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R Marcus

Publications and source records attributed to R Marcus.

At least 109 records · Page 6Linked to original sources

Comparative effects of high- and low-intensity resistance training on thigh muscle strength, fiber area, and tissue composition in elderly women.

The effects of 52 weeks resistance training at one of two exercise intensities on thigh muscle strength, fiber cross-sectional area (CSA), and tissue composition were studied in healthy 65-79-year-old women. Subjects were assigned to either a control (CO), high-intensity (HI) or low-intensity (LO) training group. Exercise regimens consisted of three sets of leg press, knee extension, and knee flexion exercises, 3 days/week, at either 80% of one-repetition maximum (1-RM) for seven repetitions (HI) or 40% of 1-RM for 14 repetitions (LO). Dynamic muscle strength was evaluated by 1-RM, thigh lean tissue mass (LTM), fat mass, and bone mineral density (BMD, g/cm2) by dual energy X-ray absorptiometry, and fiber CSA of vastus lateralis m. by histomorphometry. Muscle strength increased, on average (+/- SEM), by 59.4 +/- 7.9% and 41.5 +/- 7.9% for HI and LO, respectively, compared to 1.3 +/- 4.8% in CO (P = 0.0001). Type I fiber CSA increased over time (P < 0.05) in both exercise groups, with a trend for increased type II area (HI, P = 0.06; LO, P = 0.11). There was no significant effect of either exercise program on thigh tissue composition, except for BMD at the 1/3 site (middle third of the femur), where LO and CO groups experienced a decline (P < 0.05) of -2.2 +/- 0.5% and -1.8 +/- 0.6%, respectively, while HI maintained BMD (+1.0 +/- 1.0%). Both training programs produced significant gains in thigh muscle strength, which were associated with fiber hypertrophy, although these did not translate into appreciable alterations in thigh tissue composition.

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Effects of growth hormone and estrogen on T lymphocytes in older women.

OBJECTIVE: To assess the effect on peripheral blood T lymphocytes of recombinant human growth hormone administered to healthy older women. DESIGN: Prospective, open study. SETTING: Veterans Administration clinical research unit and community surrounding Palo Alto, California. PARTICIPANTS: Thirty-three women were recruited in two age groups: 20 to 40 years (n = 13) and 70 years or older (n = 24). Subjects were healthy, community-dwelling volunteers. INTERVENTIONS: Recombinant human growth hormone at a dose of 0.025 mg/kg body weight/day was administered to the older subjects by daily subcutaneous injection over a 6-month study period. MAIN OUTCOME MEASURES: Mean percentage and number of peripheral blood CD45RA + ("naive") T cells, mean counts per minute (CPM) of [3H]-thymidine incorporation following stimulation of peripheral blood mononuclear cells with phytohemaglutinin (T cell proliferation). RESULTS: Before therapy, mean percentage and number of peripheral blood CD45RA + T cells and T cell proliferative responses were significantly reduced in older compared with younger women. The fraction of older women with CD45RA + T cell levels or T cell proliferative responses in the young range was significantly decreased in those who were receiving estrogen (1/10) compared with those who were not (9/14). After treatment with growth hormone, there were no significant changes in the mean CD45RA + T cell levels or proliferative responses of the older women. CONCLUSIONS: The results suggest that T cell changes associated with the age-related decline in secretion of growth hormone cannot be reversed by growth hormone therapy during the eighth decade.

Adult↗

Lack of effect of recombinant human growth hormone (GH) on muscle morphology and GH-insulin-like growth factor expression in resistance-trained elderly men.

