Fat Cross-sectional Area Research Articles

Role of peripheral quantitative computed tomography in identifying disuse osteoporosis in paraplegia

Disuse osteoporosis is a major long-term health consequence of spinal cord injury (SCI) that still needs to be addressed. Its management in SCI should begin with accurate diagnosis, followed by targeted treatments in the most vulnerable subgroups. We present data quantifying disuse osteoporosis in a cross-section of the Scottish paraplegic population to identify subgroups with lowest bone mineral density (BMD). Forty-seven people with chronic SCI at levels T2-L2 were scanned using peripheral quantitative computed tomography at four tibial sites and two femoral sites, at the Queen Elizabeth National Spinal Injuries Unit, Glasgow (UK). At the distal epiphyses, trabecular BMD (BMDtrab), total BMD, total bone cross-sectional area (CSA) and bone mineral content (BMC) were determined. In the diaphyses, cortical BMD, total bone CSA, cortical CSA and BMC were calculated. Bone, muscle and fat CSAs were estimated in the lower leg and thigh. BMDtrab decreased exponentially with time since injury at different rates in the tibia and femur. At most sites, female paraplegics had significantly lower BMC, total bone CSA and muscle CSA than male paraplegics. Subjects with lumbar SCI tended to have lower bone values and smaller muscle CSAs than in thoracic SCI. At the distal epiphyses of the tibia and femur, there is generally a rapid and extensive reduction in BMDtrab after SCI. Female subjects, and those with lumbar SCI, tend to have lower bone values than males or those with thoracic SCI, respectively.

Skeletal Muscle and Mortality Results From the InCHIANTI Study

Sarcopenia, the age-related loss of muscle mass, may not be an isolated process but is associated with an increase in fat mass. The aim of this study was to estimate the mortality risk of sarcopenia in the presence or absence of obesity. Data are from 934 participants aged 65 years or older, enrolled in the "Invecchiare in Chianti" study, and followed for 6 years. At baseline, a peripheral quantitative computerized tomography (pQCT) scan was performed on all participants to evaluate the muscle density, and the muscular and fat cross-sectional areas of the calf. Walking speed was measured on a 7-m track. Cox proportional hazard models were performed to estimate the association of pQCT measures (per 1 standard deviation increase) with mortality. Unadjusted analyses showed significant associations of muscle density (hazard ratio [HR] 0.78, 95% confidence interval [CI] 0.69-0.88), muscle area (HR 0.75, 95% CI 0.66-0.86), and fat area (HR 0.82, 95% CI 0.73-0.92) with mortality. After adjustment for potential confounders, no body composition parameter was significantly associated with mortality. Walking speed (used as a reference measure to verify whether the negative results were due to peculiarities of the study sample) confirmed its well-established association with mortality risk (HR 0.73, 95% CI 0.60-0.88). These results did not change after the analyses were stratified according to sarcopenia and body mass index groups, and restricted to participants with frailty or a high inflammatory profile. Calf skeletal muscle and fat mass are not significant risk factors for mortality in community-dwelling older adults. Walking speed confirmed to be a powerful predictor of health-related events.

Ethnic differences in bone geometry and strength are apparent in childhood

PurposeEthnic differences in bone strength and structure likely contribute to the disparity in fracture rates, however few studies have assessed bone structure in multiethnic cohorts of children. The purpose of this study was to investigate ethnic differences in bone strength in childhood and to characterize the structural bases for these differences. MethodsPeripheral quantitative computed tomography (pQCT 3000, Orthometrix) was used to assess bone parameters at the radius and tibia in Caucasian (CA, n=21), African American (AA, n=23), and Hispanic (HI, n=29) children (10.9±0.1 yrs). At the distal site (8%), we measured compressive bone strength (BSI), trabecular and total bone density, and total bone area. Polar strength-strain index, total and cortical bone area, and cortical density were assessed at the midshaft (50%). Muscle cross-sectional area (CSA) and fat CSA were measured at the tibia (66%) and the radius (50%). Physical activity and calcium intake were assessed by questionnaire. Analysis of covariance was used to compare bone outcomes among ethnic groups adjusting for age, sex, limb length and muscle CSA. ResultsAge, BMI, and body composition were similar among the 3 groups, however AA children were taller and had longer bone length. At all sites, AA and HI children had higher bone strength (SSIp and BSI +10–37%) than CA children due mainly to greater bone tissue density (2–18%>CA) at the distal sites of the radius and tibia. The greater bone strength at the midshaft was due to both a higher bone density (2–5%) and greater bone area than CA (7–18%). ConclusionAA and HI children have significantly higher bone strength than CA children, due to greater bone volumetric density and greater cortical area. AA and HI children also have higher bone strength relative to load. These observations suggest that ethnic differences in bone strength manifest in childhood.

