Biomedical subjects

R M Malina

Publications and source records attributed to R M Malina.

At least 19 recordsLinked to original sources

PubMed2006

Adiposity and cardiac dimensions among 9- to 18-year-old youth: the Québec Family Study.

The relationship between adiposity and cardiac dimensions were considered in healthy 9- to 18-year-old boys (n=198) and girls (n=154). Indicators of adiposity included the body mass index (BMI), sum of skinfolds (SSF) and trunk-to-extremity ratio (TER). The following left ventricular (LV) dimensions were measured by echocardiography: internal diameter (LVIDd); posterior wall thickness (PWT) and intraventricular septal wall thickness. LV mass (LVM) was estimated. In boys, 11 of 45 correlations were significant. The magnitude of the correlations increased across age groups and most of the correlations were significant in the oldest age group. In girls, 18 of 45 correlations were significant, but there were inconsistent patterns in the magnitude of the correlations across age groups. Correlations between BMI and LVIDd and LVM were highest in youth 13-15 years, whereas other correlations involving the BMI were rather constant across age groups. Correlations involving SSF were significant only in 9-12 and 13-15 year olds. There were no significant correlations involving TER in female subjects. In the total sample of boys, only correlations between the BMI and LV parameters were significant (r=0.14-0.38), except for the relationship between SSF and PWT (r=0.21). The TER was weakly associated with LV parameters. In the total sample of girls, correlations for LV parameters were significant for both the BMI (r=0.20-0.43) and SSF (r=0.18-0.28; except for LVIDd). TER was not significantly related to LV parameters except LVIDd (r=0.16). The findings indicate that the BMI is an important determinant of LV structure.

Adiposity↗

PubMed2006

A multidisciplinary selection model for youth soccer: the Ghent Youth Soccer Project.

OBJECTIVES: To determine the relationships between physical and performance characteristics and level of skill in youth soccer players aged 12-16 years. METHODS: Anthropometry, maturity status, functional and sport-specific parameters were assessed in elite, sub-elite, and non-elite youth players in four age groups: U13 (n = 117), U14 (n = 136), U15 (n = 138) and U16 (n = 99). RESULTS: Multivariate analyses of covariance by age group with maturity status as the covariate showed that elite players scored better than the non-elite players on strength, flexibility, speed, aerobic endurance, anaerobic capacity and several technical skills (p<0.05). Stepwise discriminant analyses showed that running speed and technical skills were the most important characteristics in U13 and U14 players, while cardiorespiratory endurance was more important in U15 and U16 players. The results suggest that discriminating characteristics change with competitive age levels. CONCLUSIONS: Characteristics that discriminate youth soccer players vary by age group. Talent identification models should thus be dynamic and provide opportunities for changing parameters in a long-term developmental context.

Adolescent↗

PubMed2006

Changes in the BMI of Polish conscripts between 1965 and 2001: secular and socio-occupational variation.

OBJECTIVE: To describe changes in the body mass index (BMI) of nationally representative samples of young adult Polish males between 1965 and 2001, and to investigate variation in the incidence of underweight, overweight and obesity between 1965 and 2001 in the young adult males in the context of the socio-political transformation that occurred in Poland since 1989. SUBJECTS: Four 10% nationwide random samples of 29-year-old Polish conscripts examined in 1965, 1986, 1995 and 2001. The conscripts were divided into four socio-occupational groups based on paternal education, occupation and degree of urbanization. MEASUREMENTS: Height, weight and BMI (weight (kg)/height (m2)). RESULTS: The proportion of overweight and underweight young adult males in the population increased between 1965 and 2001. The fraction of underweight decreased only among sons of farmers and entrepreneurs between 1986 and 1995 and then increased in all socio-occupational groups between 1995 and 2001. On the other hand, the proportion of overweight young adults gradually increased in all groups between 1965 and 2001. CONCLUSION: Socio-occupational position of the family is an important factor influencing underweight and overweight in young adult males. This factor apparently operates through a differential distribution of income, which influences components of lifestyle most likely associated with level of habitual physical activity and/or diet.

