Exercise as it relates to Disease/Exercise and its effects on cardiovascular disease

Ho SS, Dhaliwal SS, Hills AP, Pal S. The effect of 12 weeks of aerobic, resistance or combination exercise training on cardiovascular risk factors in the overweight and obese in a randomized trial. BMC public health. 2012 Dec;12(1):1-0.

What is the background of this research?

Cardiovascular disease (CVD) is one of the leading causes of illness and death in the world, accounting for 31% of mortality. As alarming as these numbers are, the World Health Organisation has estimated that over 75% of premature CVD can be stopped. Hypertension, diabetes, obesity, smoking are known factors to increase the risk of CVD. Studies in the past have shown links to exercise and a reduction in CVD risk factors. Finding ways to reduce the damage of this disease will have a real-world impact, helping to save lives and improve the quality of many lives too. This study aimed to compare health benefits associated with aerobic, resistance, or combination training as it related to CVD. The study conducted a 12-week training program in which participants would be placed into three groups (aerobic, resistance, combination of the two). The aim is to see how different exercise interventions would impact the health and weight of the participants.

Where is the research from?

This research was registered with the Australian New Zealand Clinical Trials Registry. Three of the four authors were from the Curtin University of Technology in Perth, Western Australia. The other author was from Griffith University in Brisbane, Queensland. Part of the research was funded by the Curtin DRG grant and ATN centre for Metabolic Fitness. Suleen Ho coordinated the trial and data collection, Andrew Hills assisted in writing the manuscript, Satvinder Dhaliwal focused on all statistics and analysing them and Sebely Pal designed and supervised the study.

What kind of research was this?

The research was a randomised parallel study, this means all subjects were placed in one of the four groups at random. It is a parallel design as there are more than two intervention groups, with there being three groups and a control group. This is also a form of primary research as the data collected for the study is from the authors themselves, although in their full report they reference several sources to support their research. It is quantitative research as the authors focus on statistical analysis from the data extracted rather than conducting surveys of their participants.

What did the research involve?

The research involved a 12-week training plan with 64 participants, the participants were randomly placed into one of the four groups. Group 1 was the control group (n = 16); Group 2 was the aerobic training group (n = 15); Group 3 was the resistance training group (n = 16); Group 4 was the combination group (n = 17). All participants were classified as overweight or obese individuals, the aim was to see how different forms of moderate-intensity exercise would impact their overall cardiovascular risk profile and weight.

What were the basic results?

There were large improvements in the combination group when compared to the control and resistance training groups. The aerobic training group also saw improvements but not to the extent of the combination group where the most significant change is seen in all areas. Cardio-respiratory fitness and fat loss were most prevalent in the combination group and to a lesser degree, the aerobic, minimal changes were seen in the resistance training group.

What conclusions can we take from this research?

A combination of resistance training and aerobic training provides the greatest health benefits in general, as well as provides greater cardio-respiratory fitness improvements. The authors took a deep dive to extract as much data as possible, this study can be taken seriously by the reader as the research is extensive. This was not just a basic look at weight change over 12 weeks, this was a deep dive into all physiological changes occurring in the body. Anthropometric measurements were taken in the form of DXA scans, BMI calculations, and several circumference measurements. Enzymatic colorimetric kits were used to measure serum triglyceride and total cholesterol. Plasma glucose and plasma insulin were also measured. A cardio-respiratory fitness test was conducted at baseline and again at 12-weeks to add another parameter to analyse. The authors took into account that the participants were mostly sedentary and unhealthy and conducted this fitness test on an Astrand-Rhyming Submaximal Cycle Ergometer. Would have been interesting to look at some surveys taken from baseline and at the end of the experiment, measuring overall mood change or some other form of qualitative data could provide a deeper insight.

Practical advice

The authors mentioned in the study design that all participants were asked to keep their food intake the same during the study, each participant had a food diary in which they were to write down exactly what they ate each day. One problem, the table of data showing the energy intake average of each group changed significantly from baseline, 8 weeks, and again at 12 weeks. Energy intake for the control group was initially much lower than the intervention groups, this could skew the data, if dietary intake were consistent across all participants the results may have varied. Studies have shown a link between particular food groups and an increased CVD risk. Highly refined carbohydrates and sugar-sweetened beverages have both been linked to increased CVD and type 2 diabetes risk. This would not be an easy study to organise however, relying on generally unhealthy individuals to adhere to a meal plan or prescribed macronutrients for months at a time would be difficult. The other variable would be ensuring everyone is at the right energy intake in regards to their size, people at the low end of the weight range should not be consuming as much as those on the high end, they would lose less weight and skew the data. By increasing the calories of each individual as their output rises, preventing weight loss, it would be possible to narrow down the true effect exercise has on CVD. If weight loss was the main factor in improving CVD risk factors then health professionals could focus more on the diet side rather than the exercise/overall output side.

Further information/resources

One further resource that provides an interesting study design is a randomised control trial that was addressing the effects of exercise during weight loss on bone health in older adults. Considerations could be made that even without exercise interventions, someone with cardiovascular disease (usually being overweight or obese) could improve their cardiovascular risk profile by being in a calorie deficit, leading to weight loss. This study had a stand-alone weight loss group which consisted of participants having their calories reduced to lose 0.3kg per week throughout the study, this group went along with the exercise intervention groups. Although this resource does not relate specifically to exercise and its effects on CVD, it aids as a tool to provide future studies with a research design to extract more valuable data on the topic.