The effect of sports training on the age-related changes of body composition and isokinetic peak torque in knee extensors of junior speed skaters

To elucidate the effect of sports training on age-related changes of body composition and isokinetic peak torque (IPT) in knee extensors, junior speed skaters were tested in comparison with relatively sedentary age-matched controls. Subjects consisted of 132 male and 71 female junior speed skaters (SSs; aged 10-18 years). Two-hundred and thirty-six males and 265 females between the ages of 10 to 18 in the same geographic area were also tested as controls (Cs). Lean Body Mass (LBM) and relative body fat (%) were estimated from skinfolds, using the equations for preadolescent boys and girls. An isokinetic dynamometer (Cybex II) was used to measure IPT (Nm) produced at angular velocities corresponding to 0, 30, 180, 300 deg.sec-1 during maximal knee extensions. SSs were heavier in body weight and LBM from age 13 for males and from age 16 for females than the Cs, and there were significant differences in LBM between SSs and Cs after age 16 regardless of sex. The female Cs showed a gradual increase in relative body fat (%) after age 14, however, such a trend was absent in female SSs. IPT increased in any angular velocity with age from 10-18 years in the male Cs, and from 10-15 years in the female Cs. On the other hand, male SSs tended to be stronger after age 13 and female SSs stronger after age 16. Significant differences between the two groups were obtained only at lower angular velocities from 16 years of age in both sexes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of high-intensity strength training on cardiovascular function

Thirteen healthy, untrained males (age 44 +/- 1 yr, range 40-55 yr) were studied to determine the effects of 16 wk of high-intensity, variable-resistance, Nautilus strength training on cardiovascular function. A control group consisting of 10 untrained males (age 52 +/- 2 yr, range 40-64 yr) underwent the same evaluation procedures as the training group. Maximal oxygen uptake (VO2max), cardiac output during submaximal exercise, and body composition were determined before and after training. In addition, the physiological responses to an acute training session were evaluated. Muscular strength increased markedly, as evidenced by a 44% average increase in the "one-repetition maximum" in the various exercises. Body weight and percent body fat did not change with training, though fat-free weight did increase (66.9 +/- 2.6 vs 68.8 +/- 2.7 kg, P less than 0.05) significantly. Maximal oxygen uptake did not change significantly in either the training or the control group, and there were no changes in the hemodynamic responses to submaximal exercise after training. These findings indicate, therefore, that high-intensity, variable-resistance strength training produces no adaptative improvement in cardiovascular function. The physiological responses measured during a training session provide evidence that this lack of cardiovascular adaptation may be due to the low percentage of VO2max elicited by this form of exercise.     

Relation between cardiovascular risk factors at adult age,and physical activity during youth and adulthood: the Leuven Longitudinal Study on Lifestyle,Fitness and Health

This study investigated the relationship between sports participation/physical activity during youth (13 - 18 years of age) and adulthood (30 - 40 years of age), and cardiovascular risk factors (body fat and fat distribution, blood pressure, lipoprotein levels and cardiorespiratory fitness) at 40 years of age. Subjects were 166 Flemish males from "The Leuven Longitudinal Study on Lifestyle, Fitness and Health". Physical activity was assessed by means of a sports participation inventory and the Tecumseh community Health Study Questionnaire. In addition to correlation and multiple stepwise regression analyses, different groups (at risk, not at risk) were contrasted on sports participation/physical activity parameters using ANOVA. Long-term exposure during adulthood to daily physical activity was slightly related to a low/high risk profile for waist circumference, percent body fatness, triglycerides and peak VO(2). Sports participation during adolescence was not related to levels of cardiovascular risk factors at 40 years of age.     

The correlation between peak oxygen uptake (VO2peak) and running performance in children and adolescents. aspects of different units

The method of removing the confounding effect of body mass on peak oxygen uptake simply by dividing the measured values by body mass has been questioned. The aim of the study was to find an expression of body mass for compensating for differences in body mass so as to achieve the best correlation to running performance. In a cross-sectional study, design peak oxygen uptake (VO2peak) was measured in 107 boys in the age range 8-17 years and 88 girls in the age range 8-16 years. The present study indicates that VO2peak do not increase in proportion to body mass during running, rather that VO2peak is inversely related to body mass. When using allometric regression standards with the sexes separated in gender groups, there was a tendency that boys achieved scaling factors closer to unity than did the girls. The increase in subcutaneous fat in the girls throughout the pubertal years is the most likely reason why body mass increased proportionally more than VO2peak in girls. The present study indicates that VO2peak when expressed as milliliters per kilogram per minute (ml kg(-1) min(-1)) is a poor denominator for VO2peak as a function of running performance in children and adolescents.     