Adult↗

PubMed2006

Opportunity for natural selection and gene flow in an isolated Zapotec-speaking community in southern Mexico in the throes of a secular increase in size.

Our object in this paper is to analyze the opportunity for natural selection and gene flow in an isolated Zapotec-speaking community in the valley of Oaxaca, southern Mexico, that is undergoing a secular increase in body size. Surveys were conducted in the community in 1968, 1978, and 2000, including anthropometric and census data. No secular change was found in the growth status of schoolchildren and adult height between 1968 and 1978; subsequently, major secular gains in height occurred among children and adolescents between 1978 and 2000. The 1978 household data were used to compute gene flow (3.3%) and opportunity for selection intensity (I = 1.312). Migration and other demographic information was obtained from household census data for 1978 and 2000, and mortality information was extracted from community records and archives. These data were used to compute gene flow and opportunity for natural selection. Gene flow increased from 3.3% to 4.7% and intensity of natural selection decreased from 1.312 to 0.272 from 1978 to 2000. Variance in fertility increased slightly over time (12.25 to 13.69). Opportunity for selection was dominant during the prereproductive period in 1978, but approached 0 for the mortality component in 2000, resulting in a marked decrease in the mortality component (Im) of selection (0.626 and 0.019, respectively) and total opportunity for selection (I = 1.312 and 0.272, respectively). Secular increase in height and markedly decreased opportunity for natural selection (1) were associated with better health and nutritional conditions. Genotype-environment interaction and environmental influences are apparently the predominant causes of the secular trend. If natural selection plays a role in causing the secular trend, it is a small one.

Adolescent↗

PubMed2005

Anthropometry and somatotype of competitive female figure skaters 11-22 years. Variation by competitive level and discipline.

AIM: Variation in anthropometric characteristics and somatotype of female figure skaters by level of competition and discipline was examined. METHODS EXPERIMENTAL DESIGN: ANCOVA with age as the covariate was used to compare the anthropometry of skaters by level (test stream, pre-elite, elite) and discipline (free, dance, pair), while MANCOVA was used to compare somatotype. SETTING: purposive sampling reflecting the skating population by level and discipline was used to recruit skaters in 4 American, and 7 Canadian figure skating clubs. PARTICIPANTS: a total of 161 competitive female figure skaters 11-22 years of age (15.7+/-2.4 years) comprised the sample. MEASURES: a battery of 15 anthropometric dimensions was taken on each skater. Several dimensions, ratios and Heath-Carter somatotypes were derived. RESULTS: Test skaters are heavier and generally larger than pre-elite skaters. Test stream skaters also have larger limb circumferences, estimated calf and arm musculature, and a thicker sum of skinfolds, and are more endomorphic than pre-elite skaters. Elite skaters are more mesomorphic than pre-elite skaters. The sitting height/stature (SH/ST) ratio is significantly lower in pre-elite skaters, while elite and test stream skaters do not differ in this indicator of proportions. Free skaters are taller and heavier; have a higher body mass index (BMI), limb circumferences and sum of skinfolds; and proportionally shorter legs than dancers and pair skaters. Free skaters, dancers and pair skaters, however, do not differ in somatotype. CONCLUSIONS: The results suggest that figure skating favors lightness, leanness, higher mesomorphy and lower endomorphy at more elite levels. Shortness, leanness and linearity of physique appear to be selective factors associated with specialization in dance and pair skating.

Adolescent↗

PubMed2002

Effects of crank length on maximal cycling power and optimal pedaling rate of boys aged 8-11 years.

