儿童身高生长追踪研究

以北京市106名儿童为样本 ,为研究各年龄生长速度的集中趋势、变异状况以及与生长速度有关的参数 ,追踪观察这些儿童自6、7岁至 18岁时共12年的身高变化 ,并做有关参数分析。报告了各年龄组身高生长速度的均值及标准差 ,该组儿童身高生长突增开始年龄 (男10.73±1 .12岁 ,女 9.00± 1.18岁 )及速度 (男4.51± 0.65cm/年 ,女 4.95± 0.79cm/年 ) ;身高生长高峰发生年龄 (男 1 3.0 7±1.08岁 ,女11.32± 1.32岁 )及速度高峰值 (男10 .01± 1.59cm/年 ,女8.13± 1.03cm/年 ) ;以及生长突增结束年龄 (男16.18± 1.02岁 ,女 13.96± 1.09岁 )。分析了最终身高与生长突增有关指标的相关关系。     

The peak oxygen uptake of British children with reference to age, sex and sexual maturity

The purposes of this study were to provide baseline data on the peak oxygen consumption (VO2) of British children, aged 11-16 years and to examine the peak VO2 of children in relation to their pubertal stage of development. The peak VO2 of 226 boys and 194 girls was determined during either treadmill running or cycle ergometry. The sexual maturity of 320 of the children was estimated using Tanner's indices. Peak VO2 increased with chronological age in both sexes and from about the age of 12 years boys exhibited significantly higher (P less than 0.05) values than girls. Boys' peak VO2 in relation to body mass was consistent over the age range studied and was superior (P less than 0.05) to girls' values at all ages. It appears that mass-related peak VO2 is independent of sexual maturity in both sexes. The more mature boys demonstrated a significantly higher (P less than 0.05) peak VO2 (1.min-1) than the less mature boys on both ergometers. The more mature girls demonstrated significantly higher (P less than 0.05) peak VO2 (1.min-1) than the less mature girls only on the cycle ergometer. On both ergometers the differences between the peak VO2 of the girls and boys were more pronounced in the mature children whether expressed in relation to body mass or not. Comparison of the results with earlier data drawn from smaller samples failed to provide evidence to suggest that British children's peak VO2 has declined in recent years. No study with which to compare our maturity peak VO2 data appears to be available.     

Comparison of running performances and prevalence of overweight and obesity in Hungarian and Ukrainian adolescents

The 20-m shuttle run (20-mSRT) is a widely used field test to estimate peak oxygen consumption (VO2peak) and thus to assess aerobic fitness of adolescents (11). The purpose of this study was to analyse differences in basic anthropometric measurements (stature, body mass, percent body fat, BMI) and in aerobic fitness of Hungarian and Ukrainian adolescent boys and girls. We examined gender differences in maximal speed (km h-1), in peak VO2 (mL kg-1 min-1) and maximal heart rate (HRmax min-1). Two hundred ninety-two Ukrainian (mean age=16.5±0.5) and 374 (mean age=16.5±0.5) Hungarian adolescents volunteered to participate in this study. Differences were analysed using factorial analysis of the variance (ANOVA) and Student's t-test. Statistical significance was set at p<0.05. Hungarian boys and girls were significantly taller, heavier and had higher percent body fat than their Ukrainian counterparts. Altogether 10% of Hungarians and 7% of Ukrainians were classified overweight or obese according to Cole's BMI classification (4). VO2peak of Ukrainians (mean=49.44±5.29 mL kg-1 min-1) were significantly higher than that of Hungarians (mean=41.93±8.40 mL kg-1 min-1). Maximal heart rate also differed significantly (Ukrainians mean=201.12±8.43 min-1 vs. Hungarians mean=185.38±18.38 min-1).In conclusion, aerobic fitness of the Ukrainian adolescents was significantly higher than that of the Hungarians independently of BMI or gender.     

