Effect of Bmi and Level of Physical Activity on Blood Pressure and Heart Rate

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ABSTRACT

Heart Rate and Blood Pressure are influences by several factors, ranging from gender, body composition, diet to physical. Such factors cause fluctuations in blood pressure and heart rate, dependent upon their overall effect on the functioning of the cardiovascular system. The following study was conducted in order to examine the effects of numerous external factors, in particular Body Mass Index (BMI) and level of exercise per week, on the cardiovascular system. specifically body mass index and the level of physical activity. Blood pressure and heart rate measurements were obtained using Omron monitors. The subjects (PHY2042 students) measured weight, height, gender, diet and level of exercise. The data was then collated and analysed through regression analysis and analysis of covariance. These two statistical methods help to identify and analyse the relationship between the variables and arterial pressure and heart rate

INTRODUCTION

Blood pressure is the force exerted by the blood flow against an area of the blood vessel wall. It is the arterial pressure in systemic circulation. High blood pressure, also known as hypertension is defined as having a consistent systolic arterial pressure greater than or equal to 140 mmHg and/or a diastolic arterial pressure greater than or equal to 90 mmHg. An individual receiving medication for high blood pressure is also defined as having hypertension. Hypertension is considered to be one of the leading causes of cardiovascular diseases. Predisposition to diseases such as coronary heart disease, heart failure, stroke, peripheral vascular disease and renal failure is directly impacted with the increase in blood pressure. The risk of disease increases as the level of blood pressure increases. Hypertension places an excess workload on the heart and blood vessels, which in turn leads to negative consequences on the body. The importance in addressing hypertension is due to the risks it poses on physiological function. Arterial pressure and heart rate vary significantly depending on the environment, activity, disease state and distinct genetic factors of individuals. Genetic factors such as gender have shown to influence the level of blood pressure observed in each respective gender. Recent studies state that there is a greater incidence of hypertension in males than in females at similar ages (Reckelhoff 2001).

However the period of development in males and females plays a crucial role in influencing the level of blood pressure (Reckelhoff 2001). This further suggests that age also plays a factor in the changes of arterial pressure and therefore heart rate.  Although in respect to this study, almost all subjects are of a similar age, therefore its effect is unlikely to be apparent. Gender related differences in body composition (weight, height and fat distribution) also contribute to the varying blood pressure levels and heart rate. As stated previously, physical activity will also influence the level of blood pressure and heart rate. Strenuous physical activity can cause an elevation in blood pressure as well as heart rate, where sleeping will cause both to decrease. Here, blood pressure and heart rate vary in order to adapt to the environment the body has been subjected to, resulting in varied levels of blood pressure and heart rate. These factors influence blood pressure levels and heart rate; the direct relationship between them is unclear. Therefore, this study was undertaken to investigate the numerous factors that influence blood pressure and heart rate, more specifically body mass index and its effects on heart rate and blood pressure. It is expected that blood pressure and heart rate will fluctuate significantly in as a result of an individuals BMI. This is because of the level of physical activity undertaken by the individual in question.

METHODS:

The practical involved a total of 598 PHY2042 students, male and female, aged between 18 and 22 years of age. Students were asked to take the role of both the subject and the collector of data. During the practical blood pressure, heart rate, height, weight, diet, level of physical activity and gender were all measured and recorded. Students measured resting heart rate and blood pressure using Omron monitors. Subjects were asked to remain in a relaxed, seated position for 15 minutes prior to their initial blood pressure reading.  Every three minutes thereafter, consecutive readings were taken until concordant results that differ by ≥10mmHg systolic or ≥6mmHg diastolic are obtained. Measurements of weight, height, level of physical activity and gender were measured separately by the subjects and then recorded for the purpose of statistical analysis. A more detailed explanation of the methods used may be found in the PHY2042 Body Systems Lab Manual. The collated data was tabulated for the purpose of analysis and comparison of the variables influencing heart rate and blood pressure. Furthermore, the data was extrapolated into regression analysis to again, examine the relationship between several variables on an individuals blood pressure and heart rate. For example, Figure 4 (please see results section) analysed the influence of body mass on arterial pressure and heart rate. In contrast Figure 6 (Please see results section), takes a holistic approach to the analysis of factors affecting heart rate and blood pressure. This regression analysis identifies the relationship between body mass index and arterial pressure and heart rate according to the level of physical activity undertaken by the individuals. In particular, the regression plots utilised lines of best fit (ordinary least squared and ordinary least products) to highlight errors and variations between the variables necessary to examine the data. Analysis of covariance aims to alanyse the influence of the various categorical variables on the relationship between their effect on heart rate and blood pressure.

RESULTS

Table 1: Characteristics of the sample: categorical variables

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Data was compiled from a total of 598 individuals enrolled in PHY2042. This table provides an overview of the participants involved in the practical investigation, including diet, gender and level of physical activity per week.