Die effek van inoefening op enkele koronêre risikofaktore en hulle onderlinge verwantskap by Suid-Afrikaanse bestuurslui

Abstract

Research has indicated that coronary risk factors are interrelated in a complex manner. The purpose of this study was firstly, to determine if physical activity can influence the atherogenity of the individual risk factors by changing the relationship that exists between the coronary risk factors, and secondly to determine if this interrelationship between the risk factors had any effect on physical activity's relationship with the individual risk factors. Executives (N = 325) of 20 different companies were evaluated with regard to participation in physical activity, smoking habits, lifestyle as well as some morphological and biochemical parameters. The biochemical analysis included measures of total cholesterol, triglycerides, HDL-cholesterol and glucose. The LDL-cholesterol and TC/HDL-ratio values were calculated. Blood pressure measurements and a physical work capacity170 test on a Monark cycle ergometerwas also done on each of the respondents. The relationship between a total of 17 coronary risk factors was investigated by means of cluster, stepwise multiple regression and two-way analyses of variance. For the purpose of the two-way analyses of variance the respondents were placed into tertiles (low, moderate, high) with regard to participation in physical activity, total cholesterol, LDL-cholesterol, HDLcholesterol, triglycerides, systolic and diastolic blood pressure as well as percentage body fat, age, smoking habits and lifestyle. Intergroup differences were determined with the Newman-Keuls follow-up test and practical significance with the effect size calculation of Cohen. Body weight and the Quetelet-index showed the strongest relationship with each other

in the cluster analysis. Total cholesterol and LDL-cholesterol were strongly related to each other as was HDL-cholesterol and the physical activity index (PAI) and systolic and diastolic blood pressure. In the stepwise multiple regression analyses the other coronary risk factors contributed 4.5%, 36.7%, 11.1 % and 10.3% to the respective variances of a family history of heart disease, the Belloc and Breslow-index, age and smoking. The other coronary risk factors showed better relationships with LDL-cholesterol, TC/HDLratio, HDL-cholesterol and total cholesterol and contributed 95.6%, 87.9%, 81.2% and 95.6% to their respective variances. With regard to the effect of physical activity on these relationships, the stepwise multiple regression analyses indicated that among inactive participants, the other coronary risk factors contributed more to the variances of percentage body fat (60.9% vs 45.1%), the Belloc and Breslow-index (44.0% vs 23.9%) and smoking (21.5% vs 7.9%) than was the case when the same analyses were done on the highly physically active respondents. These results seem to indicate that physical activity may lower the atherogenity of the above mentioned coronary risk factors through the effect it (physical activity) has on their respective relationships with the other coronary risk factors. The results of the two-way analyses of variance that were done support this conclusion. It was found that the effect of physical activity on the relationships between the coronary risk factors was of such nature that it would lower the atherogenity of all the coronary risk factors that were used in this study. It has become clear that the interrelationship and interdependence that exists between the different coronary risk factors has to be taken into consideration when physical activity's relationship with the individual risk factors is studied.