It is generally reported that cycle crank length affects maximal cycling power of adults and that optimal crank length is related to leg length. This suggests that the use of standard length cycle cranks may provide nonoptimal test conditions for children. The purpose of this study was to determine the effects of cycle-crank length on maximal cycling power and optimal pedaling rate of 17 boys aged 8-11 years. The boys performed maximal cycle ergometry with standard (170 mm) cycle cranks and with a crank length that was 20% of estimated leg length (LL20). Power produced when using the 170 mm cranks [mean (SEM)] [364 (18) W] did not differ from that produced with the LL20 cranks [366 (19)]. Optimal pedaling rate was significantly greater for the LL20 cranks [129 (4) rpm] than for the 170 mm cranks [114 (4) rpm]. These data suggest that standard 170 mm cranks do not compromise maximal power measurements in boys aged 8-11 years so that the test apparatus does not bias physiological or developmental inferences made from tests of maximal cycling power.

Age Factors↗

PubMed2002

Growth status and estimated growth rate of young distance runners.

A mixed-longitudinal design was used to evaluate the growth status (size attained) and estimated growth rate of competitive young distance runners. Twenty-seven male and 27 female distance runners were enrolled in the study based on race performance times. Ages ranged from 8.0 to 15.1 years at initial visit. Twenty males and 16 females were followed at approximate annual intervals for 4 or 5 years. Stature (cm) and body mass (kg) were measured on each occasion and annual growth velocities were estimated. Stature and body mass were plotted relative to age- and sex-specific U.S. reference data, while estimated velocities of stature (cm/yr) and body mass (kg/yr) were plotted relative to age- and sex-specific percentiles from the Zurich Longitudinal Study. Differences in growth pattern between the runners and the reference values were compared statistically with a growth curve estimation regression model. Mean statures of male and female distance runners approximate the reference medians, while mean body masses are slightly below reference medians. Mean stature and body mass also maintain a constant position relative to the reference values in both sexes over time. Estimated velocities for stature and body mass are, on average, similar to age- and sex-specific medians for Swiss youth. Slope values indicate no significant difference in growth patterns between young distance runners and reference values. The findings are consistent with other data indicating that intensive endurance training during childhood and adolescence does not influence size attained and rate of growth in stature and body mass.

Adolescent↗

PubMed2001

Blood lipids of young distance runners: distribution and inter-relationships among training volume, peak oxygen consumption, and body fatness.

This study describes the distribution of blood lipid concentrations and examines relationships among training volume (TV, kilometers per week), peak oxygen consumption (VO2peak), body fatness, and blood lipid concentrations in 48 male and 22 female distance runners, aged 10-19 years. Comparisons were made to a current reference sample and clinical cut-off points. Relationships were assessed by partial correlations allowing for age and sexual maturity. Compared to reference median values, mean concentrations of total cholesterol (P=0.07) and low density lipoprotein-cholesterol (P<0.005) were higher, while high density lipoprotein-cholesterol (HDL-C; P=0.24) was comparable in male distance runners. Blood lipid concentrations in female distance runners were comparable to reference median values. Although some subjects had dyslipidemic values, most possessed clinically normal concentrations of blood lipids. The TV was weakly correlated with blood lipid concentrations, but may have been indirectly related with HDL-C through its relationship with VO2peak in males runners (r=0.32). In female runners, correlations between sum of skinfolds (SSF), the trunk-to-extremity ratio (TER) and blood lipid concentrations were low (r=0.16 to -0.27), with one exception (TER and HDL-C, r=-0.60). The most consistent relationships existed among TV, VO2peak, SSF, and HDL-C with partial correlations ranging from low (r=0.10 TV) to moderate (r=0.37 SSF, r=0.41 VO2peak). The correlation between VO2peak and HDL-C remained significant after allowing for age and SSF, while the partial correlation between SSF and HDL-C, allowing for age and VO2peak, was reduced and not significant (r=-0.19, P=0.20). In female runners, the correlation between VO2peak and HDL-C was r=0.32, whereas the partial correlation between SSF and HDLC, allowing for age and VO2peak, was r=0.00. Blood lipid concentrations of young male distance runners were not, on average, different to the general population of the youth of the United States. The young distance runners showed considerable heterogeneity in blood lipid phenotypes, including dyslipidemic values. The results highlight the complex relationships among TV, VO2peak, body fat and HDL-C, and indicate the unique contribution of VO2peak as an important predictor of HDL-C in young distance runners.

