Clinical assessment of body composition after spinal cord injury. An observational study.

Background: Persons who sustain a spinal cord injury (SCI) experience a dramatic loss of muscle and bone, and a dramatic increase in adipose tissue. It has been suggested that the muscle atrophy, obesity, and sublesional osteoporosis (SLOP) that occurs after SCI is due in part to the loss of voluntary control of the skeletal muscles in the lower extremities, impaired energy metabolism below the level of the lesion, and cessation of sufficient mechanical strain on bone. The prevalence of obesity and SLOP after SCI leads to increased cardiovascular disease and fracture risk, respectively. Current body composition screening procedures for the general population fail to identify individuals with SCI who are obese or have SLOP. Muscle contractions provide physiological loads on bone; thereby a muscle-bone relationship is proposed with proportional declines in muscle and bone after SCI. In addition, both positive and negative relationships have been proposed between adipose tissue and bone; increased skeletal load bearing from excess adipose tissue mass may account for the positive associations reported to date. Due to a lack of load bearing activity after SCI, there should be a negative association between adipose tissue and bone. Objectives: The primary objective is to characterize body composition among adults with chronic SCI using valid, reliable, and interpretable measures, and to suggest screening procedures for the detection of obesity and SLOP in this population. The secondary objectives are to explore the associations between: 1) muscle and bone, and 2) adipose tissue and bone. Design and Setting: Cross sectional observational. Population: A sample of 16 individuals (13 men, 3 women) with chronic SCI participated in this study. The neurological level of lesion ranged from C3-T12, with 9 motor complete and 7 incomplete SCI. Average±standard deviation for age was 51.12±12.37 years, and duration of injury 16.5±7.87 years. An additional 29 individuals with chronic SCI were included when exploring the relationship between muscle and bone. Forty-one individuals (31 men, 9 women) were included in this analysis; the neurological level of lesion ranged from C2-T12, with 13 motor complete and 28 incomplete SCI. Average±standard deviation for age was 48.7±13.36 years, and duration of injury 114.22±10.4 years. Methods: Lean tissue, adipose tissue, and bone tissue were measured via surrogates of body adiposity, as well as two different scanning technologies. Lean tissue was assessed via muscle cross sectional area (CSA) (mm2) and muscle density (mg/cm3), and measured using peripheral quantitative computed tomography (pQCT). Adipose tissue was assessed via body mass index (BMI) (kg/m2), waist circumference (WC) (cm), and % body fat, and measured using a floor scale, tape measure, and dual energy x-ray absorptiometry (DXA), respectively. Bone tissue was assessed via hip, distal femur, and proximal tibia areal bone mineral density (aBMD) (g/cm2) using DXA, as well as cortical thickness (mm) and total volumetric bone mineral density (vBMD) (mg/cm3) at the 1/3 proximal tibia, and trabecular vBMD (mg/cm3) and total vBMD (mg/cm3) at the distal tibia using pQCT. The relationships between muscle and bone, and adipose tissue and bone, were determined by correlating muscle CSA with indices of bone strength, and indices of obesity with indices of SLOP, respectively. Results: The majority of participants had lean tissue values below able-bodied norms (67-100%). When using the able-bodied definition of BMI >30 kg/m2, 19% of individuals were obese, whereas 63% and 81% were obese when using SCI-specific definitions of BMI >25 kg/m2 or >22 kg/m2, respectively. One hundred percent of individuals had SLOP using distal femur Z-score, and over 50% were at risk of fracture using distal femur fracture threshold of <0.78 g/cm2. Weak (r=0.42) to moderate (r=0.57) correlations were found between muscle CSA and indices of bone strength, supporting the theory of a muscle-bone unit. No correlations were found between adipose tissue and bone. Conclusions: Based on the cohort data, we propose that individuals with ≥2 risk factors (female, ≥60 years of age, duration of injury (DOI) ≥10, tetraplegia, motor complete) should be screened for obesity using % body fat from DXA as well as a combination of carefully interpreted SCI-specific BMI and WC. In addition, these same individuals should be screened for SLOP using a distal femur Z-score and fracture threshold from DXA. It is clear that due to the prevalence of obesity and SLOP in this population, intervention for prevention or treatment is essential. The presence of a muscle-bone unit indicates that muscle atrophy contributes to a reduction in bone strength; this is clinically important, as muscle strength is potentially amenable to rehabilitation intervention. No correlation was found between adipose tissue and bone. Future work should continue to explore these relationships using appropriate technology