Anaerobic power of arms in teenage boys and girls: relationship to lean tissue

The purpose of this study was to describe anaerobic peak and mean power characteristics of arms as a function of age, gender and body composition among 50 girls and 50 boys 14 to 19 years of age. Peak (PP) and mean power (MP) output were determined during arm cranking (Wingate anaerobic test). Fat-free weight (FFW) was estimated from skinfolds, and lean arm volume (LAV) was determined by water displacement, corrected for fat volume. PP and MP increased progressively and significantly (P less than 0.05) with age for boys but not for the girls. Boys had significantly larger absolute PP and MP outputs than girls at comparable ages. PP and MP corrected for lean tissue volume were greater in older than younger boys (P less than 0.05), but did not vary significantly with age for girls. Absolute (W) PP and MP were highly correlated with LAV (r = 0.82; r = 0.75) and FFW (r = 0.84; r = 0.78) among boys. The respective r values for girls were 0.60 and 0.49 (LAV); 0.78 and 0.60 (FFW). Absolute peak and mean power, respectively, were more highly correlated with LAV (r = 0.90; r = 0.84) and FFW (r = 0.90; r = 0.85) for the combined data for boys and girls than for similar gender specific comparisons. In conclusion, both anaerobic PP and MP of arms during adolescence are highly correlated with lean tissue volume and fat-free weight, particularly among boys.     

Sex differences in height and sitting height in the Belgian population

Sex differences in growth were studied in a longitudinal study of 39 boys and 31 girls for sitting height. Individual growth patterns were determined by means of Preece Baines model 1. The results showed no significant bias in the fits of height and sitting height in boys and girls. Girls fits were significantly better than those of the boys for both height and sitting height. Univariate analysis by means of Mann-Whitney test showed significant sex differences for all function and biological parameters of height and sitting height excepted for s₁ parameter (the rate constant controlling pubertal velocity). Linear discriminant analysis revealed that the strongest sex differences for the timing and size parameters at adolescent. Peak velocity at adolescent was slightly less discriminating between the two sexes and velocity at take-off showed the least sex difference. These trends were similar for height and sitting height. Decomposition of sex differences in adult size showed that the major contributor to adult the sex differences is the effect of the later onset of the adolescent growth spurt in boys than in girls. Sex differences in adult phenotypes of height and sitting height are to a slightly lesser extent due to the greater adolescent gain in boys while prepubertal sex differences are almost negligible.     

Scaling peak VO2 to body mass in young male and female distance runners.

This study examined age- and sex-associated variation in peak oxygen consumption (VO2) of young male and female distance runners from an allometric scaling perspective. Subjects were from two separate studies of 9- to 19-yr-old distance runners from the mid-Michigan area, one conducted between 1982 and 1986 (Young Runners Study I, YRS I) and the other in 1999-2000 (Young Runners Study II, YRS II). Data from 27 boys and 27 girls from YRS I and 48 boys and 22 girls from the YRS II were included, and a total of 139 and 108 measurements of body size and peak VO2 in boys and girls, respectively, were available. Subjects were divided into whole year age groups. A 2 x 9 (sex x age group) ANOVA was used to examine differences in peak VO2. Intraindividual ontogenetic allometric scaling was determined in 20 boys and 17 girls measured annually for 3-5 yr. Allometric scaling factors were calculated using linear regression of log-transformed data. Results indicated that 1) absolute peak VO2 increases with age in boys and girls, 2) relative peak VO2 (ml x kg(-1) x min(-1)) remains relatively stable in boys and in girls, 3) relative peak VO2 (ml x kg(-0.75) x min(-1)) increases throughout the age range in boys and increases in girls until age 15 yr, and 4) peak VO2 adjusted for body mass (ml/min) increases with age in boys and girls. The overall mean cross-sectional scaling factor was 1.01 +/- 0.03 (SE) in boys and 0.85 +/- 0.05 (SE) in girls. Significant age x sex interactions and significant scaling factors between sexes identify the progressive divergence of peak VO2 between adolescent male and female distance runners. Mean ontogenetic allometric scaling factors were 0.81 [0.71-0.92, 95% confidence interval (CI)] and 0.61 (0.50-0.72, 95% CI) in boys and girls, respectively (P = 0.002). There was considerable variation in individual scaling factors (0.51-1.31 and 0.28-0.90 in boys and girls, respectively). The results suggest that the interpretation of growth-related changes in peak VO2 of young distance runners is dependent upon the manner of expressing peak VO2 relative to body size and/or the statistical technique employed.     