The effects of systematic resistance training in the elderly

The aim of the study was to examine the effects of a maximal resistance training following the principles of the most effective resistance training known from sport adapted to elderly people. Twenty-four subjects were randomly assigned into a training group (10 females and 4 males, age; 76.2 +/- 3.2 years) that underwent a training program and a control group (6 females and 4 males, age; 76.6 +/- 2.7 years) that did not participate in the training program. Before and after the training period, both groups were identically examined (blood and urine sample, spiroergometric testing, morphological measurements). The training group underwent a 12-week training program. Eight different exercises for the largest muscle groups of the largest joints were defined as one training circle. Training took place twice a week and commenced with two training circles per week (one circle per training session). After every four weeks, one training circle per week was added until four training circles per week were reached. Before, after every four weeks (changes in training amount) and after the training period, the maximum strength was measured. Data was analysed by the independent T-test and the analysis of variance, in case of significance, the dependent T-test and the Scheffé-test were used. In the resistance training group, the fat-free body mass was increased by approximately 2.9 +/- 0.5 kg, with no significant difference between females and males. Ergometrical fitness was increased by approximately 15 %, while the maximum oxygen uptake was increased by approximately 12 %. Maximum strength was increased between 26 % (bench pull) and 38 % (leg press). Resistance training that consisted of two training sessions per week was found to be at least as efficient as resistance training that included three training sessions per week, provided that the number of sets performed were equal. Seventy-five-year-old females were found to have a significantly higher body fat content than males of the same age (37 % versus 26 %, respectively). However, the decrease in body fat mass due to resistance training was found to be equal in both females and males (- 4 +/- 0.8 kg). Furthermore, there was almost no difference in muscle strength between the sexes for this age group (for example; leg press: females 86 kg versus males 82 kg).     

Responses of pre- and post-menopausal females to aerobic conditioning

This study sought to determine whether the ability to improve cardiorespiratory endurance and body composition is affected by the menopausal status of females. Twenty premenopausal females and 18 postmenopausal females, ages 35-49 and 47-66 yr, respectively, were randomly assigned to exercise and control groups depending on menopausal status. Both exercise groups (PRE-EX, N = 16; POST-EN, N = 14) participated in a progressive walking program (4 days/week for 9 weeks) at an intensity of 80% the age-adjusted heart rate maximum (80% HRM). Following training, both exercise groups significantly improved submaximal exercise capacity (SEC) as measured by oxygen consumption (l/min; ml/kg . min) and treadmill walking time at 80% HRM. The PRE-EX group significantly improved percent body fat and lean body weight, while there was no significant change in total body weight. The POST-EX group significantly improved total body weight and percent body fat with no significant change in lean body weight. Although some of these changes in body composition were statistically significant, overall the alterations were minimal. ANCOVA revealed exercise, not menopause, to be the effective treatment for improving percent body fat and SEC80%HRM. There were no significant differences between the PRE-EX and POST-EX groups in their ability to improve SEC80%HRM or to reduce percent body fat. The POST-EX group had a significantly greater reduction in total body weight, while the PRE-EX group had significantly greater increases in lean body weight. These findings suggest that the ability to favorably alter body composition and cardiorespiratory endurance through the aerobic conditioning of females is independent of menopausal status.     