Overweight children have poor bone strength relative to body weight, placing them at greater risk for forearm fractures

Introduction: Obesity is thought to be a protective factor for bones in adults but not in children based on the evidence of the greater incidence of forearm fractures in obese children. Our objective was to investigate the effect of adiposity on bone strength in relation to the mechanical challenge placed onto the forearm bones in case of a fall. Methods: Cross sectional areas (CSA) were obtained at the mid- and distal radius by peripheral quantitative computed tomography in 486 children (241 boys), mean age 8.3 years (range 6.9–9.7), participating in the LOOK Project. The following parameters were measured: bone mass and bone CSA (both sites), and muscle and fat CSA (mid-forearm only). Bone strength indices combining bone size and total volumetric density were calculated at each site. Results/Discussion: Overweight children (BMI > percentile equivalent to 25 kg/m2 in adults) have higher bone parameters than normal-weight peers (Z-scores +0.6 to +0.9SD, p Conclusion. Overweight children have stronger bones due to greater muscle size. However, children with high fat mass relative to muscle mass (increased adiposity) have poorer bone strength, independent of weight, which may contribute to the increased risk of fracture in obese children.

Effect of Aerobic Leg Exercise Training on Subcutaneous Adipose Tissue of Thigh in Young Japanese Women

A one-legged training model was adopted to assess the influence of moderate-intensity exercise training on subcutaneous adipose tissue, especially focusing on the trained limb. Eight young sedentary Japanese women (ages 21-23 yr) participated in a 12-week training program. The leg was assigned randomly to trained or untrained limb. Each subject performed a supervised 60-min one-legged cycle ergometer training session three times a week. The exercise intensity was set at approximately 40% of peak VO(2) ("moderate" intensity, i.e., below the estimated lactate threshold), which was determined before training. Each subject performed a one-legged incremental cycle exercise test until exhaustion to determine the peak VO(2) of each leg (the trained and untrained legs being investigated separately). The areas of subcutaneous fat and the remaining nonfat tissues of the thigh were evaluated by our novel visualized measuring system based on ultrasonography. The fat cross-sectional areas of the trained and untrained thigh were not different after training (trained: 68.6+/-17.8 vs. untrained: 68.3+/-18.5 cm(2)). The non-fat (muscle and bone) area was also similar between the trained and untrained limb. In addition, there was no systematic influence of the training on the total and lean body mass. After training, the duration time of the one-legged cycle incremental exercise test by the trained leg was significantly improved unilaterally (trained: 1049+/-122 vs. untrained: 930+/-109 s, p<0.05) without any difference of peak VO(2). The results indicate that moderate one-legged aerobic training did not induce any compositional change in the trained thigh; rather, what did improve were certain peripheral factor alone relating to endurance.

Subcutaneous Fat and Body Fat Mass Have Different Effects on Bone Development at the Forearm in Children and Adolescents

The present study investigated whether subcutaneous fat differs in the impact on bone development from fat mass (FM). We analyzed 295 healthy children and adolescents (age 5-19 years, 139 males) for FM by measuring four skinfold thicknesses and for bone development and body composition at the forearm by peripheral quantitative computed tomography in a cross-sectional investigation. Relative cross-sectional fat area (FA) was a surrogate for relative subcutaneous FM at the forearm and was associated positively with percent fat in prepubertal individuals and pubertal females but negatively in pubertal males. Percent FM was associated with trabecular bone mineral density (BMDtrab) in prepubertal individuals (females r = 0.394, males r = 0.242) and pubertal individuals (females r = 0.215, males r = -0.275). Bone mineral count was correlated with percent FM in pubertal males (r = -0.287). FA was correlated with BMDtrab (r = 0.285) and with cortical bone mineral density (BMDcort, r = -0.296) in pubertal females. The ratio FA/ FM was negatively correlated with BMDcort (r = -0.299) in pubertal females. Pubertal females with relatively high subcutaneous fat area (high ratio FA/FM) were characterized by lower bone strength (P = 0.047). FM and the relative amount of subcutaneous fat have effects on bone formation and resorption that depend on gender and puberty. Especially in pubertal females, higher levels of subcutaneous fat may decrease bone strength due to increased cortical remodeling.

