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Biomedical subjects

H C Kemper

Publications and source records attributed to H C Kemper.

At least 73 records · Page 4Linked to original sources
PubMed1995

Longitudinal development of lipoprotein levels in males and females aged 12-28 years: the Amsterdam Growth and Health Study.

BACKGROUND: In the Amsterdam Growth and Health Study, the longitudinal development of risk factors for coronary heart disease (CHD) was investigated. METHODS: Serum cholesterol (TC), high density lipoprotein (HDL) and the TC/HDL ratio were measured at the ages of 13, 14, 15 and 16 years (adolescence) and at the ages of 21 and 27 years ([young] adulthood). RESULTS: No cohort, time of measurement, drop-out or test/learning effects were found for TC, HDL and the TC/HDL ratio. For males the longitudinal development of TC showed a dip in the adolescent period, while females showed constant values. For both males and females TC values increased during young adulthood, but females had higher (P < or = 0.001) absolute values than males. The HDL values for males decreased throughout the measurement period, while for females a stable period during adolescence was followed by a slight increase during adulthood. For the TC/HDL ratio males showed an increase during young adulthood, while females stayed more or less constant over the whole measurement period. The percentages of subjects above (or below for HDL) objective risk values increased with age: from 0% to 1% during adolescence to 11% (males) and 14% (females) for TC, 5% (males) and 1% (females) for HDL and 13% (males) and 1% (females) for the TC/HDL ratio. CONCLUSIONS: In a relatively young and healthy population TC and TC/HDL values tended to rise with age (especially in males) indicating that prevention related to these risk factors for CHD should start early in life.

Adolescent↗
PubMed1995

Validity and repeatability of a modified Baecke questionnaire on physical activity.

BACKGROUND: In a pilot study for the European Prospective Investigation into Cancer and Nutrition (EPIC) a modification of the Baecke questionnaire on physical activity was tested for repeatability and relative validity in a population of 134 men and women aged 20-70 years. METHODS: For the assessment of repeatability Pearson's correlation coefficients and percentages of agreement after classification in tertiles were computed between administrations of the questionnaire at baseline, and after 5 and 11 months. Relative validity was determined by comparing the questionnaire to a four times repeated 3-day activity diary. RESULTS: Repeatability after 5 and 11 months was good, with test-retest correlation coefficients between 0.65 and 0.89 for main sections of the questionnaire. The percentages of agreement, exceeding chance (Cohen's kappa) were 57% and 56% for men (at 5 and 11 months respectively) and 41% and 46% for women. The correlations with the diaries were 0.56 in men and 0.44 in women. Agreement apart from chance between classification in tertiles for both methods was 35% for men and 10% for women. CONCLUSIONS: These data show that repeatability is good and relative validity as compared to an activity diary is moderate but well within the range of values found in other studies. The questionnaire is more valid in men than in women.

Adult↗
PubMed1995

Comparison of a quantitative dairy questionnaire with a dietary history in young adults.

BACKGROUND: There is growing interest in the potential role of calcium in the prevention of osteoporosis. Therefore a quantitative dairy questionnaire (DQ) was developed to estimate the calcium intake from dairy products. The aim of this study was to evaluate the relative validity and reproducibility of the DQ in 27-29 year old males and females. METHODS: The DQ was validated against a cross-check dietary history method (DH) in 160 subjects, and the reproducibility was assessed in 29 subjects by repeating the administration of the DQ with a one-year interval. RESULTS: In the validity study, the nutrient calcium and the food groups cheese and milk and milk products measured by the DQ tend to show higher intakes as compared to the results of the DH. However, only for the calcium intake was the difference between the DQ and DH (7%) significant. The Bland-Altman plot showed that this bias was constant over the range of calcium intakes. The Pearson correlation coefficients between the DQ and the DH varied from 0.58 to 0.65. On average, about 52% of the subjects were classified in the same quartile in the DQ and the DH for the intake of calcium as well as dairy products. The weighted kappas were between 0.60 and 0.67. In the reproducibility study, the Pearson correlation coefficient for the calcium intake assessed by the DQ one year apart was 0.78. CONCLUSIONS: These data indicate that the DQ is reasonably accurate in young adults as a means of assessing the calcium intake from dairy products.