Nutritional status and body composition of juvenile elite female gymnasts

BACKGROUND: The purpose of this study was to examine body composition, dietary intake and energy expenditure in 12 young female elite gymnasts aged 10.1 +/- 0.3 years, doing a physical exercise of 15 hrs x week-1. The results were compared with a control group consisting of nine volunteer school girls age matched doing less than 4 hrs x wk-1 of physical exercise. METHODS: Assessments included dietary intake for 7 days, anthropometric measurements (body weight, height, arm circumference, triceps and subscapular skinfolds, body mass index). Body fat percentage was estimated using the Slaughter equation. Anthropometric measurements and nutritional intake were recorded in autumn. RESULTS: The gymnasts were shorter and had lower body weight compared with controls (p<0.05). Percentage of body fat was significantly lower in gymnasts versus controls (p<0.01). Gymnasts had higher percentage of fat free mass (p<0.01) than the reference group. Daily energy intake met daily energy requirement in both groups. Distribution of energy for both groups was almost identical, with approximately 14% from protein, 48% from carbohydrate, and 37% from fat. The average intakes of polyunsaturated fat were low in the two groups. The main daily intake of most nutrients in both groups were in accordance with recommendations; exceptions were dietary fibre, E and B6 vitamins. CONCLUSIONS: The primary finding of this investigation is that in both groups, the mean daily energy intake met the energy requirement. Thus, the gymnasts did not restrict total energy. The overall nutrient intake of the two groups may appear adequate. Prepubertal gymnasts have higher percentage of fat free mass and daily energy expenditure and dietary intakes, but lower percent body fat than age matched controls.     

Premenarcheal gymnasts possess higher bone mineral density than controls

PURPOSE: The purpose of this study was to examine bone mineral density (BMD), body composition, dietary intake, physical activity, and energy expenditure (EE) in premenarcheal gymnasts (N = 16; age = 10.5 +/- 1.5 yr) in comparison to age- (+/- 0.35 yr), height- (+/- 2.6 cm), and weight- (+/- 1.5 kg) matched controls (N = 16; age = 10.5 +/- 1.3 yr). It was hypothesized that premenarcheal gymnasts would have higher BMD, fat-free soft tissue (FFST) mass, physical activity, and EE, but lower fat mass, percent body fat, and dietary intake than controls. METHODS: Dual energy x-ray absorptiometry was used to measure whole body, femur, and lumbar spine (L1-4) BMD, FFST, and fat mass. Three-day diet records were used to estimate mean daily dietary energy, macronutrient, and calcium intakes. Physical activity and EE were estimated by the Seven-Day Physical Activity Recall. RESULTS: The BMD means of the gymnasts were significantly higher (P < 0.05) than controls at all sites, except whole body, as were lumbar spine and femoral neck bone mineral apparent densities, despite lower protein intake expressed per kg FFST mass. Fat mass was significantly lower in gymnasts versus controls (P < 0.01) as was percent body fat (P < 0.001). Very hard physical activity during weekdays (P < 0.0001) and estimated EE (P < 0.01) were significantly higher in gymnasts compared with controls. CONCLUSION: Premenarcheal gymnasts have higher BMD than age-, height-, and weight-matched controls.     

Gender differences in peak muscle performance during growth

Gender-related differences in maximal leg muscle power were examined in 496 females and 426 males aged 8 to 20 years. Cycling peak power (CPP, including the force required to accelerate the flywheel of the cycle ergometer) was measured during three sprints. Optimal velocity (Vopt, velocity at CPP) was also determined. No gender-differences were observed in anthropometric characteristics and cycling performance between 8- and 14-year-old. From age 14, however, males showed a higher CPP than females, but also a higher lean leg volume (LLV, assessed by anthropometry). Allometric relationship between CPP and LLV (CPP = a . LLV ( b)) showed a clear gender-differentiation between 14- and 16-year-old: LLV exponent (b) was 1.05 in males vs. 0.74 in females. From 16 years onwards, analysis of covariance (ANCOVA) showed that the slopes of the CPP-LLV relationship were similar in both genders, but the intercepts differed. In other words, for a similar LLV, males showed greater CPP than females. It was suggested that this sex-related difference was due to total body fat increase, and more specifically lower-limb fat increase during puberty in girls, whilst the boys experienced increased lean body mass. Considering that the same gender-related difference was observed for optimal velocity adjusted for leg length, other factors such as fibre type variability or (and) neuromuscular activation might also be partly responsible for the higher peak muscle performance observed in males.     