Cross-Sectional Fat Area at the Forearm in Children and Adolescents

Background: Cross-sectional fat area (FA) and muscle area have been recently used to describe local body composition at the forearm in children and adolescents. The present analysis intends to characterize FA in a normal collective. Methods: FA was measured by peripheral quantitative computed tomography in a study collective (DONALD study) of 296 children and adolescents. FA was analyzed in relation to fat mass (FM) measured by 4 skinfold thicknesses. Results: FA was significantly correlated with FM (r = 0.8). FA was positively associated with height in prepubertal individuals and pubertal females, but negatively associated with height in pubertal males. Median and range of FA are displayed for different height ranges and pubertal stages in males and females to enable analyses of FA in subgroups. Conclusion: Because of the positive dependence of FA on height in prepubertal individuals and pubertal females, reference values of FA may be based on height. But reference values in pubertal males or in a mixed pubertal population should be rather based on pubertal stages than on height.

Pelvic body composition measurements by quantitative computed tomography: Association with recent hip fracture

Introduction Loss of subcutaneous fat, decreased muscle cross-sectional area (CSA) and increased muscle adiposity are related to declining physical function and disability in the elderly, but there is little information about the relationship of these tissue changes to hip fracture. Thus we have compared body composition measures in women with hip fractures to age-matched controls, using quantitative computed tomography (QCT) imaging of the hip to characterize total adiposity, muscle CSA and muscle attenuation coefficient, a measure of adiposity. Materials and methods 45 Chinese women (mean age 74.71 ± 5.94) with hip fractures were compared to 66 healthy control subjects (mean age 70.70 ± 4.66). Hip QCT scans were analyzed to compute total adipose CSA as well as CSA and attenuation values of muscle groups in the CT scan field of view, including hip extensors, abductors, adductors and flexors. The total femur areal BMD (aBMD) was estimated from the QCT images. Logistic regression was employed to compare body composition measures between fracture subjects and controls after adjustment for age, height, BMI and aBMD. Receiver–operator curve (ROC) analyses determined whether combinations of aBMD and body composition had higher area under curve (AUC) than aBMD alone. Results and conclusions Fracture subjects had lower fat CSA ( p < 0.0001) than controls but had higher muscle adiposity as indicated by lower attenuation in the adductor, abductor and flexor groups (0.00001 < p < 0.02). Fracture subjects also had lower extensor and adductor CSA values ( p < 0.0001). After age and BMI adjustment, the total fat CSA, the extensor and adductor CSA values, and the adductor attenuation values remained significantly lower in the fracture subjects (0.001 < p < 0.05). In ROC analyses, models combining aBMD with soft tissue measures had higher AUC than models containing only BMD (0.001 < p < 0.05). Combining body composition with skeletal measures may improve fracture prediction compared to bone measures alone.

Spasticity may defend skeletal muscle size and composition after incomplete spinal cord injury

Cross-sectional. (1) To determine the effects of the level of spinal cord injury (SCI) on skeletal muscle, intramuscular fat (IMF) cross-sectional areas (CSAs) and relative IMF; (2) to determine the relation, if any, of spasticity to each of these variables after incomplete SCI. In-patient study at the Shepherd Center, Atlanta, GA, USA. Thirteen individuals with incomplete SCI were classified according to their level of injury into a high level of injury group (HLI, C5-C7, n=8) and a low level of injury group (LLI, T12-L2, n=5). Spasticity was determined for thigh muscles using a modified Ashworth scale at 6 weeks post-injury. T1-weighted magnetic resonance (MR) images were taken 6 weeks post-injury to measure thigh skeletal muscle and IMF CSAs. Spasticity was significantly evident in the HLI group compared to the LLI group (P=0.023). Six weeks post-injury, muscle CSA was 103+/-18 cm(2) in the HLI group and 80+/-20 cm(2) in the LLI group (P=0.042). Relative IMF was 3.6+/-2.0% in HLI and 7.5+/-4.0% in LLI (P=0.021). Additionally, spasticity accounted for 54% of the variability in muscle CSA for all subjects (r (2)=0.54, P=0.006). Spasticity may be an important factor in defending skeletal muscle size and indirectly preventing IMF accumulation early after incomplete SCI.

