Oxygen Uptake During Exoskeletal-Assisted Walking in Persons With Paraplegia.

OBJECTIVE: To determine the cardiometabolic demands associated with exoskeletal-assisted walking (EAW) in persons with paraplegia. This study will further examine if training in the device for 60 sessions modifies cost of transport (CT). DESIGN: Prospective cohort study. Measurements over the course of a 60-session training program, approximately 20 sessions apart. SETTING: James J. Peters Bronx Veterans Affairs Medical Center, Center for the Medical Consequences of Spinal Cord Injury Research Center. PARTICIPANTS: The participants' demographics (N=5) were 37-61 years old, body mass index (calculated as weight in kilograms divided by height in meters squared) of 22.7-28.6, level of injury from T1-T11, and 2-14 years since injury. INTERVENTIONS: Powered EAW. MAIN OUTCOME MEASURES: Oxygen consumption per unit time (V˙O2, mL/min/kg), velocity (m/min), cost of transport (V˙O2/velocity), and rating of perceived exertion (RPE). RESULTS: With training: EAW velocity significantly improved (Pre: 51±51m; 0.14±0.14m/s vs Post: 99±42m; 0.28±0.12m/s, P=.023), RPE significantly decreased (Pre: 13±6 vs Post: 7±4, P=.001), V˙O2 significantly improved (Pre: 9.76±1.23 mL/kg/m vs Post: 12.73±2.30 mL/kg/m, P=.04), and CT was reduced from the early to the later stages of training (3.66±5.2 vs 0.87±0.85 mL/kg/m). CONCLUSIONS: The current study suggests that EAW training improves oxygen uptake efficiency and walking velocities, with a lower perception of exertion.

Visceral adiposity in persons with chronic spinal cord injury determined by dual energy X-ray absorptiometry.

OBJECTIVE: To determine visceral adipose tissue (VAT) volume (VATvol) by dual energy X-ray absorptiometry (DXA) in spinal cord injured (SCI) and able-bodied (AB) participants and to explore the relationships between VATvol and routine anthropometric measures. METHODS: Sixty-three subjects with SCI and 126 healthy male AB controls were stratified as low risk [LR: waist circumference (WC) < 102 cm] and moderate to high risk (MHR: WC ≥ 102 cm) for identification of risk for cardiometabolic disease: AB-LR, SCI-LR, AB-MHR, and SCI-MHR. Anthropometrics and standard body composition measurements by DXA with analysis to derive VATvol were performed. RESULTS: Comparison of the four subgroups demonstrated the highest subcutaneous adipose tissue volume (SATvol) in the AB-MHR group (P < 0.01), and the highest VATvol in the SCI-MHR group (P < 0.01). Furthermore, when compared to the AB group, participants with SCI had a 27% increase in VATvol for every centimeter increase in WC and a 20% increase in VATvol for every unit increase in BMI. CONCLUSIONS: Because cutoff values for the routine surrogate measures of adiposity underestimate visceral adiposity in persons with SCI, the risk of adverse metabolic consequences would also be underestimated, which necessitates adjustment of the these cutoff values or, preferably, to perform its direct measurement.

Lipoprotein heterogeneity in persons with Spinal Cord Injury: a model of prolonged sitting and restricted physical activity.

