A Claessens

Predictors of 6-minute walk test results in lean, obese and morbidly obese women.

The aim of this study was first, to assess the presence of medical conditions that might interfere with walking; second, to assess the differences in walking capacity, perceived exertion and physical complaints between lean, obese and morbidly obese women; and third, to identify anthropometric, physical fitness and physical activity variables that contribute to the variability in the distance achieved during a 6‐minute walk test in lean and obese women.

Exercise capacity in lean versus obese women

The aim of this study was to assess the nature and magnitude of the differences in submaximal and maximal exercise capacity parameters between lean and obese women. A total of 225 healthy obese women 18–65 years (BMI> or=30 kg/m2) and 81 non‐athletic lean women (BMI< or=26 kg/m2) were selected. Anthropometric measurements (weight and height), body composition assessment (bioelectrical impedance method) and a maximal exercise capacity test on a bicycle ergometer were performed. Oxygen uptake (VO2), carbon dioxide production (VCO2), expired ventilation (VE), respiratory quotient (RQ), breathing efficiency (VE/VO2), mechanical efficiency (ME) and anaerobic threshold (AT) were calculated. At a submaximal intensity load of 70 W, VO2 (l/min) was larger in the obese women and was already 78% of their peak VO2, whereas in the non‐obese it was only 69% (P=0.0001). VE (l/min) was larger, VE/VO2 did not differ and ME was lower in obese compared to the lean women. AT occurred at the same percentage of peak VO2 in both lean and obese women. At peak effort, achieved load, terminal VO2 (l min−1 kg−1), VE, heart rate, RQ respiratory exchange ratio and perceived exertion were lower in obese subjects compared to the non‐obese. Obese subjects mentioned significantly more musculoskeletal pain as a reason to end the test, whereas in lean subjects it was leg fatigue. Lean women recovered better as after 2 min they were already at 35% of the peak VO2, whereas in the obese women it was 47% (P=0.0001). Our results confirm that exercise capacity is decreased in obesity, both at submaximal and peak intensity, and during recovery. Moreover, at peak effort musculoskeletal pain was an important reason to end the test and not true leg fatigue. These findings are important when designing exercise programs for obese subjects.

Study of differences in peripheral muscle strength of lean versus obese women: an allometric approach

OBJECTIVE: To investigate whether peripheral muscle strength is significantly different between lean and obese women controlled for age and physical activity, using an allometric approach.DESIGN: Cross-sectional study of isometric handgrip and isokinetic leg and trunk muscle strength.SUBJECTS: 173 obese (age 39.9±11.4 y, body mass index (BMI) 37.8±5.3 kg/m2) and 80 lean (age 39.7±12.2 y, BMI 22.0±2.2 kg/m2) women.MEASUREMENTS: Anthropometric measures (weight, height) and body composition (bioelectrical impedance method), isometric handgrip (maximal voluntary contraction on the Jamar dynamometer), isokinetic trunk flexion–extension, trunk rotation, and knee flexion–extension (Cybex dynamometers).RESULTS: Absolute isokinetic strength output (that is, strength uncorrected for fat-free mass) was larger in obese compared to lean women, except for knee flexion and isometric handgrip, which were not significantly different (P>0.05). Pearson correlation coefficients between strength measures and fat-free mass (kg) were low to moderate both in lean (r=0.28–0.53, P<0.05) and in obese (r=0.29–0.49, P<0.001) women. There was no correlation with fat mass (kg) in the lean, whereas in the obese women a weak positive relation could be observed for most isokinetic data (r=0.21–0.39, P<0.01). When correcting for fat-free mass (raised to the optimal exponent determined by allometric scaling), all strength measurements were at least 6% lower in obese when compared to the lean women, except for trunk flexion, which was at least 8% stronger in obese women.DISCUSSION: The higher absolute knee extension strength measures of leg and the similar extension strength of the trunk in the obese sample compared to the lean might be explained by the training effect of weight bearing and support of a larger body mass. However when the independent effect of fat-free mass is removed, these strength measures, as well as oblique abdominal muscle and handgrip strength, turned out to be lower in obese women. These observations could be the reflection of the overall impairment of physical fitness as a consequence of obesity and its metabolic complications.