Vastus lateralis muscle samples were obtained by needle biopsy from 18 healthy elderly men (65-82 yr) participating in a double blind, placebo (PL)-controlled trial of recombinant human GH (rhGH) and exercise and assessed for muscle morphology and skeletal muscle tissue expression of GH and insulin-like growth factors (IGFs). Subjects initially underwent progressive resistance training for 14 weeks and were then randomized to receive either rhGH (0.02 mg/kg BW.day, sc) or PL while undertaking a further 10 weeks of training. Muscle samples were obtained at baseline and at 14 and 24 weeks. The mean (+/- SEM) cross-sectional areas of type I and II fibers were similar (type I, 3891 +/- 167 microns2; type II, 3985 +/- 200 microns2) at baseline and increased (P < 0.01) by 16.2 +/- 4.1% and 11.8 +/- 3.8%, respectively, after the initial 14-week training period. After treatment (weeks 14-24), two-way repeated measures ANOVA revealed a main effect of time for type I (P < 0.01) and type II fibers (P < 0.05), but no group effect or interaction. The increase in cross-sectional area for the PL group was significant (P = 0.01) for type I (11.5 +/- 3.6%) and approached significance (P = 0.06) for type II fibers (11.1 +/- 5.6%). For rhGH, the change in type I (6.3 +/- 5.9%) and II (7.1 +/- 5.2%) fiber area was not significant. No apparent change in tissue GH receptor, IGF-I, IGF-I receptor, IGF-II, or IGF-II receptor messenger ribonucleic acids occurred as a result of exercise after the 14-week pretreatment period or after treatment with rhGH or PL. These results indicate that rhGH administration in exercising elderly men does not augment muscle fiber hypertrophy or tissue GH-IGF expression and suggests that deficits in the GH-IGF-I axis with aging do not inhibit the skeletal muscle tissue response to training.

Aged↗

Bone mass and subtle abnormalities in ovulatory function in healthy women.

Women with occasional anovulatory or short luteal phase menstrual cycles have been reported to lose bone mineral density (BMD) at a greatly accelerated rate compared to women without such abnormalities. To investigate this association, we performed a longitudinal study of BMD in a group of healthy premenopausal women enrolled in a comprehensive study of ovulatory function. Subjects had collected daily urine samples that were analyzed for estrone and progesterone metabolites by enzyme-linked immunoassay. The 53 participants collected urine for an average of 4.1 cycles. Computer algorithms identified 7 (13.2%) women with luteal phase abnormalities (> 1 anovulatory cycle or cycle with luteal phase length < or = 10 days) and 17 (32.1%) women with other menstrual abnormalities. Areal BMD (grams per cm2) was measured at the lumbar spine, hip, and whole body using dual energy x-ray absorptiometry; BMD was measured 2-3 times over an average observation period of 17.5 months. At baseline, women with luteal abnormalities had mean BMD similar to those of the 29 women with no abnormal cycles: lumbar spine, 1.06 vs. 1.09 g/cm2; total hip, 0.95 vs. 0.94 g/cm2; whole body, 1.15 vs. 1.11 g/cm2 (P > 0.10; adjusted for age and weight at baseline, parity, physical activity level, and calcium intake). When compared at follow-up to women with no abnormal cycles, women with luteal abnormalities tended to gain BMD at the spine and hip (P > 0.10). On whole body measurement, women with luteal abnormalities tended to lose BMD compared to women with no abnormal cycles (-1.1%/yr vs. 0%/yr; P = 0.08); however, the magnitude of loss was not unusual for women in this age range and was within the coefficient of variation for replicate measurements. Neither mean luteal phase length, percent time in luteal phase, nor average daily excretion of progesterone metabolites was associated with baseline BMD or percent annual change in BMD at any measurement site. Thus, we did not confirm a relationship between luteal abnormalities and accelerated bone loss in this population of healthy premenopausal women.

Adolescent↗

Correlates of osteopenia in patients with cystic fibrosis.

OBJECTIVE: As the expected survival improves for individuals with cystic fibrosis, these individuals face myriad medical complications. The goals of this study were to examine the prevalence of osteopenia in children and adults with cystic fibrosis and to elucidate the risk factors associated with deficits in bone mineral. METHODOLOGY: We compared bone mineral levels in 49 patients (30 female and 19 male) ages 8 through 48 years with those of age- and sex-matched control subjects. Lumbar spine, femoral neck, and whole-body bone mineral were measured by dual-energy radiographic absorptiometry and expressed in terms of bone mineral content, areal bone density (BMD), and bone mineral apparent density (BMAD), which corrects for differences in bone size. Clinical variables were evaluated as potential correlates of bone mineral. RESULTS: Patients with cystic fibrosis had significantly less bone mineral than did control subjects at all sites using all expressions of bone mass. Mean BMD z scores were -1.7 (lumbar spine), -1.9 (femoral neck), and -1.2 (whole body). BMAD z scores also were significantly low for age and gender. Twenty-six of the 49 patients (8 adolescents) had significant osteopenia according to their BMD z scores; 14 of the 45 patients (5 adolescents) with available BMAD z scores had significantly low values at one or more sites. Age, pubertal stage, body mass, caloric expenditure, illness severity, glucocorticoid therapy, and gonadal function predicted bone mineral status. Serum parathyroid hormone and calcium, carbohydrate intake, and weight-bearing activity had limited predictive value. Daily calcium intake and cystic fibrosis transmembrane regulator genotype did not predict bone mineral status. CONCLUSIONS: Osteopenia is common at all ages in cystic fibrosis, suggesting that inadequate bone mineral accretion as well as increased bone loss contribute to the deficits in bone mineral observed. Several clinical factors seem to contribute to these deficits.