Adolescent↗

PubMed2001

Stability of indicators of the metabolic syndrome from childhood and adolescence to young adulthood: the Québec Family Study.

The stability of indicators of the metabolic syndrome from childhood and adolescence to young adulthood was examined. The sample included 76 males and 71 females measured between the ages of 8 and 18 years and again as young adults (12 year follow-up). Indicators included the sum of three trunk skinfolds (SF3), mean blood pressure (MBP), and fasting blood glucose (GLY), high-density lipoprotein cholesterol (HDL-C), ratio of total cholesterol to HDL-C (CHOL/HDL), and triglycerides (TG). The indicators were subjected to principal components analysis to obtain a composite risk factor index (RFI). Partial interage correlations, controlling for initial age and length of follow-up, were 0.70 and 0.50 for SF3, 0.40 and 0.54 for MBP, 0.58 and 0.56 for HDL-C, 0.51 and 0.57 for CHOL/HDL, 0.37 and 0.20 (NS) for TG, 0.30 and 0.14 (NS) for GLY, and 0.51 and 0.46 for the RFI, in males and females, respectively. The results indicate that indicators of the metabolic syndrome are moderately stable from childhood and adolescence into young adulthood.

Adolescent↗

PubMed2001

Stability of adiposity phenotypes from childhood and adolescence into young adulthood with contribution of parental measures.

OBJECTIVE: The stability of several indicators of body composition and adipose tissue distribution over 12 years was quantified. RESEARCH METHODS AND PROCEDURES: The participants were 77 boys and 76 girls who were evaluated along with their parents at baseline as children and adolescents (8 to 18 years of age) and remeasured as young adults 12 years later. Indicators of body composition included the body mass index, fat mass, fat free mass, percentage of body fat, sum of six skinfolds (SF6), and the first principal component of six age-adjusted skinfold residuals. Relative adipose tissue distribution was represented by the second principal component of skinfold residuals and a trunk-to-extremity skinfold ratio, adjusted for SF6. RESULTS: Partial interage correlations, controlling for initial age and length of follow-up, were 0.65 and 0.59 for the body mass index, 0.59 and 0.64 for fat mass, 0.65 and 0.57 for fat free mass, 0.50 and 0.57 for percentage of body fat, 0.66 and 0.44 for SF6, 0.64 and 0.42 for the first principal component of six age-adjusted skinfold residuals, 0.19 and 0.31 for the second principal component of skinfold residuals, and 0.41 and 0.47 for trunk-to-extremity skinfold ratio, adjusted for SF6, in men and women, respectively. Multiple regression analyses indicated that the significant partial R(2) values of parental measurements on the prediction of their offspring in young adulthood ranged from 2% to 9%. DISCUSSION: The results indicate moderately high stability of indicators of body composition and somewhat lower stability of measures of adipose tissue distribution. Overall, parental measures offer less predictive value than do measures of childhood and adolescent body composition and adipose tissue distribution.

Adipose Tissue↗

PubMed2001

Relationship between stunting in infancy and growth and fat distribution during adolescence in Senegalese girls.