Effects of acute supine rest on mid‐thigh cross‐sectional area as measured by computed tomography

The loss of hydrostatic pressure that occurs as a person moves from the standing to the supine position causes a fluid redistribution that may confound the measurement of thigh cross-sectional area (CSA) if data are obtained while tissue fluid content is in flux. To determine the effects of changing postural position on thigh tissue CSA, mid-thigh axial scans of 13 older women were obtained at 5, 10 and 15 min of supine rest using computed tomography (CT). Scans were analysed for changes in CSA of subcutaneous fat (SF), low density muscle (LDM) and normal density muscle (NDM). A significant decrease from baseline was found in the CSA of NDM at 15 min [2.3+/-0.8 cm2 (+/-SE), 1.6%, P<0.05], with no change in LDM or SF CSA among any of the time intervals. The results of the current study suggest that potential measurement error can be minimized when baseline and follow-up CT-derived images of mid-thigh CSA are obtained within the first 10 min the subject assumes the supine position and that the CSA of NDM and LDM may be affected differently by supine rest.

Estrogen Replacement, Muscle Composition, and Physical Function: The Health ABC Study

Although the beneficial effects of estrogen use on cardiovascular and cognitive function in postmenopausal women have been recently discredited, controversy remains regarding its usefulness for maintaining skeletal muscle mass or strength. Therefore, the purpose of this study was to determine whether estrogen use is associated with enhanced muscle composition and, if so, whether this translates into improved strength and physical function. Cross-sectional analysis of 840 well-functioning community-dwelling white women (current estrogen replacement therapy (ERT) users = 259, nonusers = 581) aged 70-79 yr participating in the Health, Aging and Body Composition Study. Muscle composition of the midthigh by computed tomography included cross-sectional area (CSA) of the quadriceps, hamstrings, intermuscular fat and subcutaneous fat, and muscle attenuation in Hounsfield units (HU) as a measure of muscle density. Isometric hand grip and isokinetic knee extensor strength were assessed by dynamometry. Physical function was assessed using a summary scale that included usual 6-m walk and narrow walk speed, repeated chair stands, and standing balance. In analyses of covariance adjusted for relevant confounders, quadriceps muscle CSA and HU were greater in current ERT than non-ERT women (P < 0.05). Grip strength was also greater (P < 0.05) in women taking ERT while knee extensor strength approached significance (P < 0.10). However, differences in muscle composition and strength were modest at < or =3.3%. There was no difference by ERT status for the hamstring muscles, fat CSA, or for physical function. The associations between ERT and muscle composition and strength were minor and did not translate into improved physical function. Initiation of ERT for preservation of muscle composition and function may not be indicated.

Growth Hormone Changes Bone Geometry and Body Composition in Patients with Juvenile Idiopathic Arthritis Requiring Glucocorticoid Treatment: A Controlled Study Using Peripheral Quantitative Computed Tomography

Osteopenia and growth retardation have been described in children with chronic arthritis. GH has an impact on both. In the present controlled study, we used peripheral quantitative computed tomography to evaluate forearm bone mass, density, and geometry as well as forearm muscle and fat area in 17 patients with juvenile idiopathic arthritis (JIA) receiving treatment with GH for 3.8 +/- 1.1 yr compared with an untreated age- and sex-matched control group (n = 17). All patients had a mean age of 15.3 +/- 2.5 yr and a mean duration of illness of 8.2 +/- 4.4 yr. Height, weight, body mass index, bone parameters, and muscle area were significantly decreased in both groups compared with those in healthy age-matched children. Compared with untreated JIA patients, GH-treated JIA patients had significant higher bone mineral content as well as total cross-sectional area (CSA), cortical CSA, and muscle CSA. Fat CSA was lower in the GH-treated group. A significant difference between groups for height-corrected cortical and muscle areas was only seen in male patients. Cortical CSA relative to muscle CSA was not different between groups. These findings are compatible with an anabolic effect of GH on muscle and bone development.

