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Biomedical subjects

J Lefevre

Publications and source records attributed to J Lefevre.

At least 37 records · Page 2Linked to original sources
PubMed1997

Skeletal maturation, somatic growth and physical fitness in girls 6-16 years of age.

The importance of chronological age (CA) and skeletal age (SA) in explaining variation in somatic dimensions, and the independent contributions of CA, SA, stature (ST) and weight (WT) to variability in physical fitness were investigated in a sample of 6593 girls 6-16 years of age. Body dimensions included lengths, breadths, circumferences, skinfolds, and Heath-Carter somatotype, while fitness tests included measures of health- and performance-related fitness, and cardiovascular and lung functions. Age-specific correlations were calculated between SA and anthropometric dimensions, fitness tests and cardiovascular and lung functions, while age-specific stepwise multiple regressions were used to investigate the relative importance of SA, CA, ST and WT in explaining fitness and cardiovascular and lung functions. SA is most highly correlated with lengths and then with breadths, circumferences and skinfolds in this order. SA per se or in interaction with CA is the only significant predictor of somatic characteristics. Among fitness items, physical working capacity and static strength correlate highest with SA. Bent arm hang, leg lifts and sit-ups correlate negatively with SA but values are low, while all other components correlate at non-significant or low levels. Results of the multiple regression analysis indicate that, with few exceptions, CA, SA, ST and WT and their interactions explain less than 10% of the variance in most physical fitness items. However, for PWC, arm pull strength, and bent arm hang, the interaction terms explain between 12% and 67% of the variance.

Adolescent↗
PubMed1997

Development and tracking in fitness components: Leuven longtudinal study on lifestyle, fitness and health.

In the Leuven Growth Study of Belgian Boys the growth and physical performance of Belgian boys followed longitudinally between 12 and 19 years were studied. Subsequently, a subsample (n = 240) of Flemish-speaking males were reexamined at 30 and 35 years. A first question relates to the individual growth patterns in a variety of physical fitness characteristics. The three strength tests (static, functional, explosive) show curves that are qualitatively similar to those for height and weight. Their adolescent spurts occur after the height spurt. Flexibility and the two speed tests appear to reach maximum velocities prior to the height and weight spurts. Longitudinal principal component analysis was applied to the study of growth patterns of several somatic and motor characteristics. The results for height show three components sufficient to provide an adequate representation of the original information. The first component characterizes the general position of an individual growth curve. Components 2 and 3 reflect fluctuation in percentile level during the age period studied and can be conceived as indices of stability and are related to age at peak height velocity (APHV) and peak height velocity (PHV), respectively. Relationships between somatic characteristics, physical performance, and APHV have been studied in a sample of 173 Flemish boys, measured yearly between +/- 13 and +/- 18 years and again as adults at 30 years of age. The sample was divided into three contrasting maturity categories based on the APHV. There are consistent differences among boys of contrasting maturity status during adolescence in body weight, skeletal lengths and breadths, circumferences, and skinfolds on the trunk. There are no differences in skinfolds on the extremities. None of the differences in somatic dimensions and ratios among the three contrasting maturity groups are significant at 30 years of age except those for subscapular skinfold and the trunk/extremity skinfold ratio. During adolescence, speed of limb movement, explosive strength and static strength are negatively related to APHV; thus, early maturers performed better than late maturers. However, between late adolescence and adulthood (30 years), the late maturers not only caught up to the early maturers, but there were significant differences for explosive strength and functional strength in favor of late maturers. Finally, age-specific tracking, using inter-age correlations, of adult health- and performance-related fitness scores were investigated. In addition, the independent contribution of adolescent physical characteristics to the explanation of adult fitness scores was also studied. Tracking between age 13 and age 30 years was moderately high (46% of variance explained) for flexibility, low to moderate (between 19% and 27% of variance explained) for the other fitness parameters and low for pulse recovery and static strength (7% to 11% of variance explained). Between age 18 and age 30 years the tracking was high for flexibility, moderately high for explosive and static strength, and moderate for the other fitness parameters except for pulse recovery. The amount of variance of adult fitness levels explained increased significantly when other characteristics observed during adolescence entered the regressions or discriminant functions.

Adolescent↗
PubMed1997

Prediction of adult stature and noninvasive assessment of biological maturation.

The Tanner-Whitehouse method to predict adult stature uses current stature, current skeletal age (SA), and chronological age (CA), and, if available, change (gain) in stature and SA over the previous year. Since assessment of SA requires invasive techniques, a method is proposed to predict adult stature noninvasively and to use percentage of adult stature as a maturity indicator. Age-specific multiple regression equations were calculated in a sample of 102 Flemish boys 13 through 16 yr who were followed during adolescence and remeasured at 30 yr of age. The proposed procedure, the Beunen-Malina method for prediction of adult stature, includes four somatic dimensions (current stature, sitting height, subscapular skinfold, triceps skinfold) and CA. In this age range multiple correlations (Rs between 0.70 and 0.87) and SEEs (between 3.0 and 4.2 cm) compare favorably with the original Tanner-Whitehouse method. Furthermore, when maturity groups based on percentage of adult stature calculated from the Beunen-Malina predictions are contrasted for somatic dimensions and performance characteristics, differences are similar to those observed when maturity grouping is based on skeletal maturity.