Trends in BMI among Belgian children, adolescents and adults from 1969 to 1996

OBJECTIVE: To document secular data on changes in the distribution of body mass index (BMI), to determine the probability of overweight at 40 y of age in Belgian males in relation to the presence or absence of overweight at different ages in adolescence, and to estimate tracking of BMI in Belgian males in Belgium aged 12–40 y.DESIGN: Cross-sectional and mixed longitudinal surveys in nationally representative samples of Belgian males and females.SUBJECTS: Cross-sectional—more than 21 000 boys and 9698 girls; to examine secular trends—3164 boys and 5140 girls; to examine tracking—161 males.MEASURES: Body mass and height to determine BMI.RESULTS: In Belgian children the degree of overweight has increased between 1969 and 1993. Tracking of BMI is high in adolescence (r=0.77) and adulthood (r=0.69–0.91) and moderate from adolescence to adulthood (r=0.49). In Belgian males, the probability of overweight at 40 y of age in the presence of overweight at different ages in adolescence is important (odds ratios 5.0–6.9).CONCLUSIONS: Cross-sectional and longitudinal data, trends and tracking of BMI from 1969 until 1996 in Belgium indicate an increase in the degree of childhood overweight and obesity. Moreover, the risk of an overweight male adolescent becoming an overweight adult is substantial. Measures to restrict the Belgian overweight and obesity epidemic should be taken.

Influence of weight-bearing exercises on bone acquisition in prepubertal monozygotic female twins: A randomized controlled prospective study

The aim of this study was to determine whether high-impact exercises have an osteogenic effect in 21 prepubertal female monozygotic twins aged 8.7 (SD 0.7) years. Bone mineral density (aBMD), bone mineral content (BMC), bone area, and body composition were derived from DXA. Skeletal maturity was assessed by the Tanner-Whitehouse technique. Anthropometric dimensions (28 dimensions) were measured and also used to derive adiposity and muscularity indices, and information about physical activity was obtained by questionnaire. These measurements were taken before and after the exercise period. The exercise program consisted of high-impact exercises. During 9 months, one girl of each twin pair performed the exercises 3 times a week under supervision of a teacher while their sisters served as control group. At baseline there were no differences between the groups. After 9 months, exercisers (Ex) and controls (Con) had similar increases in height and weight. Significant lower adiposity was observed in the exercise group vs the control group. None of the bone indices differed significantly between the two groups. When the analyses were done for a subgroup of twin pairs (n=12) who did not participate in high-impact sports during their leisure time, significant differences were obtained for aBMD and BMC of the proximal femur in favor of the exercise group. These results indicate that for prepubertal girls who are not involved in sport activities or who are only involved in low-impact sport activities this exercise program has an osteogenic effect on the proximal femur, but for girls who are already involved in high-impact sports this protocol does not have any additional effect on the bone status.

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

SummaryThis 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 (70% 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. This indicated that in addition to fitness scores, anthropometric dimensions, and skeletal maturation, behavioural characteristics also added significantly to the prediction of adult fitness levels.

Association between bone, body composition and strength in premenarcheal girls and postmenopausal women.

Aim: The study examined whether associations between bone, body composition and strength are age dependent. Subjects and methods: Two age levels (premenarcheal girls and postmenopausal women on HRT) were studied in a 10-month follow-up. Bone, lean and fat mass were measured by dual-energy X-ray absorptiometry (DXA), and strength was measured using an isokinetic dynamometer. Results: In girls, significant correlations were found between mass (lean, fat and body mass), strength and most bone characteristics (r = 0.15–0.93). At the proximal femur changes in bone mineral density (BMD) were moderately related to changes in body composition. In the women, body mass and lean mass were significantly correlated with most bone characteristics (r = 0.34–0.82). Low to moderate correlations were observed between changes in bone and changes in body composition. After controlling for lean mass the relation between strength and bone was no longer significant. Conclusions: In premenarcheal girls, bone is partly determined by mass, with lean mass the most important predictor at the femoral sites. In postmenopausal women, lean mass is an important determinant of bone mineral content (BMC) and BMD, but changes in BMD are related to changes in fat. The relation between strength and BMD is mainly attributable to the relation between lean mass and BMD. The contributory effects of soft tissue to bone change over different life periods.

