Healthcare practitioners, whom perform accurate sub-maximal exercise tests in healthy individuals, need to understand the physiological demands and normal cardiovascular (CV) responses with exercise. Exercise testing delivers valid information about the physiological systems of individuals that may identify healthy individuals at risk of developing future cardiovascular disease (CVD). Exercise is a common way to assess physiological stress experienced by an individual, because CV abnormalities that are not present at rest, can be elicited during exercise testing and be used to determine the adequacy of cardiac function. Cardiovascular markers like, resting heart rate (HR) and systolic blood pressure (SBP) have been used as simple non-invasive and useful biomarkers of the fundamental status of blood circulation and the CV system in healthy individuals. Studies have contributed to exercise under sub-maximal and maximal stress testing. Modern- day literature lacks information on the safe HR and SBP responses to an increase in workload during a sub-maximal exercise protocol in healthy individuals. Consequently, the first purpose of this study was to identify the current evidence in the literature on CV response during a sub-maximal incremental exercise protocol. Different protocols and modalities contribute to various CV responses over a wide age group and gender. Heart rate and SBP increases in a linear fashion with an increase in workload, irrespective of protocol and modality. The amount of this increase, or the response of these markers, is still a grey area in the literature, especially in healthy individuals. The second purpose of this study was to analyse the HR and SBP response in healthy adults during a sub-maximal incremental exercise test, with an increase in workload (watt). The systematic review found mean changes from baseline for HR and SBP to be 75.7% and 63.5% respectively, on bicycle protocols (N = 3). The treadmill protocols (N = 2) found similar mean changes from baseline of 113.3% for HR and 36.1% for SBP. Descriptive measures as well as Linear regression analyses were performed, using Generalised estimated equations (GEE). An independent t-test was used to compare the males with the female participants: HR and SBP response to an increase in workload (watt). GEE adjustments were made for age, body mass index (BMI) and workload (watt). Significant difference levels were set at p ≤ 0.05. The present once-off subject availability results revealed that male subjects were heavier and taller than their female counterparts (p ≤ 0.05). They also had a noteworthy higher SBPrest, as well as BMI (p ≤ 0.05). The results from the GEE analyses we presented prediction equation, with all variables significant, except for the BMI (p = 0.972 females; p = 0.169 males). In conclusion, the literature review indicated a lack of information on the HR and SBP response with workload in healthy adults. It is advised that further research is needed to test the prediction equations in healthy individuals to determine the validity and reliability. They need to be tested in a controlled clinical environment, where the participants are monitored more thoroughly. By putting these predicted equations to the test, healthcare practitioners will be able to identify an exaggerated HR and SBP response with an increase in workload. If the individual’s response is exaggerated, the healthcare practitioner can intervene to prevent future cardiovascular events. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013

Healthcare practitioners, whom perform accurate sub-maximal exercise tests in healthy individuals, need to understand the physiological demands and normal cardiovascular (CV) responses with exercise. Exercise testing delivers valid information about the physiological systems of individuals that may identify healthy individuals at risk of developing future cardiovascular disease (CVD). Exercise is a common way to assess physiological stress experienced by an individual, because CV abnormalities that are not present at rest, can be elicited during exercise testing and be used to determine the adequacy of cardiac function. Cardiovascular markers like, resting heart rate (HR) and systolic blood pressure (SBP) have been used as simple non-invasive and useful biomarkers of the fundamental status of blood circulation and the CV system in healthy individuals. Studies have contributed to exercise under sub-maximal and maximal stress testing. Modern- day literature lacks information on the safe HR and SBP responses to an increase in workload during a sub-maximal exercise protocol in healthy individuals. Consequently, the first purpose of this study was to identify the current evidence in the literature on CV response during a sub-maximal incremental exercise protocol. Different protocols and modalities contribute to various CV responses over a wide age group and gender. Heart rate and SBP increases in a linear fashion with an increase in workload, irrespective of protocol and modality. The amount of this increase, or the response of these markers, is still a grey area in the literature, especially in healthy individuals. The second purpose of this study was to analyse the HR and SBP response in healthy adults during a sub-maximal incremental exercise test, with an increase in workload (watt). The systematic review found mean changes from baseline for HR and SBP to be 75.7% and 63.5% respectively, on bicycle protocols (N = 3). The treadmill protocols (N = 2) found similar mean changes from baseline of 113.3% for HR and 36.1% for SBP. Descriptive measures as well as Linear regression analyses were performed, using Generalised estimated equations (GEE). An independent t-test was used to compare the males with the female participants: HR and SBP response to an increase in workload (watt). GEE adjustments were made for age, body mass index (BMI) and workload (watt). Significant difference levels were set at p ≤ 0.05. The present once-off subject availability results revealed that male subjects were heavier and taller than their female counterparts (p ≤ 0.05). They also had a noteworthy higher SBPrest, as well as BMI (p ≤ 0.05). The results from the GEE analyses we presented prediction equation, with all variables significant, except for the BMI (p = 0.972 females; p = 0.169 males). In conclusion, the literature review indicated a lack of information on the HR and SBP response with workload in healthy adults. It is advised that further research is needed to test the prediction equations in healthy individuals to determine the validity and reliability. They need to be tested in a controlled clinical environment, where the participants are monitored more thoroughly. By putting these predicted equations to the test, healthcare practitioners will be able to identify an exaggerated HR and SBP response with an increase in workload. If the individual’s response is exaggerated, the healthcare practitioner can intervene to prevent future cardiovascular events. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013

