Use of head-mounted displays (HMDs) and hand-held displays (HHDs) may affect the effectiveness of stability control mechanisms and impair resistance to falls. This study aimed to examine whether the ability to control stability during locomotion is diminished while using HMDs and HHDs. Fourteen healthy adults (21–46 years) were assessed under single-task (no display) and dual-task (spatial 2-n-back presented on the HMD or the HHD) conditions while performing various locomotor tasks. An optical motion capture system and two force plates were used to assess locomotor stability using an inverted pendulum model. For perturbed standing, 57% of the participants were not able to maintain stability by counter-rotation actions when using either display, compared to the single-task condition. Furthermore, around 80% of participants (dual-task) compared to 50% (single-task) showed a negative margin of stability (i.e., an unstable body configuration) during recovery for perturbed walking due to a diminished ability to increase their base of support effectively. However, no evidence was found for HMDs or HHDs affecting stability during unperturbed locomotion. In conclusion, additional cognitive resources required for dual-tasking, using either display, are suggested to result in delayed response execution for perturbed standing and walking, consequently diminishing participants’ ability to use stability control mechanisms effectively and increasing the risk of falls.
The aim of the project is to develop and evaluate a training environment for the prevention of falls with the help of an application in virtual reality (VR). The participants of our study walk on a treadmill with fall protection while immersing themselves in a virtual scenario where they have to overcome virtual obstacles. Potential parameters reflecting the plasticity of the neuromotor system are investigated in order to search for possible learning effects and their stabilization. In addition, it will be determined how many perturbations (i.e. obstacles) are necessary to establish a learning process. The results will be used to check the experimental setup and to prepare a main study for the development of a training program that helps preventing slip, trip, and fall (STF) accidents using a VR environment. So far two pilot measurements have been completed and parameters that may indicate learning effects were calculated. Initial results do not reveal clear learning effects, however, they inform about relevant adjustments for setting up systematic investigations and provide important details about strategies for data acquisition and analysis.
The reproduction and simulation of workplaces, and the analysis of body postures during work processes, are parts of ergonomic risk assessments. A commercial virtual reality (VR) system offers the possibility to model complex work scenarios as virtual mock-ups and to evaluate their ergonomic designs by analyzing motion behavior while performing work processes. In this study a VR tracking sensor system (HTC Vive tracker) combined with an inverse kinematic model (Final IK) was compared with a marker-based optical motion capture system (Qualisys). Marker-based optical motion capture systems are considered the gold standard for motion analysis. Therefore, Qualisys was used as the ground truth in this study. The research question to be answered was how accurately the HTC Vive System combined with Final IK can measure joint angles used for ergonomic evaluation. Twenty-six subjects were observed simultaneously with both tracking systems while performing 20 defined movements. Sixteen joint angles were analyzed. Joint angle deviations between ±6∘ and ±42∘ were identified. These high deviations must be considered in ergonomic risk assessments when using a VR system. The results show that commercial low-budget tracking systems have the potential to map joint angles. Nevertheless, substantial weaknesses and inaccuracies in some body regions must be taken into account. Recommendations are provided to improve tracking accuracy and avoid systematic errors.
Occupational safety and health (OSH) is active at all levels of the hierarchy of controls to prevent accidents associated with slips, trips and falls (STF). Training programs related to STF prevention are increasingly supported by virtual reality (VR) techniques. A review revealed a wide range of applications in practical and scientific areas. Trainings for operational practice vary regarding objectives, target groups, application contexts, media, and effectiveness, if available. Trainings in scientific studies are well designed for specific purposes at hand, but not suitable for direct application in operational practice. Research is required to bridge the gap. An investigation on gait stability and control in a VRbased obstacle avoidance training scenario has been conducted to contribute to developments in STF prevention. Initial results indicated a high level of presence and no evidence for detrimental effects on body and gait stability through application of VR techniques. This provides a sound basis for analysis of other data still required and for guiding similar and subsequent studies along knowledge gained by training programs available.
Locomotor training based in virtual reality (VR) is promising for motor skill learning, with transfer of VR skills in turn required to benefit daily life locomotion. This study aimed to assess whether VR-adapted obstacle avoidance can be transferred to a physical obstacle and whether such transfer is retained after 1 week. Thirty-two young adults were randomly divided between two groups. A control group (CG) merely walked on a treadmill and an intervention group (IG) trained crossing 50 suddenly-appearing virtual obstacles. Both groups crossed three physical obstacles (transfer task) immediately after training (T1) and 1 week later (T2, transfer retention). Repeated practice in VR led to a decrease in toe clearance along with greater ankle plantarflexion and knee extension. IG participants crossed physical obstacles with a lower toe clearance compared to CG but revealed significantly higher values compared to the VR condition. VR adaptation was fully retained over 1 week. For physical obstacle avoidance there were differences between toe clearance of the third obstacle at T1 and the first obstacle at T2, indicating only partial transfer retention. We suggest that perception–action coupling, and thus sensorimotor coordination, may differ between VR and the physical world, potentially limiting retained transfer between conditions.
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