Tracking within-athlete changes in whole body fat percentage in wheelchair athletes

Purpose: To evaluate tracking of within-athlete changes in criterion measures of whole-body fat percentage (dual energy X-ray absorptiometry; DXA) with skinfold thickness measures (Σ 4, 6, or 8) in wheelchair basketball players. Methods: This longitudinal study tracked body composition of sixteen international wheelchair basketball players at 5 time points over a 15-month training/competition period. The primary outcome was DXA-derived whole-body fat percentage (BF%), with Σ 4, 6, or 8 skinfolds (mm) as the predictor variable. Data were analysed using a linear mixed model with restricted maximum likelihood (random intercept, with identity covariance structure) to derive the within-athlete prediction error for predicting criterion BF% from Σ skinfolds. This prediction error allowed us evaluate how well a simple measure of the Σ skinfolds could track criterion changes in BF%; that is, we derived the change in Σ skinfolds that would have to be observed in an individual athlete to conclude that a substantial change in criterion BF% had occurred. All data were log-transformed prior to analysis. Results: Σ 8 skinfolds were the most precise practical measure for tracking changes in BF%. For the monitoring of an individual male wheelchair basketball player, a change in Σ 8 skinfolds by a factor of greater than 1.28 (multiply or divide by 1.28) is associated with a practically meaningful change in BF% (≥1 percentage point). Conclusions: Σ 8 skinfolds can track changes in BF% within individual wheelchair athletes with reasonable precision, providing a useful field monitoring tool in the absence of often impractical criterion measures<br

Assessment of body composition in spinal cord injury: A scoping review.

The objective of this scoping review was to map the evidence on measurement properties of body composition tools to assess whole-body and regional fat and fat-free mass in adults with SCI, and to identify research gaps in order to set future research priorities. Electronic databases of PubMed, EMBASE and the Cochrane library were searched up to April 2020. Included studies employed assessments related to whole-body or regional fat and/or fat-free mass and provided data to quantify measurement properties that involved adults with SCI. All searches and data extractions were conducted by two independent reviewers. The scoping review was designed and conducted together with an expert panel (n = 8) that represented research, clinical, nutritional and lived SCI experience. The panel collaboratively determined the scope and design of the review and interpreted its findings. Additionally, the expert panel reached out to their professional networks to gain further stakeholder feedback via interactive practitioner surveys and workshops with people with SCI. The research gaps identified by the review, together with discussions among the expert panel including consideration of the survey and workshop feedback, informed the formulation of future research priorities. A total of 42 eligible articles were identified (1,011 males and 143 females). The only tool supported by studies showing both acceptable test-retest reliability and convergent validity was whole-body dual-energy x-ray absorptiometry (DXA). The survey/workshop participants considered the measurement burden of DXA acceptable as long as it was reliable, valid and would do no harm (e.g. radiation, skin damage). Practitioners considered cost and accessibility of DXA major barriers in applied settings. The survey/workshop participants expressed a preference towards simple tools if they could be confident in their reliability and validity. This review suggests that future research should prioritize reliability and validity studies on: (1) DXA as a surrogate 'gold standard' tool to assess whole-body composition, regional fat and fat-free mass; and (2) skinfold thickness and waist circumference as practical low-cost tools to assess regional fat mass in persons with SCI, and (3) females to explore potential sex differences of body composition assessment tools. Registration review protocol: CRD42018090187 (PROSPERO)

Superficial femoral artery endothelial responses to a short-term altered shear rate intervention in healthy men.