Hemoglobin levels and skeletal muscle: results from the InCHIANTI study.

Anemia is associated with reduced physical performance and muscle strength. The aim of the study was to explore whether anemia and hemoglobin levels are associated with differences in quantitative and qualitative measures of muscle and fat. The study sample consisted of 909 participants 65 years and older enrolled in the "Invecchiare in Chianti" (InCHIANTI) study, a prospective population-based study of older people aimed at identifying risk factors for late-life disability. All the analyses were performed considering continuous hemoglobin levels as well as the dichotomous anemia variable (defined according to World Health Organization criteria as hemoglobin <12 g/dL in women and <13 g/dL in men). A peripheral quantitative computed tomography (pQCT) scan was performed in all participants to evaluate total, muscular, and fat cross-sectional areas of the calf and relative muscle density. Ankle extension strength was measured using a hand-held dynamometer. Linear regression analyses were used to assess the multivariate relationship of pQCT and skeletal muscle strength measures with hemoglobin levels and anemia after adjustment for demographics, chronic conditions, medication use, and other biological variables. Participants were aged 74.8 +/- 6.8 years. In our sample, 94 participants (10.3%) were anemic. Hemoglobin levels were significantly associated with muscle density (beta = 0.225 [SE, standard error 0.098], p=.02), muscle area/total area ratio (beta=0.778 [SE 0.262], p=.003), fat area/total area ratio (beta=-0.869 [SE 0.225]; p<.001). Skeletal muscle strength and muscle density were highly associated with anemia (beta=-3.266 [SE 1.173], p=.005 and beta=-0.816 [SE 0.374], p=.03, respectively). Results did not change when analyses were rerun in a restricted sample of participants not affected by major medical conditions. The present study shows that hemoglobin levels are associated with the parameters of body composition obtained by pQCT, and that decreases in muscular strength measures occur in the presence of anemia.

THE RELATIONSHIP BETWEEN GLUCOSE TOLERANCE AND INTRAMUSCULAR FAT AFTER LONG-TERM SPINAL CORD INJURY

Disorders of carbohydrate metabolism are highly prevalent in patients with spinal cord injury (SCI). Intramuscular (IM) fat in the thigh has been shown to be negatively correlated with glucose tolerance in able-bodied (AB) populations. PURPOSE To examine the distribution of fat in the thighs of SCI and AB individuals, and to determine the relationship between these fat stores and oral glucose tolerance. METHODS Twelve complete SCI (2 female, 42 ± 12 years, 177.8 ± 12.7 cm, 79.4 ± 8.8 kg, injury level C3–C7, 8 ± 5 years post injury, mean ± SD) and nine AB controls (6 female, 29 ± 9 years, 169.1 ± 9.4 cm, 68.8 ± 17.2 kg) underwent oral glucose tolerance tests and MR imaging of the left thigh. Images were analyzed for IM fat cross-sectional area (CSA), and the resulting areas and percentages were correlated with fasting, 60, 90, and 120-minute glucose and insulin levels. Independent t-tests and simple linear regression were performed to detect between group differences and relationships between variables, respectively. RESULTS Persons with SCI had significantly more IM fat CSA (14.5 ± 6.0; 4.7 ± 2.5 cm2) significantly less muscle CSA (58.6 ± 21.6; 94.1 ± 32.5 cm2), and thus significantly greater IM fat percentages than AB (17.3 ± 4.4; 4.6 ± 2.6 %). The SCI group had significantly greater 90 (148.2 ± 36.5; 97.8 ± 14.7 mg/dL) and 120-minute blood glucose (142.0 ± 19.7; 97.2 ± 15.7 mg/dL), as well as significantly greater 90 (93.1 ± 68.6; 34.5 ± 8.5 μIU/mL) and 120-minute insulin levels (106.8 ± 54.7; 37.7 ± 15.6 μIU/mL). Strong positive correlations were found between blood glucose levels and percent IM fat at both 90 (r2 = .52) and 120- minutes (r2 = .71) after ingestion of glucose. CONCLUSION There is a strong relationship between IM fat of the thigh and impaired glucose tolerance in individuals with SCI. These data emphasize the importance of continued contractile activity and diet management following rehabilitation to aid in the prevention of disorders of carbohydrate metabolism. Supported by The Shepherd Center and NIH grant HD 39676(GAD)

