Rachel E. Cowan

Impact of Surface Type, Wheelchair Weight, and Axle Position on Wheelchair Propulsion by Novice Older Adults

OBJECTIVE To examine the impact of surface type, wheelchair weight, and rear axle position on older adult propulsion biomechanics. DESIGN Crossover trial. SETTING Biomechanics laboratory. PARTICIPANTS Convenience sample of 53 ambulatory older adults with minimal wheelchair experience (65-87y); men, n=20; women, n=33. INTERVENTION Participants propelled 4 different wheelchair configurations over 4 surfaces: tile, low carpet, high carpet, and an 8% grade ramp (surface, chair order randomized). Chair configurations included (1) unweighted chair with an anterior axle position, (2) 9.05 kg weighted chair with an anterior axle position, (3) unweighted chair with a posterior axle position (Delta0.08 m), and (4) 9.05 kg weighted chair with a posterior axle position (Delta0.08 m). Weight was added to a titanium folding chair, simulating the weight difference between very light and depot wheelchairs. Instrumented wheels measured propulsion kinetics. MAIN OUTCOME MEASURES Average self-selected velocity, push frequency, stroke length, peak resultant and tangential force. RESULTS Velocity decreased as surface rolling resistance or chair weight increased. Peak resultant and tangential forces increased as chair weight increased, as surface resistance increased, and with a posterior axle position. The effect of a posterior axle position was greater on high carpet and the ramp. The effect of weight was constant, but was more easily observed on high carpet and ramp. The effects of axle position and weight were independent of one another. CONCLUSION Increased surface resistance decreases self-selected velocity and increases peak forces. Increased weight decreases self-selected velocity and increases forces. Anterior axle positions decrease forces, more so on high carpet. The effects of weight and axle position are independent. The greatest reductions in peak forces occur in lighter chairs with anterior axle positions.

The 6-min push test is reliable and predicts low fitness in spinal cord injury.

PURPOSE The objective of this study is to assess 6-min push test (6MPT) reliability, determine whether the 6MPT is sensitive to fitness differences, and assess if 6MPT distance predicts fitness level in persons with spinal cord injury (SCI) or disease. METHODS Forty individuals with SCI who could self-propel a manual wheelchair completed an incremental arm crank peak oxygen consumption assessment and two 6MPTs across 3 d (37% tetraplegia (TP), 63% paraplegia (PP), 85% men, 70% white, 63% Hispanic, mean age = 34 ± 10 yr, mean duration of injury = 13 ± 10 yr, and mean body mass index = 24 ± 5 kg.m). Intraclass correlation and Bland-Altman plots assessed 6MPT distance (m) reliability. Mann-Whitney U test compared 6MPT distance (m) of high and low fitness groups for TP and PP. The fitness status prediction was developed using N = 30 and validated in N = 10 (validation group (VG)). A nonstatistical prediction approach, below or above a threshold distance (TP = 445 m and PP = 604 m), was validated statistically by binomial logistic regression. Accuracy, sensitivity, and specificity were computed to evaluate the threshold approach. RESULTS Intraclass correlation coefficients exceeded 0.90 for the whole sample and the TP/PP subsets. High fitness persons propelled farther than low fitness persons for both TP/PP (both P < 0.05). Binomial logistic regression (P < 0.008) predicted the same fitness levels in the VG as the threshold approach. In the VG, overall accuracy was 70%. Eighty-six percent of low fitness persons were correctly identified (sensitivity), and 33% of high fitness persons were correctly identified (specificity). CONCLUSION The 6MPT may be a useful tool for SCI clinicians and researchers. 6MPT distance demonstrates excellent reliability and is sensitive to differences in fitness level. 6MPT distances less than a threshold distance may be an effective approach to identify low fitness in person with SCI.

Subjective measures of exercise intensity to gauge substrate partitioning in persons with paraplegia.

BACKGROUND The Borg Rating of Perceived Exertion (RPE) Scale and talk test (TT) are commonly recommended for persons to gauge exercise intensity. It is not known whether they are suitable to estimate substrate partitioning between carbohydrate and fat in persons with SCI. OBJECTIVE Investigate substrate partitioning/utilization patterns associated with RPE and TT. METHODS Twelve participants with chronic paraplegia underwent 2 arm crank exercise tests on nonconsecutive days within 2 weeks. Test 1 was a graded exercise test (GXT) to volitional exhaustion. Test 2 was a 15-minute self-selected steady state (SS) voluntary arm exercise bout simulating a brief, yet typical exercise session. RESULTS For the GXT, very light intensity exercise (RPE < 9) and TT stage before last positive were associated with highest contribution of fat oxidation (~35%-50%) to total energy expenditure (TEE). Fat oxidation was low at all stages, with the highest rate (0.13 ± 0.07 g/min) occurring at stage 1 (10 W). Corresponding average RPE was 7 ± 2 and the TT was positive for all participants at this stage. For the SS, fuel partitioning throughout exercise was dominated by carbohydrate oxidation (1.47 ± 0.08 g/min), accounting for almost all (~94%) of TEE with only a minute contribution from fat oxidation (0.02 ± 0.004 g/min). A positive TT was associated with an average contribution of fat oxidation of ~10%. CONCLUSIONS RPE but not the TT appears suitable to predict exercise intensities associated with the highest levels of fat oxidation. However, such intensities are below authoritative intensity thresholds for cardiorespiratory fitness promotion, and therefore the applicability of such a prediction for exercise prescriptions is likely limited to individuals with low exercise tolerance.

