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: The objective of this study was to investigate the kinematics of the wrist, elbow and shoulder during manual wheelchair maneuvers. A high incidence of musculoskeletal injuries has been reported due to the overuse and high repetitive motion of wrist, elbow and shoulder during wheelchair propulsion. Studies have been conducted with the use of a dynamometer or treadmill to simulate propulsion on level or inclined surface. However, during indoor maneuvering, turning and initiation of wheelchair movement is unavoidable. Six unimpaired subjects and six spinal cord injured subjects were recruited to perform three types of wheelchair maneuvers: straight-line wheelchair propulsion, turning and initiation of wheelchair movement with their comfortable speed. Using the motion analysis system (Vicon 370, Oxford), upper extremity kinematics were determined. Two general findings were indicated from the results: a) the joint movement were highest during straight-line propulsion when compared with turning motion; and b) the joint movement among the SCI subjects were higher than those of the unimpaired subjects during wheelchair maneuvers.01/2002; 3.
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ABSTRACT: The primary purpose of this study was to compare static and dynamic optimization muscle force and work predictions during the push phase of wheelchair propulsion. A secondary purpose was to compare the differences in predicted shoulder and elbow kinetics and kinematics and handrim forces. The forward dynamics simulation minimized differences between simulated and experimental data (obtained from 10 manual wheelchair users) and muscle co-contraction. For direct comparison between models, the shoulder and elbow muscle moment arms and net joint moments from the dynamic optimization were used as inputs into the static optimization routine. RMS errors between model predictions were calculated to quantify model agreement. There was a wide range of individual muscle force agreement that spanned from poor (26.4% Fmax error in the middle deltoid) to good (6.4% Fmax error in the anterior deltoid) in the prime movers of the shoulder. The predicted muscle forces from the static optimization were sufficient to create the appropriate motion and joint moments at the shoulder for the push phase of wheelchair propulsion, but showed deviations in the elbow moment, pronation-supination motion and hand rim forces. These results suggest the static approach does not produce results similar enough to be a replacement for forward dynamics simulations, and care should be taken in choosing the appropriate method for a specific task and set of constraints. Dynamic optimization modeling approaches may be required for motions that are greatly influenced by muscle activation dynamics or that require significant co-contraction.Journal of Biomechanics 09/2014; · 2.50 Impact Factor
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ABSTRACT: This study aims to realize a kinematic simulation of handcycling propulsion in order to investigate some ergonomic aspects specific to this mode of propulsion. We hypothesize that adjustments concerning crank position could minimize the joint range of upper extremity motions and/or avoid reaching the joint limit, which are considered as risk factors for repetitive strain injuries (RSI). One paraplegic and one able-bodied participants performed a handcycling test at a 70 rpm crank rate. A 3D analysis of upper extremity motion was made using a Vicon system (Vicon 370). From the data obtained, an inverse kinematic model at seven degrees of freedom was realized. Inputs to the model include the length of the user's arm segments, the position of the user's shoulder and the size of crank used. Joint kinematics are outputs from the model. The movement was simulated by moving the crank axis, or modifying the distance between the two cranks (±10 cm).From our results, the initial position (synchronous mode and a backrest angle close to 90°), like the “downward” and the “backward” positions, seems to generate a lower joint range of motion than other position adjustments. We were able to formulate a hypothesis as to an optimal crank adjustment to reduce risk factors for RSI. This study must be considered as a first step and needs further investigations with a larger population by seeking movement invariant in order to generalize our results.Relevance to industryResults from such a model would serve to guide future research and to help establish guidelines in order to reach an optimal arm crank wheelchair position based on user characteristics. The results of this study provide some ergonomic recommendations for handcycle design and in this way contribute to the further development of novel wheelchair design.International Journal of Industrial Ergonomics 07/2008; 38(s 7–8):577–583. · 1.21 Impact Factor