Effect of a maximal treadmill test on percent body fat using leg-to-leg bioelectrical impedance analysis in children

AIM: The purpose of this investigation was to determine the effect of a maximal treadmill exercise test on percent body fat (%BF) in children using leg-to-leg bioelectrical impedance analysis (LBIA) (Tanita Model #TBF-300A). METHODS: Fifty-four children (24 females; 30 males) between 7-10 years of age participated in this study. LBIA measures of %BF were obtained immediately before and within 5 min after completing a maximal oxygen consumption test on a motorized treadmill. RESULTS: No pre- to post-test differences in %BF were observed in either group (mean difference: females 1.6%, males 1.5%). Impedance values significantly decreased postexercise (P < 0.05) in the female subjects. No significant differences were observed for fat mass, fat free mass, total body water or body weight postexercise when compared to pre-exercise values in either group. Correlations (P = 0.0001) of 0.997 were observed between pre- and postexercise measures of %BF. CONCLUSIONS: A maximal treadmill exercise test conducted prior to LBIA has no impact on %BF in children. Therefore, normal daily activities performed prior to LBIA assessment may have a limited impact on LBIA body composition measurement in children. As such, compliance with stringent pretesting exercise guidelines may not be essential when using LBIA to assess %BF in children.     

Thermal and metabolic responses of high and low fat women to cold water immersion.

BACKGROUND: At rest during cold exposure, the amount of body fat plays an important role in the maintenance of core temperature. High fat (HF) individuals would therefore have an advantage as compared with their low fat (LF) counterparts. Since females usually have a higher amount of body fat than males they are expected to maintain core temperature at a lower energy cost. METHODS: The purpose of the present investigation was to dichotomize female subjects by percent fat (LF = 20.5 +/- 2%, n = 6 vs. HF = 30 +/- 3%, n = 6) to elucidate the thermal and metabolic responses during acute exposure to 17 degrees C water for 120 min. The following variables were measured: rectal temperature (Tre; degrees C), mean skin temperature (Tsk; degrees C), oxygen consumption (VO2; ml x kg(-1) x min(-1)), and tissue insulation (I; degrees C x m2 x W(-1)). The experiment-wise error rate was set a priori at p = 0.05. RESULTS: Unexpectedly, only one of the variables demonstrated a main effect for fat (p < 0.05). Tre demonstrated a significant (p < 0.05) group by time interaction. However, Tsk and I demonstrated a main effect for time (p < 0.05). While VO2 demonstrated an increase across time, these changes were non-significant (p > 0.05). It appears that the HF group demonstrated a similar thermal (I and Tsk) and metabolic (VO2) response as compared with the LF counterparts. However, the LF groups maintained a lower Tre as compared with the HF subjects. Perhaps leaner subjects or colder water temperatures would elucidate the value of body fat in females, and demonstrate a differential response with respect to females varying in percent body fat.     

Oxygen saturation increases during childhood and decreases during adulthood among high altitude native Tibetians residing at 3,800-4,200m

This report describes age differences in oxygen saturation throughout the life cycle in a sample of high altitude native Tibetans residing in villages at 3,800-4,200 m altitude in the Tibet Autonomous Region, China. Oxygen saturation of 3,812 Tibetans was measured by pulse oximetry and a subsample of 1,582 healthy, nonpregnant, nonsmokers from 1 week to 80 years of age was selected for analyses. Infants under 1 year of age had 5-6% lower oxygen saturation than the peak of 89.8% attained at 11 years of age. There was a steady increase in mean oxygen saturation-for-age during the first decade of life, but not during the second decade. Adult males exhibited a slight decrease starting in the 20-29 year age range. Adult females maintained the peak oxygen saturation through the 40-49 year age range, exhibiting a decrease in oxygen saturation beginning in the 50-59 year age range and as a result had higher oxygen saturation than males during the female reproductive span. Thus, developmental factors during infancy and childhood, but not adolescence, enhanced oxygen transfer in this high altitude native resident Tibetan sample. The age of onset of aging processes detrimental to oxygen transfer differed for females and males.     

Athletic amenorrhea: lack of association with body fat

The most commonly tested hypothetical cause of athletic amenorrhea has been low body fat. Test results have conflicted because of mixed groups of athletes and methodologic problems. In this study, we measured body fat only in distance runners (greater than 53 km X wk-1) of the same somatotype who clearly had regular menses or secondary amenorrhea; this permitted more valid group comparison of body fat using hydrostatic weighing. The regularly menstruating group (N = 7) had 12 periods X yr-1 at intervals of 26.5 +/- 1.0 (SE) days with a duration of 4.1 +/- 0.4 days. In the athletic amenorrhea group (N = 7), menstrual periods had been absent for 1 to 10 yr (average = 3.9 +/- 1.3 yr); they were gynecologically evaluated to restrict the group to those with athletic amenorrhea. The groups were similar in a number of categories: weight, height, age, menarcheal age, weekly training mileage, days/week training, years of training, and maximum oxygen uptake. Percent body fat for the two groups was the same: 17.7 +/- 2.1% for the amenorrheic athletes and 17.4 +/- 1.2% for the regularly menstruating athletes (P = 0.91). These data do not support the idea that low body fat per se causes athletic amenorrhea.     

