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). Leveractivated (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 STand 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: Sign ificant 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.     

Effect of fore-aft seat position on shoulder demands during wheelchair propulsion: part 2. An electromyographic analysis

BACKGROUND/OBJECTIVES: Shoulder pain is common in persons with complete spinal cord injury. Adjustment of the wheelchair-user interface has been thought to reduce shoulder demands. The purpose of this study was to quantify the effect of seat fore-aft position on shoulder muscle activity during wheelchair propulsion. METHODS: Shoulder electromyography (EMG) was recorded while 13 men with paraplegia propelled a wheelchair in the following 2 seat positions: (a) shoulder joint center aligned with the wheel axle (anterior) and (b) shoulder joint center 8 cm posterior to the wheel axle (posterior) in 3 test conditions (free, fast, and graded). Duration of EMG activity and median and peak intensities were compared. RESULTS: During free propulsion, the median EMG intensity of all muscles was similar between anterior and posterior seat positions. The major propulsive muscles (pectoralis major and anterior deltoid) demonstrated significant reductions in their median and peak intensities in the posterior seat position. Pectoralis major median intensity was significantly reduced in the posterior position during fast (52% vs 66% maximal muscle test [MMT]) and graded (41 % vs 49% MMT) conditions, and peak intensity was significantly reduced in the free condition (29% vs 52% MMT) and the fast condition (103% vs 150% MMT). Anterior deltoid intensity was significantly reduced in the posterior position during fast propulsion only (26% vs 31% MMT). For all muscles, EMG duration was similar between positions in all test conditions. CONCLUSIONS: Reduction in the intensity of the primary push phase muscles (pectoralis major and anterior deltoid) during high-demand activities of fast and graded propulsion may reduce the potential for shoulder muscle fatigue and injuries.     

Effect of reverse manual wheelchair propulsion on shoulder kinematics,kinetics and muscular activity in persons with paraplegia

Objective: Shoulder pain after spinal cord injury (SCI) is attributed to increased mobility demands on the arms and negatively impacts independence and quality of life. Repetitive superior and posterior shoulder joint forces produced during traditional wheelchair (WC) locomotion can result in subacromial impingement if unopposed, as with muscular fatigue or weakness. ROWHEELS^® (RW), geared rear wheels that produce forward WC movement with backward rim pulling, could alter these forces.

Design: Cross sectional.

Setting: Research laboratory at a rehabilitation hospital.

Participants: Ten manual WC users with paraplegia.

Outcome measures: Propulsion characteristics and right upper extremity/trunk kinematics and shoulder muscle activity were collected during ergometer propulsion: (1) self-selected free speed reverse propulsion with RW, (2) matched-speed reverse (rSW), and (3) forward propulsion (fSW) with instrumented Smartwheels (SW). Inverse dynamics using right-side SW rim kinetics and kinematics compared shoulder kinetics during rSW and fSW.

Results: Free propulsion velocity, cycle distance and cadence were similar during RW, rSW and fSW. Overall shoulder motion was similar except that peak shoulder extension was significantly reduced in both RW and rSW versus fSW. Anteriorly and inferiorly directed SW rim forces were decreased during rSW versus fSW propulsion, but posteriorly and superiorly directed rim forces were significantly greater. Superior and posterior shoulder joint forces and flexor, adductor, and external rotation moments were significantly less during rSW, without a significant difference in net shoulder forces and moments. Traditional propulsive-phase muscle activity was significantly reduced and recovery-phase muscle activity was increased during reverse propulsion.

Conclusion: These results suggest that reverse propulsion may redirect shoulder demands and prevent subacromial impingement, thereby preventing injury and preserving independent mobility for individuals with paraplegia.     

The effect of level of spinal cord injury on shoulder joint kinetics during manual wheelchair propulsion.