In animal and in-vitro models, increased oscillatory shear stress characterized by increased retrograde shear-rate (SR) is associated with acutely decreased endothelial cell function. While previous research suggests a possible detrimental role of elevated retrograde SR on endothelial-function in the brachial artery in humans, little research has been conducted examining arteries in the leg. Examinations of altered shear pattern in the superficial femoral artery (SFA) are important, as this vessel is both prone to atherosclerosis and leg exercise is a common form of activity in humans. Seven healthy men participated; bilateral endothelial-function was assessed via flow-mediated-dilation (FMD) before and after 30-minute unilateral inflations of a thigh blood pressure cuff to either 75 mmHg or 100 mmHg on two separate visits. Inflation of the cuff induced increases in maximum anterograde (p<0.05), maximum retrograde (p<0.01), and oscillatory shear index (OSI) (p<0.001) in the cuffed leg at both inflation pressures. At 100 mmHg the increases in SR were larger in the retrograde than the anterograde direction evidenced by a decrease in mean SR (p<0.01). There was an acute decrease in relative FMD in the cuffed leg alone following inflation to both pressures. These results indicate that in the SFA, altered SR profiles incorporating increased retrograde and OSI influence the attenuation in FMD after a 30-minute unilateral thigh-cuff inflation intervention. Novel information highlighting the importance of OSI calculations and assessments of flow profiles add to current body of knowledge regarding the influence of changes in SR patterns on FMD. Findings from the current study may provide additional insight when designing strategies to combat impaired vascular function in the lower extremity where blood vessels are more prone to atherosclerosis in comparison to the upper extremity

Superficial Femoral Artery Cuff-Inflation Intervention (Doppler Screen Capture).

<p>Screen capture of the Doppler velocity profile before and at 30-minute of the (A) 75 mmHg and (B) 100 mmHg cuff inflation in the cuffed leg.</p

Supine blood pressure and heart rate.

<p>Data are for participants before and after both interventions (n = 7).</p><p>Values are mean±SD. Abbreviations: SBP  =  systolic blood pressure; DBP  =  diastolic blood pressure; MAP  =  mean arterial pressure; HR  =  heart rate. P value refers to paired t-tests between the pre-intervention values between the two testing days. No differences were found pre- to post-intervention at either cuff pressures.</p><p>Supine blood pressure and heart rate.</p

Superficial femoral artery hemodynamics.

<p>Data is responses to 30min cuff-inflation at 75 mmHg and 100 mHg (n = 16).</p><p>Values are mean±SD. Abbreviations: MBV  =  average mean blood velocity; PBV  =  average peak blood velocity; “P value vs. 0.5″ refers to single sample t-tests between the MBV/PBV ratio and 0.5 (the blood velocity profile is a perfect parabola). “P value pre vs. post” refers to paired t-tests between pre-intervention (before) and at 30-min of intervention (at 30min). *p<0.001, significantly different from anterograde MBV/PBV ratio.</p><p>Superficial femoral artery hemodynamics.</p

Superficial Femoral Artery 75 mmHg Cuff-Inflation Intervention.

<p>On the left (A): mean, anterograde (+ ve), and retrograde (-ve) SR patterns pre- and during the intervention in the cuffed leg. On the right (B): relative FMD before and after the intervention in the cuffed and non-cuffed leg; mean and individual data are presented (n = 7). Error bars represent SD.</p

Superficial Femoral Artery 100 mmHg Cuff-Inflation Intervention.

<p>On the left (A): mean, anterograde (+ ve), and retrograde (-ve) SR patterns pre- and during the intervention in the cuffed leg. On the right (B): relative FMD before and after the intervention in the cuffed and non-cuffed leg; mean and individual data are presented (n = 7). Error bars represent SD.</p