Maintaining balance under all conditions is an absolute requirement for humans. Orientation in space and balance maintenance requires inputs from the vestibular, the visual, the proprioceptive and the somatosensory systems. All the cues coming from these systems are integrated by the central nervous system (CNS) to employ different strategies for orientation and balance. How the CNS integrates all the inputs and makes cognitive decisions about balance strategies has been an area of interest for biomedical engineers for a long time. More interesting is the fact that in the absence of one or more cues, or when the input from one of the sensors is skewed, the CNS "adapts" to the new environment and gives less weight to the conflicting inputs [1]. The focus of this paper is a review of different strategies and models put forward by researchers to explain the integration of these sensory cues. Also, the paper compares the different approaches used by young and old adults in maintaining balance. Since with age the musculoskeletal, visual and vestibular system deteriorates, the older subjects have to compensate for these impaired sensory cues for postural stability. The paper also discusses the applications of virtual reality in rehabilitation programs not only for balance in the elderly but also in occupational falls. Virtual reality has profound applications in the field of balance rehabilitation and training because of its relatively low cost. Studies will be conducted to evaluate the effectiveness of virtual reality training in modifying the head and eye movement strategies, and determine the role of these responses in the maintenance of balance.

Virtual environments have been investigated for fitness and medical rehabilitation. In this study, the Sony EyeToy Ò and PlayStation 2 Ò were used with the AntiGrav TM game to evaluate their potential for improving postural balance. The game required lateral head, body, and arm movements. The performance on balance tests of subjects who trained for 3 weeks with this game was compared to the performance of controls who were not trained. Training subjects showed improvement for two of the three tests (each testing a different facet of balance), suggesting specificity of training, while control subjects did not show significant improvement on any test. Simulator sickness questionnaire results showed a variety of mild symptoms, which decreased over the training sessions. Motor learning analysis of the game scores showed that mastery had been achieved on the easier level in the game, but not on the second level of difficulty. This reflects the potential for continued learning and training through advanced levels within a game. A model parameter using the time constants of game score improvement was developed, which could be used to quantify the difficulty for any video game design. The results suggest that this video game could be used for some aspects of balance training.

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Maintaining balance under all conditions is an absolute requirement for humans. Orientation in space and balance maintenance requires inputs from the vestibular, the visual, the proprioceptive and the somatosensory systems. All the cues coming from these systems are integrated by the Central Nervous System (CNS) to employ different strategies for orientation and balance. How the CNS integrates all the inputs and makes cognitive decisions about balance strategies has been an area of interest for biomedical engineers for a long time. More interesting is the fact that in the absence of one or more cues, or when the input from one of the sensors is skewed, the CNS "adapts" to the new environment and gives less weight to the conflicting inputs [1]. The focus of this paper is a review of different strategies and models put forward by researchers to explain the integration of these sensory cues. Also, the paper compares the different approaches used by young and old adults in maintaining balance. Since with age the musculoskeletal, visual and vestibular system deteriorates, the older subjects have to compensate for these impaired sensory cues for postural stability. The paper also discusses the applications of virtual reality in rehabilitation programs not only for balance in the elderly but also in occupational falls. Virtual reality has profound applications in the field of balance rehabilitation and training because of its relatively low cost. Studies will be conducted to evaluate the effectiveness of virtual reality training in modifying the head and eye movement strategies, and determine the role of these responses in the maintenance of balance.

<div>Virtual environments have been investigated for</div><div>fitness and medical rehabilitation. In this study, the Sony</div><div>EyeToy (R)and PlayStation 2 (R) were used with the Anti-Grav(TM) game to evaluate their potential for improving</div><div>postural balance. The game required lateral head, body, and</div><div>arm movements. The performance on balance tests of</div><div>subjects who trained for 3 weeks with this game was</div><div>compared to the performance of controls who were not</div><div>trained. Training subjects showed improvement for two of</div><div>the three tests (each testing a different facet of balance),</div><div>suggesting specificity of training, while control subjects did</div><div>not show significant improvement on any test. Simulator</div><div>sickness questionnaire results showed a variety of mild</div><div>symptoms, which decreased over the training sessions.</div><div>Motor learning analysis of the game scores showed that</div><div>mastery had been achieved on the easier level in the game,</div><div>but not on the second level of difficulty. This reflects the</div><div>potential for continued learning and training through</div><div>advanced levels within a game. A model parameter using</div><div>the time constants of game score improvement was developed, which could be used to quantify the difficulty for any video game design. The results suggest that this video game could be used for some aspects of balance training.</div>

Balance control, spatial orientation and upright posture require an accurate integration of sensory inputs. In order to understand the integration in terms of motor learning and balance improvement, experiments were conducted in a virtual environment. The objectives of the current work were to: 1) examine the postural muscle responses, head movements, and game performance in young healthy subjects when they were exposed to unpredictable situations in the virtual environment 2) examine the extent of learning transfer that occurred in the virtual environment to the real world by means of pre and post posture tests 3) propose and validate the theoretical model that simulates experimental results. Results revealed that game performance increased during training in the virtual environment. The postural test results, electromyogram and head movement data have implications in using the virtual environment in balance and vestibular rehabilitation, for alleviating simulator sickness symptoms, and enhancing spatial knowledge and memory. The model simulates the experimental results very closely and sheds light on the activation of muscles under specific situations encountred in the environment. Overall, the experimental results supported our hypothesis.

Balance control, spatial orientation and upright posture require an accurate integration of sensory inputs. In order to understand the integration in terms of motor learning and balance improvement, experiments were conducted in a virtual environment. The objectives of the current work were to: 1) examine the postural muscle responses, head movements, and game performance in young healthy subjects when they were exposed to unpredictable situations in the virtual environment 2) examine the extent of learning transfer that occurred in the virtual environment to the real world by means of pre and post posture tests 3) propose and validate the theoretical model that simulates experimental results. Results revealed that game performance increased during training in the virtual environment. The postural test results, electromyogram and head movement data have implications in using the virtual environment in balance and vestibular rehabilitation, for alleviating simulator sickness symptoms, and enhancing spatial knowledge and memory. The model simulates the experimental results very closely and sheds light on the activation of muscles under specific situations encountred in the environment. Overall, the experimental results supported our hypothesis.