Incorporating multimodal feedback in automated cardiopulmonary resuscitation (CPR) training systems has emerged as a crucial advancement in medical education, aiming to improve the quality and efficacy of CPR performance. This work presents an extensive and technical literature search on automated training CPR systems, specifically focusing on the feedback modality they provide during training sessions. We completed the search in the IEEE, ACM, Springer, SAGE, Elsevier, MDPI, Scholar, and Scopus databases between 2015 and 2025 (August) using the keywords “CPR,” “Virtual Reality (VR),” “Augmented Reality (AR),” “feedback,” and “training.” We categorized our findings based on the type of feedback provided (i.e., visual, audio, haptic, or a combination of these), the display type used to render the feedback, the technology used to monitor the trainee’s performance, and the type of manikin used. We conclude with recommendations for future research.

Visual guides help to align strokes and raise accuracy in Virtual Reality (VR) sketching tools. Automatic guides that appear at relevant sketching areas are convenient to have for a seamless sketching with a guide. We explore guides that exploit eye-tracking to render them adaptive to the user’s visual attention. EyeGuide and EyeConGuide cause visual grid fragments to appear spatially close to the user’s intended sketches, based on the information of the user’s eye-gaze direction and the 3D position of the hand. Here we evaluated the techniques in two user studies across simple and complex sketching objectives in VR. The results show that gaze-based guides have a positive effect on sketching accuracy, perceived usability and preference over manual activation in the tested tasks. Our research contributes to integrating gaze-contingent techniques for assistive guides and presents important insights into multimodal design applications in VR.

Robotic exoskeletons can enhance human strength and aid people with physical disabilities. However, designing them to ensure safety and optimal performance presents significant challenges. Developing exoskeletons should incorporate specific optimization algorithms to find the best design. This study investigates the potential of Evolutionary Computation (EC) methods in robotic design optimization, with an underactuated hand exoskeleton (U-HEx) used as a case study. We propose improving the performance and usability of the U-HEx design, which was initially optimized using a naive brute-force approach, by integrating EC techniques such as Genetic Algorithm and Big Bang-Big Crunch Algorithm. Comparative analysis revealed that EC methods consistently yield more precise and optimal solutions than brute force in a significantly shorter time. This allowed us to improve the optimization by increasing the number of variables in the design, which was impossible with naive methods. The results show significant improvements in terms of the torque magnitude the device transfers to the user, enhancing its efficiency. These findings underline the importance of performing proper optimization while designing exoskeletons, as well as providing a significant improvement to this specific robotic design.

Previous studies analyzed user motor performance with Virtual Reality (VR) and Augmented Reality (AR) Eye-Hand Coordination Training Systems (EHCTSs) while asking participants to follow specific task instructions. Although these studies suggested VR & AR EHCTSs as potential training systems for sports players, they recruited participants for their user studies among general population. In this paper, we examined the training performance of 16 professional volleyball players over 8 days using EHCTSs with three display technologies (VR, AR, and 2D touchscreen) and with four distinct task instructions (prioritizing speed, error rate, accuracy, or none). Our results indicate that volleyball players performed best with 2D touchscreen in terms of time, error rate, accuracy, precision, and throughput. Moreover, their performance was superior when using VR over AR. They also successfully followed the task instructions given to them and consistently improved their throughput performance. These findings underscore the potential of EHCTS in volleyball training and highlight the need for further research to optimize VR & AR user experience and performance.

Previous studies on Eye-Hand Coordination Training (EHCT) focused on the comparison of user motor performance across different hardware with cross-sectional studies. In this paper, we compare user motor performance with an EHCT setup in Augmented Reality (AR), Virtual Reality (VR), and on a 2D touchscreen display in a longitudinal study. Through a ten-day user study, we thoroughly analyzed the motor performance of twenty participants with five task instructions focusing on speed, error rate, accuracy, precision, and none. As a novel evaluation criterion, we also analyzed the participants’ performance in terms of effective throughput. The results showed that each task instruction has a different effect on one or more psychomotor characteristics of the trainee, which highlights the importance of personalized training programs. Regarding different display technologies, the majority of participants could see more improvement in VR than in 2D or AR. We also identified that effective throughput is a good candidate for monitoring overall motor performance progress in EHCT systems.

During object manipulation in Virtual Reality (VR) systems, realistically visualizing avatars and objects can hinder user performance and experience by complicating the task or distracting the user from the environment due to possible occlusions. Users might feel the urge to go through biomechanical changes, such as re-positioning the head to visualize the interaction area. In this paper, we investigate the effect of hand avatar and object visibility in navigational tasks using a VR headset. We performed two user studies where participants grasped a small, cylindrical object and navigated it through the virtual obstacles performing rotational or translational movements. We used three different visibility conditions for the hand avatar (opaque, transparent, and invisible) and two conditions for the object (opaque and transparent). Our results indicate that participants performed faster and with fewer collisions using the invisible and transparent hands compared to the opaque hand and fewer collisions with the opaque object compared to the transparent one. Furthermore, participants preferred to use the combination of the transparent hand avatar with the opaque object. The findings of this study might be useful to researchers and developers in deciding the visibility/transparency conditions of hand avatars and virtual objects for tasks that require precise navigational activities.

