## 5 Conclusions  
To address the knowledge gap in the literature regarding the efficiency and benefits of using AR tools as a training method, this study aimed to perform experiments on human subjects with different training methods and different levels of task complexity. The current study adopted the ECG measure approach to evaluate the workload of AR users on maintenance tasks. The findings indicate that for more challenging tasks, AR instruction has an essential benefit over traditional paper-based instruction in reducing both the time taken for maintenance and physical stress. AR resulted in a time reduction of 14.94% for complex tasks. Moreover, utilizing paper-based instruction led to an unstable heart rhythm, an increase in HR, and a shift in autonomic balance, primarily due to increased activation of the sympathetic nerves. The findings revealed that physical stress for AR users was reduced while they performed the two maintenance tasks. With both tasks performed in an AR setting, the HRV metrics remained approximately constant. This study concludes that AR-based instruction is more efficient and less stressful than paper-based instruction, indicating that AR systems may offer independent benefits in reducing physical workloads. Both subjective and physiological measures (ECGs) support these findings. HRV indices and frustration ratings strongly suggested an increase in physical stress when the participants performed a complex task using paper-based instruction. The current study adopted the ECG measure approach to evaluate the workload of AR users on maintenance tasks. This aids in understanding the benefits and drawbacks of AR instructional techniques, which are transforming traditional instruction systems. Moreover, the results of this study can help manufacturing stakeholders better understand the benefits of AR technology as an instruction tool for manual tasks. Furthermore, the present study's results provide a foundation for the appropriate application of this technology in industrial sectors across the globe.  
Conceptualization, M.H.A.; Data curation, F.M.A. and M.H.A.; Formal analysis, M.H.A.; Funding acquisition, F.M.A.; Investigation, M.H.A.; Methodology, F.M.A. and M.H.A.; Project administration, M.H.A.; Resources, F.M.A. and I.M.A.-h.; Software, M.H.A. and M.M.N.; Supervision, F.M.A. and I.M.A.-h.; Validation, F.M.A., M.H.A., I.M.A.-h., M.M.N., H.K. and N.H.; Visualization, M.H.A. and H.K.; Writing--original draft, F.M.A. and M.H.A.; Writing--review and editing, F.M.A., M.H.A., I.M.A.-h., M.M.N., H.K. and N.H. All authors have read and agreed to the published version of the manuscript.  
This study was funded by King Saud University Researchers Supporting Project.  
This study was conducted in accordance with the Declaration of Helsinki and approved by the Human Participants Review Subcommittee of the Institutional Review Board at King Khalid University Hospital, College of Medicine, King Saud University (protocol code E-19-4467 and date of approval 23 January 2020).  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
All data supporting the reported results are included in the manuscript.  
The authors appreciate the support from Researchers Supporting Project number (RSPD2023R814), King Saud University, Riyadh, Saudi Arabia.  
The authors declare no conflicts of interest.