Upper limb joint kinetics during manual wheelchair propulsion

Abstract

Manual wheelchair users are at a high risk of pain and developing injuries to the upper extremities. Recent research has documented that repetitive motion and high loads during manual wheelchair propulsion were, at least in part, responsible for strain injury and pain. Reducing mechanical inefficiency during wheelchair propulsion is crucial to decreasing physical strain and pain in daily life. To improve the mechanical efficiency of manual wheelchair propulsion, insight into the underlying biomechanical mechanisms and kinetic as well as kinematic assessment are required. For better understanding, the investigation of the kinetic demands during the propulsion beyond the standard level is required. Investigators have used various devices to determine kinetic parameters for propulsion, such as a wheelchair treadmill, ergometer, and wheelchair dynamometer. These devices have the considerable advantage that subjects can be tested in their own personal wheelchair, allowing for proper analysis of physiology, kinematics, and kinetics. Dynamic calibration of the developed device has been emphasized in order to compare the result of one study to another. Determining the inertial and resistance component of the developed wheelchair dynamometer is indispensable. The purpose of the present study is two-fold. We developed a torque transducer-mounted inertial- type wheelchair dynamometer and then implemented a dynamic calibration test to characterize its properties. Next, we recruited experienced and inexperienced manual wheelchair users as subjects for the propulsion motion analysis in order to compare their kinematic and kinetic parameters.The hypotheses and the purpose of this study are described in Chapter 1, and the basic theories about manual wheelchair propulsion mechanics from recent studies are summarized in Chapter 2. The methods and process of development and calibration of a wheelchair dynamometer are explained in Chapter 3. The strengths of the developed wheelchair dynamometer are easy and convenient to calculate the rear wheel torque as well as inexpensiveness compare with the other ergometers or dynamometers. It has the strength to give a measured torque. It is more accurate and actual value compared with the pure inertial type dynamometer (without sensors). We believe this sensor mounted wheelchair dynamometer is the most reasonable choice for the study. In addition, we estimated the unknown radial force of propulsion through the application of the mathematical models for optimization. Finally, experimental method and results of the propulsion motion with two groups of volunteers (novice and experienced) under the four different speed-load conditions (light-slow, light-fast, heavy-slow, heavy-fast) are described in Chapter 4. The results of within- and between- comparisons of kinematic and kinetic parameters of two groups under the four conditions were summarized as follows;1.The experienced had larger variances of the linear velocities and contact times than those of the novices.2.The propulsion angles of the experienced were larger than those of the novices in all conditions.3.The experienced had various propulsion patterns and wide range of propulsion trajectories.4.Joint angles had not significant differences within- and between- groups.5.The maximum propulsion torques of the experienced were larger than those of the novices in all conditions.6.The propulsion powers of the experienced were larger than those of the novices except the light-slow condition.7.The variances of the propulsion force (both radial and tangential) of the experienced were larger than those of the novices.8.The shoulder joint moment had the largest variance with conditions then the wrist joint moment, and the elbow joint moment had the smallest variance. The variance of the maximum shoulder joint moment with conditions was over four times of variance of the maximum wrist joint moment and eight times of the maximum elbow joint moment.9.The maximum joint moments increased significantly with the increase of speed and load both in the experienced and the novices.10.The maximum elbow extension moments of the experienced were always larger than those of the novices in all conditions although the maximum shoulder and wrist joint moments had insignificant differences.11.We could acquire more realistic results by using the measured torque value and wrist joint moments to the optimization method for estimation the radial propulsion force with object function of minimizing work.The experienced subjects were all professional wheelchair tennis players with five or more years of experience. Therefore, we believed that they have mechanical efficiency to use manual wheelchairs. Quick and large manipulation ability according to the environmental change is considered one of the important factors that how to propel the manual wheelchair efficiently. This efficiency could be confirmed by the results of the propulsion powers comparison with the novices. Sophisticated strategies of the efficient manual wheelchair propulsion could be understood by observation of the physical responses of each upper limb joint to the changes of load and speed. We expect the methods and results of this study could be helpful to evaluate the mechanical efficiency of the manual wheelchair propulsion quantitatively.