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Biomedical subjects

H C Kemper

Publications and source records attributed to H C Kemper.

At least 91 records · Page 5Linked to original sources
PubMed1990

Tracking of health and risk indicators of cardiovascular diseases from teenager to adult: Amsterdam Growth and Health Study.

Cardiovascular disease is recognized as a serious public health problem. Because the underlying pathological processes start shortly after birth, tracking of recognized cardiovascular disease indicators during childhood and adolescence can help in developing preventive pediatric strategies. A prospective follow-up of both genetic and behavioral lifestyle parameters (serum cholesterol, blood pressure, percentage body fat, maximal oxygen uptake (VO2max), smoking, physical inactivity, and type A behavior) was designed. In the Amsterdam Growth and Health Study a population of 93 males and 107 females was measured annually from 1977 to 1980 and a fifth measurement was made in 1985. In that way longitudinal data covering a period of 8 years was collected for a group of adolescents/adults between 13 and 21 years of age. Analyses of these parameters provided the following results: The stability over the 9 years of tracking cardiovascular disease indicators, measured as the interperiod correlations, is fairly high. It varies from 0.4 to 0.8 in percentage body fat, cholesterol, and VO2max. Blood pressure values are low (between 0.3 and 0.4). The probability of 13-year-olds having relatively high values of cardiovascular disease indicators on the basis of a quartile distribution with that at age 21 indicated a moderate to high predictive value. According to the literature, the levels of subjects that are continuously relatively high over the years are more in the direction of optimal health than risk values. The exception is for percentage body fat. Interrelation of the seven cardiovascular disease indicators in constantly relatively high-risk and relatively low-risk groups during the teenage period, measured during young adulthood (21.5 years), appeared to be weak: only males and females with a high percentage body fat and a low VO2max showed significantly high total cholesterol, low high-density lipoprotein cholesterol, and high total cholesterol/high-density lipoprotein cholesterol levels. From the three environmental cardiovascular disease indicators (smoking, physical activity, and type A/B behavior) measured in 1985, only physical activity was significantly correlated among males and females with high-density lipoprotein cholesterol, percentage body fat, and VO2max. It can be concluded that measurement of percentage body fat in the early teenage period seems to be the most important cardiovascular disease indicator in predicting risk levels in the young adult. The amount of physical activity measured at young adult age is the only behavioral parameter to show a significant interrelation with other cardiovascular disease risk indicators.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1990

The physical and physiological workload of refuse collectors.

In order to secure a safer and healthy work situation, the heavy physical loads imposed on 23 refuse collectors (aged 26-54) working in the city of Haarlem, in The Netherlands, were studied in a series of three experiments between 1984 and 1987. The aims were respectively (1) to study the load for workers collecting dustbins or polythene bags; (2) to introduce changes to reduce the load to avoid exceeding the overload criteria by individual refuse collectors; and (3) to investigate the effects of interventions to improve the efficiency of refuse collecting. The maximal isometric lifting force (Fmax) and the maximal aerobic power (VO2max) of 23 refuse collectors were measured in the laboratory. Fmax was measured with an isometric dynamometer pulling with one arm from the floor; the mean value was 912 (+/- 127)N. VO2max was measured running on a treadmill; the mean value was 43.3 (+/- 0.8)ml O2 per kg body mass per min. The physical load on the oxygen transport system was measured through work analysis and by a continuous registration of the heart rate over three working days. Criteria for overload were set at a mean external load of 20% Fmax and a mean energy expenditure of 30% VO2max and an energy expenditure of 50% VO2max or more for a maximum of 60 min per day. Replacement of dustbins by polythene bags resulted in a 70% increase in the total amount of refuse collected, an increase in throwing frequency, but a lower mean load per throw, and no significant differences in the mean heart rate over the working day. When polythene bags were used the mean values did not exceed the overload criteria, but 39% of the individual collectors did have a workload that was too high with respect to one of the criteria. In the last experiment the collectors were advised to reduce their work load by (a) lifting no more than two bags at a time; (b) reducing their walking pace; and (c) taking more breaks. Although compliance with the recommendations was good, and the weight lifted and the walking speed decreased, the physiological load remained the same. This may have been caused by a 15% increase in the total amount of refuse that had to be collected at that time.

Adult↗
PubMed1989

The validity of the use of heart rate in estimating oxygen consumption in static and in combined static/dynamic exercise.

The accuracy of using the HR/VO2 relation determined in running to predict VO2 from HR in tasks involving static and combined static/dynamic exercise was examined in a group of 8 healthy subjects (age 20-27 years). The HR measured in weight-holding tasks (with static exercise) and weight-carrying tasks (with combined static/dynamic exercise) with weights varying from 4-12 kg was inserted into the linear relation between HR and VO2 in the running task (dynamic exercise). The predicted VO2 was compared with measured value. The conclusions were as follows. It is not accurate to use a simple dynamic task to predict VO2 from a measured HR in static work. The percentage differences vary between 78 and 186%. In combined static-dynamic work a simple dynamic task can be accurately used to predict VO2 from measured HR, while carrying small weights (4, 8 and 10 kg). However, more static work (12 kg) makes the estimations poorer with a significant percentage difference in VO2 of 38%.