Individual differences in adolescent religiosity in Finland: familial effects are modified by sex and region of residence.

Data from 16-year-old Finnish twin pairs were used to estimate familial effects on religiosity and the modification of those effects by sex and residential region. The sample of 2265 twin boys and 2521 twin girls formed 779 monozygotic and 1614 dizygotic pairs, 785 of the same sex and 829 of opposite sex. We compared religiosity scores of twins living in more rural and traditional northern Finland with those living in the more urban and secular southern region. Girls had higher religiosity scores than did boys, and twins living in northern Finland had higher religiosity scores than those resident in southern Finland. Correlations for monozygotic twins were slightly higher than those for dizygotic twins, and covariance modeling found modest heritability of religiosity [11% (95% CI 0-24) for girls; 22% (95% CI 6-38) for boys], and substantial shared environmental effects [60% (95% CI 49-69) and 45% (95% CI 31-57)] among girls and boys, respectively. The correlation between shared environmental effects in boys and girls was estimated to be 0.84 (95% CI 0.73-0.99). In analyses distinguishing region of residence, girls living in southern Finland were found to have significantly higher unshared environmental effects than girls in northern Finland, while boys living in the urban south appeared to have lower shared environmental effects, and higher additive genetic effects, than boys living in the rural north.     

Physical fitness of children aged 5 and 6 years

Maximal oxygen uptake (Vo2 max) of 85 healthy kindergarten children, 46 boys and 39 girls, aged 5 and 6 years, was determined by means of track running. Their physique, skinfold thickness, grip and back muscle strength, and performances of 25 m-run, 50 m-run, standing broad jump, and 5 min-endurance run were also measured. Skinfold thickness of girls was significantly larger than that of boys. Boys were significantly superior to girls in all the motor performances. The Vo2 max per unit of body weight was 49.46 ml/kg/min for boys and 46.30 ml/kg/min for girls, the sex difference being significant at the 0.001 level. The correlation coefficient between Vo2 max per kg body weight and 5 min-endurance run performance was 0.417 for boys and 0.049 for girls, while that between absolute Vo2 max and body weight was 0.899 for boys and 0.563 for girls. The regression equation of the absolute value of Vo2 max (liter/min) on body weight (kg) was: Y=0.051X-0.025 for boys and Y=0.024 + 0.408 for girls, the regression coefficient of boys being twice as large as that of girls. It appears that at ages 5-6 sex differences are exhibited ont only in muscle strength and agility but also in endurance run and aerobic work capacity.     

Exercise performance and magnetic resonance imaging-determined thigh muscle volume in children

This study examined the relationships between thigh muscle volume (TMV) and aerobic and anaerobic performance in children. A total of 32 children, 16 boys and 16 girls, aged 9.9 (0.3) years completed a treadmill running test to exhaustion for the determination of peak oxygen uptake (peak V˙O₂) and a Wingate Anaerobic Test (WAnT) for the determination of peak power (PP) and mean power (MP). The volume of the right thigh muscle was determined using magnetic resonance imaging. TMV was not significantly different in boys and girls [2.39 (0.29) l vs 2.18 (0.38) l, P > 0.05]. Peak V˙O₂ and MP were significantly higher in boys than girls (P < 0.01) whether expressed in absolute, mass-related or allometrically scaled terms. Absolute PP was not significantly different in boys and girls but mass-related and allometrically scaled values were higher in boys (P < 0.01). TMV was correlated with absolute peak V˙O₂, PP and MP in both sexes (r = 0.52–0.89, P < 0.01). In boys, mass-related PP was correlated with TMV (r =0.53, P < 0.01), and in girls mass-related peak V˙O₂ was correlated with TMV (r = −0.61, P < 0.01). However, in neither sex were allometrically scaled peak V˙O₂, PP or MP correlated with TMV (P > 0.05). There were no significant differences between boys and girls in terms of peak V˙O₂, PP or MP when expressed in a ratio to TMV or allometrically scaled TMV. In conclusion, this study has demonstrated that, when body size is appropriately accounted for using allometric scaling, TMV is unrelated to indices of aerobic and anaerobic power in 10-year-old children. Furthermore, there appear to be no qualitative differences in the muscle function of boys and girls in respect of aerobic and anaerobic function. Accepted: 4 February 1997     

