Die fisieke werkvermoë van inwoners in twee Transvaalse stedelike gemeenskappe

Abstract

It is extremely difficult to ascertain directly the role of physical activity/physical fitness in the prevention of coronary artery disease. Cardiorespiratory exercise or physical activity that complies to specific requirements, facilitates positive changes in the coronary artery disease risk profile, apparently reducing the overall risk for coronary heart disease and coronary heart disease deaths. In this respect, physical, inactivity or low physical working capacity is regarded as a primary risk factor for coronary heart disease. Some of the numerous studies on this subject had shown that coronary artery disease is less frequent among physically active or physically fit individuals, than among physically inactive or physically unfit individuals. In this respect, good evidence exists to indicate that an increase in physical activity helps ' extend life and its desirable qualities into old age and that people with a high exercise index have half as much risk for coronary artery disease as their comparable colleagues with a low index. The incidence of coronary artery disease and coronary artery disease deaths attracted extensive interest, because it is brought directly in relation with health-care expenditures. The tendencies along which certain ageing and/or growth patterns in a population group develop, is necessary information for the planning of timely intervention programmes and/or precautionary measures. Few studies concerning physical working capacity profiles of white South African population groups according to different age groups, exist. The aim of this study was to determine the physical working capacity of the residents of two Transvaal city communities, namely Vanderbijlpark and Witbank. Some other selected physical parameters namely body stature, body mass and the Quetelet ratio were, due to their inter-dependence to physical working capacity, included as part of this particular study. To achieve above mentioned objective, part of the data obtained during a survey at Vanderbijlpark and Witbank was analysed. Data was obtained from a systematically stratified randomized sample of white male and white female residents of the two cities between the ages of 10 and 64 years. The aim was to get approximately 1500 residents of each city involved in the project. The age groups in this study were divided as follows: 10-14; 15-19; 20-24; 25-29; 30-34; 35-39; 40-44; 45 49; 50-54 and 55-64 years. Before partaking in any form of physical activity a comprehensive medical/physical history questionnaire and informed consent was completed and signed. The sequence of the physical activity part was as follows: measurement of stature, body mass, completion of combined medical/physical activity questionnaire and informed consent and the determination of the physical working capacity. The measurements were done in the following manner: Measurement of stature. An anthropometer which is mounted to a Detecto-scale was used to determine the stature to the nearest centimeter. The subjects were barefoot. The head, back and gluteus touch the anthropometer, while the subject stretches up maximally. The hair along the vertex was pushed aside so that the lower branch of the anthropometer was in firm contact with the scalp. The direction of vision was horizontal. Measurement of body mass. All the subjects, wearing only light summer clothes, were weighed on a Detecto-scale. Body mass was registered to the nearest 0, 1 kilogram. Quetelet ratio. The Quetelet ratio (M/H2) which bears a close relationship to the percentage body fat (Kemper, 1986:71) and which is preferred by epidemiologists (Shephard, 1986b:31) was used in this study. Determination of physical working capacity. A multistage submaximal physical working capacity test up to 70%-85% of the age-predicted maximal heart rate of the subject, according to the protocol of Sinning (1875:65-70) and Watson (1983: 156-157) was executed. All subjects except those with contra-indications like acute miocardial infarction, unstable angina pectoris and acute infection (ACSM, 1986: 13-14) underwent a physical working capacity test. Pregnant women, subjects with amputations of the lower extremities and/or using certain types of medication like beta blockers were also excluded from the physical working capacity test. A Monark cycle ergometer (model 864) was used for the determination of the physical working capacity. The following results were found: 3.1 The smallest difference (0,31 cm) in average stature between boys and girls was found to occur in the 10-14 year old age group. 3.2 The average maximum stature of 177,63 cm was found in men between 20-24 years. They were 2,84 cm taller than the average stature of men in the 55-64 year old category. The average maximum stature in women of 164,57 cm was found in the 30-34 year old age group. They were 2,42 cm taller than women inmthe 50-54myear old age group . 3.3 The biggest average Quetelet ratio in both sexes (27, 11) 6r highest percentage 1 increase (50, 1 % 6r 48,2 % ) respectively in the men and women, compared to the 10-14 year old boys and girls, were respectively found in the age groups 50-54 year old men and 55-64 year old women. 3.4 A Quetelet ratio of bigger than 25, which is considered as a health risk, was present in men and women respectively from the age of 25-29 years and 40-44 years. 3.5 The relation between relatively big increases in body mass (16,3 kg) and Quetelet ratio (3,37) with the small increase in stature in the age group, 15-19 year old girls probably indicate a big increase in fat mass, which has a detrimental effect on an increase in PWC after 15 years of age in women. Fat deposits at the breasts and the hips probably account for part of this decrease. 3.6 It seems that the growth spurt has a favourable effect on the peak average PWC170.kg-l of the 15-19 year old boys (2,27 watt.kg-1) and the 10-14 year old girls (1,89 watt.kg-1). 3.7 It seems that after the above mentioned peak values, the average PWC170.kg-l basically follows, , a straight line with all the consecutive age groups except the 55-64 year old men and the 50-55 year old women. 3.8 The average PWC170.kg-l of adult men partaking in the VIGHOR project, namely 1,95 watt.kg-1, compares unfavourably to values of 3,0 watt.kg-1 and 2,5 watt.kg-1 respectively indicated by Mellerowicz & Smodlaka (1981 :398), as well as Jones & Campbell to be the average index of men (1982:250). 3.9 The average PWC170.kg-l of the adult women partaking in the VIGHOR project, namely 1,63 watt.kg-1, compares unfavourably with the average value of 2,5 watt.kg-1 as proposed by Mellerowicz & Smodlaka (1981:398). 3.10 A gradual decrease (0, 75 %-1 % per year from approximately 30 years) in the functioning of several organs and physiological functions of the body, as well as the age related decrease in maximal heart rate, vital capacity, muscle strength and nervous system functioning, probably contributes to the equable decrease (6,8%-55% as well as 19%-49,6%) in the PWC max.kg-1 with increasing age in men and women respectively. 3.11 International comparisons of fitness patterns specifically PWC170.kg-l are hampered by the absence of true random samples. 3.12 One of the main advantages of this particular community study was the accessibility of data for the constructing of percentile norms which permit comparison of any individual's scores with the norms.