analysis, since they were still being filed at the time of this study. The fact that there were almost no patent filings in 2016 supports the claim in [26], that the year 2016 marked a technological breakthrough in the domain of virtual reality. Before 2016, commercial virtual reality systems required users to connect a headset, controllers, and sensors to an external high-end computer, which was an expensive, bulky, and inconvenient setup. Thus, the current all-in-one virtual reality systems are a big step forward, occurring only a few years ago [29]. Virtual reality was rated the most often referenced technology in digital human modeling and simulation research and application trends by researchers, developers, and digital human modeling industry stakeholders in 2020 [30]. Furthermore, not only is the global  
Figure 1: Systematic review flow diagram, adapted from PRISMA 2020 [21]. virtual reality market projected to grow from USD 6.30 billion in 2021 to USD 84.09 billion in 2028 [19], but this rise may be much greater, given that the COVID-19 pandemic boosted the use of virtual reality [31]. Therefore, this scenario suggests that the exponential increase in patenting filings, related to virtual reality and digital human modeling, will continue for a few more years. Figure 3 illustrates patent origin locations. The United States and China have a comparable amount of patent filings, with 44% and 41%, respectively. Figure 4 illustrates the top 10 patents assignees. The significant concentration of patent filings in a few assignees is intriguing: the top 10 assignees filed 24% of all patents. Microsoft has the most patent filings and is responsible for 20% of the top 10 assignees' patent filings. Six of the top ten assignees are major players of technology (Microsoft, Apple, Intel, Facebook, IBM, and Bytedance) and two are in industrial automation (Rockwell and Siemens). It is also worth noting that one university (New York University) accounts for 7% of all patents filed in this subject. Figure 3: By nation, the number of patent records. Figure 2: Patent publishing trends. Next, we examined at the patent submissions in terms of distribution, based on the International Patent Classification (IPC). The IPC is a method for determining a standard classification for registered patents, allowing the search of and access to the technical information available in documents related to the same topic [32]. This classification facilitates the search for patent filings and allows access to the technical information included within them. The patents are classified based on their technical content. The International Patent Categorization is a hierarchical patent classification system used in over 100 countries to uniformly classify patent material. It creates a separation into classes and subclasses that are applicable to various technical domains and aids in the standardization of patent classification. Figure 5 illustrates that IPC is composed of letters and numbers and follows a hierarchical pattern [32]. Figure 6 shows the top 10 IPCs of reviewed patent filings. This group's patents are all classified as Section G (Physics), which contains all physics-related content.