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Investigations of patients of health care workers infected with HIV. The Centers for Disease Control and Prevention database.

OBJECTIVE: To assess the risk for transmission of the human immunodeficiency virus (HIV) from an infected health care worker to patients. DESIGN: Survey of investigators from health departments, hospitals, and other agencies who had elected to notify patients who had received care from health care workers infected with HIV. MEASUREMENTS: Information was collected about infected health care workers, their work practices, their patients' HIV test results, procedures that they did on those of their patients who were tested for HIV, and patient notification procedures. RESULTS: As of 1 January 1995, information about investigations of 64 health care workers infected with HIV was reported to the Centers for Disease Control and Prevention; HIV test results were available for approximately 22,171 patients of 51 of the 64 health care workers. For 37 of the 51 workers, no seropositive patients were reported among 13,063 patients tested for HIV. For the remaining 14 health care workers, 113 seropositive patients were reported among 9108 patients. Epidemiologic and laboratory follow-up did not show any health care worker to have been a source of HIV for any of the patients tested. CONCLUSION: Despite limitations, these data are consistent with previous assessments that state that the risk for transmission of HIV from a health care worker to a patient is very small. These data also support current recommendations that state that retrospective patient notification need not be done routinely.

Centers for Disease Control and Prevention, U.S.↗

Gymnasts exhibit higher bone mass than runners despite similar prevalence of amenorrhea and oligomenorrhea.

Female athletes exhibit a higher prevalence of exercise-associated amenorrhea and oligomenorrhea compared with nonathletic women, and both conditions are related to reduced bone mineral density (BMD), particularly at the spine. This study investigated bone mass and oligomenorrhea and amenorrhea in two groups of competitive female athletes with different skeletal loading patterns: gymnasts and runners. Bone mineral density (g/cm2) of the femoral neck, lumbar spine (L2-4), and whole body was assessed by dual energy X-ray absorptiometry (QDR-1000/W, Hologic Inc., Waltham, MA) in collegiate gymnasts (n = 21) and runners (n = 20), and nonathletic college women (n = 19). The runners and gymnasts had similar values for percent body fat (14.7 +/- 2.2% and 15.6 +/- 2.9%, respectively), which were lower (p < 0.001) than controls (22.3 +/- 3.0%). Lean body mass (LBM) did not differ among the groups, but when adjusted for body surface area, gymnasts had a higher LBM/height2 (p = 0.0001) compared with runners and controls. Muscle strength was significantly greater (p < 0.05) in gymnasts for quadriceps, biceps, and hip adductor force, compared with runners and controls. Gymnasts had a significantly later menarche age (16.2 +/- 1.7 years) compared with runners (14.4 +/- 1.7 years) and controls (13.0 +/- 1.2 years). The prevalence of oligo- and amenorrhea was 47% for gymnasts (6 amenorrheic, 4 oligomenorrheic), 30% for runners (3 amenorrheic, 3 oligomenorrheic), and 0% for controls. Furthermore, athletic groups had similar menstrual histories given the higher proportion of gymnasts who had experienced primary amenorrhea. When evaluated since menarche, however, runners had somewhat longer histories due to an earlier age at menarche and slightly older ages. Dietary calcium intake did not differ among groups, although mean values were below the RDA of 1200 mg/day. By athletic group, BMD at any site did not differ among women with amenorrhea versus oligomenorrhea versus eumenorrhea, although there was a trend for the regularly menstruating athletes in both groups to have slightly higher values. Lumbar spine BMD was lower (p = 0.0001) in runners (0.98 +/- 0.11 g/cm2) compared with both gymnasts and controls (1.17 +/- 0.13 and 1.11 +/- 0.11 g/cm2, respectively). Femoral neck BMD differed among all groups (p = 0.0001): gymnasts = 1.09 +/- 0.12 g/cm2 > controls = 0.97 +/- 0.10 g/cm2 > runners = 0.88 +/- 0.11 g/cm2. Whole body BMD was lower (p < 0.01) in runners (1.04 +/- 0.06 g/cm2) compared with gymnasts and controls (1.11 +/- 0.08 and 1.09 +/- 0.06 g/cm2, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

