ABSTRACT

Exercise is important to the physical health and well-being of all people and helps in the prevention of cardiovascular disease, high blood pressure, obesity, and diabetes. This is especially true for persons with disabilities, who tend to have lower activity levels in general. The Game^Cycle exercise system is an interface between an arm ergometer and a computer game and was designed to provide motivation to individuals who use wheelchairs to exercise on a regular basis. This paper discusses the design and testing of a wireless fire-button located within the ergometer handgrips. This will allow users to play a wider variety of video games with the Game^Cycle system and control more game functions without use of a keyboard or mouse.

BACKGROUND

In 1997, a survey by the Centers for Disease Control found that only 15 percent of adults performed the recommended 30 minutes of moderate physical activity 5 or more days per week. The Surgeon General is aiming to increase the exercising adult population to 30 percent by 2010, indicated in the Healthy People 2010 objectives. One of the specifically targeted populations is people with disabilities. (1) Studies show that sedentary individuals with spinal cord injuries (SCI) are less fit than their physically active counterparts or the sedentary unimpaired population. (2) This may be due in part because the activity level of persons with SCI tend to decrease after their injury. (3) Physical activity can help to prevent the development of cardiovascular disease, as well as modify other risk factors including high blood pressure, blood lipid levels, insulin resistance, and obesity. (4) Within the population of those with disabilities, activity and exercise may also improve flexibility, functioning in activities of daily living, and self-esteem. Several studies, including van der Woude et al, have indicated that arm cycling with an ergometer can provide high levels of physical challenge. (5) Persons with disabilities who arm cycle will have higher fitness levels, including increased oxygen consumption and increased heart rate.

Figure 1. User at Game^Cycle

The Game^Cycle system is an interface between a standard arm ergometer and a computer game, allowing for game playing while exercising. As the user turns the arm ergometer, the speed of the game piece (e.g. car, player) moves proportionately to the rate of ergometer. In addition, the support frame of the ergometer can pivot left and right to determine the heading of the game piece. These motions simulate the motion of a computer joystick. The user is provided feedback though a computer monitor showing the video game. The addition of game play to exercise could improve the chances that the user will exercise more often and achieve or maintain their fitness level. Figure 1. User at Game^Cycle Results from an initial Phase I study of subjects using the Game^Cycle system showed that oxygen consumption and carbon dioxide production were significantly higher (p<0.005) when using the Game^Cycle system versus an arm ergometer without game play. Also, it was found that there were not significant differences in ratings of perceived exertion between conditions with or without game play. This would indicate that users expended more calories while using the Game^Cycle system with game play without an increase in perceived exertion.

STATEMENT OF THE PROBLEM

The original Game^Cycle system did not provide the user with the fire-buttons found on joysticks. This limited the variety of video games that could be played using the Game^Cycle and the game controlling functions accessible without a keyboard and mouse. For optimum user convenience, the fire-buttons should be integrated into the arm ergometer handgrip so that the user will not have to take their hand off the handgrip to press the button. This will allow for continuous cranking and exercise. The signal transmitter in the handgrip needs to be self-contained so that there is no need for external wires and two expensive slip rings to prevent wires from tangling while turning the arm ergometer. Radio frequency (RF) should be used for signal transmission because "line of sight" is not guaranteed for infrared transmission. The fire-button on the handgrip face should be impervious to moisture to prevent corrosion of the electrical components inside. The fire-button also needs to be positioned in a comfortable position that the user can reach while cranking the arm ergometer

RATIONALE

Some users from the Phase I study showed an interest in having "fire-control" buttons in order to allow them to use additional features of a wider variety of video games. Thus, buttons would let a person use more features of games they enjoy and add to the motivation of exercising with the Game^Cycle system. Additionally, the button permits the game operation and menu selection to be accomplished with less use of a keyboard and mouse.

DESIGN

The Game^Cycle control system emulates a game joystick. Standard gaming ports accommodate any two axes, four-button joystick. Therefore, it is possibile to add four fire-buttons to the Game^Cycle system.

DEVELOPMENT

Because RF circuitry is expensive to develop from scratch, for proof of concept, a commercially available wireless door chime was purchased from RadioShack (CAT # 63-872A ). It consisted of two push button RF transmitters and one receiver that omits a chime when the transmitter button is depressed. The transmitter and receiver electronic boards were utilized in the Game^Cycle fire-button design. In order to fit the transmitter board inside the handgrip, an oblique angle handgrip was designed as a modified handcycle handgrip. The handgrip was turned from a black delrin round stock. On the top end, a 1" diameter 2" deep chamber was hollowed out. A delrin removable plug was fashioned to close off the chamber. A rubber O-ring was utilized to give the plug a snug fit and to keep moisture out of the chamber. Two silver-oxide batteries (Energizer 357 1.55V/155mAh) were fit into the inside portion of the plug. A momentary tactile switch was fitted into a 1/8" deep pocket on the handgrip surface and secured with an epoxy. The switch was positioned for easy access by the user's index finger. The transmitter electronic board was slid into the chamber prepared in the handgrip. Input wires were attached to the switch button mounted on the handgrip face. Power for the electronics was obtained from the two batteries fixed in the chamber plug. When the handgrip fire-button is depressed, information is sent via radio frequency (RF) to the receiver board. Thus, the fire-button requires no external wiring.

When the receiver board detects the transmitter's RF signal, the receiver normally produces a current through the speaker (chime). For the Game^Cycle, the speaker leads were connected to a reed relay (5V, 20mA). When energized, the relay grounds the fire-button pin number 2 of the 15 pin game port interface. The computer is then alerted that the fire-button has been pressed and an appropriate event then occurs in the video game being played.

EVALUATION/DISCUSSION

A working prototype has been fabricated and successfully operates with the Game^Cycle system. In a sample video game, Need for Speed II (Electronic Arts), items could be selected from game menus by pressing the fire-button. Navigation through the menu was accomplished by turning the arm ergometer crank. During game play, the fire-button was able to control one function of choice that is normally controlled by a keyboard key.

Continuation of work on the fire-buttons will include creating an identical handgrip/fire-button for the opposite side of the ergometer. With two fire-buttons, interference issues may need to be addressed. Other types of switches will be investigated to determine which is most functional and comfortable for the user. Also, custom transmitter and receiver circuit boards will be fabricated to replace the purchased boards.

Additional modifications to the Game^Cycle user interface will remove some limitations of the original design. A variety of handgrips will be made to accommodate users with impaired hand function. The arm crank length and width out to the handles will be made adjustable to fit various sized users of the Game^Cycle system. These changes would enhance the device functionality, universality, and the comfort and safety for the user.

REFERENCES

ACKNOWLEDGMENTS

This study is partially funded by the NIH STTR Grant # 1R43HD42944-01, NIDRR Model System SCI (Grant # H133N000019)