Shoulder Pain Is Associated With Rate of Rise and Jerk of the Applied Forces During Wheelchair Propulsion in Individuals With Paraplegic Spinal Cord Injury.

OBJECTIVE: To investigate the association between propulsion biomechanics, including variables that describe smoothness of the applied forces, and shoulder pain in individuals with spinal cord injury (SCI). DESIGN: Cross-sectional, observational study. SETTING: Non-university research institution. PARTICIPANTS: Community dwelling, wheelchair dependent participants (N=30) with chronic paraplegia between T2 and L1, with and without shoulder pain (age, 48.6±9.3y; 83% men). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Rate of rise and jerk of applied forces during wheelchair propulsion. Participants were stratified in groups with low, moderate, and high pain based on their Wheelchair User Shoulder Pain Index score on the day of measurement. RESULTS: A mixed-effect multilevel analysis showed that wheelchair users in the high pain group propelled with a significantly greater rate of rise and jerk, measures that describe smoothness of the applied forces, compared with individuals with less or no pain, when controlling for all covariables. CONCLUSIONS: Individuals with severe shoulder pain propelled with less smooth strokes compared to individuals with less or no pain. This supports a possible association between shoulder pain and rate of rise and jerk of the applied forces during wheelchair propulsion.

Changes in supraspinatus and biceps tendon thickness: influence of fatiguing propulsion in wheelchair users with spinal cord injury.

STUDY DESIGN: A quasi-experimental, pretest-posttest design. OBJECTIVES: To identify acute changes in the supraspinatus and biceps tendon following fatiguing wheelchair propulsion and to associate tendon changes with risk factors associated with shoulder pain in persons with spinal cord injury (SCI). SETTING: Biomechanical laboratory Swiss Paraplegic Research. METHODS: A population-based sample of 50 wheelchair users with SCI at lesion level T2 or below participated. Fatigue was measured by using the rate of perceived exertion and heart rate. Linear regression techniques were used to assess the association between the dependent and independent variables. Dependent variables included absolute differences in supraspinatus and biceps tendon thickness, contrast, and echogenicity ratio assessed with ultrasound before and after a fatiguing wheelchair propulsion intervention. Independent variables included susceptibility to fatigue (Yes/No), the acromio-humeral distance, sex, time since injury, activity levels, and body weight. RESULTS: A reduction in supraspinatus tendon thickness after fatiguing wheelchair propulsion (-1.39 mm; 95% CI: -2.28; -0.51) was identified after controlling for all potential confounders. Females who fatigued (n = 4) displayed a greater reduction in supraspinatus tendon thickness as compared with those who did not fatigue (n = 7). In contrast, higher body weight was associated with an increase in supraspinatus tendon thickness and a greater acromio-humeral distance before the intervention was associated with an increase in biceps tendon thickness. CONCLUSIONS: Acute changes in the supraspinatus and biceps tendon after fatiguing wheelchair propulsion may explain the high prevalence of tendon injuries in this population. Future research should determine the consequences of tendon changes and its relationship to tendinopathy.

Shoulder Pain in Persons With Tetraplegia and the Association With Force Application During Manual Wheelchair Propulsion.

Objective: To investigate the association between propulsion biomechanics, including force application and spatio-temporal characteristics, and shoulder pain in persons with tetraplegia. Design: Cross-sectional, observational study. Setting: Non-university research institution. Participants: 16 community dwelling, wheelchair dependent persons with a chronic tetraplegia between C4 and C7, with and without shoulder pain (age, 49.1±11.7 years; 94% men, 23.4±9.5 years past injury). Interventions: Not applicable. Main Outcome Measures: Force application and spatio-temporal characteristics of wheelchair propulsion on a treadmill (0.56 m/s, 10W and 0.83 m/s, 15W). Participants were stratified in groups with low, moderate, and high pain based on their Wheelchair User Shoulder Pain Index (WUSPI) score on the day of measurement. Results: The mixed-effect multilevel analysis showed that wheelchair users with high levels of shoulder pain applied propulsion force more effectively (and with a lower medial component) and over a longer push angle, thus shortening the recovery time as compared with persons with low or moderate levels of shoulder pain. Conclusions: In contrast with previous results from persons with a paraplegia, persons with tetraplegia and high levels of shoulder pain propel their wheelchair more optimal with regard to risk factors for shoulder pain. Our results therefore affirm that there is a different interaction of shoulder pain and propulsion biomechanics in persons with a tetraplegia which should be considered when further analyzing risk factors for shoulder pain in wheelchair users or applying literature results to different patient populations.