BACKGROUND: Persons with spinal cord injury (SCI) often have low levels of physical activity, which predispose to increased adiposity and decreased high density lipoprotein cholesterol (HDL-C) concentrations, and, generally, normal low density lipoprotein cholesterol (LDL-C) concentrations. In spite of the mixed lipoprotein profile, the SCI population has been reported to have an elevated risk of cardiovascular-related morbidity and mortality. Nuclear magnetic resonance spectroscopy may permit a more precise quantification of lipoprotein particle (P) species, enabling a more accurate inference of risk for cardiovascular disease (CVD) in the SCI population. METHODS: Fasting blood samples were obtained on 83 persons with chronic SCI and 62 able-bodied (AB) subjects. Fasting plasma insulin (FPI), triglycerides (TG), and P number and size of VLDL (very low density lipoprotein), LDL, and HDL subclasses were determined. AB and SCI subjects were stratified based on HDL-C (i.e., Low <40 and Normal ≥ 40 mg/dl): AB-Normal (n = 48), AB-Low (n = 14), SCI-Normal (n = 49), and SCI-Low (n = 34). Factorial analyses of variance were performed to identify group differences in lipoprotein measurements. Pearson correlations were performed between the number of P by lipoprotein subclass, size, FPI, and TG. RESULTS: The SCI-Normal group was not significantly different from the AB-Normal group for body composition, FPI, TG or LP-IR and had negligible differences in the lipoprotein P profile, except for fewer number and smaller size of HDL-P. The SCI-Low group had a similar lipoprotein profile to that of the AB-Low group, but with a lipid P composition associated with a heightened atherogenic risk and greater tendency toward insulin resistance by the Lipoprotein-Insulin Resistance (LP-IR) score. In the SCI-Low group, the decreased number and reduced size of lipoprotein P were more prevalent and may be associated with increased waist circumference (i.e., abdominal adiposity), relatively elevated TG values (compared to the other subgroups), and an underlying subclinical state of insulin resistance. CONCLUSIONS: Prolonged sitting and restricted physical activity in individuals with SCI had the most profound effect on the HDL-C and its lipoprotein P subclasses, but not on LDL-C, however its P subclasses were also unfavorably affected but not to the same degree. The quantification of lipoprotein P characteristics may be a potent tool for the determination of risk for CVD in persons with SCI.

The relationship between the postprandial lipemic response and lipid composition in persons with spinal cord injury.

OBJECTIVE: To determine the influence of lipid concentration, lipid particle size, and total abdominal fat (TAF) on postprandial lipemic response (PPLr) in persons with spinal cord injury (SCI). METHODS: Thirty-five persons with SCI (17 paraplegia, 18 tetraplegia) and 18 able-bodied (AB) individuals participated. Following a 10-hour fast, blood was drawn for lipids, apolipoprotein (apo) A1 and B concentrations, and low-density (LSP) and high-density (HSP) lipoprotein particle sizes. A high-fat milkshake was consumed (∼1.3 g fat/kg). Blood was drawn at 2, 4, and 6 hours to determine PPLr, (triglyceride (TG) area under the curve). TAF and visceral (VF) fat were measured by ultrasonography; total body fat (TBF) by dual-energy X-ray absorptiometry. Differences between the groups were determined by independent sample t-tests. Pearson correlation coefficients determined the relationship among PPLr and lipids, and TAF. RESULTS: There were no significant differences in fasting TG, low-density lipoprotein (LDL), apoB, TAF, or PPLr values between the groups. In SCI, PPLr significantly correlated with: apoB (r = 0.63, P < 0.01, LSP (r = 0.57, P < 0.01), and TAF (r = 0.36, P < 0.01). After controlling for age and duration of injury, PPLr significantly correlated with apoB (r = 0.66, P = 0.001), TBF (r = 0.45, P = 0.03), VF (r = 0.66, P = 0.02), and TAF (r = 0.56, P = 0.007). CONCLUSIONS: Although concentrations of LDL cholesterol and apoB were not different between SCI and AB groups, LSP, apoB, and TAF correlated with PPLr in persons with SCI. ApoB was associated with a greater PPLr in those with motor complete SCI, after controlling for age and duration of injury.

An effective oral vitamin D replacement therapy in persons with spinal cord injury.