Associations between physical activity, nutritional practices and health-related anthropometry in Flemish males: a 5-year follow-up study

OBJECTIVE: To examine the extent to which extent health-related anthropometric characteristics such as body mass index, waist–hip ratio, waist girth, percentage of body fat and weight gain are associated with physical activity and nutritional habits in a prospective follow-up study.DESIGN: A 5-y prospective follow-up study.SUBJECTS: 132 healthy men from The Leuven Longitudinal Study on Lifestyle, Physical Fitness, and Health.MEASUREMENTS: The main outcome measures in this study were body mass index, waist–hip ratio, waist girth, percentage of body fat and significant weight gain at the ages of 35 and 40 y. An unhealthy body composition was defined as a body mass index above 26, a waist–hip ratio above 0.95, a waist girth and body fat percentage above percentile 75 at the end of the 5-y follow-up period and a significant weight gain of 5 kg or more between the two examination periods. Anthropometric characteristics were derived from clinical examination. Physical activity at the age of 35 and 40 and nutritional habits at the age of 40 were determined from questionnaires.RESULTS: Physical activity was the most important predictor for the waist–hip ratio in this sample. In contrast, nutritional habits show a stronger relationship with body mass index. The absolute amount of energy intake is not as important as the dietary factors in predicting subjects with overweight or an unhealthy body composition. The index of occupational activities appears to be the most important physical activity variable.CONCLUSION: The relative contribution of physical activity and nutritional habits in health-related anthropometry varies with the characteristic considered. It is important to include all components of physical activity, and occupational activities in particular, in determining these relationships in a general population sample.

Secular trends in somatic and motor characteristics of physical education students

This study investigated changes in somatic and motor characteristics of 3,514 physical education students at the Katholieke Universiteit Leuven (Belgium) from the academic years 1941–1942 to 1988–1989. To facilitate data handling, the span of 47 years was divided into nine cohorts for anthropometric variables, and 4 cohorts for the motor data which were available only since the 1968–1969 academic year. A total of 21 anthropometric variables (since 1959) and 9 motor performance tests (since 1968) are included in the analysis. Descriptive statistics were calculated for all variables and for each cohort, and analyses of variance were done to test the significance of secular trends. For weight and length dimensions a significant increase was noted; current students are, on average, 4.2 kg heavier and 5.8 cm taller than those in 1941–1946. In contrast, however, there is no change and even a negative trend in circumferences and breadth dimensions. Current students had, on average, significantly narrower shoulders and hips by 0.5 cm and 1.0 cm for biacromial and bicristal breadths, respectively, than students in the 1959–1963 cohort, and a significantly smaller hip circumference by 3.3 cm between the 1959–1963 and 1984–1988 cohorts. Current students had a thicker triceps skinfold than students 25 years ago, with average values of 8.0 mm and 6.3 mm, respectively. However, no significant differences were observed in the subscapular and suprailiac skinfolds. For motor performance, current students obtained better results in flexibility, several strength tests, and running speed than students of 15 years ago. However, no change was observed in average speed of limb movement. It is hypothesized that the changes in both somatic characteristics and motor performance are related in part to changes in secondary school physical education programs and to changes in the first year university physical education curriculum. Published 1992 by Wiley‐Liss, Inc.

Body size, biological maturation, and sport participation related to cortical bone in adolescent girls

The purposes of this study were twofold: (1) to describe the growth of metacarpal bone dimensions in a large sample (n = 819) of Flemish girls, 12–18 years, and (2) to investigate the relationship among cortical bone dimensions, biological maturation, and participation in sports activities. Besides body mass and stature, Tanner‐Whitehouse skeletal age (SA) was estimated and menarcheal status was assessed. Second metacarpal bone dimensions were measured on radiographs. Sports participation was determined by a standardized questionnaire. Results show that whereas medullary diameter decreased, all other second metacarpal dimensions increased significantly with age. When the girls were divided into five subgroups by SA, significant differences were found for metacarpal bone dimensions among the groups. Analysis of covariance revealed that skeletal maturity significantly differentiated for medullary diameter, cortical thickness, cortical area, and percent cortical area, even when chronological age, body mass, and stature were partialled out. However, no differences were found between contrasting SA groups for metacarpal length and periosteal diameter when chronological age, body mass, and stature were held constant. The metacarpals of postmenarcheal girls are ∼4% longer and ∼7% wider, and had ∼14% more bone area than age‐matched, premenarcheal peers. No differences were found in periosteal diameter between pre‐ and postmenarcheal 14–15‐year‐old girls. Finally, sports participation was not associated with cortical bone in this group of healthy females (−0.16 ≤ r ≤ 0.17).