OBJECTIVE: To study the long-term impact of stunting during infancy on maturation, growth and fat distribution in adolescence. DESIGN: A cohort of 406 Senegalese adolescent girls of rural origin underwent clinical and growth assessments every year from 1995 to 1999. SUBJECTS: Mean coverage rate was 82% at each round. Adolescent girls were 11.4+/-0.5 y of age in 1995 and 15.5+/-0.5 y of age in 1999. Their growth status during infancy was known. About 20% of the girls had a height-age (H-age) below -2 Z-scores (chronic malnutrition or stunting) when they were 6-18 months of age. As adolescents, the girls were divided into two groups on the basis of H-age: those stunted and those non-stunted during infancy. MEASUREMENTS: Sexual maturation was assessed by stage of breast development and menarche. Height, body mass, sitting height, bi-iliac and bi-acromial diameters, and six skinfolds were measured. RESULTS: Differences in sexual maturation between previously stunted and non-stunted girls were not significant. Girls stunted at infancy caught up in body weight and subcutaneous fat mass during puberty, but they did not catch up on stature, sitting height or skeletal breadths (bi-acromial and bi-iliac diameters) until the final observation in 1999. Stunted girls did not have less subcutaneous fat (sum of six skinfolds) or a lower BMI. Regional variation in subcutaneous fat distribution (Z-score profile) indicated greater accretion at the biceps and subscapular sites in stunted compared to the non-stunted girls. Regional fat distribution was also assessed by principal component analysis (PCA) performed on the residuals of the six skinfolds measured during the final round (1999). PCA identified three components. Stunted and non-stunted girls were similar for the first (trunk-extremity contrast) and second (anterior-posterior contrast) components. However, there was a difference for the third component: stunted girls tended to accumulate more subcutaneous fat on the upper part of the body (trunk or arms) than non-stunted girls. CONCLUSION: Stunted Senegalese girls have a potential for catching up in growth during puberty. The greater accumulation of subcutaneous fat on the upper body in stunted girls may be a consequence of complex hormonal adjustments at the onset of puberty.

Adipose Tissue↗

PubMed2001

Blood lipids in young distance runners.

PURPOSE: The purpose of this study was to examine the age-and sex-associated variation in blood lipids among young athletes. METHODS: A mixed-longitudinal design was used to examine the development of blood lipids in competitive young distance runners followed from 1982 to 1985. Serial data included 99 annual measurements for 27 male subjects and 84 annual measurements for 27 female subjects aged 9-18 yr. Total cholesterol (TC), high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C), and triglycerides (TG) were determined by standard procedures. RESULTS: In general, cross-sectional age group means showed that TC and LDL-C remained stable and HDL-C declined with age, especially in male subjects. TG increased with age. Age-related trends were statistically significant for HDL-C and TG in boys only (P < 0.05). TC and LDL-C were slightly greater in boys at all ages except 11, 15, and 17 yr (P > 0.05). HDL-C was similar between the sexes until 13 yr when values became greater in girls (3.2-13.8 mg.dL(-1)) (P < 0.05 in 17+ yr). No clear pattern of sex differences emerged for TG. Compared with the general population, blood lipids of young distance runners showed the following trends: 1) TC was above reference medians, 2) LDL-C tended to approximate or to be slightly above reference medians, 3) TG fluctuated about the reference medians, and 4) HDL-C was higher in distance runners compared to the reference medians before age 14 yr, but in the older age groups, especially male subjects, HDL-C either approximated or fell slightly below the reference medians. There was considerable variability in blood lipid levels among the runners. In 21 male and 18 female subjects with serial data for 3-5 yr, HDL-C declined 22.4 and 18.3 mg.dL(-1) (P < 0.05), whereas TG increased 18.0 and 14.0 mg.dL(-1)(P < 0.05 in female subjects only) in male and female subjects, respectively. Tracking coefficients over intervals of 3-5 yr were moderate to high (0.48-0.90), except for TG in male subjects (0.08). CONCLUSIONS: The results indicate that the development of blood lipids in young distance runners is similar to youth in the general population. In contrast to observations in adult endurance athletes, young distance runners did not possess a superior blood lipid profile except for HDL-C in the younger age groups.

Adolescent↗

PubMed2001

Seven-year stability of physical activity and musculoskeletal fitness in the Canadian population.

