Exercise as it relates to Disease/Short-term exercise-training and aortic systolic pressure augmentation in overweight individuals

This Wikibook article review was on the journal article “Effects of short-term exercise-training on aortic systolic pressure augmentation in overweight and obese individuals” by Millen et al. (2013)

What is the background to this research?
Individuals who’s body mass index (BMI) classifies them as overweight or obese have a higher risk of developing chronic diseases. These diseases include but are not limited to; type II diabetes, hypertension, stroke and cardiovascular disease. The research article focusses on the cardiovascular diseases associated with individual’s whom are overweight or obese, in particular the stiffening of the aorta and subsequent pressure augmentation of the aorta.

The study by Fagard and Cornelissen in 2005, proved that brachial systolic and diastolic blood pressure decreased as a result of exercise in both obese and normal weight individuals However, prior to the study there was no evidence that proved changes in aortic systolic augmentation from short-term exercise.

Therefore, this article aimed to determine whether a six-week aerobic exercise program would reduce aortic systolic augmentation in overweight and obese persons.

Where is the research from?
This study was conducted at the University of Witwatersrand in Johannesburg, South Africa. It involved testing thirty-five sedentary individuals who were classified by BMI as either over weight or obese. Millen, Norton, Avidon, and Woodiwiss, were responsible for the protocol and analysis of results from the study. These authors have proven to be reliable in this field of study, collaborating on the piece ”Effects of short-term exercise training on tissue Doppler indices of left ventricular diastolic function in overweight and obese individuals”.

What kind of research was this?
Participants were recruited for the study through advertisements on the local radio station and in the local newspapers. The participants had to meet the requirements of being between thirty and fifty-seven years of age, with a BMI that falls between 25.0kg/m2 and 29.99kg/m2 for the overweight category and greater than 30.0kg/m2 to be classified as obese. Once the thirty-five individuals were chosen, they were randomly split between two groups, with even percentages of overweight (40%) and obese (60%) people across the two samples. These groups were randomised to reduce bias for certain individuals performing the desired tasks.

What did the research involve?
After the groups were randomly selected, participants were asked to abstain from heavy physical activity twenty-four hours prior to testing as well was fast overnight before hand. The individual’s anthropometry, blood pressure, and pulse waves were taken after 15 minutes of rest between 6:00am and 11:00am on test days. Each participant had to then undergo a maximal exercise test while using a 12-lead ECG to ensure no-one participated in the study that had any ECG abnormalities. One of the two groups then started the six-week control period of no exercise, followed by a six-week aerobic program, with the other group doing the exercise for the first six weeks followed by six weeks of no exercise.

The participants had a choice in the method of completing the equal to or greater than three days a week of exercise across the six weeks. They are as follows;
 * Option one – 60-75% of VO2 peak for fifty minutes including a five minute warm-up and three minute cool down at 50-60% of VO2 peak. This was performed on a stationary bike or treadmill.
 * Option two – thirty-three minutes of interval exercise with five minute warm-up and three minute cool down at 50-60% VO2 peak. The interval involved four by four minutes of exercise at 80-90% VO2 peak alternating with three minutes at 50-60% VO2 peak. Similarly, this option was performed on a stationary bike or treadmill.

Each participant was required to wear a polar heart rate monitor to ensure they did not exceed their maximum heart rate. These strict protocols allow for valid and reliable results to be obtained form the study. However, each participant only received one supervised session per week from a minimum of three available. This does decrease accuracies in the results as participants could be exercising at a lower intensity than required for the study while they are unsupervised. Furthermore, this does create safety issues for the participants as they are undertaking exercise without the supervision of a health professional.

What were the basic results?
The participants saw improvements in their cardiorespiratory fitness across both groups of the study. This can be seen in the increase in relative VO2 peak from 27.0 ± 5.1 to 28.8 ± 5.8 mL/kg/min after 6 weeks of training. The time to VO2 peak increased as well, from 12.55 ± 2.79 to 14.36 ± 2.45. Changes were also noted in brachial systolic blood pressure, diastolic and mean arterial blood pressure, decreasing by 5.6%, 8.5%, and 7.2% respectively.

On the contrary, after the six-week program, no changes could be seen in aortic augmentation pressure, nor aortic and peripheral augmentation index. Moreover, the pulse wave velocity was not altered for either of the two groups.

Pulse wave velocity and aortic augmentation index are considered to be indicators of aortic stiffness, particularly in this specific population. With this being said, the results from the study demonstrate no change in these indices as a result from a short-term exercise regime.

What conclusions can we take from this research?
From the results obtained, it can be seen that the program was adequate to cause changes in the participant’s physiological attributes. Such as; VO2 peak and mean arterial blood pressure. However, the research did not provide evidence of the benefits of short-term exercise on aortic systolic pressure augmentation in the specific population group.

The participants did demonstrate an adherence to the required exercise of 97%, this was however relying heavily on their self-directed exercising and reporting for the majority of the program. Therefore, inaccuracies in the results could have arisen from the lack of supervision present throughout the entirety of the study, thus causing false-negative or false-positive data in this particular research article.

Practical advice
The study by Millen, Norton, Avidon, and Woodiwiss has not provided evidence for changes in aortic systemic augmentation by way of exercising. The implementation of changes such as increasing the population size or the supervision during exercising could potentially cause the desired alterations. Further studies must be conducted that assess the effect of long-term exercise for the chronic disease in this specific population.

On the contrary, this protocol could be implemented as a means of improving one’s cardiorespiratory fitness. The results indicate the advantageous effect of increasing the VO2 peak, whilst simultaneously reducing the brachial systolic and diastolic blood pressure.

Further Readings
Below are links to websites that offer more information on cardiovascular disease and overweight individuals
 * https://www.healthdirect.gov.au/obesity
 * https://www.heartfoundation.org.au/about-us/what-we-do/heart-disease-in-australia/