Resting metabolic rate and energy balance in amenorrheic and eumenorrheic runners

This study investigated metabolic and nutritional factors in association with athletic menstrual dysfunction (AMD). Three groups of women were studied: amenorrheic runners (amenorrheic), eumenorrheic runners (eumenorrheic), and eumenorrheic sedentary controls (sedentary). Amenorrheic and eumenorrheic were similar in age, weight, percent body fat by hydrodensitometry, training pace and mileage, best 10 km race time, years running, and maximal oxygen consumption. When adjusted for body weight or for fat-free mass by analysis of covariance, RMR was significantly lower in amenorrheic than in eumenorrheic and sedentary. The daily caloric intakes of the groups did not differ significantly, but the amenorrheic scored significantly higher than the eumenorrheic and sedentary on a scale of aberrant eating patterns. Amenorrheic high mileage runners seem to have a less adequate diet than eumenorrheic runners but appear to maintain energy balance and stable weight through a reduction in RMR.     

Adherence to Unsupervised Exercise

In brief: Forty-seven male police officers (mean age 41.0 years) were randomly assigned to three exercise groups: unsupervised, supervised, and control. Training consisted of walking and jogging three days per week for 20 weeks. The attrition rate for the unsupervised group (35%) was lower than for the supervised group (45%). The main reason the subjects gave for dropping out was lack of time. Both groups increased significantly compared to the control group in treadmill performance time, maximum oxygen uptake, and maximum oxygen pulse; and decreased significantly in resting heart rate, heart rate response to a step test, percent body fat, total skinfold fat, and waist girth.     

Adiposity, lipid levels, and brief endurance training in nonobese adolescent males

Physical activity during childhood and adolescence may influence the development of childhood obesity and cardiovascular disease later in life. Research focused prospectively on the effects of training on lipid levels in nonobese subjects, and studies using noninvasive measurements of subcutaneous and intraabdominal fat are lacking. It was hypothesized in nonobese sedentary adolescent males that a brief endurance-type exercise training intervention would reduce body fat and improve lipid profiles. Thirty-eight healthy, nonobese sedentary adolescent males (mean age 16 +/- 0.7 years old; 18 controls, 20 trained) completed a 5-week prospective, randomized, controlled study. Adiposity was measured using magnetic resonance images of the thigh and abdomen (subcutaneous abdominal adipose tissue [SAAT] and intraabdominal adipose tissue [IAAT]). Lipid measurements included serum triglycerides (TG), total cholesterol (TC), HDL and LDL cholesterol. There was no change in body weight in either control or training groups. Training led to small but significant reductions in thigh fat (-4.6 +/- 1.5%, p < 0.03) and SAAT% (1.7 +/- 0.8%, p < 0.02). There was no change in IAAT%. Unexpectedly in the control group there were significant increases in thigh fat (5.2 +/- 1.7%, p<0.01), SAAT% (1.8 +/- 0.6, p < 0.007) and IAAT% (4.5 +/- 1.1, p < 0.0007). Training-induced changes in adiposity were not accompanied by changes in circulating lipids. In nonobese adolescent males a brief period of endurance training led to reductions in body fat depots without weight change while body fat increased rapidly in the control group. Exercise training did not change lipid levels, the latter may require more sustained alterations in patterns of physical activity.     

Circulo-respiratory fitness in United States Air Force Academy cadets.

A sample of 79 United States Air Force Academy cadets was used to determine mean maximal oxygen consumption and percent body fat values for the cadet wing. The individuals selected represented all four classes and included no intercollegiate athletes. Maximal oxygen consumption testing was completed on a bicycle ergometer and percent body fat measurements were accomplished by the Wright-Wilmore method. The average max VO2 for these cadets was 47.91 (S.D.=4.58). This value compares very favorably with established norms by this age group. The mean percent body fat of 12.07 also depicts a highly fit population. The effect of altitude and the conversion for use with treadmill values is discussed. The USAFA cadet appears to have an excellent level of circulo-respiratory fitness, especially when compared with other military samples within the same age span.     

