Upper Limb Cycle Ergometer for Supine Exercise (2013)

Prolonged bed rest can lead to 10–15% loss of muscle strength in one week and up to 35%–50% loss over five weeks [1]. Strength and endurance loss during bed rest often requires additional time for reconditioning, resulting in longer lengths of stay. When performed regularly during bed rest, lower limb resistance exercise has been demonstrated to successfully neutralize the atrophic effects of bed rest in able-bodied persons [2–5]. Although devices exist for lower limb exercise while in the supine position, we were unable to find commercially available devices for upper limb exercise in the supine position. There is a need for a device that provides supine upper limb exercise, e.g. for persons with spinal cord injuries who are on bed rest healing pressure ulcers. Thus the purpose of this project was to develop an upper limb cycle ergometer that can be used while in the supine position.The prototype was developed by combining parts from an Arjo Maxi Move patient lift and a Vital Fitness RB330 recumbent exercise bicycle (Fig. 1). The base and lifting mechanism from the Arjo patient lift and the cycle crank, flywheel, resistance mechanism, and monitor from the RB330 exercise bicycle were used in the prototype. The RB330 monitor displayed and controlled the resistance level as well as other exercise information. A custom boom was developed to extend the cycle crank over the bed and to support the components of the exercise bicycle, also acting as a guard for the shaft. Safety guards were developed to cover the flywheel and belt drive (Fig. 2). Lastly, to prevent excessive loading on the user a series of safety switches (Fig. 3) to interrupt the descent of the boom were placed on the bottom of the cycle crank guard. The safety switches were tested by lowering the boom onto a scale and measuring the force needed to stop the descent of the motor. Custom parts (boom and guards) for the device were designed in SolidWorks (Dessault Systems).The device was shown to a group of clinicians working at the Minneapolis VA Spinal Cord Injury and Disorders (SCI/D) Center. We also showed pictures of the current prototype to ten persons who use wheelchairs, including two who recently completed a prolonged episode of bed rest after a flap procedure and who were undergoing rehabilitation to recover their strength and endurance. We asked for qualitative feedback from the clinicians and wheelchair users.Figure 2 (left) shows the completed prototype. The original controls for the patient lift can be used to change the elevation of the boom, allowing it to be lowered for easier transport, elevated for clearance as it is moved into position over a patient, and then lowered into position for the patient to exercise (Fig. 2, middle). The base of the patient lift has brakes that can be engaged when in place to stabilize the device during exercise. The original monitor and controls for the exercise bicycle can be used to change the amount of resistance provided and display information about the duration and intensity of the exercise (Fig. 2, right). Testing of the safety switches (Fig. 3) indicated that they stopped any further descent of the boom at a force of 3.3 lbs.It was determined that the upper limb cycle ergometer can also be used while seated in a wheelchair or while standing in a standing frame (Fig. 4). Clinicians at the Minneapolis VA SCI/D Center were excited about the ergometer and asked when they could start using it clinically. All ten wheelchair users indicated that they would use the device if it were available. The two persons undergoing rehabilitation after a period of bed rest believed that they might be home already if this device had been available for their use during their episode of bed rest.The prototype developed shows potential to be a useful clinical tool in spinal cord injury centers as well as other health care facilities. The user has unobstructed access to the crank handles throughout the crank cycle, access to the monitor to adjust resistance and to view feedback regarding exercise intensity and duration, and the additional safety features (guards, switches, etc.) protect the user from foreseeable risks. Quantitative clinical studies are being planned to evaluate the effectiveness of the prototype for providing exercise for persons with spinal cord injury who are on bed rest. Qualitative focus group testing is also being planned to inform further design refinements.The research reported here was supported by the Department of Veterans Affairs, Veterans Affairs, Veterans Health Administration, Rehabilitation Research and Development Service. The authors acknowledge the contribution of mechanical engineering students from the University of Minnesota: Nicole Beaver, Jenna Olson, Nicholas Tomsche, and Daniel Wolff.