HIGH TUMOUR NECROSIS FACTOR-α LEVELS ARE ASSOCIATED WITH EXERCISE INTOLERANCE AND NEUROHORMONAL ACTIVATION IN CHRONIC HEART FAILURE PATIENTS

Immune activation plays an important role in the progression of chronic heart failure (CHF). We sought to investigate whether different degrees of tumor necrosis factor-α (TNF-α) activation are associated with exercise intolerance, neurohormonal activation and alterations in muscle mass and function in patients with CHF without cardiac cachexia. Patients were divided into quartiles according to their TNF levels (first quartile: 0.98–4.90pg/ml, second quartile: 5.00–6.60pg/ml; third quartile 6.80–9.00pg/ml; fourth quartile 9.80–32.00pg/ml). Patients underwent cardiopulmonary exercise testing, quadriceps muscle strength test, quadriceps fatigue test, and assessment of thigh muscle and fat cross-sectional area (CSA) by computerized tomography scanning. Patients in the highest TNF quartile had the lowest peak oxygen consumption [13.1 (±4.1)ml/kg/min vs 18.1 (±5.3), 18.8 (±4.8) and 18.7 (±5.6)ml/kg/min, P<0.01] the greatest relation of ventilation and dioxide production (VE/VCO2) slope (P<0.05) and the most elevated catecholamine levels (P<0.05) compared to patients in the first three quartiles. Patients with the lowest TNF levels had preserved thigh muscle size and quadriceps strength. Strength/muscle CSA was similar in the four groups. Muscle strength during fatigue testing was significantly lower in the fourth quartile (P=0.01) compared with the other three groups. In CHF patients only the highest levels of TNF are associated with poor functional status and neurohormonal activation. This group of patients may represent the appropriate target population for TNF antagonism.

CT imaging of trunk muscles in chronic low back pain patients and healthy control subjects

Increasing documentation on the size and appearance of muscles in the lumbar spine of low back pain (LBP) patients is available in the literature. However, a comparative study between unoperated chronic low back pain (CLBP) patients and matched (age, gender, physical activity, height and weight) healthy controls with regard to muscle cross-sectional area (CSA) and the amount of fat deposits at different levels has never been undertaken. Moreover, since a recent focus in the physiotherapy management of patients with LBP has been the specific training of the stabilizing muscles, there is a need for quantifying and qualifying the multifidus. A comparative study between unoperated CLBP patients and matched control subjects was conducted. Twenty-three healthy volunteers and 32 patients were studied. The muscle and fat CSAs were derived from standard computed tomography (CT) images at three different levels, using computerized image analysis techniques. The muscles studied were: the total paraspinal muscle mass, the isolated multifidus and the psoas. The results showed that only the CSA of the multifidus and only at the lowest level (lower end-plate of L4) was found to be statistically smaller in LBP patients. As regards amount of fat, in none of the three studied muscles was a significant difference found between the two groups. An aetiological relationship between atrophy of the multifidus and the occurrence of LBP can not be ruled out as a possible explanation. Alternatively, atrophy may be the consequence of LBP: after the onset of pain and possible long-loop inhibition of the multifidus a combination of reflex inhibition and substitution patterns of the trunk muscles may work together and could cause a selective atrophy of the multifidus. Since this muscle is considered important for lumbar segmental stability, the phenomenon of atrophy may be a reason for the high recurrence rate of LBP.

Cross-Sectional Areas of Fat and Muscle in Limbs During Growth and Middle Age

Age changes in the cross-sectional areas (CSAs) of fat and muscle tissues of limbs were investigated by using a B-mode ultrasonic technique for 245 males and 275 females aged 6 to 60 years. Four measurement sites were selected in the right limbs: the forearm, upper arm, lower leg and thigh. In an age span from 13 to 15 years, fat CSA for males decreased, while that for females increased at every site. Fat CSAs for both sexes increased in their thirties, but from then there was no more increase with aging. During early childhood, females had similar growth curves in muscle CSAs to those of males. An apparent sex separation in muscle CSAs took place at 13 years of age and after, the relative gender differences in muscle CSAs became larger with growth in the upper extremity than in the lower one. For both sexes, muscle CSA in every site remained almost constant during middle age. This age change in fat and muscle CSAs of limbs during the period of growth generally resembles that reported previously for total fat and fat free mass, respectively. However, age trend in fat CSAs during middle age, a lack of increase on reaching and after the forties differs from that described by prior studies for fat mass.