Adolescent↗
PubMed1995

A meta-analysis of the effect of calcium intake on bone mass in young and middle aged females and males.

Evidence of a direct relationship between dietary calcium and bone mass in young adults is inconsistent. Therefore, a meta-analysis was performed to evaluate the existing literature concerning this relation in premenopausal women and adult men between the ages of 18 and 50. A computer-aided search of published papers from 1966 through 1994 was conducted. The quality of each study was assessed by examining the study design. The results of the well-designed studies wer combined to obtain quantitative conclusions. A total of 33 eligible studies were identified in the literature, representing 27 cross-sectional studies, two longitudinal and four intervention studies. The results of the cross-sectional studies in permenopausal females showed a significant correlation coefficient (r = 0.13, 95%-confidence interval = 0.09-0.16) as well as partial correlation coefficient (partial r = 0.08, 95%-confidence interval = 0.05-0.12), both weighted by sample size. The intervention studies found that calcium supplementation of approximately 1000 mg/d in premenopausal women can prevent the loss of 1% of bone/y at all bone site except in the ulna. In conclusion, the studies published to date seem to offer overall evidence that calcium intake is positively associated with bone mass in premenopausal females. This association is fairly consistent across the different study designs and is strengthened by the fact that the results are based only on studies with a high methodological quality. In males, too few studies (only three) were published to draw firm conclusions.

Adolescent↗
PubMed1994

Medical examiner data in injury surveillance: a comparison with death certificates.

Increasingly, researchers use medical examiner reports to study the epidemiology of fatal injuries, often assuming that reports of all fatal injuries are included in medical examiner databases. This study evaluated that assumption by comparing the medical examiner database with the death certificates of persons who died of fatal injuries in Iowa during 1990-1991. The authors also examined the association between demographic variables and the presence of a medical examiner report. Overall, medical examiners reported 68.7% of fatal injuries. Among broad categories of injury deaths, the percentages of medical examiner reports varied: 36.9% of fatalities from unintentional falls, 79.2% of transportation fatalities, 82.6% of intentional fatalities, and 57.3% of other external causes of death. Age and sex were also associated with the presence of a medical examiner report. Women's deaths were half as likely as men's to be reported by the medical examiner. Deaths among the elderly were underreported as well. Among the elderly, fatalities from unintentional falls and, to a lesser extent, transportation fatalities were less likely to be investigated by a medical examiner, but intentional fatalities were more likely to be. Although medical examiner reports may contain detailed information, they underreport the actual number of injury deaths. This underreporting is of special concern for injury research, since certain demographic groups were found to be underrepresented in medical examiner reports.

Accidental Falls↗
PubMed1994

Weight-bearing activity during youth is a more important factor for peak bone mass than calcium intake.

In a 15 year longitudinal study (Amsterdam Growth and Health Study) is evaluated the effect of daily calcium intake (CAI) during adolescence and young adulthood on the development of peak bone mass at age 27 when the influence of weight-bearing activity (WBA) and body weight was accounted for. A group of 84 males and 98 females were measured longitudinally from age 13 until age 28. Measurements were taken six times of anthropometric characteristics. Lifestyle was also evaluated six times by cross-check interviews of CAI and WBA. Bone mineral density (BMD) of the lumbar spine was determined at age 27 by dual x-ray absorption. Three periods were considered, that is, the adolescent period, the period 13-21 years, and the total period (13-27 years). In multiple linear regression analyses, only WBA and body weight were significant positive contributors to the final model of lumbar BMD at age 27. In all three periods WBA was the best predictor in males and body weight in females. ANOVA was performed on BMD and the highest and lowest quartiles of calcium intake with the significant predictor variables of the linear regression model as covariates. Again calcium intake appeared not a significant predictor of BMD in the three periods in both sexes. Regular weight-bearing exercise and at least a normal age-related body weight in adolescence and young adulthood are of key importance in reaching the highest lumbar peak bone mass at the age of 27 years.

Absorptiometry, Photon↗
PubMed1994

Anthropometry and lung function of 10- to 12-year-old Bolivian boys.