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Differential effects of swimming versus weight-bearing activity on bone mineral status of eumenorrheic athletes.

To examine the role of skeletal loading patterns on bone mineral density (BMD), we compared eumenorrheic athletes who chronically trained by opposite forms of skeletal loading, intensive weight-bearing activity (gymnastics, n = 13), and nonweightbearing activity (swimming, n = 26) and 19 nonathletic controls. BMD (g/cm2) of the lumbar spine, femoral neck, trochanter, and whole body was assessed by dual energy X-ray absorptiometry (DXA). Subregion analysis of the whole body scan permitted BMD evaluation of diverse regions. Swimmers were taller (p = 0.0001), heavier (p < 0.005), and had a greater bone-free lean mass (p < 0.001) than gymnasts and nonathletic controls. When adjusted for body surface area, there was no difference in lean mass between swimmers and gymnasts, and both were higher than controls (p < 0.01). Gymnasts had a lower (p < 0.005) fat mass than swimmers and controls. There were no group differences for spine or whole body BMD, but gymnasts had higher spine BMD corrected for body mass than either swimmers or controls. Gymnasts (1.117 +/- 0.110) had higher femoral neck BMD than controls (0.974 +/- 0.105), who were higher than swimmers (0.875 +/- 0.105) (p = 0.0001). This result still applied when BMD was normalized for body weight and bone size. Trochanter BMD of gymnasts (0.898 +/- 0.130) was also higher than controls (0.784 +/- 0.097) and swimmers (0.748 +/- 0.085) (p = 0.0002), and remained higher when corrected for body mass.(ABSTRACT TRUNCATED AT 250 WORDS)

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Factors contributing to skeletal health of postmenopausal Mexican-American women.

Incidence rates of hip fracture are lower in Hispanic (HC) than non-Hispanic Caucasians (NHC). To investigate factors that may affect skeletal health of Hispanics, we recruited 152 healthy community-dwelling Mexican-American Caucasian women into a 4-year longitudinal study that evaluates bone mass, nutritional status, muscle strength, mobility, falls, and other factors that may contribute to fracture risk. Results from the baseline component of the study are reported herein. Average bone mineral densities (BMD) evaluated by dual-energy X-ray absorptiometry (DXA) in this study group did not differ from BMDs in healthy, NHC women of similar age. Hip axis length (HAL), however, was significantly shorter than that reported for nonosteoporotic NHC. Factors independently associated with greater BMD and BMC at certain skeletal sites were lean body mass, fat mass, acculturation, years of estrogen use, sun exposure, hip adductor strength, grip strength, erythrocyte folate, and serum glucose concentrations. Factors independently associated with lower BMD and BMC at certain skeletal sites were age, parity, and vertebral deformities (all p < 0.05). Thus, the decreased risk of hip fracture in HC compared with NHC does not appear to be due to high bone mass. However, other factors such as HAL and body composition may play a role in maintenance of skeletal integrity.

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The bone mineral status of patients with Marfan syndrome.

