## 5 Discussion of the Application and Effectiveness of AR in Industrial Assistance and Training  
The adoption of technologies such as AR in the field of industrial assistance and training is at an early stage, but with great potential to revolutionise industry as an innovative way of transmitting essential skills and knowledge through the continuous training of employees, workers and professionals. Its application extends to workshops, factories and construction projects, where AR allows workers to access real-time information, visualise complex processes and receive remote assistance, resulting in more practical training and  
Figure 6: Meta–analysis forest plot after removing significantly different studies [40, 41, 46, 51, 72, 77, 86, 88]. more efficient problem solving. However, the integration of this technology into assistance and training within the industrial sector presents challenges that are detailed and discussed, complemented by academic findings from previous research. Immersive AR training promotes interactive learning and skills development through simulation-based instruction by recreating a real environment in a virtual context, providing a risk-free learning experience. This methodology, supported by research such as that of [PERSON] et al. [40], has proven to be essential for exploring and practising in complex environments without facing the inherent dangers of a real industrial environment. It is particularly useful in the training of personnel in technical and healthcare disciplines. Conversely, AR serves as an invaluable tool in the analysis of manufacturing processes, enabling the visualisation and comprehension of intricate configurations in production. Its applications encompass real-time control, failure analysis, task simulation, workflow optimisation and energy optimisation. These contributions are pivotal to optimisation and quality control in manufacturing within Industry 4.0, as evidenced by studies such as [PERSON] et al. [44]. In the field of design, AR tools are emerging as catalysts for the 3D visualisation of prototypes and models. These tools foster a more immersive and participatory design process, optimising the accuracy and efficiency of the creative process, according to [PERSON] et al. [71]. Thus, a more faithful and tangible representation of the projects under development is achieved. AR-supported industry learning tools provide an immersive, hands-on learning experience. These tools encompass a range of services, including personalised assistance and on-site training, as well as virtual training and AR tutorials, which are tailored to industrial needs. [PERSON] and [PERSON] [69] highlight that these tools have enhanced information retention and facilitated the understanding of complex procedures. In the context of Industry 4.0, real-time feedback provided by AR stands out as an essential application, as it enables instant communication and correction during manufacturing, fabrication and assembly processes. For instance, [PERSON] et al. [73] investigated the utilisation of AR devices for remote support in manufacturing. Similarly, [PERSON] et al. [55] applied AR in task assistance, utilising advanced techniques such as 3D spatial mapping and RGB-D data, resulting in rapid and precise real-time responses. [PERSON] et al. [64] designed an AR system for manufacturing assistance, providing dynamic feedback and motion prediction. Nevertheless, despite the proliferation and diversity of AR applications in industry, a gap in design methodology has been identified: the absence of a unified and systematic baseline approach to designing adaptive AR assistance instructions for industrial operations. This gap becomes even more palpable when considering the complexity and variability of industrial operations, where each process or task has specific characteristics, risks and requirements. AR has the potential to offer customised and adaptive solutions for each of these scenarios.