Anthropometric measurements of 23 HAHSES, 44 HALSES, 43 LAHSES, and 28 LALSES boys (see Introduction to this Supplement) are presented here. They include body height (H), body weight (BW), upper arm circumference (UAC), and skinfold thickness taken at four locations. From these measurements, body fat, lean body mass, and body mass index (BMI = BW/H2) were calculated. The degree of maturation was assessed according to Tanner, orchidometry, and by quantification of testosterone in saliva. Lung function data include: vital capacity (VC), forced expired volume per 1 s (FEV1), functional residual capacity (FRC), residual volume (RV), and total lung capacity (TLC). The results show enhanced lung volumes in both HA groups in comparison to LA groups, with HALSES boys having the greatest increase, even though the LSES boys were significantly smaller compared to the HSES boys at both altitudes and their growth was delayed by approximately 2 years. From the anthropometric data it appears that physical growth of prepubertal boys is dependent on SES but not on high-altitude exposure. We tentatively conclude that chronic hypoxia per se does not affect physical growth in prepubertal boys in an Andean environment and that development of lung function is accelerated in relation to linear growth as has been suggested by other authors (15).

Altitude↗
PubMed1994

The nutritional intake of Bolivian boys. The relation between altitude and socioeconomic status.

The nutrition of 57 native Bolivian boys living at high altitude (HA) in La Paz (+/- 4000 m) and of 63 boys living at low altitude (LA) in St. Cruz (+/- 400 m) is described. The dietary information was obtained with a 24-h recall method, by interviewing the child and mother. The food items are listed in household measures and weight if possible. All food items were converted into grams, and nutrients were calculated by using food composition tables of Latin America. The results show that the energy and nutrient intake of the HSES boys was significantly higher (p < 0.05) than the intake of the LSES boys, at both altitudes. At HA the mean energy intake of the HSES boys was about 9.8 MJ per day (+/- 0.7); for the LSES boys an intake was found of 8.4 MJ per day (+/- 0.4). At LA the HSES boys had an energy intake of 10.7 MJ per day (+/- 0.6) and the LSES boys 7.7 MJ per day (+/- 0.3). The daily protein intake was in HAHSES boys 85 g (+/- 8), LAHSES 100 g (+/- 8), HALSES 60 g (+/- 4), and LALSES 52 g (+/- 3). In comparison with the recommended daily requirements the dietary intakes of the HSES boys seem too "rich," and of the LSES boys to some extent too "poor." These results are reflected in smaller body height and body weight of LSES boys and a higher fat mass in HSES boys irrespective of altitude.

Adult↗
PubMed1994

Habitual physical activity in 10- to 12-year-old Bolivian boys. The relation between altitude and socioeconomic status.

This study describes habitual physical activity (HPA) of Bolivian boys living at different altitudes and from different socioeconomic status. The boys were living at high altitude (HA) in La Paz (4000 m) and at low altitude (LA) in Santa Cruz (400 m). At both altitudes samples of 10- to 12-year-old boys were chosen from a relatively low socioeconomic status (LSES) and a relatively high socioeconomic status (HSES). At HA 19 boys from LSES and 10 boys from HSES were measured and at LA 14 boys from LSES and 13 boys from HSES. HPA was measured by 24-h heart rate (HR) monitoring. Also an interview was completed to recall the HPA. By comparing the registered HR data with the time they were asleep the mean HR during sleep was calculated (HRsleep). The maximal HR (HRmax) was measured from a maximal exercise test on a bicycle ergometer. Heart rate reserve (HRR = HRmax-HRsleep) was used to measure the mean level of physical activity of the subjects. The results show that HRsleep (= HRrest) in HA boys with 70 (+/- 6) beats/min was significantly lower (p < 0.05) than in LA boys with 77 (+/- 10) beats/min. HRmax was also significantly lower (p < 0.05) in HA boys (187 +/- 12 beats/min) compared to LA boys (195 +/- 8 beats/min). Because HA influences HRsleep and HRmax in the same way, HRR is not significantly different between boys of HA and LA. The mean heart rate over 24 h (HRmean) in HA boys (87 +/- 7 beats/min) was significantly lower than in LA boys (93 +/- 8 beats/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Altitude↗
PubMed1993

Joint moments and muscle activity in the lower extremities and lower back in lifting and lowering tasks.