不同年龄、性别体检人群人体组成成分对比分析

目的探讨人体组成成分指标在不同年龄性别间的差异,为更精准的个体化营养及运动管理提供依据。方法选取成年健康体检受检者1 656名,按年龄分为6组:18~29岁组(n=79),30~39岁组(n=346),40~49岁组(n=463),50~59岁组(n=471),60~69岁组(n=236),70岁以上组(n=61)。采用In Body 720人体成分分析仪生物电阻抗法检测人体组成成分。结果不同性别者腰臀比,身体水分、蛋白质、矿物质含量,体脂百分比,肌肉量,基础代谢率的分布不同(P<0.05),体质量指数、健康评估得分无差异(P>0.05)。不同年龄组比较发现,男性身体水分含量分布无差异(P>0.05),其余各指标分布有差异(P<0.05);而女性各指标分布均有差异(P<0.05)。基础代谢率在18~39岁间随年龄增长而增高,40岁之后开始下降。体质量指数在18~59岁间随年龄增长而增高,60岁后开始降低。蛋白质、肌肉量、健康评估得分均在50岁之后呈现下降趋势。女性矿物质、肌肉量及身体水分含量随年龄增加而减少,且早于男性。体脂百分比及腰臀比值均随年龄增长而增长,女性增长速度快于男性。结论不同年龄、性别成年受检者人体成分指标有差异。40岁以前是体质量控制的重要年龄段。40岁以后,应随基础代谢率降低而减少能量摄入。女性较男性应更早重视维持机体蛋白质、矿物质含量,增肌减脂,应特别关注腰部减脂。     

中老年人群肝脏脂肪含量与骨密度的相关性研究

目的探讨中老年人群肝脏脂肪含量与腰椎骨密度的相关性。方法2016年3月至6月纳入184名北京社区中老年居民,其中男68名、女116名,对其进行腹部MRI mDIXON-Quant序列扫描和腰椎定量CT(QCT)扫描,测量肝脏脂肪含量和腰1~腰3椎体骨密度。根据肝脏脂肪含量的四分位数分为四组,采用单因素方差分析比较不同肝脏脂肪含量组间骨密度及身高、体重、体质量指数(BMI)、腰围、臀围等变量的差异,并对肝脏脂肪含量和骨密度做Spearman相关性分析和偏相关分析。结果随着肝脏脂肪含量的升高,BMI、腰围呈上升趋势,而腰椎骨密度逐渐降低。肝脏脂肪含量与腰椎骨密度呈低度负相关(r=-0.203,P=0.003),校正年龄、体重之后,仍呈负相关(r=-0.291,P<0.001),男性中r=-0.283(P=0.021),女性r=-0.210(P=0.025)。结论中老年人群肝脏脂肪含量与腰椎骨密度呈低度负相关。     

Bone marrow fat content in the elderly: a reversal of sex difference seen in younger subjects

Purpose:

To investigate vertebral bone marrow fat content in elderly subjects related to sex, age, and bone mineral density (BMD) and relate these findings to published data in younger subjects.

Materials and Methods:

A total of 259 healthy subjects (145 females, 114 males; age range, 62–90 years) underwent proton (¹H) MR spectroscopy of L3 vertebral body and BMD of the lumbar spine with results stratified according to age. Ninety age‐ and BMD‐matched subjects were selected to determine sex differences in marrow fat content and BMD.

Results:

In females, vertebral marrow fat content rose sharply between 55 and 65 years of age while in males vertebral marrow fat content rose gradually throughout life. Vertebral marrow fat content in females more than 60 years was approximately 10% higher in females than males, i.e., a reversal of sex difference reported in marrow fat content for subjects less than 60 years.

Conclusion:

Marrow fat content increases sharply in female subjects between 55 and 65 years of age while male subjects continue to increase marrow fat at a more gradual steady rate. Females older than 60 years have a higher marrow fat content than males. This increased deposition in marrow fat concurs with recognized changes in extraosseous fat distribution in postmenopausal females. J. Magn. Reson. Imaging 2012;36:225–230. © 2012 Wiley Periodicals, Inc.