Changes in neuromuscular activation, heart rate and rate of perceived exertion over the course of a wheelchair propulsion fatigue protocol.

Shoulder pain is common in persons with spinal cord injury and has been associated with wheelchair use. Fatigue related compensation strategies have been identified as possibly impacting the development of shoulder injury and pain. The purpose of this study was to investigate the progression of performance fatigability (i.e., decline in objective measure of performance including neuromuscular activation and increase in heart rate) and perceived fatigability (i.e., increased perceived exertion) during a 15-min fatigue protocol including maximum voluntary overground wheelchair propulsion. Fifty participants with paraplegic spinal cord injury completed three 4-min rounds of wheelchair propulsion, separated by 90 s of rest, on a figure-8 course consisting of two turns and full stops per lap in their manual wheelchairs (ClinicalTrials.gov: NCT03153033). Electromyography (EMG) signal of five muscles acting on the shoulder joint, heart rate (HR), and rate of perceived exertion (RPE) were measured at the beginning and end of every 4 min of propulsion. Root Mean Square (RMS) and Mean Power Frequency were calculated from EMG data. There was a significant increase in %RMS of the pectoralis major pars sternalis and trapezius pars descendens, HR, and RPE with greatest changes during the first 4 min of the protocol. The observed changes in neuromuscular activation in only two of the shoulder muscles may impact muscular imbalances and the development of shoulder injuries and should be further studied. The current study gives clearer insight into the mechanisms of performance fatigability and perceived fatigability throughout a wheelchair propulsion fatigue protocol.

The non-intuitive, in-vivo behavior of aponeuroses in a unipennate muscle.

Experimental observations and theoretical models suggest that the loading of muscular aponeuroses is complex, causing strain patterns that are not reconcilable with the frequently assumed mechanical "in series" arrangement of aponeuroses with muscles and tendons. The purpose of this work was to measure the in-vivo longitudinal strains of the distal and proximal aponeuroses and force of the unipennate Medial Gastrocnemius (MG) muscle during locomotor activities. Sonomicrometry crystals and a force buckle transducer were implanted to measure aponeurosis strains and MG forces in the left hindlimb of four healthy female sheep while walking at different speeds and inclination angles on a motorized treadmill. The resulting aponeurosis strains versus the corresponding muscle forces resulted in a complex interaction that is not reconcilable with a mechanical "in series" arrangement of aponeuroses with either the free tendon or muscle, as has frequently been assumed when trying to determine the storage and release of mechanical energy in muscles or the stiffness and elastic modulus of in-vivo aponeurosis tissues. We conclude that the interaction of muscle tissue with aponeuroses in the sheep MG allows for elongation of the aponeuroses at low forces in the passive muscle, while elongation in the active muscle is greatly reduced possibly due to the complex shear forces and pressures produced when the muscle is activated. It is likely that the observed aponeurosis mechanics are similar in other unipennate skeletal muscles, but the current study was limited to a single muscle and therefore does not allow for such extrapolation at this time.

Evolution of rehabilitation services in response to a global pandemic: reflection on opportunities and challenges ahead.