The mechanical loading on the body during the act of lifting has been estimated frequently. The opposite act of lowering has received much less attention. The aim of the present study was to compare the mechanical loading of the musculoskeletal system in lifting and lowering. Eight subjects repetitively lifted and lowered a load, using two different techniques (a leg and a back technique). The ankle, knee, hip and lumbosacral joint moments were estimated and the myoelectrical (EMG) activity of seven (leg and back) muscles was recorded. The differences between the lifting and lowering phase for the leg technique were similar to those observed when the back technique was applied. The joint moment curves in lifting showed a high level of agreement with the (time-reversed) moment curves in lowering. Peak moments in lowering were only slightly lower than in lifting (peak lumbar moments were 5.4% lower). These small differences were related to different acceleration profiles at the centre of gravity of the body/load complex. The EMG activity was considerably lower in lowering than in lifting. The mean EMG in lowering (average for seven muscles) was only about 69% of the EMG in lifting. This was attributed to the different types of muscle actions involved in lifting (mainly concentric) and lowering (mainly eccentric). Furthermore, the EMG results suggest that similar inter-muscular coordination is involved in lowering and lifting. The results give rise to the assumption that in lifting and lowering similar muscle forces are produced to meet the (nearly) equal joint moments, but in lowering these forces are distributed over a smaller cross-sectional area of active muscle, which might imply a higher risk of injury.

Acceleration↗
PubMed1993

Nutrient intake and biological maturation during adolescence. The Amsterdam growth and health longitudinal study.

The study evaluates the association of the food intake and the rate of biological maturation of 200 boys and girls in Amsterdam during their adolescence. The subjects were followed in a longitudinal survey over a period of 9 years, between the ages of 13 and 22 years. In the first four years (1976-1980) annual measurements were performed (school period). In 1985 a fifth measurement was made at the age of 21 years. Biological maturation was estimated from X-ray photographs of the left hand and wrist and rated according to the Tanner-Whitehouse II method. On the basis of the annual measurements in the first four years a distinction was made between late maturers (LMs) and early maturers (EMs). The individual food intake was obtained with a cross-check dietary history method: a dietitian interviewed the entire range of foods and drinks, making allowance for regular meals as well as in-between meals, separately for normal schooldays and weekend days. Analysis of variance was used to test the effects of maturation (M), time of measurement (T) and interaction (M x T). The results show that EMs of both sexes consumed less energy and protein per kg body weight, but were fatter at young adult age and showed less habitual physical activity than LMs during the whole period of observation. The conclusion could be drawn that late maturation seems to coincide with an energy intake that is more appropriate to their higher activity pattern than early maturation during adolescence. This results in a significantly lower body fat mass in late maturing boys and girls compared to early maturers.

Adolescent↗
PubMed1992

Is range of motion of the hip and ankle joint related to running injuries? A case control study.

This study concerns a case-control study on the relation between range of motion (ROM) of the hip and ankle joints and running injuries. Sixteen male runners who had sustained a medically treated running injury during the year prior to the ROM measurements were matched for weekly running distance and age with sixteen male runners who had not sustained such an injury. All subjects were fit at the time of measurement. ROM was measured by standardized goniometry after a warm-up on a cycle-ergometer. Within non-injured subjects all goniometric measurements showed no significant (p > 0.05) differences between the left and right side of the body. Within injured subjects all goniometric measurements showed no significant (p > 0.05) differences between the injured and non-injured side of the body. Runners who had sustained a running injury showed a significant (p > 0.001) more restricted ROM of the hip joints (average ROM value 59.4 degrees +/- 8.0 degrees) in comparison to runners who had no been injured during the same period (average value ROM 68.1 degrees +/- 5.2 degrees). No such differences (p > 0.05) were found with regard to ankle ROM (average ROM value injured 12.8 degrees +/- 3.4 degrees and average ROM value non injured 14.0 degrees +/- 2.7 degrees). These findings suggest that ROM can be characterized as a more or less stable anthropometric trait.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Incidence, severity, aetiology and prevention of sports injuries. A review of concepts.