Adolescent↗
PubMed1996

Physique as a risk factor for ulnar variance in elite female gymnasts.

The aims of this study were: 1) to determine ulnar variance variability of elite, female gymnasts; 2) to evaluate the relationship between ulnar variance and physique, maturity status, and training characteristics of these gymnasts. All 156 skeletally immature female gymnasts were participants at the World Championships Artistic Gymnastics, Rotterdam, The Netherlands, in 1987. Chronological ages varied between 13.1 and 20.6 yr (mean = 15.9 +/- 1.3 yr). A large set of anthropometric dimensions was taken and somatotype was determined by the Heath-Carter technique. Skeletal age was assessed by the Tanner-Whitehouse II method. Menarcheal status and training data were collected by questionnaire. Ulnar variance was determined according to Hafner et al. Gymnasts differ significantly from reference girls with respect to physique and maturational status: gymnasts were smaller and delayed in skeletal maturity with about 1.5 yr. For those who had attained menarche, mean age at menarche was 15.1 +/- 1.3 yr. Ulnar variance shows a normal distribution in the gymnasts, ranging from -10.5 mm to +5.9 mm, which is somewhat more positive, i.e., an ulnar overgrowth, than reference wrists. The relationship between ulnar variance and somatic and maturational features suggests that female gymnasts who are more mature and have a physique characterized as relatively tall with a high lean body mass are at greater risk for developing a positive ulnar variance. No relationship between ulnar variance and training characteristics was evident. It is concluded that the observed positive ulnar variance in this sample of elite female gymnasts is less pronounced than originally stated in most "case reports."

Adolescent↗
PubMed1995

Inhibition of diacylglycerol kinase by the antitumor agent calphostin C. Evidence for similarity between the active site of diacylglycerol kinase and the regulatory site of protein kinase C.

Calphostin C is an anti-tumor agent that binds to the regulatory domain of protein kinase C and inhibits the binding of phorbol dibutyrate. Recent studies suggest that there may be structural similarities between protein kinase C (PKC) and diacylglycerol kinase (DGK). Both enzymes bind diacylglycerol and phosphatidylserine, and sequencing of the 80 kDa diacylglycerol kinase shows that it contains zinc finger-like sequences, similar to those occurring in PKC. Similarities in some enzymatic properties of PKC and DGK led us to examine whether regulatory-site inhibitors of PKC also might inhibit DGK. For these studies, the membrane-bound DGK was partially purified from porcine testis membranes. Calphostin C inhibited DGK with an IC50 in the micromolar range. The inhibition of DGK by calphostin C was competitive with respect to diacylglycerol and was not affected by the presence or absence of phosphatidylserine. Other inhibitors of protein kinase C were without effect, with the exception of Adriamycin, which inhibited at millimolar concentrations. Staurosporine, which binds to the catalytic domain of protein kinase C, did not inhibit DGK. The results suggest that there are functional similarities between the substrate binding site of DGK and the regulatory site of protein kinase C.

Alkaloids↗
PubMed1995

Fatness and physical fitness of girls 7 to 17 years.

A two-fold approach was used to investigate the association between fatness and fitness of girls 7 to 17 years of age: first, age-specific correlations between fatness and measures of health-related and motor fitness, and second, comparisons of fitness levels of girls classified as fat and lean. A representative sample of 6700 between 7 to 17 years was surveyed. Adiposity (fatness) was estimated as the sum of five skinfolds (biceps, triceps, subscapular, suprailiac, medial calf). Physical fitness included health-related items (step test, PWC170, the sit and reach, sit-ups and leg lifts, flexed arm hang) and motor performance items (standing long jump, vertical jump, arm pull strength, flamingo stand, shuttle run, plate tapping). Age-specific partial correlations between fatness and each fitness item, controlling for stature and weight, were calculated. In addition, in each age group the fattest 5% (presumably the obese) and the leanest 5% were compared on each fitness test. After controlling for stature and weight, subcutaneous fatness accounts for variable percentages of the variance in each fitness item. Estimates for health-related fitness items are: cardiorespiratory endurance-step test (3% to 5%) and PWC170 (0% to 16%), flexibility-sit and reach (3% to 8%), functional strength-flexed arm hand (6% to 17%) and abdominal strength-sit-ups/leg lifts (1% to 8%). Corresponding estimates for motor fitness items are more variable: speed of limb movement-plate tapping (0% to 3%), balance-flamingo stand (0% to 5%), speed and agility-shuttle run (2% to 12%), static strength-arm pull (4% to 12%), explosive strength-standing long jump/vertical jump (11% to 18%). At the extremes, the fattest girls have generally poorer levels of health-related and motor fitness.