OBJECTIVE: The effects of spinal cord injury level on shoulder kinetics during manual wheelchair propulsion were studied. DESIGN: Single session data collection in a laboratory environment. METHODS: Male subjects were divided into four groups: low level paraplegia (n=17), high level paraplegia (n=19), C7 tetraplegia (C7, n=16) and C6 tetraplegia (C6, n=17). Measurements were recorded using a six-camera VICON motion analysis system, a strain gauge instrumented wheel, and wheelchair ergometer. Shoulder joint forces and moments were calculated using the inverse dynamics approach. RESULTS: Mean self-selected propulsion velocity was higher in the paraplegic (low paraplegia=90.7 m/min; high paraplegia=83.4 m/min) than tetraplegic (C7=66.5 m/min; C6=47.0 m/min) groups. After covarying for velocity, no significant differences in shoulder joint moments were identified. However, superior push force in subjects with tetraplegia (C7=21.4 N; C6=9.3 N) was significantly higher than in those with high paraplegia (7.3 N), after covarying velocity. CONCLUSIONS: The superior push force in the tetraplegic groups coupled with weakness of thoraco-humeral depressors increases susceptibility of the subacromial structures to compression. RELEVANCE: Increased vertical force at the shoulder joint, coupled with reduced shoulder depressor strength, may contribute to shoulder problems in subjects with tetraplegia. Wheelchair design modifications, combined with strength and endurance retention, should be considered to prevent shoulder pain development.     

Three dimensional upper extremity motion during manual wheelchair propulsion in men with different levels of spinal cord injury

This investigation compared three dimensional upper extremity motion during wheelchair propulsion in persons with 4 levels of spinal cord injury: low paraplegia (n=17), high paraplegia (n=19), C7 tetraplegia (n=16), and C6 tetraplegia (n=17). Upper extremity motion was recorded as subjects manually propelled a wheelchair mounted on a stationary ergometer. For all motions measured, subjects with paraplegia had similar patterns suggesting that the wheelchair backrest adequately stabilizes the trunk in the absence of abdominal musculature. Compared with paraplegic subjects, those with tetraplegia differed primarily in the strategy used to contact the wheel. This was most evident among subjects with C6 tetraplegia who had greater wrist extension and less forearm pronation.     

Stiff-legged gait in spastic paresis. A study of quadriceps and hamstrings muscle activity.

Stiff-legged gait, ascribed to limited knee flexion during swing in spastic paresis, has previously received little detailed investigation. In this study, data from 23 patients referred for dynamic electromyographic evaluation of spastic stiff-legged gait were analyzed to identify timing of the activity of eight muscles during the gait cycle. Stride characteristics and foot switch data were also analyzed. Inappropriate activity in at least one of the quadriceps muscles during the preswing and/or initial swing phases was found in all 23 patients. Nine patients (39%) had hamstring activity during preswing. This group of 9, compared with the other 14 patients, had a significant reduction in average gait velocity and stride length (P less than 0.05) suggesting that preswing hamstring activity in stiff-legged gait may be counterproductive. No relation was found between biceps femoris (short head) activity and the amount of peak knee flexion attained in swing indicating that other factors are more important in attaining knee flexion. Delayed heel rise was observed in 21 patients (91%), which could imply insufficient calf muscle strength. Further, patients with markedly delayed heel rise achieved less peak knee flexion in swing than patients with normal or only moderately delayed heel rise (P less than 0.05). This may support the notion that adequate calf muscle strength is important in initiating knee flexion in the terminal stance/preswing phase. Results from this study provide preliminary quantitative information about stiff-legged gait that may prove useful in guiding management techniques.     

Electromyographic and kinematic analysis of the shoulder during four activities of daily living in men with C6 tetraplegia

The pattern of motor paralysis that commonly follows C6 tetraplegia creates an increased demand on upper limb function. The present investigation documented shoulder motion and muscular activity during planar motions and four activities of daily living (ADLs) in 15 men with spinal cord injuries (SCI) resulting in C6 tetraplegia. Three-dimensional (3-D) shoulder motion was recorded using a VICON motion system, and intramuscular electrodes recorded electromyographic (EMG) activity of 12 shoulder muscles. Active flexion and abduction required greater EMG than control subjects lifting a 2-kg weight. Relative EMG was similar for most muscles during hair combing, drinking, and reaching forward, although increased humeral elevation commonly resulted in a greater relative muscular effort. Hair combing had the most humeral elevation (90 degrees) with moderate to high levels of activation (32% to 63% maximum) recorded in the anterior deltoid, supraspinatus, infraspinatus, and scapular muscles. During reaching for the perineum, posterior deltoid and subscapularis activity dominated.     