The rapidly evolving COVID-19 public health emergency has disrupted and challenged traditional healthcare, rehabilitation services, and treatment delivery worldwide. This perspective paper aimed to unite experiences and perspectives from an international group of rehabilitation providers while reflecting on the lessons learned from the challenges and opportunities raised during the COVID-19 pandemic. We discuss the global appreciation for rehabilitation services and changes in access to healthcare, including virtual, home-based rehabilitation, and long-term care rehabilitation. We illustrate lessons learned by highlighting successful rehabilitation approaches from the US, Belgium, and Japan.

Effect of Fatiguing Wheelchair Propulsion and Weight Relief Lifts on Subacromial Space in Wheelchair Users.

Objective: This study aimed to identify targets of intervention for reducing shoulder pain in wheelchair users with spinal cord injury (SCI) by (1) examining changes in subacromial space [acromiohumeral distance (AHD) and occupation ratio (OccRatio)] with fatiguing wheelchair propulsion, and different loading conditions [unloaded position vs. weight relief lifts (WRL)]; (2) associating these changes with wheelchair user capacity, as well as (3) identifying subject characteristics associated with subacromial space, such as sex, lesion level, time since injury, body mass index and impaired shoulder range of motion. Methods: Fifty manual wheelchair users with SCI [11 females, age = 50.5 (9.7) years, time since injury = 26.2 (11.4) years] participated in this quasi-experimental one-group pretest-posttest study. Ultrasound images were used to define AHD during an unloaded position, and during personal and instructed WRL before and after fatiguing wheelchair propulsion. Furthermore, supraspinatus and biceps thickness defined from ultrasound images were used to calculate OccRatios. Wheelchair user capacity was quantified as functional strength (maximum resultant force reached during maximum isometric forward push) and anaerobic work capacity (highest power output reached during 15-m sprint test). Multilevel mixed-effects linear regression analyses controlling for between subject variability and covariables were performed to address the research questions. Results: AHD was significantly smaller during personal WRL (p < 0.001) and instructed WRL (p = 0.009, AHD both 11.5 mm) compared to the unloaded position (11.9 mm). A higher wheelchair user capacity (higher anaerobic work capacity) reduced the impact of WRL on AHD decrease. The fatiguing wheelchair propulsion had no effect on AHD (p = 0.570) and on OccRatio of supraspinatus (p = 0.404) and biceps (p = 0.448). Subject characteristics related to a larger subacromial space were lower lesion level, shorter time since injury, impaired external rotation, a lower body mass index and a higher anaerobic work capacity. Conclusion: This study showed a significant reduction in AHD during WRL with no effect of fatiguing wheelchair propulsion on the subacromial space in wheelchair users with SCI. A higher anaerobic work capacity was beneficial in stabilizing the shoulder during WRL. Our findings may assist clinicians in designing a shoulder injury prevention program.

Compensation Strategies in Response to Fatiguing Propulsion in Wheelchair Users: Implications for Shoulder Injury Risk.

OBJECTIVE: The aims of the study were to examine whether fatigue-inducing wheelchair propulsion changes neuromuscular activation and propulsion biomechanics and to determine predictor variables for susceptibility to fatigue. DESIGN: This study with a quasi-experimental, one-group, pretest-posttest design investigates a population-based sample of wheelchair users with a spinal cord injury (n = 34, age: 50.8 ± 9.7 yrs, 82% males). Neuromuscular activation and propulsion biomechanics during treadmill propulsion at 25 W and 45 W were assessed before and after a protocol designed to cause fatigue. RESULTS: With the induced fatigue, wheelchair users propelled with increased neuromuscular activation in the pectoralis major pars sternalis, deltoideus pars acromialis and upper trapezius (45 W, P < 0.05), and a slightly reduced push angle (25 W: 75-74 degrees, P < 0.05, 45 W: 78-76 degrees, P < 0.05). Wheelchair users susceptible to fatigue (47%) were more likely to have a complete lesion, to be injured at an older age, and had less years since injury. This group propelled in general with shorter push angle and greater maximum resultant force, had a greater anaerobic capacity, and had less neuromuscular activation. CONCLUSIONS: Compensation strategies in response to fatiguing propulsion could increase the risk for shoulder injury. Predictor variables for susceptibility to fatigue inform interventions preserving shoulder health and include lesion characteristics, propulsion technique, anaerobic capacity, and neuromuscular activation. TO CLAIM CME CREDITS: Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME OBJECTIVES: Upon completion of this article, the reader should be able to: (1) Explain a neuromuscular compensation strategy and the corresponding muscles in response to fatiguing wheelchair propulsion; (2) Recommend propulsion biomechanics associated to reduced susceptibly to fatiguing wheelchair propulsion; and (3) List examples of predictor variables of susceptibility to fatigue. LEVEL: Advanced. ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Start-up propulsion biomechanics changes with fatiguing activity in persons with spinal cord injury.