Osteopenia at the hip and low total body calcium content have been reported in women with Marfan syndrome. Using dual X-ray absorptiometry (DXA), we evaluated the lumbar spine L2-L4 and proximal femur bone mineral density (BMD,/cm2) in 32 women and 16 children with Marfan syndrome. The women were 38 +/- 10 (SD) years old (23-58 years); their mean height was 178.7 +/- 8 cm. The children (9 boys and girls were 9.9-17.5 years old. Children were tall for their ages but of normal weight. All subjects were moderately active, without previous nontraumatic fracture. In the women, BMD was reduced at L2-L4, femoral neck (fnk), trochanter (tr), and intertrochanter (intr) (p < 0.0001-0.006), compared with age-predicted values. Z scores for L2-L4 and for the fnk, tr, and intr, were -0.59 +/- 1.06,-1.25 +/- 0.99,-1.03 +/- 0.91, respectively. The average hip axis length (HAL) of 11.5 +/- 0.093 cm was at the 80th percentile for women. No significant change was observed in 1 year follow-up BMD measurements in 13 women (fnk = -0.23 +/- 2.3%/year; L2-L4 = -0.43 +/- 1.57%/year). In Marfan children, BMD correlated with age, height, and pubertal development. Femoral neck BMG was reduced (Z = -0.74 +/- 1.22,p < 0.05) with a nonsignificant trend toward decreased BMD at L2-L4 (Z = 33 +/- 1.48). Resorption markers in Marfan women were normal and did not correlate with bone status. We conclude that women with Marfan syndrome have both axial and peripheral osteopenia as well as an increased HAL. This combination of findings likely increases substantially their long-term risk for hip fracture. Presence of osteopenia in Marfan children indicates that the skeletal deficits of Marfan syndrome may reflect inadequate bone acquisition.

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Effects of a one-year high-intensity versus low-intensity resistance training program on bone mineral density in older women.

The purpose of this study was to determine the effects of a 12-month resistance training program, of two different intensities, on bone mineral density (BMD) in healthy, older women. Twenty-six Caucasian women (aged 65-79 years) completed the study. Subjects were randomly assigned to one of three groups: high-intensity (HI; n = 8), low-intensity (LI; n = 7), and control (CON; n = 11). The active groups performed 10 exercises, 3 days/week under supervision. Exercise intensity was maintained at 80% of one-repetition maximum (1-RM) for the HI groups, and at 40% 1-RM for the LI group. The volume of work was maintained constant between the two groups by assigning the LI group twice as many repetitions for each exercise. Maximal muscular strength and BMD of the lumbar spine and total hip were measured at baseline and at 12 months. Strength was evaluated using the 1-RM method, and BMD was determined by dual-energy X-ray absorptiometry. Exercise session attendance was similar for the two groups (81.0% HI; 76.8% LI). Muscular strength improved in the exercisers compared with the CON group (p < or = 0.05). Percentage change in lumbar spine BMD was 0.7 +/- 1.9%, 0.5 +/- 2.4%, and -0.1 +/- 2.3% for the HI, LI, and CON groups, respectively. Percentage change in total hip BMD was 0.8 +/- 2.3% (HI), 1.0 +/- 1.7% (LI), and 0.9 +/- 1.3% (CON). Group differences in BMD change were not significant (p > 0.05). These findings suggest that high-intensity and low-intensity resistance training regimens effectively increase muscular strength, but not lumbar spine or total hip BMD, in healthy, older women.

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Effects of recombinant insulin-like growth factor-I and growth hormone on bone turnover in elderly women.