Use of cluster analysis for gait pattern classification of patients in the early and late recovery phases following stroke

The mixture of gait deviations seen in patients following a stroke is remarkably variable. An objective system for classification of gait patterns for this population could be used to guide treatment planning. Quantitated gait analysis was conducted for 47 individuals at admission to in-patient rehabilitation and again at 6 months post-stroke for 42 subjects. Non-hierarchical cluster analysis was used to classify the gait patterns of patients based on the temporal-spatial and kinematic parameters of walking. Four clusters of patients were identified at both assessment intervals. At the admission test walking velocity, peak knee extension in mid stance and peak dorsiflexion in swing were the three factors that best characterized the groups. At 6 months the explanatory variables were velocity, knee extension in terminal stance, and knee flexion in pre swing. Differences in muscle strength and muscle activation patterns during walking were identified between groups.     

Valgus deformities of the feet and characteristics of gait in patients who have rheumatoid arthritis

To investigate the cause of valgus deformity of the hindfoot in patients who have rheumatoid arthritis and to characterize the effects of the deformity on gait, two groups of patients were evaluated clinically, radiographically, and with gait analysis in the laboratory. Group 1 consisted of seven patients who had seropositive rheumatoid arthritis and normal alignment of the feet and Group 2, of ten patients who had rheumatoid arthritis and valgus deformity of the hindfoot. In Group 2, the disease was of longer duration and the feet were more painful than in Group 1. There was no evidence of muscular imbalance, equinus contracture, valgus deformity of the tibiotalar joint, or isolated deficiency of the tibialis posterior (such as weakness, tenosynovitis, or rupture of the tendon) that could have contributed to the development of the valgus deformity. In the patients who had valgus deformity, quantitated electromyography demonstrated that the intensity and duration of activity of the tibialis posterior was significantly increased, apparently in an effort to support the collapsing longitudinal arch of the foot. Gait studies revealed decreases in velocity, stride length, and single-limb-support time, as well as delayed heel-rise in both groups, but the decreases were more marked in the patients who had valgus deformity. The results of this study suggest that valgus deformity of the hindfoot in rheumatoid patients results from exaggerated pronation forces on the weakened and inflamed subtalar joint. These forces are caused by alterations in gait secondary to symmetrical muscular weakness and the effort of the patient to minimize pain in the feet. Radiographs also suggested an association between the valgus deformity of the feet and valgus deformity of the knees in patients who have rheumatoid arthritis.     

Toe walking: muscular demands at the ankle and knee

OBJECTIVE: To compare the relationship between electromyographic activity and internal moment in heel-toe and toe walking. DESIGN: Simultaneous recording of stride characteristics and kinematic, kinetic, and intramuscular electromyographic data; paired t tests identified significant between-condition differences. SETTING: Gait laboratory. PARTICIPANTS: Ten able-bodied subjects. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Kinematic, moment, power, and electromyographic variables (ankle, knee). RESULTS: Compared with heel-toe walking, toe walking showed greater plantarflexion during stance (P<.001), higher plantarflexor moments (peak, mean) during loading response (P<.001) and midstance (P<.001), lower mean plantarflexor moments during terminal stance (P=.002), premature soleus (P=.001) and gastrocnemius (P<.001) activity, and higher levels of mean soleus and gastrocnemius activity during stance. During toe walking, the peak internal knee extensor moment was lower in midstance (P=.002), and power absorption was reduced in loading response; however, vastus intermedius electromyographic activity was not reduced. CONCLUSIONS: During toe walking, terminal stance soleus and gastrocnemius activity was greater, despite a lower mean internal plantarflexor moment. The dichotomy between internal moments and muscle effort (ie, electromyographic activity) was consistent with the reduction in force-generation capacity of the calf muscles when the ankle was in a plantarflexed position.