Race and gender differences in the relationships between anthropometrics and abdominal fat in youth

Objective: We examined the influence of race and gender on abdominal adipose tissue (AT) distribution for a given anthropometric measure including waist circumference (WC), waist‐to‐hip ratio (WHR) and waist‐to‐height (W/Ht) in youth. Methods and Procedures: Subjects included healthy 62 black and 98 white youth. A single transverse image of the abdomen (L4–L5) was obtained using computed tomography. Results: For a given BMI, there was a significant (P < 0.05) main effect of race and sex on the relationship between BMI and WC, such that boys and whites had a higher WC than girls and blacks. There was a significant (P < 0.05) main effect and interaction effect of gender on the relationship between WC and visceral AT, such that boys had a higher visceral AT than girls, and the difference was magnified with increasing WC. For a given WC, black boys and girls had higher abdominal subcutaneous AT (SAT) than white peers, wherein the magnitude of the difference is increased with increasing WC. For a given W/Ht, black boys had significantly (P < 0.05) lower visceral AT than white boys, but with no difference in girls. Black boys and girls had higher SAT than white peers, wherein the magnitude of the difference is increased with increasing W/Ht. Discussion: Our findings demonstrate a significant race and gender differential in the abdominal AT distribution for a given BMI, WC, WHR, and W/Ht. Future studies should take these differences into consideration when developing race‐ and gender‐specific anthropometric cut‐offs for obesity and obesity‐related health risks in youth.     

Physical activity levels of normal-weight and overweight girls and boys during primary school recess

Objective: This study aimed to compare moderate‐to‐vigorous physical activity (MVPA) and vigorous physical activity (VPA) in normal‐weight and overweight boys and girls during school recess. Research Methods and Procedures: Four hundred twenty children, age 6 to 10 years, were randomly selected from 25 schools in England. Three hundred seventy‐seven children completed the study. BMI was calculated from height and weight measurements, and heart rate reserve thresholds of 50% and 75% reflected children's engagement in MVPA and VPA, respectively. Results: There was a significant main effect for sex and a significant interaction between BMI category and sex for the percent of recess time spent in MVPA and VPA. Normal‐weight girls were the least active group, compared with overweight boys and girls who were equally active. Fifty‐one boys and 24 girls of normal weight achieved the 40% threshold; of these, 30 boys and 10 girls exceeded 50% of recess time in MVPA. Eighteen overweight boys and 22 overweight girls exceeded the 40% threshold, whereas 8 boys and 8 girls exceeded the 50% threshold. Discussion: Overweight boys were significantly less active than their normal‐weight male counterparts; this difference did not hold true for girls. Even though nearly double the number of normal‐weight children achieved the 40% of MVPA during recess compared with overweight children, physical activity promotion in school playgrounds needs to be targeted not only at overweight but at other health parameters, as 40 overweight children met the 40% MVPA target proposed for recess.     

Sex difference in the effect of puberty on the relationship between fat mass and bone mass in 926 healthy subjects, 6 to 18 years old

