The increasing use of virtual reality (VR) and augmented reality (AR) systems has opened the possibility of providing immersive experiences to the general population around the world. However, most of the existing systems do not provide highly effective force-feedback experiences to the user. To provide such augmented systems in combination with force-feedback, novel ideas must be introduced that can be easily integrated with the existing VR and AR technologies. This work proposes a first-person VR game integrated with a soft exoskeleton that enhances the quality of interaction between the subject and the virtual environment (VE) through an additional force-feedback element. The effect of introducing the force-feedback element on the user is analyzed by using biosensors and questionnaire feedback. The biosensors are used to measure the level of anxiety induced in the subject during interaction with the virtual environment. Conditions in which this interaction occurs with and without force-feedback are compared. The questionnaire analyzes the perceived change in emotions of users as a result of the introduction of the force-feedback element. This game can be played by most individuals, regardless of age and physical fitness.

Human's skeletal muscles have sensory systems. Human-machine interfaces that consider muscle effort should improve the usability and manipulability of daily products. This paper presents an interface design method that considers muscle effort and illustrates possible applications. A three-dimensional musculoskeletal model is developed based on the upper extremity model with 29 muscles and 16 joints. Muscle activity is estimated by using the OpenSim. We define the muscle effort as the mean of each muscle activity, and the muscle effort is used to determine the physical design or the physical response of the human interface. We applied the proposed physical design modification method to the design of the key height of a keyboard. The key height is changed proportional to the normalized muscle effort. The estimated muscle effort suggests that users can type every keys of the modified keyboard with a similar muscle effort. We also explore to improve the manipulation feeling of the key touching of mobile devices by changing the feedback response according to the estimated muscle effort when users touch keys. The experimental results indicate that the manipulation feeling can be improved by changing the feedback response according to the muscle effort.