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A Reappraisal of Ventilatory Thresholds in Wheelchair Athletes With a Spinal Cord Injury: Do They Really Exist?

ABSTRACT: The ventilatory threshold (VT) separates low- from moderate-intensity exercise, the respiratory compensation point (RCP) moderate- from high-intensity exercise. Both concepts assume breakpoints in respiratory data. However, the objective determination of the VT and RCP using breakpoint models during upper-body modality exercise in wheelchair athletes with spinal cord injury (SCI) has received little attention. Therefore, the aim of this study was to compare the fit of breakpoint models (i.e., two linear regression lines) with continuous no-breakpoint models (i.e., exponential curve/second-order polynomial) to respiratory data obtained during a graded wheelchair exercise test to exhaustion. These fits were compared employing adjusted R2, and blocked bootstrapping was used to derive estimates of a median and 95% confidence intervals (CI). V̇O2-V̇CO2 and V̇E/V̇O2-time data were assessed for the determination of the VT, and V̇CO2-V̇E and V̇E/V̇CO2-time data for the determination of the RCP. Data of 9 wheelchair athletes with tetraplegia and 8 with paraplegia were evaluated. On an overall group-level, there was an overlap in the adjusted R2 median ± 95% CI between the breakpoint and the no-breakpoint models for determining the VT (V̇O2-V̇CO2: 0.991 ± 0.003 vs. 0.990 ± 0.003; V̇E/V̇O2-time: 0.792 ± 0.101 vs. 0.782 ± 0.104, respectively) and RCP (V̇E-V̇CO2: 0.984 ± 0.004 vs. 0.984 ± 0.004; V̇E/V̇CO2-time: 0.729 ± 0.064 vs. 0.691 ± 0.063, respectively), indicating similar model fit. We offer two lines of reasoning: (1) breakpoints in these respiratory data exist but are too subtle to result in a significant difference in adjusted R2 between the investigated breakpoint and no-breakpoint models; (2) breakpoints do not exist, as has been argued previously.

SUBMITTER: Baumgart JK

PROVIDER: S-EPMC8664409 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundMost individuals with spinal cord injury who use manual wheelchairs experience shoulder pain related to wheelchair use, potentially in part from mechanical impingement of soft tissue structures within the subacromial space. There is evidence suggesting that scapula and humerus motion during certain wheelchair tasks occurs in directions that may reduce the subacromial space, but it hasn't been thoroughly characterized in this context.MethodsShoulder motion was imaged and quantified during scapular plane elevation with/without handheld load, propulsion with/without added resistance, sideways lean, and weight-relief raise in ten manual wheelchair users with spinal cord injury using biplane fluoroscopy and computed tomography. For each position, minimum distance between rotator cuff tendon insertions (infraspinatus, subscapularis, supraspinatus) and the coracoacromial arch was determined. Tendon thickness was measured with ultrasound, and impingement risk scores were defined for each task based on frequency and amount of tendon compression.FindingsPeriods of impingement were identified during scapular plane elevation and propulsion but not during pressure reliefs in most participants. There was a significant effect of activity on impingement risk scores (P < 0.0001), with greatest impingement risk during scapular plane elevation followed by propulsion. Impingement risk scores were not significantly different between scapular plane elevation loading conditions (P = 0.202) or propulsion resistances (P = 0.223). The infraspinatus and supraspinatus tendons were both susceptible to impingement during scapular plane elevation (by acromion), whereas the supraspinatus was most susceptible during propulsion (by acromion and coracoacromial ligament).InterpretationThe occurrence of mechanical impingement during certain manual wheelchair tasks, even without increased load/resistance, demonstrates the importance of kinematics inherent to a task as a determinant of impingement. Frequency of and technique used to complete daily tasks should be carefully considered to reduce impingement risk, which may help preserve shoulder health long-term.