Adolescent↗
PubMed1994

The role of anthropometric characteristics in modern pentathlon performance in female athletes.

In order to determine the role of body build characteristics in modern pentathletes, 65 female participants at the IXth World Modern Pentathlon Championships, 1989 (Wiener Neustadt, Austria) were investigated. Of these, 54 participate in the competition; the other 11 were reserves. Their mean (+/- S.D.) age was 22.34 +/- 3.97 years (range 16.08-32.58 years). Anthropometric characteristics (body mass, lengths, breadths, girths and skinfolds), somatotype and body composition estimates were determined. Compared with other female athletes (e.g. swimmers, runners, fencers), the elite modern pentathletes were rather tall (x = 168.1 cm) and, as indicated by the body mass index (x = 21.6), they had a high mass relative to their stature. Based on skinfolds, body fat was estimated as 16%, and anthropometrically determined somatotype was on average 2.5-3.9-2.8. The relationship between the athletes' anthropometric characteristics and modern pentathlon performance was investigated by means of Pearson zero-order correlations between the physical traits and the competitive performance scores. Significant correlations were found mainly for the 'fat' variables, such as skinfolds, percent fat and the endomorphy component, r varying from -0.34 to -0.58, which indicated an inverse relationship between the amount of fatness and modern pentathlon performance. To investigate this relationship further, Pearson zero-order correlations were calculated between the respective factors scores, derived from a rotated factor pattern (Varimax) carried out on selected somatic variables, and the performance scores. The results demonstrated that, in relation to anthropometric characteristics, modern pentathlon performance in females is mainly associated with the 'fat development' factor, and to a lesser degree with the 'bone-muscle development' factor. Variables representing linearity of physique seem to be unrelated to modern pentathlon performance. Stepwise regression analysis revealed that 42.4% of the variance in modern pentathlon performance can be explained by the following anthropometric variables: sum of 10 skinfolds, biacromial breadth and humerus diameter. To obtain a high level of modern pentathlon performance, it would seem that a female athlete must above all have a low level of body fatness and, to a lesser degree, a relatively high level of lean body mass.

Adolescent↗
PubMed1994

Size, fatness and relative fat distribution of males of contrasting maturity status during adolescence and as adults.

The somatic characteristics of boys of contrasting biological maturity status during adolescence are compared from 13-18 years and at 30 years of age. Within the mixed longitudinal Leuven Growth Study of Belgian Boys, 173 boys were followed annually from 13-18 years and were subsequently measured at 30 years of age. Age at peak height velocity (PHV) was estimated for 149 boys and the sample was then divided into three contrasting maturity categories based on the age at PHV: early (PHV < 13.37 years), average (PHV between 13.85 and 14.80 years) and late (PHV > 15.27 years) maturers. Using ANOVA for repeated measures and one-way ANOVA, differences in 18 somatic dimensions and five ratios of body proportions and subcutaneous fat distribution among the three maturity groups were tested from 13-18 years and at 30 years of age. There are consistent differences among boys of contrasting breadths, circumferences,and skinfolds on the trunk. There are no differences in skinfolds on the extremities. None of the differences in somatic dimensions and ratios among the three contrasting maturity groups are significant at 30 years of age except those for subscapular skinfold and the trunk/extremity skinfold ratio. Thus, during adolescence and in adulthood, late maturing boys have a distribution of subcutaneous fat that is associated with lower risk for several adult degenerative diseases.

Adipose Tissue↗
PubMed1993

Fractures, physical activity, and growth velocity in adolescent Belgian boys.

The relationship of fractures to physical activity and growth velocity in stature and metacarpal II bone dimensions was investigated in adolescent Belgian boys. Peak fracture incidence occurred between 12 and 14 yr of age and preceded the age at peak height velocity. The peak fracture rate occurred during mid adolescence (+/- 2 SD of the age at peak height velocity) and was twice as high as the rates before and after this period. The majority of fractures occurred during active participation in sports and general physical activities. The age at peak growth velocity for metacarpal cortical thickness, an indirect measure of bone mineral content, was about 6 months later than the ages at peak height velocity and peak growth velocity for metacarpal length. Peak fracture incidence occurred during a period when the amount of time spent in sports physical activity was low compared with later years. A lag in cortical bone thickness and mineralization, relative to linear skeletal growth, and unknown factors associated with active participation in sports, rather than an increase in the amount of physical activity, appear to be the predominant factors associated with the increased fracture incidence in Belgian boys during the growth spurt.