BACKGROUND: Knowledge of population patterns of physical activity levels and musculoskeletal fitness are important in the selection of appropriate target groups for public health interventions. PURPOSE: To examine the stability of physical activity levels and musculoskeletal fitness in the Canadian population. METHODS: The sample included 951 male and 958 female subjects, aged 11-69 yr, for whom the appropriate measurements were available in the 1981 Canada Fitness Survey and its 7-yr follow-up, the Campbell's Survey. Participants were divided into 2-yr age groups in childhood (11-18 yr) and 10-yr age groups in adulthood (19-69 yr). Measures of physical activity were estimated activity energy expenditure (AEE) and time spent on activity, whereas indicators of musculoskeletal fitness consisted of sit-ups, push-ups, grip strength, and sit-and-reach (trunk flexibility). RESULTS: 7-yr inter-age correlations ranged from -0.08 to 0.39 for AEE, -0.10 to 0.33 for time on activity, 0.42 to 0.80 for sit-ups, -0.07 to 0.73 for push-ups, 0.44 to 0.82 for grip strength, and 0.47 to 0.85 for sit-and-reach. In general, significant tracking correlations for physical activity levels were limited to adulthood, whereas significant tracking of musculoskeletal fitness was observed at all ages for all indicators except push-ups. Male subjects exhibited greater stability in push-ups than female subjects. The average percentage of participants remaining in the lower and upper quintiles of the distribution over 7 yr was greater for musculoskeletal fitness (36-68%) than for physical activity level (30-34%). CONCLUSION: Physical activity level is not a very stable characteristic in the Canadian population; however, indicators of musculoskeletal fitness are moderately stable over 7 yr.

Adolescent↗

PubMed2001

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.

Adolescent↗

PubMed2000

7-year stability of blood pressure in the Canadian population.

BACKGROUND: The purpose of the study was to examine the 7-year stability of systolic (SBP) and diastolic (DBP) blood pressures in the Canadian population. METHODS: The sample included 1,503 participants 7-69 years of age from the 1981 Canada Fitness Survey who were remeasured in Campbell's Survey of 1988. Both SBP and DBP were adjusted for the effects of body mass index (BMI) using regression procedures. RESULTS: Interage correlations from baseline to follow-up ranged from -0.17 to 0.61 for SBP and from -0.22 to 0. 51 for DBP. With few exceptions, correlations were positive and significant, and were highest and most consistent in adulthood. Further, between 27 and 39% of participants in the upper or lower quintiles in 1981 remained there in 1988. There were few differences in adiposity between those who remained in the upper or lower quintiles and those who did not. One exception was that males who remained in the upper quintile of SBP had greater values for BMI, sum of skinfolds, and waist circumference at baseline. Among adults, the best predictor of future blood pressure was baseline blood pressure, which accounted for between 12 and 34% of the variance in follow-up blood pressure, followed by age, follow-up BMI, and, in females, baseline physical activity levels. CONCLUSIONS: Blood pressure demonstrated low to moderate stability over 7 years in Canada, and baseline level of adiposity was related to the stability of SBP in males.

Adolescent↗

PubMed2000

Cardiac dimensions, physical activity, and submaximal working capacity in youth of the Québec Family Study.

The relationships between cardiac dimensions and physical activity and submaximal working capacity were examined in 198 boys and 154 girls, aged 9-18 years, who were participants in the first phase of the Québec Family Study. The sample was divided into three age groups, 9-12 years, 13-15 years, and 16-18 years. Indicators of physical activity included estimated daily energy expenditure (EE) and time spent in moderate-to-vigorous physical activity (median metabolic equivalents of energy expenditure above resting metabolic rate >/=4.8). Submaximal physical working capacity (PWC(150)) was determined using a submaximal exercise test on a Monark cycle ergometer. Echocardiographically determined dimensions included posterior wall thickness, septal wall thickness, and left ventricular mass (LVM). The analyses were based on partial correlation and analysis of covariance, controlling for age and body surface area. Relationships between EE/physical activity variables and cardiac dimensions were low and, at best, moderate (r < 0.45). With subjects grouped into tertiles by indicators of physical activity, LVM was significantly different only among 16- to 18-year-old girls (157 g vs 134 g in the highest and lowest quartiles, respectively; P < 0.05). Correlations between cardiac dimensions and PWC(150) were also low (r < 0.30), with few significant relationships. In general, cardiac dimensions were not related to habitual physical activity and PWC(150) in young subjects aged 9-18 years. However, significant correlations were positive, as expected. LVM may be related to submaximal power output in boys since it accounts for 3% of the variance, after adjusting for age and BSA.