Project description:Highlights • Shorter time since injury and higher mobility levels as well as poor physical health are associated with higher risk of falls and fall-related injuries, respectively in wheelchair users with spinal cord injury.• The findings indicate good discriminant ability and clinical utility of the factors presented to identify wheelchair users who are at risk of falls and fall-related injuries. Objective To identify risk factors for falls and fall-related injuries for wheelchair users with spinal cord injury (SCI). Design Cross-sectional study. Setting Community setting. Participants Fifty-nine community dwelling wheelchair users (N=59), 47.5% male, median age of 52.5 years (IQR, 21 years) with chronic SCI, median time since injury of 16.6 years (IQR, 27.3 years). Interventions No intervention. Main Outcome Measures Outcomes were incidence of falls and fall-related injuries. Participants reported on falls and fall-related injuries experienced in the previous 6 months. Independent variables were self-reported and performance-based measures. Self-reported measures included demographics, characteristics of SCI, fear of falling, psychological measures, functional independence, wheelchair skills, environmental barriers, quality of life, and community participation. Performance-based measures included transfer quality and sitting balance assessments. Logistic regression analyses were conducted to identify factors influencing falls and fall-related injuries. Results In total, 152 falls and 30 fall-related injuries were reported from a total of 37 fallers. After logistic regression analysis, the model with the greatest levels of clinical utility and discriminative ability for falls (sensitivity 81%; specificity 55%; area under the receiving operating characteristic curve [AUC] statistics=0.73; 95% CI, 0.60-0.86) included the variables of shorter time since SCI, high mobility level, and having received education on fall prevention. The model for fall-related injuries (sensitivity 79%; specificity 75%; AUC statistics=0.77; 95% CI, 0.59-0.96) included the variables of older male individual, lower physical health score, and having received education on fall prevention. Conclusions The regression models presented may be used to identify wheelchair users with SCI at greater risk of falls and fall-related injuries. The findings may help to refer those in need to tailored fall and fall-related injury prevention programs. The findings presented in this study were based on a relatively small sample convenience; therefore, further prospective studies with a larger sample size are warranted.

Project description:ObjectiveTo assess the effectiveness of group wheelchair maintenance training and investigate participant characteristics associated with responsiveness to training.DesignRandomized controlled trial with an immediate group and a waitlist control group (WLCG) who received the intervention after a 6-month delay.SettingFour Spinal Cord Injury Model Systems Centers.ParticipantsManual (MWC; n=80) and power wheelchair (PWC; n=67) users with spinal cord injury (N=147).InterventionsTwo 90-minute structured wheelchair maintenance training program classes with 12-20 people per class and separate classes for MWC and PWC users. Each class included in-person hands-on demonstrations and practice of wheelchair maintenance.Main outcome measuresSeparate analysis was completed for MWC and PWC users using the Wheelchair Maintenance Training Questionnaire (WMT-Q) capacity (ability to complete), performance (frequency of completion) and knowledge at baseline, 1 month, 6 months, 6 months pretraining (WLCG only), and 1 year (immediate only).ResultsAfter the intervention, participants in both the immediate and WLCG improved in maintenance capacity (MWC and PWC, P<.001) and performance (MWC and PWC, P<.001) with training. Only PWC users improved knowledge of wheelchair maintenance (P<.001). For both WLCGs (MWC and PWC), there was no difference between the 6-month pretraining time point and baseline. MWC users who responded to training had lower WMT-Q scores for all domains, whereas this was only the case for knowledge for PWC users.ConclusionsGroup wheelchair skills training is effective at improving capacity to complete maintenance and performance of maintenance activities for MWC and PWC users, even in a cohort of experienced wheelchair users. For MWC users, improvements were tied to lower WMT-Q scores at baseline, whereas PWC users improved in capacity and performance independent of baseline score. Delivering this training in a structured group format has a lower cost, which might improve adoption into clinical practice.

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A Reappraisal of Ventilatory Thresholds in Wheelchair Athletes With a Spinal Cord Injury: Do They Really Exist?

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