Adolescent↗
PubMed1992

Age-specific correlation analysis of longitudinal physical fitness levels in men.

This study investigated the age-specific tracking of adult health- and performance-related fitness scores. In addition, the independent contribution of adolescent physical characteristics to the explanation of adult fitness scores was also studied. The sample consisted of 173 adults observed at age 30 years. These subjects had been followed at annual intervals from age 13 to age 18 years and were remeasured at age 30 years. At each age nine fitness tests were administered together with the recording of anthropometric dimensions, biological maturation, sports participation and family characteristics. Tracking was measured by the inter-age correlations at each age between 13 and 18 years and the performance scores at 30 years. The independent contribution of characteristics observed during adolescence to the explanation of adult fitness was investigated through stepwise multiple regression analysis and discriminant analysis with the adult fitness scores as the dependent variables and the fitness, maturation, anthropometric characteristics, sports participation and family background as the independent variables. Tracking between age 13 and age 30 years was moderately high (46% of variance explained) for flexibility, low to moderate (between 19% and 27% of variance explained) for the other fitness parameters and low for pulse recovery and static strength (7% to 11% of variance explained). Between age 18 and age 30 years the tracking was high for flexibility, moderately high for explosive and static strength, and moderate for the other fitness parameters except for pulse recovery. The amount of variance of adult fitness levels explained increased significantly when other characteristics observed during adolescence entered the regressions or discriminant functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Growth and menarcheal status of elite female gymnasts.

The growth and maturity status of 201 elite female gymnasts was considered. The subjects were participants at the 24 World Championship Artistic Gymnastics in 1987. In addition to age at menarche, weight, stature, biacromial, and bicristal breadths, the sitting height/stature ratio, and the Health-Carter anthropometric somatotype of gymnasts 13-20 yr of age were compared with reference data for a nationally representative sample of Flemish girls. Median age at menarche (probit analysis) in gymnasts is 15.6 +/- 2.1 yr compared with 13.2 +/- 1.2 yr in Flemish girls. Anthropometric dimensions increase with age until about 16 yr and then tend to plateau. In contrast to body size, there is little variation in somatotype with age. Compared with adolescent girls, elite gymnasts are considerably shorter and lighter with narrower shoulders and hips, but the differences are more apparent after 17 yr. Elite gymnasts do not differ from nonathletes in relative leg length, but they have proportionally broader shoulders relative to hips. Differences in somatotype occur primarily in endomorphy (especially lower in gymnasts) and to a lesser extent in mesomorphy (higher in gymnasts).

Adolescent↗
PubMed1992

Physical activity and growth, maturation and performance: a longitudinal study.

The effects of increased physical activity upon physical growth, maturation and performance were investigated in samples of 32 active and 32 nonactive Belgian boys followed longitudinally from 13 to 18 yr of age. Active boys participated in sports activities for more than 5 h.wk-1.yr-1 during each of the first 3 yr of the study, in addition to compulsory physical education. Nonactive boys participated in less than 1.5 h.wk-1.yr-1 during the first 3 yr of the study, but did participate in required school physical education. Anthropometric dimensions included lengths, breadths, circumferences, and skinfolds. A physical fitness test battery was administered at each observation including nine health- and performance-related tests. Skeletal maturation was assessed; sociocultural determinants and sports participation were obtained through written questionnaires verified by a control interview. No significant effects of increased physical activity were observed on growth in somatic dimensions, including skinfolds, age at peak height velocity, skeletal maturation, and most of the physical fitness components. More active boys obtained better results from 14 yr onward only for pulse recuperation and for bent arm hang. These results can be generalized to the average population but do not necessarily apply for highly trained and selected elite athletes.

Adolescent↗
PubMed1991

Anthropometric characteristics of outstanding male and female gymnasts.

Anthropometric data of outstanding gymnasts were gathered on the occasion of the 24th World Championship Artistic Gymnastics, held at Rotterdam, The Netherlands, in October 1987. In total 165 males and 201 females were investigated, constituting 84% of the total number of participants. The data of these gymnasts were descriptively compared with both reference data and data reported in previous studies on gymnasts competing at international events. Also, based on the data obtained, 'gymnastic-specific' anthropometric reference values (i.e. profile charts), were established for both male and female gymnasts. Finally, the maturational characteristics (skeletal age and menarche) of the 'Rotterdam' female gymnasts were described.

Adolescent↗
PubMed1984

Formation of calcium-parvalbumin complex during contraction. A source of "unexplained heat"?

Computer simulation of the kinetics of the distribution of Ca between troponin, parvalbumin and the sarcoplasmic reticulum, during contraction and relaxation shows that parvalbumins can contribute significantly to the rate of relaxation and to the post contractile translocation of calcium. The binding of Ca to parvalbumin is an exothermic process which may account for about 20% of the 'unexplained heat' during contraction.

Animals↗