Load on Shoulder and Elbow Joints During Autonomous Hand-Cycling

Hand cranking is an alternative method to handrim propulsion for imparting power to a wheelchair. As such it is important that the method does not overload the shoulder or elbow as these joints are at risk of overuse injury in the wheelchair user population. The majority of hand-cycling wheelchair is done under what could be termed 'autonomous control'. During autonomous control the wheelchair user is travelling at a desired speed and automatically adjusts his or her propulsion/cranking style to the terrain being traversed. Therefore, it is important to understand the loading on the upper limbs during this type of cranking. The experimental system was tested using 3 healthy subjects and the joint powers and torques were measured during the autonomous cranking phase, along with heart rate. From the results it is clear people regulate their hand-cranking in response to increases in heart rate. The maximum cranking power was found to occur at 1.1 rad/s, which produced 3.8W. When the arm was at full stretch from the body (at 180°) the shoulder was working at its hardest. This is because the hand position on the tip of crank is furthest from the shoulder. The elbow was found to be very weak when it travels past 100 ° flexion angle, this means the elbow joint is having to work hard when cranking between 270° to 70°. It is suggested that adapting the cranking position and cranking length could reduce the maximum power requirements on shoulder and elbow. It is also thought that correct gear ratio settings for individual performances could also reduce overuse injury on shoulder and elbow. © 2011 by JSME.