**1. Introduction**

This chapter examines virtual environments which usually represent computer simulated environments, otherwise called virtual worlds or virtual reality and its application in physical therapy. Virtual environments present computer-generated three-dimensional (3D) representation of a physical presence of places in the real world as well as in the imaginary world. Users mainly interact with virtual environments using virtual reality headsets. Many of the current virtual reality environments are primarily visual experiences display either on a computer screens or through other stereoscopic displays. Applications of virtual environments are mainly focused on artificial reality that projects users into a 3D space generated by the computer with some sort of tracking devices which may be the virtual reality headsets worn or another 3D tracking device attached to the body of the user such as the electromagnetic tracker system. Research in virtual environments has made significant impact in the entertainment industry and in the training field such as the flight simulator (Stern, 1995).

Fig. 1. Virtual Reality Parachute Trainer. Source:

http://www.news.navy.mil/view\_single.asp?id=3523 Courtesy: The work of the United States Federal Government under the terms of Title 17, Chapter 1, Section 105 of the US Code.

Virtual Environments in Physical Therapy 3

these complex set of processes involved in walking. Liepert and his colleagues in 2000 along with Jack and his fellow researchers in 2001 showed indications that virtual environments can be used to simulate artificial images that trigger biofeedback mechanisms that can aid in

In the work of Jack and his colleagues (Jack et al., 2001), a PC-based desktop system was developed that employed virtual environments for rehabilitating the hand function in stroke patients. The system uses two input devices, a CyberGlove and a Rutgers Master II-ND (RMII) force feedback glove, that allow users to interact with the virtual environment. The virtual environment presents four rehabilitation routines, each designed to exercise one specific parameter of hand movement e.g., range of motion. The authors used performancebased target levels to encourage patients to use the system and to individualize exercise difficulty based on the patient's specific need. Three chronic stroke patients were employed to carry out pilot clinical trials of the system daily for two weeks. Objective evaluations revealed that each patient showed improvement on most of the hand parameters over the

In 2002, Boian and his colleagues used a similar virtual environment in a different context to rehabilitate four post-stroke patients in the chronic phase. The system developed was distributed over three sites (rehabilitation site, data storage site, and data access site) and connected to each other through the Internet. At the rehabilitation site, the patients underwent upper-extremity therapy using a CyberGlove and a Rutgers Master II (RMII) haptic glove integrated with PC-based system that provides the virtual environment. The patients interacted with the system using the sensing gloves, and feedback was given on the computer screen. The data storage site hosted the main server for the system. It had an Oracle database, a monitoring server, and a web site for access to the data. The data access site was a 'place-independent' site, being any computer with Internet access. The therapist or physician could access the patients' data remotely from any location with Internet connections. The patients exercised for about two hours per day, five days a week for three weeks, within the virtual environment to reduce impairments in their finger range of motion, speed, fractionation and strength. Results showed that three of the four patients had improvements in their thumbs' range of motion and finger speed over the three-week trial while all the patients had significant improvements in finger fractionation, and modest

Similarly, in the same year, Alma S. Merians, with some members of Boian's research group continued related work using the CyberGlove and the RMII glove, coupled with virtual reality technology, to create an interactive, motivating virtual environment in which practice intensity and feedback were manipulated to present individualized treatments to retrain movements in three patients who were in the chronic phase following stroke. The patients participated in a two-week training program, spending about three-and-half hours per day on dexterity tasks using real objects and virtual reality exercises. The virtual reality simulations were targeted for upper-extremity improvements in range of motion, movement speed, fractionation, and force productions. Results showed that one of the three patients, the most impaired at the beginning of the intervention, gained improvement in the thumb and fingers in terms of range of motion and speed of movement. Another patient improved in fractionation and range of motion of his thumb and fingers. The third patient made the greatest gains as that patient was reported to have gained improvements in the range of motion and strength of the thumb, velocity of the thumb and fingers, and fractionation.

motor recovery.

course of the training.

gains in finger strength.

In another view, some researchers like Strickland, Hodges, North and Weghorst (1997) describe virtual environments as computer presence and feel of another place with tracking of what the person does in this imaginary scene. They argued that when the headsets are used to remove the real background of the user, the mind is fooled and the senses are made to accept as reality this new imaginary environment. Some simulations of virtual environments add more sensory information to depict the imaginary world as close to reality as possible and advanced haptic systems are now being coupled with tactile information (force feedback) to create systems for medical and gaming applications. Advances in telecommunications have enabled remote communication environments which now provide virtual presence of users with the concepts of telepresence and telexistence (Liang et al., 2006; Szigeti et al., 2009). The example above demonstrates the use of virtual environment in parachute training. The system provides a parachute simulation where students learn how to control flight movements through a series of computer-generated scenarios.