Motivation: Recently, with urbanisation becoming an increasing trend, the African population have been introduced to the westernised lifestyle. This contributed to severe health implications and a rapid increase in cardiovascular morbidity and mortality in the African population. In South Africa and other sub–Saharan African countries, the prevalence of cardiovascular disease is increasing rapidly. The African population is thus regarded as a high risk group, and we deem it necessary and important to investigate additional possible cardiovascular risk markers in the attempt to improve the diagnosis of cardiovascular diseases and the treatment thereof. We investigate double product as a possible cardiovascular risk marker in African and Caucasian men from South Africa. Recent studies have suggested that increased double product values might be an independent predictor of cardiovascular morbidity and mortality. However, investigations on double product and endorgan damage are limited in this population group. The strength of associations between double product and various measurements of end–organ damage, including intima–media thickness, left ventricular hypertrophy and albumin–to–creatinine ratio, are compared with the associations between the more traditional risk factor, systolic blood pressure, and the measurements of end–organ damage. Aim: The aim of this study is to investigate the usability of double product as a possible cardiovascular risk marker in African and Caucasian men from South Africa. Methodology: The manuscript presented in Chapter 3 made use of the cross–sectional SABPA (Sympathetic Activity and Ambulatory Blood Pressure in Africans) study, where 101 urbanised African and 101 Caucasian male school teachers from the North West Province of South Africa were recruited. Anthropometric measurements were taken in triplicate using standard methods. The cardiovascular measurements included 24–hour ambulatory blood pressure and electrocardiogram measurements. Double products were calculated as the product of 24–hour, daytime and night–time mean systolic blood pressure and mean heart rate values. The carotid intima–media thickness was also obtained following the prescribed protocols. A registered nurse collected blood samples and the biochemical measurements were performed by independent laboratories, blinded to the subject’s cardiovascular profile. Means and proportions were compared by standard t–tests and the x2 –tests, respectively. The association between markers of end–organ damage and double product were investigated using single, partial and multiple regression analyses. All p–values <= 0.05 were deemed significant. Results and conclusions: Results from this study showed that Africans displayed significantly higher systolic blood pressure values, heart rate values and subsequent double product values compared to the Caucasians. Despite these significant differences, double product only showed borderline significant correlations with the markers of end–organ damage in African men, while no correlations were evident in Caucasian men. In African men, systolic blood pressure displayed stronger and significant correlations with intimamedia thickness, left ventricular hypertrophy, and albumin–to–creatinine ratio than double product. These findings suggest that double product may not be a good marker of increased risk for end–organ damage and subsequent cardiovascular–related mortality. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2011.

Motivation: Recently, with urbanisation becoming an increasing trend, the African population have been introduced to the westernised lifestyle. This contributed to severe health implications and a rapid increase in cardiovascular morbidity and mortality in the African population. In South Africa and other sub–Saharan African countries, the prevalence of cardiovascular disease is increasing rapidly. The African population is thus regarded as a high risk group, and we deem it necessary and important to investigate additional possible cardiovascular risk markers in the attempt to improve the diagnosis of cardiovascular diseases and the treatment thereof. We investigate double product as a possible cardiovascular risk marker in African and Caucasian men from South Africa. Recent studies have suggested that increased double product values might be an independent predictor of cardiovascular morbidity and mortality. However, investigations on double product and endorgan damage are limited in this population group. The strength of associations between double product and various measurements of end–organ damage, including intima–media thickness, left ventricular hypertrophy and albumin–to–creatinine ratio, are compared with the associations between the more traditional risk factor, systolic blood pressure, and the measurements of end–organ damage. Aim: The aim of this study is to investigate the usability of double product as a possible cardiovascular risk marker in African and Caucasian men from South Africa. Methodology: The manuscript presented in Chapter 3 made use of the cross–sectional SABPA (Sympathetic Activity and Ambulatory Blood Pressure in Africans) study, where 101 urbanised African and 101 Caucasian male school teachers from the North West Province of South Africa were recruited. Anthropometric measurements were taken in triplicate using standard methods. The cardiovascular measurements included 24–hour ambulatory blood pressure and electrocardiogram measurements. Double products were calculated as the product of 24–hour, daytime and night–time mean systolic blood pressure and mean heart rate values. The carotid intima–media thickness was also obtained following the prescribed protocols. A registered nurse collected blood samples and the biochemical measurements were performed by independent laboratories, blinded to the subject’s cardiovascular profile. Means and proportions were compared by standard t–tests and the x2 –tests, respectively. The association between markers of end–organ damage and double product were investigated using single, partial and multiple regression analyses. All p–values <= 0.05 were deemed significant. Results and conclusions: Results from this study showed that Africans displayed significantly higher systolic blood pressure values, heart rate values and subsequent double product values compared to the Caucasians. Despite these significant differences, double product only showed borderline significant correlations with the markers of end–organ damage in African men, while no correlations were evident in Caucasian men. In African men, systolic blood pressure displayed stronger and significant correlations with intimamedia thickness, left ventricular hypertrophy, and albumin–to–creatinine ratio than double product. These findings suggest that double product may not be a good marker of increased risk for end–organ damage and subsequent cardiovascular–related mortality. / Thesis (M.Sc. (Physiology))--North-West University, Potchefstroom Campus, 2011.