Objective: Understanding factors influencing bone mineral accrual is critical to optimize peak bone mass during childhood. The epidemic of pediatric obesity and reported higher incident of fracture risk in obese children led us to study the influence of fat mass on bone mineral content (BMC) in children. Research Methods and Procedures: Height; weight; pubertal stage; and BMC, non‐bone fat‐free mass (nbFFM), and fat mass (FM) by DXA were obtained in a multiethnic group of healthy children (444 girls/482 boys; 6 to 18 years old) recruited in the New York metropolitan area. Regression techniques were used to explore the relationship between BMC and FM, with age, height, nbFFM, pubertal stage, sex, and ethnicity as covariates. Results: Because there were significant sex interactions, separate regression analyses were performed for girls and boys. Although ln(nbFFM) was the greatest predictor of ln(BMC), ln(FM) was also a significant predictor in prepubertal boys and all girls but not in pubertal boys. This effect was independent of ethnicity. Discussion: FM was a determinant of BMC in all girls but in only prepubertal boys. Our study confirms nbFFM as the greatest predictor of BMC but is the first to find a sex difference in the effect of puberty on the relationship of FM to BMC. Our results suggest that, in two individuals of the same sex and weight, the one with greater fat mass will have lower BMC, especially pubertal boys. The implications of these findings for achievement of optimal peak bone mass in a pediatric population with an unprecedented incidence of overweight and “overfat” status remain to be seen.     

Urinary growth hormone excretion in 657 healthy children and adults: normal values, inter- and intraindividual variations.

Urinary growth hormone (u-GH) excretion was measured in 547 healthy children and 110 adults by ELISA with a detection limit of 1.1 ng/l u-GH after prior concentration of the urine samples (20- to 30-fold). u-GH excretion values were significantly dependent on the pubertal stage (p less than 0.0001) with maximum values in Tanner stage 3 for girls and 4 for boys. This corresponded to a peak in u-GH excretion between 11.5-14.5 years in girls and 12.5-16 years in boys. Additionally, u-GH excretion in adults was significantly higher than in prepubertal children (p less than 0.001). The day/night ratio of u-GH excretion (pg/h) was significantly higher in females than in males (p less than 0.01). In Tanner stages 1-4, u-GH excretion during the day was lower than that at night, whereas the opposite was true in late puberty and in adult women. The interindividual variation of u-GH excretion within the same Tanner stage was considerable and approximately double the intraindividual variation. The day-to-day variation could be further reduced by collection of three consecutive urine samples. The variations were larger if night samples instead of 24-hour samples were considered. The expression of u-GH excretion in nanograms per gram creatinine did not diminish the observed variation and blunted the pubertal increase in u-GH excretion. In conclusion, (1) u-GH excretion depends significantly on age, sex and pubertal maturation as does the day/night ratio of u-GH excretion. (2) The interindividual variation in u-GH excretion is considerable.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intelligence in Taiwan: Progressive Matrices means and sex differences in means and variances for 6- to 17-year-olds

Data for Raven's Progressive Matrices are reported for a sample of 6290 6- to 17-year-olds in Taiwan. The Taiwanese obtained a mean IQ of 109.5, in relation to a British mean of 100. There was no difference in mean scores of boys and girls at age 7 years. At age 10 years girls obtained significantly higher scores than boys, and at ages 13 and 16 years boys obtained significantly higher scores than girls. There was no sex difference in variance at age 7 years. At ages 10, 13 and 16 years variance was significantly greater in boys.     

24-hour, weekly, and annual patterns in traumatic and non-traumatic surgical pediatric emergencies

24 h patterns with high frequency components in the incidence of pediatric trauma were validated and quantified in one of our earlier studies. Herein, we further explored the temporal—high frequency, 24 h, weekly (7 d), hemi-weekly (3.5 d), and annual - patterns in traumatic (1990-1997; n=15,110 events) and non-traumatic pediatric surgical emergencies (PSE) (1992-2001; n=5,593 events) as well as automobile accidents (AA) (1990-1997; n=67,712) in the County of Vaud, Switzerland. The latter served as a reference system of human adult activity and risk. Two-way ANOVA, χ2, correlation, and cosinor analyses were used as statistical tools. A 24 h pattern, reproducible from year to year, was validated in traumatic and non-traumatic PSE and AA. The 24 h patterns were not correlated and differed from one another in terms of their acrophase (peak time) and amplitude. A gender-related difference was found only in the non-traumatic time series for weekly (7 d) and hemi-weekly (3.5 d) patterns. The latter were detected in boys but not girls. No statistically significant difference was found in the acrophase and amplitude between boys and girls in the temporal patterns of other periods. An annual pattern was validated in automobile accidents (acrophase: 4th of September ±37 d (SD)) and pediatric trauma (acrophase: 14th of June ±10 d), but not in non-traumatic PSE. These results suggest that environmental modulations differ between the incidence of traumatic and non-traumatic PSE. Presumably, the two phenomena involve different aspects of the temporal organization and/or different levels of susceptibility of a set of biological rhythms to environmental factors.     