Growth of fat and lean tissue components at the mid-upper arm in well-off North West Indian children.

Attained means and standard deviations of the mid-upper arm fat cross-sectional area (CSA) and M + B (lean) CSA estimated from the arm circumference and the triceps and biceps skinfolds are presented for 327 girls and 341 boys 6-16 years of age. Tempo unconditional 1-year velocities of the two components were also calculated based on repeated measurements of 244 girls and 253 boys after a period of about 1 year. Although the attained mean total CSA displays a similar pattern in both sexes, the fat and lean components show opposite patterns. Fat CSA is distinctly larger in girls and increases continuously, while fat CSA in boys stabilizes from 10 to 13 years and then decreases. Lean CSA in girls stabilizes at about 13 years, while that of boys continues to increase. Left hand grip strength of boys is greater and increases from 6 to 16 years. The 1-year velocity curves of the girls are shifted by about 1-2 years to the left of the curves for boys, but the pattern is similar. The important features displayed are as follows: occurrence of two spurts of increased velocities, preadolescent and adolescent spurts, an adolescent decline in fat CSA velocities in boys which reaches a nadir at about 14 years, occurrence of an adolescent peak of lean CSA in boys at 14 years, high postpeak velocities of lean CSA in both sexes, which indicates continued growth of lean tissue, and a peak in strength that occurs after that in lean tissue. © 1994 Wiley-Liss, Inc.

Changes in lower limb muscle cross-sectional area and tissue fluid volume after transition from standing to supine.

Lower limbs show acute fluid shift in response to transition from upright to supine body position. It is hypothesized that this would affect tomographic estimations of muscle mass and composition. Seven healthy subjects were investigated during the initial 120 min of bed rest, using repeated computerized tomography (CT) and continuous bioelectrical impedance analysis (BIA). Thigh and calf muscle cross-sectional area (CSA) decreased (P < 0.05) by 1.9 and 5.5% whereas fat CSA decreased (P < 0.05) by 4.1 and 4.4%, respectively. Radiological density (RD) of muscle showed a simultaneous increase (P < 0.05) by 4.8% in calf but not (P > 0.05) in thigh. No changes occurred (P > 0.05) in muscle or fat CSA or muscle RD in either thigh or calf between the first and second hour of bed rest. Fluid shift, as estimated by BIA, showed an exponential decay in thigh (tau th = 30 min) and calf (tau c2 = 37 min) by 2.5 and 8.7%, respectively, from first to 120 min of bed rest. Moreover, the calf showed an initial rapid (tau c1 = 8 s) 2.2% decrease. The demonstrated short-term changes in leg CSA were more pronounced in the calf than in the thigh. They were similar in muscle and subcutaneous fat. These fluid shifts merit consideration when tomographic imaging techniques are used to estimate muscle mass and composition.

Measurement of abdominal fat with T1‐weighted MR images

The cross-sectional area of visceral and subcutaneous fat in the abdomen was measured with T1-weighted spin-echo images acquired with a 1.5-T magnetic resonance (MR) imager. Four axial images centered on L-4 were acquired in each patient. Outline regions of interest (ROIs) were drawn manually for subcutaneous and visceral fat. The subcutaneous fat cross-sectional area was calculated from the ROIs drawn around the outer and inner margins of subcutaneous fat. Several adaptive processing methods were evaluated for measuring fat in the complex structure of the viscera. These methods were compared with an existing MR imaging measurement method for abdominal fat in 18 patients. The adaptive method that uses the valley between the fat and nonfat distributions in the average histogram curve was judged best for research evaluations because it reduces the effects of volume averaging while using a more natural division between fat and nonfat data. Another adaptive method that yielded comparable measurements was thought to be more suitable for clinical applications. Cross-sectional area measurements of abdominal fat were compared in 18 nonobese and 17 obese women to illustrate the utility of these measurements.