Adult↗
PubMed1988

Habitual physical activity, strenuous exercise, and salivary immunoglobulin A levels in young adults: the Amsterdam Growth and Health Study.

Secretory IgA (S-IgA) levels in stimulated salvia were measured before and after a maximal treadmill test in a population of 175 young adults (84 men, 91 women). Habitual physical activity levels of this population were measured by a standardized interview, and scores were obtained for the amount of time and intensity of sports activities and total activity. Before the maximal treadmill test, men and women showed no statistically significant differences in the salivary concentrations of S-IgA, but the concentration of S-IgA in women decreased and in men increased statistically significantly (P less than 0.05) after the treadmill test. Only women showed a significant correlation between absolute values of S-IgA and the weekly amount of time spent on sports activity measured by a standardized interview expressed in minutes per week.

Adult↗
PubMed1988

Physical activity and upper respiratory tract infections in a normal population of young men and women: the Amsterdam Growth and Health Study.

A population of young adults, 92 men and 107 women, with a mean age of 21 (+/- 0.7) years, were retrospectively questioned about their habitual physical activity levels (period of 3 months) and the incidence and duration of upper respiratory tract infection (URI) symptoms (period of 6 months). We hypothesized that the incidence and duration of URI symptoms were inversely related with the level of sports activity and total physical activity. Only in women was a statistically significant (P less than 0.05) negative relation found between the incidence of URI symptoms and the level of sports activity. However, the low Spearman's rho coefficient (-0.18) indicates a very weak relation between both parameters.

Adult↗
PubMed1987

Longitudinal changes in nutritional habits of teenagers: differences in intake between schooldays and weekend days.

Longitudinal changes in nutritional habits were studied in Dutch adolescents from 12 to 17 years of age (131 girls and 102 boys). The dietary differences on schooldays and weekend days are reported. In girls only small changes in nutritional habits were seen as they grew older. In boys there was a gradual increase in food intake with age. Overall, higher nutrient intakes could be seen on weekend days. The energy intake on weekend days was consistently higher for girls and boys in all age-groups. The proportional intakes of fat and sugar were rather high, especially on weekend days. The alcohol consumption increased with age for girls as well as boys, and was for some individuals extremely high (boys) on weekend days. The observed levels of intake compared with the recommendations showed a rather low intake of polyunsaturated fatty acids, polysaccharides and iron.

Adolescent↗
PubMed1987

Longitudinal development of growth and fitness in early and late maturing teenagers.

On the basis of measurement of biological age (BA) over a period of 4 years, late maturers (LM) were compared with early maturers (EM) in a teenage population of boys (n = 102) and girls (n = 133) with respect to height, maximal aerobic power (VO2max) and maximal isometric arm strength (Fmax). BA was estimated from X-ray photographs of the left hand and wrist and rated according to the Tanner-Whitehouse II method. Direct determination of VO2max was made during treadmill running at a constant speed (8 km/h) and increasing slope until complete exhaustion. Fmax was measured by an arm pull test with a dynamometer. Analysis of variance was used to test the effects of maturation (M), time of measurement (T) and interaction (T X M). The results show that (1) VO2max and Fmax in EMs and LMs increase proportionally with body height in boys and girls; (2) in the teenage years no significant differences in Fmax standardized for body mass can be demonstrated between EMs and LMs in boys or in girls, however, (3) VO2max standardized for body mass is significantly lower in EMs than in LMs. This can be explained by the higher percentage fat mass in EMs compared to LMs in boys and girls.

Adipose Tissue↗
PubMed1986

Validation of two running tests as estimates of maximal aerobic power in children.

In order to validate the "Maximal Multistage 20 Meter Shuttle Run Test" by Leger and Lambert (1982) (20-MST) as an estimate of maximal aerobic power (VO2max) and to compare the results of this test with the results of a 6 min endurance run, 82 subjects (41 boys and 41 girls) aged 12-14 performed the 20-MST and the 6 min endurance run, and had their VO2max directly measured during maximal treadmill running. The 20-MST is a maximal running test starting at a running speed of 8.0 km X h-1, which is increased every minute and in which the pace is set by an audio signal. Performing the test, one runs a 20-meter course back and forth. The test result is expressed as "palier" (one palier is approximately one minute). The mean results of the 20-MST were, for boys, 8.0 palier (+/- 1.7) and for girls, 6.4 palier (+/- 1.5). The mean results of the 6 min endurance run were for boys, 1264.4 meters (+/- 160.8), and for girls, 1103.9 meters (+/- 144.7). The mean VO2max for boys was 53.2 ml X kg-1 X min-1 (+/- 5.4) and for girls, 44.1 (+/- 4.8) ml X kg-1 X min-1. The correlation coefficient between VO2max and the 20-MST was found to be 0.68 (+/- 3.9) for boys, 0.69 (+/- 3.4) for girls and 0.76 (+/- 4.4) for both sexes, and that of VO2max with the 6 min endurance run was 0.51 (+/- 4.6) for boys, 0.45 (+/- 4.3) for girls and 0.63 (+/- 5.3) for both sexes. The conclusion is that the 20-MST is a suitable tool for the evaluation of maximal aerobic power. Although the differences in validity between the 20-MST and the 6 minutes endurance run were statistically not significant (p greater than 0.05), for reasons of practicability the 20-MST should be preferred to the 6 minutes endurance run when used in physical education classes.