Assessment of developmental age: cross-sectional analysis of secondary sexual characteristics

The developmental age of a growing person does not necessarily correspond to his or her chronological age. The two sexes differ considerably in their developmental tempo, and there are tempo differences also within the same sex. Early developers appear older, late developers appear younger than their chronological age might suggest. Based on a sample of 8675 German boys and 8689 girls of the same ethnicity, aged between 8 and 17 years sex differences of height, weight and secondary sexual characteristics are analyzed. Girls on average, develop faster than boys. Their peak of highest increments of height occurs at 10.2 years and is positioned early within the events of sexual maturity. The peak of highest increments of height in boys occurs at age 11.2 on average and is positioned relatively early within the sequences of secondary sexual characteristics. Maturing development starts with breast-stage 2 in girls at age 10.9 and penis-stage as well as scrotum-stage 2 in boys at age 11.1 on average. The development of pubic hair follows and menarche in girls at age 12.7, respectively spermarche in boys at age 13.8, marks the border to theoretical fertility. There are remarkable differences in the tempo of sexual development between the different types of body shape. In girls the pyknomorphic types are the early developers. Breast stage 2 for instance occurs at age 10.1 in the stocky and corpulent pyknomorphic girls and at age 13.0 in the tall and slender leptomorphic girls. This is different in boys. Here are much less differences between the types of body shape, but generally it is the leptomorphic type, at whom the stages of his secondary sexual characteristics are developed a little earlier.     

Could intra-tendinous hyperthermia during running explain chronic injury of the human Achilles tendon?

Chronic tendinopathy of the human Achilles tendon (AT) is common but its injury mechanism is not fully understood. It has been hypothesised that heat energy losses from the AT during running could explain the degeneration of AT material seen with injury. A mathematical model of AT temperature distribution was used to predict what temperatures the core of the AT could reach during running. This model required input values for mechanical properties of the AT (stiffness, hysteresis, cross-sectional area (CSA), strain during running) which were determined using a combination of ultrasound imaging, kinematic and kinetic data. AT length data were obtained during hopping and treadmill running (12 kmph) using ultrasound images of the medial gastrocnemius (50 Hz) and kinematic data (200 Hz). AT force data were calculated from inverse dynamics during hopping and combined with AT length data to compute AT stiffness and hysteresis. AT strain was computed from AT length data during treadmill running. AT CSA was measured on transverse ultrasound scans of the AT. Mean ± sd tendon properties were: stiffness = 176 ± 41 Nmm(-1), hysteresis =17 ± 12%, strain during running =3.5 ± 1.8% and CSA = 42 ± 8 mm(2). These values were input into the model of AT core temperature and this was predicted to reach at least 41°C during running. Such temperatures were deemed to be conservative estimates but still sufficient for tendon hyperthermia to be a potential cause of tendon injury.     

Extreme levels of underweight and stunting among pre-adolescent children of low socioeconomic class from Madhyamgram and Barasat, West Bengal, India