Effects of prandial challenge on triglyceridemia, glycemia, and pro-inflammatory activity in persons with chronic paraplegia

Abstract Context/Objective Exaggerated postprandial lipemia has been reported after spinal cord injury (SCI). We examined metabolite and accompanying pro-inflammatory biomarker responses to repeat feeding of typical high-fat meals in individuals with chronic paraplegia. Design Descriptive trial. Methods Metabolites (triglycerides, glucose, and insulin) and inflammatory biomarkers (interleukin-6 and high-sensitivity C-reactive protein (hsCRP)) were measured under fasting conditions in 11 recreationally active individuals with chronic (>1 year) paraplegia. Subjects received high-fat meals at time point 0 and again at minute 240. Antecubital venous blood was obtained at time points −30 (fasting), 0 (first meal), 30, 60, 90, 120, 240 (second meal), 360, and 480 minutes. Correlations were examined among the study variables. Exploratory subgroup analysis was performed for subjects with levels of postprandial glucose greater than >200 mg/dl. Results Triglycerides showed a significant rise 4 hours after eating. Basal inflammatory markers were elevated, and did not undergo additional change during the testing. Additionally, subjects with excessive postprandial glucose responses showed higher hsCRP levels than those having typical glucose responses both for fasting (11.8 ± 6.5 vs. 2.9 ± 2.7 mg/l, P = 0.064) and postprandial (11.1 ± 4.9 vs. 3.7 ± 3.8 mg/l, P = 0.018) values. Conclusions Despite elevations in metabolic response markers, inflammatory markers did not change significantly after consumption of population-representative (i.e. hypercaloric) mixed-nutrient meals. Levels of fasting CRP in the high-risk range are consistent with other reports in persons with SCI and continue to pose concern for their cardiovascular disease risk. The possible association between postprandial metabolic responses and inflammatory states warrants further investigation to identify individual component risks for this secondary health hazard.

Poster 59: Environmental Barrier Perception and Behavior Among Manual Wheelchair Users with Spinal Cord Injury

Disclosures: Morgan Callahan: I Have No Relevant Financial Relationships To Disclose Objective: 1) To determine if there are injury level differences between physical barrier perception and behavior; 2) To determine if there is a relationship between physical barrier perception and behavior. Design: Cross-sectional case series Setting: Academic Medical Laboratory Participants: 50 manual wheelchair users with chronic spinal cord injury; Tetraplegia (TP)1⁄419, Paraplegia (PP)1⁄431 Interventions: Not Applicable Main Outcome Measures: All participants completed the following assessments; 1) Self-Reported Avoidances and Encounters of Environmental Features in the Environmental Aspects of Mobility Questionnaire (EAMQ); and 2) Physical/Structural Subdomain of the Perception of Environmental Barriers in the Craig Hospital Inventory of Environmental Factor (CHIEF). Results: There was no significant difference in perception of physical barriers between lesion levels (P 1⁄4.79; TP median 2, interquartile range (IQR) 1-12; PP median 3, IQR 1-11). However, behavioral differences were exhibited by injury level. Individuals with paraplegia had a higher rate of encounters with environmental features in 3 of 9 EAMQ domains (temporal, terrain, and postural, P .03), and a lower rate of avoidances per encounter in 3 of 8 EAMQ domains (temporal, terrain, and total, P .05). For individuals with tetraplegia, perception of barriers was inversely associated with encounters and positively associated with avoidances in 1 of 9 EAMQ domains (density, P .05). For individuals with paraplegia, perception of barriers was inversely associated with encounters in 2 of 9 EAMQ domains (attention and total, P .05), but there were no associations with avoidances. Conclusions: Our results indicate a divergence between perception and behavior, with motor impairment differences captured by behavior but not perception. In addition, there were limited associations between behavior and perception. More research is required on if barrier perception, behavior, or both influence participation, so that rehabilitation programs can better tailor interventions to enhance participation. Level of Evidence: Level IV

Increased Reliability of Quantitative Ultrasound Measures of the Supraspinatus Tendon Using Multiple Image Analysts and Analysis Runs

Abstract Quantitative ultrasound (QUS) is an inexpensive and promising tool for sensitive measurement of tendon pathology. However, few studies have reported the psychometric properties of measurements obtained using this technique for assessments of the supraspinatus tendon. The present study was undertaken to determine the variance contributed by several sources of error (participant, ultrasound operator, image analyst, analysis session) to QUS measures of the supraspinatus tendon. Transverse images of the supraspinatus tendon were captured from eleven subjects (22 shoulders) by two ultrasonographers, and each image was analyzed by two image analysts who each completed two analysis runs. Generalizability theory and intraclass correlations were used to assess the reliability of seven QUS metrics. Measures of tendon/cartilage thickness demonstrated the greatest degree of overall dependability (ϕ = 0.84), followed by echogenicity (ϕ = 0.56), variance (ϕ = 0.55), and entropy (ϕ = 0.47), suggesting that these measures of the supraspinatus tendon may be promising metrics for assessing differences in tendon health. Interrater reliability between ultrasound operators ranged from low to moderate for different QUS metrics, but using more than one image analyst and performing repeated measurement analysis runs on each image help increase reliability of QUS measures for the supraspinatus tendon.