Exercise as it relates to Disease/Cardiovascular and metabolic adaptations through different training intensities within middle-aged men and the considerations associated with cardiovascular disease

Cardiovascular and metabolic adaptations through different training intensities within middle aged men and the considerations associated with cardiovascular disease.

This is a critique of the research article: Left ventricular vascular and metabolic adaptations to high-intensity interval and moderate intensity continuous training: a randomized trial in healthy middle-aged men.

What is the background to this research?
Cardiovascular disease (CVD) is a collective term that refers to various diseases that have an adverse effect over the heart and blood vessels. These forms of disease are the most prevalent cause of mortality within countries of higher economic standards, while it continuous to grow through developing countries parallel to their economic growth. Due to the diverse number of contributing factors towards diseases of this form it often goes undiagnosed, thus highlighting the importance of providing individuals with sufficient knowledge to conduct safe practices regarding their health. It is hypothesised that individuals with CVD may be at increased risk with higher intensity adaptations to training, emphasising the importance in understanding potential negative reactions surrounding the epidemic.

The current trend associated with high intensity interval training (HIIT) has generated a large pool of studies providing significant amounts of evidence surrounding the various health benefits associated with the style of training however, the resources linked to potential risks for certain individuals is limited. This study examined the myocardial perfusion, metabolism and cardiac functions of healthy, sedentary, middle aged men when conducting either HIIT or moderate intensity continuous training (MICT). Thus, providing a resourceful base for reference when determining probable risk factors or benefits associated with training at high intensities for individuals suffering from CVD.

Where is the research from?
The entirety of the study was conducted regarding the Declaration of Helsinki and was approved by the ethical committee of the Hospital District of South Western Finland. It was directed within the Centre of Excellence in Cardiovascular and Metabolic research and no obvious biases were evident throughout the article, as majority of the authors had past research in exercise related adaptations through the body as well as cardiovascular research. The authors background may have been advantageous for the study as their knowledge may have provided them with an increased understanding of both benefits and risks alike. Interpretation of results may also have been conducted efficiently considering the knowledge depth present.

What kind of research was this?
The interventional study was one of pre-post design. There were two parallel groups that conducted separate training regimes with no crossover. Neither participants nor investigators were blinded regarding group allocation as the action would've been ineffective and had no influence over the final results. Studies of this design have the ability to create ideal opportunities to examine specific changes implemented through the intervention purpose. However, factors such as incidence or prevalence need to be considered as they often reduce the reliability of the studies results.

What did the research involve?
Twenty-eight untrained, non-smoking, middle aged, healthy men conducted a total of six sessions over a two-week study time frame. They were equally divided into two groups and conducted either a HIIT regime consisting of 4-6 repeated Wingate tests with approximately four minutes of rest in between each run or the MICT program where 40–60 minutes cycling was completed at 60% max workload. Developments were made through the number of repeated efforts, starting from 4 and working through to 6 respectively, while the MICT group increased in time from 40 to 50 minutes to additionally 60 minutes after every other session.

The methodology managed was sufficient for the examination at hand. Equal group participants along with the thorough physical pre-screenings ensured that participants were standardised, reducing outside confounding factors, thus emphasising the intervention as the only variable, increasing validity through statistical tests based on probability theory. However, conducting the intervention over a longer timeframe would have benefitted those investigating the adaptations as it would've allowed for more relevant considerations to be observed such as changes through left ventricular mass, which has been shown through other studies as a noteworthy adaptation. Additionally, an inadequate amount of background information was available regarding the relationship between exercise and reduced vascular function and insulin action within the heart.

What were the basic results?
The study found that the adenosine stimulated myocardial perfusion had the most significant difference between intervention groups with the HIIT group having a reduction of 19%, while the MICT had an increase of 9%. This finding was found to be connected to the myocardial glucose uptake, particularly within the HIIT group. Despite this connection to myocardial glucose uptake there was little understanding regarding the reasoning for the reduction in adenosine stimulated myocardial perfusion through the HIIT group, highlighting the requirement of additional future studies examining this component. It was also found that the myocardial vascular hyperaemic reactivity was impaired post HIIT. All other metabolic and functional adaptations of the heart were similar throughout both groups. Additionally, the insulin stimulated myocardial glucose uptake was decreased by training, with no significant differences evident throughout the groups, as well as no changes through free fatty acids.

What conclusions can we take from this research?
The authors conclusion stated that, HIIT training in healthy, previously sedentary men may lead to compromised myocardial vasodilation. The evidence suggested that the reduction in adenosine-stimulated myocardial perfusion was decidedly linked to high intensity training as well as clear impairments through the myocardial vascular hyperaemic reactivity, therefore individuals who were untrained shouldn't par take in exercise of the strenuous form. Thus, supporting the hypothesise regarding cautious exercise prescription for individuals suffering from CVD as the already prevalent conditions within their heart could increase risk or mortality and create dangerous situations for participants. However, a large majority of studies have been published that provide evidence supporting HIIT as a positive form regarding improvements through cardio-metabolic factors. Various studies have found that both HIIT and MICT interventions have had significant reductions in resting blood pressure with participants suffering from hypertension, with HIIT having larger improvements. Arguments may be made concerning what aspects were examined through the studies at hand and whether the lack of focus surrounding the in-depth adaptations to the heart on a muscular level as its this analysis that highlights the high risk associated with training at high intensities with CVD. Nevertheless, it's clear that there are advantageous aspects to HIIT within participants suffering from CVD, and even without minimal evidence for comparison of varying HIIT prescriptive variables for optimal treatments, the overarching rule for the training regime has proven effective.

Considering the large variety of evidence across numerous spectrums its hypothesised that there is not concrete answer regarding whether or not HIIT with individuals suffering from CVD is worthwhile. Rather than establishing a clear decision regarding the prescription of the training intensity, personalised considerations regarding whether or not the benefits outweigh the risks for specific individuals would be most effective. Individual assessments regarding previous aerobic fitness and current health standpoints will provide professionals with an efficient amount of information to conduct the most educated prescription of either HIIT or trainings at lower intensities levels for those suffering from CVD.

Practical advice
The conclusions state that previously sedentary males should not participate in strenuous HIIT. There is a brief mention that perhaps a slow integration of the training style would be beneficial, however the recommendations are no HIIT sessions throughout the early stages of a program. Additional resources suggest that conducting a baseline stress test, from which personalised training sessions may be calculated regarding intensities based off the heart rate maximum calculations, reduce the risks associated. It is advised that individuals suffering from CVD of any severity seek medical clearance prior to executing any training at high intensities. Once cleared, a slow progressive introduction to the training regime will allow the body to adapt efficiently, while experiencing all the health benefits associated with HIIT.

Further information/resources
For further information regarding exercise and cardiovascular health, please click the links below:

Heart Disease in Australia

Physical Activity for People With Cardiovascular Disease: Recommendations of the National Heart Foundation of Australia

High-Intensity Interval Training for Patients With Cardiovascular Disease - Is It Safe?