A cross-sectional study on 1206 children (788 boys, 618 girls) aged 1-12 years, belonging to low socioeconomic status, of Barasat and Madhyamgram, West Bengal, India, was undertaken to investigate age and sex variations in height and weight. It also evaluated the levels of underweight and stunting among them. Anthropometric measurements included weight and height. Weight-for-age (WA) and height-for-age (HA) <-2 z-scores were used to evaluate underweight (UW) and stunting (ST), respectively, following the National Center for Health Statistics (NCHS) Guidelines. Results showed that boys aged 4 and 11 years were significantly heavier than girls of corresponding ages. Boys aged 7 years were significantly taller than girls of the same age. Significant (p < 0.001) age differences existed in mean weight and height in boys (weight: F = 336.762; height: F = 565.160) as well as girls (weight: F = 275.320; height = 498.715). Results also revealed that the mean z-scores of WA (WAZ) and HA (HAZ) were less than (negative values) those of NCHS for both sexes at all ages. The overall (age combined) rate of UW was 60.4% and 51.3%; while that of ST was 51.7% and 48.4%, in boys and girls, respectively. Based on World Health Organization classification of severity of malnutrition, the prevalence of UW and ST were very high (> or = 30%) in both sexes. In conclusion, this study demonstrated that the prevalence of UW and ST were very high among the subjects. Since the nutritional status of the subjects is not satisfactory, there is need for immediate supplementary nutrition.     

Impact of ankle foot orthosis stiffness on Achilles tendon and gastrocnemius function during unimpaired gait

Ankle foot orthoses (AFOs) are designed to improve gait for individuals with neuromuscular conditions and have also been used to reduce energy costs of walking for unimpaired individuals. AFOs influence joint motion and metabolic cost, but how they impact muscle function remains unclear. This study investigated the impact of different stiffness AFOs on medial gastrocnemius muscle (MG) and Achilles tendon (AT) function during two walking speeds. We performed gait analyses for eight unimpaired individuals. Each individual walked at slow and very slow speeds with a 3D printed AFO with no resistance (free hinge condition) and four levels of ankle dorsiflexion stiffness: 0.25 Nm/°, 1 Nm/°, 2 Nm/°, and 3.7 Nm/°. Motion capture, ultrasound, and musculoskeletal modeling were used to quantify MG and AT lengths with each AFO condition. Increasing AFO stiffness increased peak AFO dorsiflexion moment with decreased peak knee extension and peak ankle dorsiflexion angles. Overall musculotendon length and peak AT length decreased, while peak MG length increased with increasing AFO stiffness. Peak MG activity, length, and velocity significantly decreased with slower walking speed. This study provides experimental evidence of the impact of AFO stiffness and walking speed on joint kinematics and musculotendon function. These methods can provide insight to improve AFO designs and optimize musculotendon function for rehabilitation, performance, or other goals.     

Serum IGF-I and IGFBP-3 levels of Turkish children during childhood and adolescence: establishment of reference ranges with emphasis on puberty

AIMS/METHODS: We established age- and sex-related reference ranges for serum insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) levels in 807 healthy Turkish children (428 boys, 379 girls), and constructed a model for calculation of standard deviation scores of IGF-I and IGFBP-3 according to age, sex and pubertal stage. RESULTS: Serum IGF-I and IGFBP-3 concentrations tended to be higher in girls compared to boys of the same ages, but the differences were statistically significant only in pubertal ages (9-14 years) for IGF-I and only in prepubertal ages for IGFBP-3 (6-8 years) (p < 0.05). Peak IGF-I concentrations were observed earlier in girls than boys (14 vs. 15 years, Tanner stage IV vs. V) starting to decline thereafter. IGFBP-3 levels peaked at age 13 and at Tanner stage IV in both sexes with a subsequent fall. Serum levels of IGF-I and IGFBP-3 increased steadily with age in the prepubertal stage followed by a rapid increase in IGF-I in the early pubertal stages. A relatively steeper increase in IGF-I but not in IGFBP-3 levels was observed at age 10-11 years in girls and at 12-13 years in boys which preceded the reported age of pubertal growth spurt. At late pubertal stages, both IGF-I and IGFBP-3 either did not change or decreased by increasing age. Interrelationships between growth factors and anthropometric measurements have been described, and the physiologic consequences of these have been discussed in detail. CONCLUSIONS: Differences in the pattern of IGF-I and IGFBP-3 in the present paper and those reported in other studies emphasize the importance of locally established reference ranges. Establishment of this reference data and a standard deviation score prediction model based on age, sex and puberty will enhance the diagnostic power and utility of IGF-I and IGFBP-3 in evaluating growth disorders in our population.