Adolescent↗
PubMed1986

Longitudinal studies on the development of health and fitness and the interaction with physical activity of teenagers.

Coronary heart disease is recognized as a serious public health problem in Western industrialized countries. Its origin is early in life, and thus preventive pediatric strategies should be developed. This paper reviews longitudinal studies of risk indicators for coronary heart disease during the adolescent period from 12 to 18 years of age. Developmental aspects of maximal aerobic power during the teenage period is reviewed, as well as the relationship of coronary heart disease and maximal aerobic power, to obesity, high blood pressure and hypercholesterolemia to habitual physical activity.

Adolescent↗
PubMed1985

Force, velocity and energy flow during the overarm throw in female handball players.

The overarm throw of 56 female handball players was analysed cinematographically. The time courses of the ball velocity, the force on the ball, the energy flow to the ball as well as the velocities of wrist, elbow and hip were calculated. The mean ball velocity at release was 17.2 m s-1. The major part (73%) of the work on the ball appeared to be done in the last 50 ms of the throw. It is shown that high maximal segmental velocities are important pre-requisites for an optimal flow of energy to the ball during that last phase of the throw. The consecutive actions of body segments from larger proximal segments to the relatively smaller distal segments seem to be connected to intrinsic muscle properties and to a flow of energy from proximal to distal segments.

Adult↗
PubMed1981

Maximal aerobic power in 13- and 14-year-old teenagers in relation to biologic age.

Maximal oxygen uptake (VO2 max) was measured on a treadmill in 375 teenagers, 13 and 14 years old. VO2 max per kg body mass in boys had a mean value of 59 ml. min-1.kg-1 and in girls of 51 ml.min-1.kg-1. Linear regression analysis across biologic age revealed that in boys as well as in girls the VO2 max increased with increasing biologic age. However, per kg body weight or per kg lean body mass VO2 max decreased. VO2 max per cm height squared and per kg body mass to the two-thirds power did not show a change with biologic age. Multiple regression analysis revealed that the increase in the absolute values of the VO2 max and the decrease in the relative values of the VO2 max with increasing biologic age was almost completely due to the increase in total body mass (i.c. height and weight).

Adolescent↗
PubMed1978

Design of a multiple longitudinal study of growth and health in teenagers.

This paper describes the design of a study to follow the development of boys and girls in secondary schools from the age of 12 through 17 on an annual basis, in order to acquire more information concerning the growth and development of teenagers. In this study, both physical and psychological characteristics are measured. Normal daily diets, usual physical activity, and attitudes towards physical education are measured to assess their influence on physical and psychological characteristics. In view of the inadequacies of pure-longitudinal and of cross-sectional designs, a multiple longitudinal design has been chosen in which four repeated measurements are made in two overlapping cohorts by which age-, time of measurement-, and cohort-effects can be distinguished. Test effects are isolated by comparing the data from the test cohorts with data from an independent sample of identical cohorts from a second "control" school.

Adolescent↗
PubMed1977

Validity and reliability of pedometers in habitual activity research.

In 12--18 year old boys actual steprate on a treadmill was compared to the scores of two types of mechanical pedometers (Russian and German), attached to the waist. Both types show deviations from actual steprate in running at speeds of 8 and 10 km - h-1 of ca. 5% (+/- 9%). In walking or running at 6 km - h-1 and in running at 14 km - h-1 both types give an overestimation of ca. 8.5% (+/- 8%). In walking at a speed of 2 and 4 km - h-1 the scores are not reliable because of the big standard deviation of ca. 34%. Oxygen uptake (ml - kg-1) and heart rate (beats - min-1) increase more in running than in walking, actual steprate (steps - min-1) however increases less in running compared to walking. If pedometers register only during running they reflect actual steprate fairly good and give a good estimation of the change in oxygen uptake as speed gathers.

Adolescent↗
PubMed1975

Biological age and habitual physical activity in relation to physical fitness in 12- and 13-year-old schoolboys.

PURPOSE: The purpose of this study was to investigate the relationship between biological age, habitual physical activity and anthropometrical and physiological characteristics in 12- and 13-year-old schoolboys (n = 70). METHODS: At the beginning and the end of the school year 1971/2 biological age was determined by measuring skeletal age from left hand X-ray photographs. Habitual physical activity was determined by questionnaire interview and pedometers. RESULTS: All anthropometrical characteristics showed significant correlations (P less than 0.05) with skeletal age except for bicipital and tricipital skinfolds. Out of 9 physical fitness tests handgrip was the only test that showed a significant correlation (0.52) with skeletal age. Pedometer scores gave significant negative correlations (P less than 0.05) with anthropometrical characteristics except for tricipital skinfold. The fitness tests bent arm hang, 12 min run walk, sit and reach and W-170 showed significant correlations (P less than 0.05) with pedometer scores.

Activities of Daily Living↗