BACKGROUND/OBJECTIVE: Vitamin D deficiency is prevalent in chronic spinal cord injury (SCI). A 3-month course of oral vitamin D(3) to 'normalize' serum vitamin D levels was investigated. DESIGN: Prospective drug-intervention study. SETTING: VA Medical Center; private rehabilitation facility. METHODS: Seven individuals with chronic SCI and vitamin D deficiency completed 3 months of oral vitamin D(3) (i.e. cholecalciferol) supplementation. At screening, baseline, and months 1 and 3, blood was collected for serum calcium, 25 hydroxyvitamin D [25(OH)D], intact parathyroid hormone (iPTH), and N-telopeptide (NTx); 24-hour urine for calcium, creatinine, and NTx was performed. Oral vitamin D(3) (2000 IU daily) and elemental calcium (1.3 g daily) were prescribed for 90 days. The results are expressed as mean ± standard deviation (SD). Analysis of variance with a Fisher's post-hoc analysis was performed to test for differences between study visits. Subjects were classified as deficient (<20 ng/ml), relatively deficient (20-30 ng/ml), or not deficient (>30 ng/ml) in 25(OH)D. RESULTS: Serum 25(OH)D levels were greater at months 1 and 3 than at baseline (26 ± 6 and 48 ± 17 vs. 14 ± 2 ng/ml; P = 0.005). Six of seven subjects were no longer deficient [25(OH)D >30 ng/ml] by month 3. Serum iPTH levels were significantly decreased at month 1 and month 3; serum NTx levels were significantly lower at month 3 than at baseline. Serum and urinary calcium levels remained within the normal range. CONCLUSION: A daily prescription of 2000 IU of oral vitamin D(3) for 3 months safely raised serum 25(OH)D levels into the normal range in persons with chronic SCI on calcium supplementation.

Assessment of measures for abdominal adiposity in persons with spinal cord injury.

Ultrasound may be a useful tool to assess abdominal adiposity, but it has not been validated in the spinal cord injury (SCI) population. This study evaluated associations between abdominal ultrasound and other methods to assess adiposity in 24 men with SCI and 20 able-bodied (AB) men. Waist (WC) and hip circumference (HC) and waist-to-hip ratio (WHR) were measured. Trunk (TRK%), android (A%) and waist fat (W%) were determined by dual energy x-ray absorptiometry (DXA); ultrasonography determined abdominal subcutaneous (SF) and visceral fat (VF). The SCI group had greater TRK% (40.0 ± 9.6 vs. 32.0 ± 10.3), W% (47.0 ± 9.7 vs. 40.6 ± 9.4), A% (43.0 ± 9.8 vs. 35.8 ± 10.6) and WHR (0.99 ± 0.1 vs. 0.92 ± 0.06) than the AB group. WC and WHR correlated with VF in the SCI group. These associations suggest that ultrasound may be a useful tool in clinical practice for the measurement of VF in weight loss programs and for the assessment of cardiometabolic disorders.

The influence of visceral fat on the postprandial lipemic response in men with paraplegia.

BACKGROUND: Postprandial lipemia (PPL) is associated with vascular dysfunction and may be an etiologic factor in the progression of atherogenic cardiovascular disease. OBJECTIVE: In 10 men with paraplegia and 10 able-bodied men, the magnitude of the PPL responses and the relationship of abdominal adiposity and the PPL responses were determined. METHODS: Anthropometrics, dual energy x-ray absorptiometry, and abdominal ultrasonography were performed to determine visceral fat and total body fat. A fasting lipid profile was performed. A high-fat milkshake (1.3 g fat/kg body mass) was administered with serum collected at baseline and at 2, 4, and 6 hours after the test meal for subsequent measurement of triglyceride. The triglyceride response was determined by the area under the triglyceride curve. RESULTS: No significant differences were noted between the groups in fasting lipid values or in measures of visceral fat. Total body fat tended to be higher in men with paraplegia than in able-bodied men (34.9 ± 10.0 vs. 27.3 ± 6.7%, p = 0.07). No significant difference between the groups was observed in triglyceride response. In men with paraplegia, visceral fat was strongly associated with the triglyceride (r = 0.8, p = 0.005), fasting low-density lipoprotein (r = 0.66, p = 0.04), and triglyceride responses (r = 0.80, p = 0.005); a significant relationship was not found between fasting high-density lipoprotein and any measure of adiposity. In men with paraplegia, triglyceride response was positively related to all measures of abdominal adiposity. CONCLUSION: Visceral abdominal fat was related to delayed triglyceride clearance after a fat load, which may contribute to coronary heart disease (CHD) risk and progression of vascular disease in men with paraplegia.