Wrist biomechanics during two speeds of wheelchair propulsion: an analysis using a local coordinate system.
ABSTRACT To describe motion, forces, and moments occurring at the wrist in anatomic terms during wheelchair propulsion; to obtain variables that characterize wrist function during propulsion and are statistically stable; and to determine how these variables change with speed.
Convenience sample of Paralympic athletes (n = 6) who use manual wheelchairs for mobility and have unimpaired arm function.
Subjects propelled a standard wheelchair on a dynamometer at 1.3m/sec and 2.2m/sec. Biomechanical data were obtained using a force and moment sensing pushrim and a motion analysis system.
Maximum angles, forces, and moments in a local, wrist coordinate system. Each variable was evaluated for stability using Cronbach's alpha. Measures found to be stable (infinity > .8) at each speed were then compared to look for differences associated with speed.
The following measures were stable at both speeds: maximum wrist flexion, ulnar deviation, and radial deviation angles, peak moments acting to cause wrist flexion, extension, and ulnar deviation, peak shear forces acting between the radial and ulnar styloids, and peak axial force acting at the wrist. Of these measures, the following measures differed (p < .05) between speeds (+/-SD): maximum radial deviation (1.3m/sec, 25.1 degrees +/- 9.0; 2.2m/sec, 21.4 degrees +/- 6.9), peak flexion moment (1.3m/ sec, 3.4N.m +/- 3.0; 2.2m/sec, 5.2N.m +/- 3.7), peak extension moment (1.3m/sec, 10.4N.m +/- 4.8; 2.2m/sec, 13.6N.m +/- 5.1), peak shear acting from the ulnar styloid to the radial styloid (1.3m/sec, 2.3N +/- 2.7, 2.2m/sec, 8.3N +/- 7.5) and maximum axial force (1.3m/sec, 50.9N +/- 18.2; 2.2m/sec, 65.9N +/- 27.6).
This study found stable parameters that characterize wrist biomechanics during wheelchair propulsion and varied with speed. Ultimately these parameters may provide insight into the cause and prevention of wrist injuries in manual wheelchair users.
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ABSTRACT: BACKGROUND: The rear-wheel camber, defined as the inclination of the rear wheels, is usually used in wheelchair sports, but it is becoming increasingly employed in daily propulsion. Although the rear-wheel camber can increase stability, it alters physiological performance during propulsion. The purpose of the study is to investigate the effects of rear-wheel cambers on temporal-spatial parameters, joint angles, and propulsion patterns. METHODS: Twelve inexperienced subjects (22.3+/-1.6 yr) participated in the study. None had musculoskeletal disorders in their upper extremities. An eight-camera motion capture system was used to collect the three-dimensional trajectory data of markers attached to the wheelchair-user system during propulsion. All participants propelled the same wheelchair, which had an instrumented wheel with cambers of 0[degree sign], 9[degree sign], and 15[degree sign], respectively, at an average velocity of 1 m/s. RESULTS: The results show that the rear-wheel camber significantly affects the average acceleration, maximum end angle, trunk movement, elbow joint movement, wrist joint movement, and propulsion pattern. The effects are especially significant between 0[degree sign] and 15[degree sign]. For a 15[degree sign] camber, the average acceleration and joint peak angles significantly increased (p < 0.01). A single loop pattern (SLOP) was adopted by most of the subjects. CONCLUSIONS: The rear-wheel camber affects propulsion patterns and joint range of motion. When choosing a wheelchair with camber adjustment, the increase of joint movements and the base of support should be taken into consideration.BioMedical Engineering OnLine 11/2012; 11(1):87. · 1.61 Impact Factor
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ABSTRACT: A six-component handrim dynamometer (HRD) is a dynamometer that rotates around the wheel axle during measurements. For this kind of dynamometer, static zero level calibration is insufficient because the proportion of the forces (i.e. handrim weight and centrifugal force) measured by each sensor varies according to the angular position and velocity of the dynamometer. The dynamic calibration presented in this paper is based on the direct correction of the sensor signals using Fourier's polynomials that take into account the influences of both the handrim weight distribution on the sensors with respect to the wheel's angular position and the effect of the wheel's angular velocity. When these corrections were applied to the signals produced by the sensors while the HRD was rotating and no effort was being exerted on the handrim, the calculated forces and torques remained close to zero, as expected. Based on these results, the wheel dynamometer can be confidently used for studying manual wheelchair locomotion under various real conditions. The method could also be applied in other situations in which a dynamometer rotates during measurements.Computer Methods in Biomechanics and Biomedical Engineering 01/2014; 17(4):416-422. · 1.39 Impact Factor
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ABSTRACT: The aim of this study was to propose a new index called Postural Force Production Index (PFPI) for evaluating the force production during handcycling. For a given posture, it assesses the force generation capacity in all Cartesian directions by linking the joint configuration to the effective force applied on the handgrips. Its purpose is to give insight into the force pattern of handcycling users and maybe used as ergonomic index. PFPI is based on the force ellipsoid which belongs to the class of manipulability indices and represents the overall force production capabilities at the hand in all Cartesian directions from unit joint torques. The kinematics and kinetics of the arm were recorded during a 1-min exercise test on a hand-cycle at 70 revolutions per minute performed by one paraplegic expert in handcycling. The PFPI values were compared to the Fraction Effective Force (FEF) which is classically associated with the effectiveness of force application. The results showed a correspondence in the propulsion cycle between FEF peaks and the most favorable postures to produce a force tangential to the crank rotation (PFPI). This preliminary study opens a promising way to study patterns of force production in the framework of handcycling movement analysis.Journal of applied biomechanics 02/2013; · 1.26 Impact Factor