Propulsion Biomechanics and Functional Performance of ... · Propulsion mechanics were measured...
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Propulsion Biomechanics and Functional Performance of Manual Wheelchair Users Mary M. Rodgers, Ph.D., P.T. 1,2 , Elizabeth K. Rasch, M.S., P.T. 2 , Margaret A. Finley, M.A., P.T. 2 , Randall E. Keyser, Ph.D. 2 , Peter R. Gorman, M.D. 1,3 1 Veterans Affairs Maryland Health Care System, Research & Development Service, Baltimore, MD; 2 University of Maryland, School of Medicine, Department of Physical Therapy and 3 Department of Neurology, Baltimore, MD Introduction Although wheelchair propulsion is a demanding task, many manual wheelchair users (MWCU) are independent in community mobility and activities of daily living (ADLs). Investigators such as Woude, et al. (1988) and Dallmeijer, et al. (1994) have suggested that power output and other biomechanical measures in wheelchair users may be related to function. However, to date no research has been conducted to investigate the connection between functional performance and the mechanics employed in wheelchair propulsion. The purpose of this study was to investigate the relationship between functional performance and propulsion mechanics. Methods Following informed consent and medical screening, 38 MWCU (29 men, 9 women; age = 37 + 9 years, years of wheelchair use = 11 + 8) were included in the study. Diagnoses included spinal cord injury (20), spina bifida (4), cerebral palsy (4), and others (10). The assistance necessary for MWCU to perform basic ADLs and community mobility was quantified using a new tool. As shown in Table 1, each of 13 items was scored on a seven level scale incorporating speed (1=total dependence, 7=total independence). Table 1. Wheelchair Users Functional Assessment (WUFA) Item 1 WHEELCHAIR PROPULSION--MANEUVERING IN TIGHT SPACE Item 2 WHEELCHAIR PROPULSION--UNEVEN TERRAIN Item 3 WHEELCHAIR PROPULSION--DOOR MANAGEMENT Item 4 WHEELCHAIR PROPULSION--STREET CROSSING Item 5 WHEELCHAIR PROPULSION--RAMP Item 6 WHEELCHAIR PROPULSION--CURB Item 7 WHEELCHAIR TRANSFER--BED Item 8 WHEELCHAIR TRANSFER--TOILET Item 9 WHEELCHAIR TRANSFER--FLOOR Item 10 TUB TRANSFER AND BATHING Item 11 DRESSING -- UPPER AND LOWER BODY DRESSING Item 12 FUNCTIONAL MOBILITY TASKS-- REACHING, CARRYING, LIFTING, AND POURING Item 13 FUNCTIONAL MOBILITY TASKS-- PICKING UP OBJECTS AND SWEEPING FLOOR Propulsion mechanics were measured during a single-stage exercise test (3 km/hr) using a stationary wheelchair ergometer instrumented with 3-D force/torque transducers in the wheel hubs (Figure 1). Orientation of the x-y-z transducer coordinates was tangential (forward+), medial-lateral (out of the wheel+) and radial (up+), respectively. Peak handrim forces and moments were averaged over three cycles. Power
Transcript of Propulsion Biomechanics and Functional Performance of ... · Propulsion mechanics were measured...