Notwithstanding the healthy influence of sporting activities on risk factors, in particular those of cardiovascular disease, it is becoming increasingly apparent that sports can present a danger to health in the form of sports injuries. The extent of the sports injury problem calls for preventative action based on the results of epidemiological research. For the interpretation of these facts uniform definitions are needed and limitations of research designs should be known. Measures to prevent sports injuries form part of what is called the 'sequence of prevention'. Firstly the extent of the sports injury problem must be identified and described. Secondly the factors and mechanisms which play a part in the occurrence of sports injuries have to be identified. The third step is to introduce measures that are likely to reduce the future risk and/or severity of sports injuries. This measure should be based on the aetiological factors and the mechanism as identified in the second step. Finally the effect of the measures must be evaluated by repeating the first step. In this review some aspects of the first and second step of the sequence of prevention are discussed. The extent of the sports injury problem is often described by injury incidence and by indicators of the severity of sports injuries. Sports injury incidence should preferably be expressed as the number of sports injuries per exposure time (e.g. per 1000 hours of sports participation) in order to facilitate the comparability of research results. However, one should realise that the outcome of research applying this definition of sports injury incidence is highly dependent on the definitions of 'sports injury' and 'sports participation'. The outcome of such research also depends on the applied research design and research methodology. The incidence of sports injuries depends on: the method used to count injuries (e.g. prospective vs retrospective); the method used to establish the population at risk; and on the representativeness of the sample. Severity of sports injuries can be described on the basis of 6 criteria: the nature of the sports injury; the duration and nature of treatment; sporting time lost; working time lost; permanent damage; and cost. Here also uniform definitions are important and necessary in order to enhance the comparability of research data. In the second step of the 'sequence of prevention' the aetiological factors that play a role in the occurrence of a sports injury have to be identified by epidemiological studies. Epidemiological research on the aetiology of sports injuries requires a conceptual model.(ABSTRACT TRUNCATED AT 400 WORDS)

Athletic Injuries↗
PubMed1991

Efficiency and effectiveness of stoop and squat lifting at different frequencies.

The study investigated the effects of frequency (10 and 20 lifts/min) and technique (squat and stoop) of repetitive lifting of a barbell (19 kg) on the relationship between mean power output (Pm) and energy cost in 9 male power-lifters. Oxygen uptake (VO2) was measured directly and continuously and power output was deduced from film analysis using an inverse dynamic analysis. Power output and VO2 were significantly greater for squat than for stoop lifting at the same frequency. The mechanical efficiency (ME), defined as Pm divided by the energy equivalence of VO2, increased from 12% at rate 10 to 18.5% at rate 20, but there was no significant difference between the two techniques. The effectiveness (EF), defined as the productive external power output (only work done on the barbell) divided by the energy equivalence of VO2, was significantly higher for the stoop lift than for the squat lift. EF is judged as a more useful measure than ME for characterizing the relative energy cost of a lifting task.

Adolescent↗
PubMed1991

Sources of variation in longitudinal assessment of maximal aerobic power in teenage boys and girls: the Amsterdam Growth and Health Study.

Maximal oxygen uptake (VO2 max), generally accepted as a valid method for measuring state and change of aerobic fitness, was repeatedly measured in 93 males and 107 females 5 times over a period of 8 years. A direct measurement was made using a treadmill running test with constant speed (8 km/hr) and increasing slope. Oxygen uptake was analyzed continuously by an open-circuit technique. The reproducibility of VO2 max estimated from interperiod correlations resulted in high test-retest correlations of approximately 0.9 in both males and females. Inspection of the longitudinal data from the multiple-longitudinal design with four measurements in three cohorts did not reveal confounding effects, such as time of measurement effects, cohort effects, and drop-out effects. A comparison of the longitudinal data evaluated over four years with data from a comparable control group that was measured once during the four-year period also failed to show any testing effects. In 40% of the males and 50% of the females no leveling-off in VO2 max could be demonstrated; that is, there was an increase of more than 150 ml in the last stage of running. A comparison of subjects who showed leveling-off with those who showed no leveling-off supports the idea that in the age range 12-23 years leveling-off is not a prerequisite for reaching a true VO2 max. Repeated measurement of VO2 max, using a maximal running test on a treadmill appears to be a reliable method to describe the individual development of aerobic fitness in males and females in the age range 12-23 years.

Adolescent↗