When working in Virtual Reality (VR), the user’s performance is affected by how the user holds the input device (e.g., controller), typically using either a precision or a power grip. Previous work examined these grip styles for 3D pointing at targets at different depths in peripersonal space and found that participants had a lower error rate with the precision grip but identified no difference in movement speed, throughput, or interaction with target depth. Yet, this previous experiment was potentially affected by tracking differences between devices. This paper reports an experiment that partially replicates and extends the previous study by evaluating the effect of grip style on the 3D selection of nearby targets with the same device. Furthermore, our experiment re-investigates the effect of the vergence-accommodation conflict (VAC) present in current stereo displays on 3D pointing in peripersonal space. Our results show that grip style significantly affects user performance. We hope that our results are useful for researchers and designers when creating virtual environments.

The virtual hand interaction technique is one of the most common interaction techniques used in virtual reality (VR) systems. A VR application can be designed with different hand visualization styles, which might impact motor dexterity. In this paper, we aim to investigate the effects of three different hand visualization styles — transparent, opaque, and invisible — on participants’ performance through a VR-based Purdue Pegboard Test (PPT). A total of 24 participants were recruited and instructed to place pegs on the board as quickly and accurately as possible. The results indicated that using the invisible hand visualization significantly increased the number of task repetitions completed compared to the opaque hand visualization. However, no significant difference was observed in participants’ preference for the hand visualization styles. These findings suggest that an invisible hand visualization may enhance performance in the VR-based PPT, potentially indicating the advantages of a less obstructive hand visualization style. We hope our results can guide developers, researchers, and practitioners when designing novel virtual hand interaction techniques.

State-of-the-art Virtual Reality (VR) and Augmented Reality (AR) headsets rely on singlefocal stereo displays. For objects away from the focal plane, such displays create a vergence-accommodation conflict (VAC), potentially degrading user interaction performance. In this paper, we study how the VAC affects pointing at targets within arm's reach with virtual hand and raycasting interaction in current stereo display systems. We use a previously proposed experimental methodology that extends the ISO 9241–411:2015 multi-directional selection task to enable fair comparisons between selecting targets in different display conditions. We conducted a user study with eighteen participants and the results indicate that participants were faster and had higher throughput in the constant VAC condition with the virtual hand. We hope that our results enable designers to choose more efficient interaction methods in virtual environments.

The vergence-accommodation conflict (VAC) limits user performance in current Virtual Reality (VR) systems. In this paper, we investigate the effects of the VAC in a single-focal VR system using three experimental conditions: with no VAC, with a constant VAC, and with a varying VAC. Previous work in this area had yielded conflicting results, so we decided to re-investigate this issue. Eighteen participants performed an ISO 9241:411 task in a study that closely replicates previous work, except that the angle of the task space was rotated 20 degrees downward, to make the task less fatiguing to perform, which addresses a potential confound in previous work. We found that the varying VAC condition had worse performance than the other conditions, which indicates that the contrasting results in previous work were very likely due to biomechanical factors. We hope that our work contributes to the understanding of the influence of the VAC in VR systems and potential strategies for improving user experience and performance in immersive virtual environments.

Relocation of haptic feedback from the fingertips to the wrist has been considered as a way to enable haptic interaction with mixed reality virtual environments while leaving the fingers free for other tasks. We present a pair of wrist-worn tactile haptic devices and a virtual environment to study how various mappings between fingers and tactors affect task performance. The haptic feedback rendered to the wrist reflects the interaction forces occurring between a virtual object and virtual avatars controlled by the index finger and thumb. We performed a user study comparing four different finger-to-tactor haptic feedback mappings and one no-feedback condition as a control. We evaluated users' ability to perform a simple pick-and-place task via the metrics of task completion time, path length of the fingers and virtual cube, and magnitudes of normal and shear forces at the fingertips. We found that multiple mappings were effective, and there was a greater impact when visual cues were limited. We discuss the limitations of our approach and describe next steps toward multi-degree-of-freedom haptic rendering for wrist-worn devices to improve task performance in virtual environments.

Despite non-co-location, haptic stimulation at the wrist can potentially provide feedback regarding interactions at the fingertips without encumbering the user's hand. Here we investigate how two types of skin deformation at the wrist (normal and shear) relate to the perception of the mechanical properties of virtual objects. We hypothesized that a congruent mapping (i.e. when the most relevant interaction forces during a virtual interaction spatially match the haptic feedback at the wrist) would result in better perception than other mappings. We performed an experiment where haptic devices at the wrist rendered either normal or shear feedback during manipulation of virtual objects with varying stiffness, mass, or friction properties. Perception of mechanical properties was more accurate with congruent skin stimulation than noncongruent. In addition, discrimination performance and subjective reports were positively influenced by congruence. This study demonstrates that users can perceive mechanical properties via haptic feedback provided at the wrist with a consistent mapping between haptic feedback and interaction forces at the fingertips, regardless of congruence.

We present the design and control of series elastic holonomic mobile platform, ASSISTON-MOBILE, aimed to administer therapeutic table-top exercises to patients who have suffered injuries that affect the function of their upper extremities. The proposed mobile platform is a low-cost, portable, easy-to-use rehabilitation device for home use. ASSISTON-MOBILE consists of four actuated Mecanum wheels and a compliant, low-cost, multi degree-of-freedom Series Elastic Element as its force sensing unit. Thanks to its series elastic actuation, ASSISTON-MOBILE is highly back-driveable and can provide assistance/resistance to patients, while performing omni-directional movements on plane. Feasibility tests and preliminary usability studies with the robot are presented. The device holds promise in improving accuracy and effectiveness of repetitive movement therapies completed at home, while also providing quantitative measures of patient progress.