Propulsion Biomechanics and Functional Performance of Manual Wheelchair Users
Mary M. Rodgers, Ph.D., P.T.1,2, Elizabeth K. Rasch, M.S., P.T.2, Margaret A. Finley, M.A., P.T. 2, Randall E. Keyser, Ph.D. 2, Peter R. Gorman, M.D.1,3
1Veterans Affairs Maryland Health Care System, Research & Development Service, Baltimore, MD; 2University of Maryland, School of Medicine, Department of Physical Therapy and 3Department of
Neurology, Baltimore, MD Introduction
Although wheelchair propulsion is a demanding task, many manual wheelchair users (MWCU) are independent in community mobility and activities of daily living (ADLs). Investigators such as Woude, et al. (1988) and Dallmeijer, et al. (1994) have suggested that power output and other biomechanical measures in wheelchair users may be related to function. However, to date no research has been conducted to investigate the connection between functional performance and the mechanics employed in wheelchair propulsion. The purpose of this study was to investigate the relationship between functional performance and propulsion mechanics. Methods
Following informed consent and medical screening, 38 MWCU (29 men, 9 women; age = 37 + 9 years, years of wheelchair use = 11 + 8) were included in the study. Diagnoses included spinal cord injury (20), spina bifida (4), cerebral palsy (4), and others (10). The assistance necessary for MWCU to perform basic ADLs and community mobility was quantified using a new tool. As shown in Table 1, each of 13 items was scored on a seven level scale incorporating speed (1=total dependence, 7=total independence).
Table 1. Wheelchair Users Functional Assessment (WUFA) Item 1 WHEELCHAIR PROPULSION--MANEUVERING IN TIGHT SPACE Item 2 WHEELCHAIR PROPULSION--UNEVEN TERRAIN Item 3 WHEELCHAIR PROPULSION--DOOR MANAGEMENT Item 4 WHEELCHAIR PROPULSION--STREET CROSSING Item 5 WHEELCHAIR PROPULSION--RAMP Item 6 WHEELCHAIR PROPULSION--CURB Item 7 WHEELCHAIR TRANSFER--BED Item 8 WHEELCHAIR TRANSFER--TOILET Item 9 WHEELCHAIR TRANSFER--FLOOR Item 10 TUB TRANSFER AND BATHING Item 11 DRESSING -- UPPER AND LOWER BODY DRESSING Item 12 FUNCTIONAL MOBILITY TASKS-- REACHING, CARRYING, LIFTING, AND POURING Item 13 FUNCTIONAL MOBILITY TASKS-- PICKING UP OBJECTS AND SWEEPING FLOOR
Propulsion mechanics were measured during a single-stage exercise test (3 km/hr) using a stationary wheelchair ergometer instrumented with 3-D force/torque transducers in the wheel hubs (Figure 1). Orientation of the x-y-z transducer coordinates was tangential (forward+), medial-lateral (out of the wheel+) and radial (up+), respectively. Peak handrim forces and moments were averaged over three cycles. Power
output was defined as (load (kg) X roll distance (6.32 m) X 32rpm)/6.1kg·m/min. All numbers in the formula were constant except for load, thus, variation in power output reflects variation in load. Pearson product moment correlation coefficients (r) were calculated to determine if significant relationships (p<0.05) existed between the functional test scores and handrim variables.
Figure 1. Prototype wheelchair ergometer Results
As shown in Figure 2, power output and the functional test (WUFA) scores were related (r = 0.79).
Peak forward tangential forces (Fx) and propulsive moments (Mz) were positively correlated with functional test scores (r = 0.35 to 0.68), while downward radial force (Fy) was inversely correlated (r = -0.37 to -0.52). When normalized by power output, Fx and Mz were inversely correlated with functional test score (r = -0.47 to -0.62) while Fy was positively correlated (r = 0.40 to 0 .48).
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Figure 2. Scatterplot showing power output measured in watts and WUFA scores. A WUFA score of 91 indicates total independence without assistive equipment.
Discussion/Conclusion
In this diverse sample of MWCU, those with the greatest functional independence produced the largest propulsive forces and torques. However, when normalized by power output, those with the lowest functional independence produced the highest propulsive forces/torques. Since performance of daily tasks in real world situations has absolute force requirements, the force producing capability of MWCU may be crucial to successful performance of routine functional tasks. Further investigation of these relationships is required. References Woude LHV, et al. Med Sci Sports Exerc,20:70-78,1988. Dallmeijer AJ, et al. J Rehab R&D;31:120-128, 1994. Acknowledgements This research was funded by the Department of Veterans Affairs, VA Rehabilitation R&D Service, Washington, DC 20420 (Merit Review Board Project # B2168RA).