We evaluated the effects of recombinant insulin-like growth factor-I (IGF-I) and growth hormone (GH) on calciotropic hormones and bone turnover markers in 16 healthy elderly women 71.9 +/- 1.3 years of age (mean +/- SEM). Subjects consumed a fixed diet providing 1000 mg of calcium and 0.9 g/kg of protein for 10 days before starting baseline 24-h urine and blood collections. Specimens were collected for 6 consecutive days before initiating subcutaneous injections of GH (25 micrograms/kg/day, n = 5) and IGF-I at 60 micrograms/kg b.i.d. (high-dose, n = 5) or at 15 micrograms/kg b.i.d. (low-dose, n = 6) for 28 days. Resorption markers included urine hydroxyproline (OHP), total pyridinolines (PYD), and N-telopeptide; formation markers include osteocalcin, skeletal alkaline phosphatase (sALP), and type I procollagen carboxy-terminal extension peptide (CICP). For each subject, baseline daily turnover markers varied substantially (DV = 16-22%). With GH and high-dose IGF-I, resorption and formation markers increased progressively to maximum levels at day 21. For GH, the increase in day 21 PYD, N-telopeptide, osteocalcin, and CICP was 143, 111, 53, and 81%, respectively (p < 0.96-0.02). For high-dose IGF-I, these increases were 108, 81, 77, and 111% (p < 0.02-0.002). However, with low-dose IGF-I no change was observed in resorption markers while osteocalcin and CICP increased progressively (day 21, % increases = 88 +/- 51, 36 +/- 14). Twenty-four hour urine collections during the last days of baseline and of study drug were taken as six 4 h aliquots. When deoxyPYD was measured on these samples in the low-dose IGF-I group, a significant increase was observed only on the 0800-1200 h aliquot. Serum phosphorus concentrations increased with GH (21.2 +/- 3.3%) and high-dose IGF-I (8.8 +/- 3.6%) by day 21 but actually decreased by day 28 (-9.7 +/- 2.7, p < 0.02) with low-dose IGF-I. Urinary phosphorus excretion decreased with high-dose IGF-I only. Twenty-four hour calcium excretion increased with all treatments. These results indicate that both GH and high-dose IGF-I activate remodeling osteons. By contrast, low-dose IGF-I may directly increase osteoblastic function with only a minimal increase in bone resorption and may therefore provide a useful means to increase bone mass. The results also suggest some of the GH action on renal phosphorus handling represents a direct action of GH on the nephron which does not involve the intermediacy of IGF-I. Finally, even under controlled conditions bone turnover markers exhibit substantial daily variation so that a very large treatment effect will be required for these markers to have clinical utility.

Aged↗

Effects of a gonadotropin-releasing hormone agonist on the calcium-parathyroid axis and bone turnover in women with endometriosis.

OBJECTIVE: Our purpose was to investigate the effects of nafarelin on bone turnover and mass (bone mineral density, in grams per square centimeter) in women with endometriosis. STUDY DESIGN: We monitored 22 young women with endometriosis during and 6 months after 6 months of nafarelin treatment. We compared the bone mineral density status of these women with that of healthy controls undergoing sequential bone mineral density measurement. RESULTS: Subjects had a 2.2% loss in L2-4 bone mineral density by 6 months, increasing 3 months later to 3% and returning toward baseline by 6 months after treatment. Radius bone mineral density did not change in the treatment group. Bone mineral density did not change in controls. Serum and urinary calcium levels rose during treatment. Hydroxyproline excretion increased and remained elevated 6 months after treatment. A rise in serum osteocalcin persisted 3 months after therapy but normalized by 6 months. CONCLUSIONS: Bone mineral density deficits with nafarelin are reversible. Increased bone turnover persists 6 months beyond treatment, demonstrating the need for careful monitoring of women receiving prolonged or repeated treatment.

Adult↗

Accuracy of equations to predict basal metabolic rate in older women.

OBJECTIVE: To assess the accuracy of several published equations for predicting basal metabolic rate (BMR) in older women. DESIGN: BMR was assessed in 116 healthy, older white women, aged 60 to 82 years, on three successive mornings by indirect calorimetry. Body composition was determined by dual energy X-ray absorptiometry or hydrostatic weighing. The measured BMRs were compared with values obtained from eight published prediction equations that used solely, or in various combinations, measures of height, weight, fat-free mass, age, and menopausal status. STATISTICAL ANALYSES PERFORMED: The root mean squared prediction error (RMSPE) was used to determine how accurately predicted BMR matched actual BMR for each subject. In addition, regression analysis was used to evaluate accuracy of predicted BMR vs directly measured BMR. RESULTS: Predicted mean BMR determined using all eight equations was significantly correlated to measured BMR (P = .0001), accounting for 30% to 52% of the variance of measured BMR. When analyzed by RMSPE, however, the equations of Owen et al (1986), Fredrix et al (1990), and Harris-Benedict (1919) predicted actual BMR for each subject within an average of 116 kcal/day, and the equation of Cunningham (1980) resulted in the largest prediction error at 208 kcal/day. APPLICATIONS/CONCLUSIONS: The regression equations of Owen et al (1986), which used body weight, Fredrix et al (1990), which used body weight and age, and Harris-Benedict (1919), which used age, weight, and height as variables, were most accurate in predicting BMR in our sample of healthy older women.

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