Adolescent↗

PubMed2000

Growth and overweight of Navajo youth: secular changes from 1955 to 1997.

OBJECTIVE: To examine the growth status, prevalence of risk of overweight and of overweight, and secular changes in growth status in Navajo youth from 1955 to 1997. SUBJECTS: 526 (256 males, 270 females) Navajo children 6-12 y of age. MEASUREMENTS: Stature and mass were measured and the body mass index (BMI) was calculated. ANALYSIS: All three variables were plotted relative to age- and sex-specific US reference data and the prevalence rates for risk of overweight and of overweight were estimated using the BMI as the criterion. The cut-off for the risk of overweight was the age- and sex-specific 85th and 95th percentiles of NHANES I, while the cut-off for overweight was a BMI>/=95th percentiles. Age-specific sex differences were compared using independent samples t-tests. Secular changes for body size were estimated by comparing age- and sex-specific means for stature, mass, and the BMI in the present study and two previous studies in 1955 and 1989. RESULTS: No statistically significant differences were observed between sexes within age groups. In both sexes, mean age-specific stature appeared to be relatively stable around the 50th percentile of US reference values. Mean age-specific mass appeared to be relatively stable between the 50th and 90th percentiles of the reference values, while the mean BMI tended to fluctuate about the 85th percentile. Approximately 41% of the Navajo boys and girls 6-12 y of age had BMIs >/=85th percentiles of US reference data. Compared to corresponding data on Navajo youth in 1955 and 1989, the current sample was larger in mass and the BMI. The estimated rate of secular change in mass was about 1.5 kg/decade in younger boys and girls, and about 3 kg/decade in older boys and girls between 1955 and 1997. The estimated rate of secular change in the BMI was about 0.5-1.0 units/decade between 1955 and 1997, while that for stature was about 2 cm/decade between 1955 and 1997. CONCLUSIONS: The results are consistent with recent findings on the Navajo Health and Nutrition Survey that overweight is a serious public health concern across the lifespan in the Navajo, and that the problem begins in childhood. Furthermore, Navajo children appear to be heavier than about a decade ago. International Journal of Obesity (2000) 24, 211-218

Arizona↗

PubMed2000

Variation in the body mass index among young adult Polish males between 1965 and 1995.

OBJECTIVE: To investigate whether the incidence of overweight and underweight individuals among young adults showed inter-generation changes or social-class differences in Poland between the mid-1960s and mid-1990s. DESIGN: Comparisons of variation in the body mass index and in height among 19-y-old Polish males drawn from three successive birth cohorts. SUBJECTS: Three 10% nation wide random samples of 19-y-old Polish conscripts, examined in 1965, 1986 and 1995, a total of ca. 80,000 individuals. MEASUREMENTS: Body mass index (weight (kg)/height (m2) and height (m). PRINCIPAL RESULT: There has been during the three decades between the mid-1960s and mid-1990s a gradual and significant increase in the proportion of both 'overweight' and of 'underweight' young males, as well as of the very tall and very short ones in the population. CONCLUSION: The above finding seems intriguing. It may suggest that certain elements of individual lifestyles, those influencing the leanness vs fatness variation among young adults, as well as those affecting growth in height, have tended to become in Poland increasingly diversified in terms of between-family differences, irrespective of social-class differences and of the general nationwide changes in living standards.

Adult↗