Comparison of shoulder muscle electromyographic activity during standard manual wheelchair and push-rim activated power assisted wheelchair propulsion in persons with complete tetraplegia.

OBJECTIVES: To compare spatio-temporal propulsion characteristics and shoulder muscle electromyographic activity in persons with cervical spinal cord injury propelling a standard pushrim wheelchair (WC) and a commercially available pushrim-activated power assisted wheelchair (PAPAW) design on a stationary ergometer. DESIGN: Repeated measures. SETTING: Motion analysis laboratory within a rehabilitation hospital. PARTICIPANTS: Men (N=14) with complete (American Spinal Injury Association grade A or B) tetraplegia (C6=5; C7=9). INTERVENTION: Participants propelled a standard pushrim WC and PAPAW during 3 propulsion conditions: self-selected free and fast and simulated 4% or 8% graded resistance propulsion. MAIN OUTCOME MEASURES: Median speed, cycle length, cadence, median and peak electromyographic activity intensity, and duration of electromyographic activity in pectoralis major, anterior deltoid, supraspinatus, and infraspinatus muscles were compared between standard pushrim WC and PAPAW propulsion. RESULTS: A significant (P<.05) decrease in electromyographic activity intensity and duration of pectoralis major, anterior deltoid, and infraspinatus muscles and significantly reduced intensity and push phase duration of supraspinatus electromyographic activity at faster speeds and with increased resistance were seen during PAPAW propulsion. CONCLUSIONS: For participants with complete tetraplegia, push phase shoulder muscle activity was decreased in the PAPAW compared with standard pushrim WC, indicating a reduction in demands when propelling a PAPAW.

Shoulder muscular demand during lever-activated vs pushrim wheelchair propulsion in persons with spinal cord injury.

BACKGROUND/OBJECTIVE: The high demand on the upper limbs during manual wheelchair (WC) use contributes to a high prevalence of shoulder pathology in people with spinal cord injury (SCI). Lever-activated (LEVER) WCs have been presented as a less demanding alternative mode of manual WC propulsion. The objective of this study was to evaluate the shoulder muscle electromyographic activity and propulsion characteristics in manual WC users with SCI propelling a standard pushrim (ST) and LEVER WC design. METHODS: Twenty men with complete injuries (ASIA A or B) and tetraplegia (C6, n = 5; C7, n = 7) or paraplegia (n = 8) secondary to SCI propelled ST and LEVER WCs at 3 propulsion conditions on a stationary ergometer: self-selected free, self-selected fast, and simulated graded resistance. Average velocity, cycle distance, and cadence; median and peak electromyographic intensity; and duration of electromyography of anterior deltoid, pectoralis major, supraspinatus, and infraspinatus muscles were compared between LEVER and ST WC propulsion. RESULTS: Significant decreases in pectoralis major and supraspinatus activity were recorded during LEVER compared with ST WC propulsion. However, anterior deltoid and infraspinatus intensities tended to increase during LEVER WC propulsion. Participants with tetraplegia had similar or greater anterior deltoid, pectoralis major, and infraspinatus activity for both ST and LEVER WC propulsion compared with the men with paraplegia. CONCLUSIONS: Use of the LEVER WC reduced and shifted the shoulder muscular demands in individuals with paraplegia and tetraplegia. Further studies are needed to determine the impact of LEVER WC propulsion on long-term shoulder function.

Upper extremity kinetics during Lofstrand crutch-assisted gait.

A three-dimensional (3D) biomechanical model was developed to determine upper extremity kinematics and kinetics of persons walking with forearm crutches. Six-component load cells and strain gauges were installed in the crutches to determine crutch forces. A six-camera VICON motion system was used to acquire coordinate data from 24 reflective markers attached to the upper extremities and crutches. Joint axes for the wrist, elbow, and glenohumeral joints were defined and joint forces and moments were determined using inverse dynamics. Accuracy of the crutch instrumentation was established by simultaneously collecting force data from a Kistler forceplate and each crutch during crutch-assisted gait with the respective crutch tip contacting the forceplate. In order to demonstrate the application of this biomechanical model, upper extremity weight bearing forces, joint motion, and stride characteristics were recorded from a subject with T-12 incomplete spinal cord injury (SCI), using a crutch-assisted reciprocal four-point gait pattern. The peak net joint forces and moments were greater for the right arm opposite the weaker left lower extremity. The largest joint forces were directed superiorly (Fz) and the asymmetrical pattern of crutch use was consistent with lower extremity strength differences. During left leg weight acceptance, increased right wrist extension motion and moment were recorded, which may contribute to wrist pathology.