Objective: Shoulder pathology is a common condition in wheelchair users that can considerably impact quality of life. Shoulder muscles are prone to fatigue, but it is unclear how fatigue affects start-up propulsion biomechanics. This study determines acute changes in start-up wheelchair propulsion biomechanics at the end of a fatiguing propulsion protocol. Design: Quasi-experimental one-group pretest-postest design. Setting: Biomechanics laboratory. Participants: Twenty-six wheelchair users with spinal cord injury (age: 35.5 ± 9.8 years, sex: 73% males and 73% with a paraplegia). Interventions: Protocol of 15 min including maximum voluntary propulsion, right- and left turns, full stops, start-up propulsion, and rests. Outcome measures: Maximum resultant force, maximum rate of rise of applied force, mean velocity, mean fraction of effective force, and mean contact time at the beginning and end of the protocol during start-up propulsion. Results: There was a significant reduction in maximum resultant force (P < 0.001) and mean velocity (P < 0.001) at the end of the protocol. Also, contact time was reduced in the first stroke of start-up propulsion (P < 0.001). Finally, propelling with a shorter contact time was associated with a greater reduction in performance (maximum velocity) at the end of the protocol. Conclusion: There are clear changes in overground propulsion biomechanics at the end of a fatiguing propulsion protocol. While reduced forces could protect the shoulder, these reduced forces come with shorter contact times and lower velocity. Investigating changes in start-up propulsion biomechanics with fatigue could provide insight into injury risk.

Shoulder pain in the Swiss spinal cord injury community: prevalence and associated factors.

PURPOSE: To determine the prevalence of shoulder pain and to identify factors associated with shoulder pain in a nationwide survey of individuals living with spinal cord injury (SCI) in Switzerland. METHODS: Data was collected through the 2012 community survey of the Swiss SCI Cohort Study (SwiSCI) (N = 1549; age 52.3 ± 14.8; 29% female). Sociodemographic and socioeconomic circumstances, SCI characteristics, health conditions as well as mobility independence and sporting activities were evaluated as predictor variables. Analyses were adjusted for item non-response (using multiple imputation) and unit-nonresponse (using inverse probability weighting). RESULTS: The adjusted prevalence of shoulder pain was 35.8% (95% CI: 33.4-38.3). Multivariable regression analysis revealed higher odds of shoulder pain in females as compared to males (odds ratio: 1.89; 95% CI: 1.44-2.47), and when spasticity (1.36; 1.00-1.85) and contractures (2.47; 1.91-3.19) were apparent. Individuals with complete paraplegia (1.62; 1.13-2.32) or any tetraplegia (complete: 1.63; 1.01-2.62; incomplete: 1.82; 1.30-2.56) showed higher odds of shoulder pain compared to those with incomplete paraplegia. CONCLUSIONS: This survey revealed a high prevalence of shoulder pain. Sex, SCI severity, and specific health conditions were associated with having shoulder pain. Implications for rehabilitation Individuals with spinal cord injury have a high prevalence of shoulder pain. Females, individuals with complete paraplegia or any tetraplegia and individuals with contractures and spasticity should receive considerable attention in rehabilitation programmes due to their increased odds of having shoulder pain.