Exercise as it relates to Disease/Which type of exercise modality best enhances quality of life and return to health in patients post myocardial infarction?

This is a critique of the article titled “Effectiveness of resistance interval training versus aerobic interval training on peak oxygen uptake in patients with myocardial infarction” by Zara Khalid, Hania Farheen, Muhammad Iqbal Tariq, Imran Amjad published in 2019 by the Journal of the Pakistan Medical Association.

What is the background to this research?
Myocardial infarction (MI), or in layman’s terms a heart attack, is an acute form of ischaemic heart disease (IHD) characterised by ischemia of the cardiac muscle, secondary to a decrease in blood flow to different regions of the heart. This directly results in the death of cardiomyocytes due to the supply of oxygen not meeting the demand of the tissue, and subsequent cardiac dysfunction; a dire health outcome. IHD was the leading cause of global mortality, accounting for 1.4 million deaths in the developed world and 5.7 million deaths in developing regions. Through addressing IHD and MI specifically, health professionals are able to reduce morbidity and mortality related to these diseases. Multiple studies have shown long term morbidity and mortality can be significantly reduced through lifestyle alteration and risk factor reduction. A large portion of these approaches involves increasing exercise levels, henceforth increasing the oxygen delivery to the cardiac muscle. In ensuring oxygen delivery is adequate post-MI through increasing exercise levels and tolerance, health professionals hope to prevent further ischemic events and improve baseline health post MI.

The article under review scrutinises the effectiveness of resistance interval training versus aerobic interval training on peak VO2 in patients with MI. In this way, the article analyses how exercise can help an individual improve their health and quality of life post-MI and which form of exercise is best at achieving these goals. Exercises for endurance significantly increases the aerobic capacity, whereas resistance training increases the muscle strength and endurance. This study aims to analyse how these different modes of exercise contribute overall to return to health post MI, informing all health professionals and patients alike on how quality of life (QOL) and functional capacity can be improved and further deterioration in health associated with potential future ischaemic events can be avoided.

Where is the research from?
Khalid, Farheen, Tariq and Amjad conducted their research in Pakistan and had their article published by the Journal of the Pakistan Medical Association which is a leading, monthly, biomedical journal of Pakistan.

Khalid, Farheen, Tariq and Amjad have all collaborated and published multiple creditable health studies, the majority involving physical activity/exercise and cardiovascular health.

There does appear to be a conflict of interest as the individual signing ethical review statement on behalf of the Institutional Review Board is also a co-author of the manuscript.

What kind of research was this?
The research in question was a randomised controlled trial (RCT) conducted over five months, with very strict inclusion criteria. This was the most appropriate form of methodology as RCT are considered the most stringent way of determining whether a cause-effect relation exists between the intervention and the outcome.

What did the research involve?
The research for this study was carried out at Railway General Hospital Rawalpindi and involved observing 26 stable patients with MI from August 2016 to January 2017. Inclusion and exclusion criteria included:


 * Haemodynamically stable patients
 * both males and females
 * age >35 years
 * able to complete the first three minutes of the exercise tolerance test without any aggravated signs or symptoms
 * no sign of poor left ventricular ejection fraction, i.e. <35%
 * no presence of any arrhythmias or significant lung disease

The protocol involved randomising the subjects into interventional (n=13) and control groups (n=13) using toss and trial method HERE. Baseline data of variables was collected. This included anthropometric measurements, primary outcomes, i.e. six-minute-walk test (6MWT) and peak oxygen uptake (VO2), as well as the secondary outcome of Quality of life (QOL). A generic standard health related quality of life tool, SF- 36, was used to determine the pre and post cardiac rehab differences in QOL parameters.

The control group was exposed to aerobic interval training (AIT), consisting of intervals of aerobic exercises on stationary cycle and treadmill, alternated with rest intervals. In contrast, the interventional group was exposed to resistance interval training on lower and upper body in addition to AIT. The total duration of the exercise regimen was 35-40 minutes. Intensity and resistance was gradually increased to accommodate the exercise load. This supervised training protocol was followed three times a week on alternate days for six weeks.

It is unclear whether or not this methodology was the best approach. Furthermore, there are some limitations to this study. Firstly, the study was conducted at a single-centre. In addition, study was a small scale study with a comparatively small sample size due to the rigorous inclusion criteria and lack of awareness about cardiac rehabilitation in their societal context the study took place in. There were also less females due to societal views surrounding women and gender roles. The trial was also not registered due to not having a registry and a focal person available during the time the study was being conducted.

What were the basic results?
The study found the following key results:


 * Baseline characteristics of subjects in both groups showed no differences with regards to age, BMI, physical activity level and co-morbidities
 * Baseline analysis of peak VO2 and 6MWT distance showed no significant difference between interventional and control group (p >0.05)
 * Post 6 weeks of cardiac rehab intervention, a significant improvement was observed statistically in the experimental group (p = 0.001)
 * QOL seemed to increase substantially, as there was a significant increase in post-exercise mean in energy/fatigue, emotional well-being and social functioning

What conclusions can we take from this research?
In conclusion, the results of this study suggest that resistance interval training is more effective than AIT for the improvement of peak VO2in cardiac patients However, most of research also says that any form of aerobic training is beneficial compared to no aerobic training at all and that mortality due to IHD can be prevented by physical activity and fitness. Further, the study concluded that a combination of resistance interval workout and AIT is superior as it significantly increases the peak VO2, aerobic capacity and QOL in patients with MI. Improvement in QOL was also noted to be associated with the physiological improvements

Peak VO2 has lately gained significance as a crucial independent predictor of cardiac morbidity and mortality. Hence exercise training induces gains in aerobic capacity and a marked increase in the chances of survival as well. Adding resistance interval training for strength in debilitated MI aids in a functionally independent lifestyle. Therefore, we suggest that although both aerobic interval training and resistance interval training are effective for the improvement of cardiac outcomes alone, the combination of resistance interval workout and AIT is superior as it significantly increases the peak VO2, aerobic capacity and QOL in patients with MI.

Practical advice
Research suggests that we need to encourage health professionals to inform people of the benefits of exercise and its ability to help improve health overall and ultimately prevent further ischemic events post-MI. It is important to remember that while a combination of AIT and RIT is beneficial for improving overall health and QOL post MI, it is imperative that a few measures are followed before and during this intervention:


 * Exercise must only be prescribed after signing informed consent and completing an ESSA adult pre-exercise screening
 * Supervised by a qualified professional
 * progress should be monitored to ensure improvement

Further information/resources
If you are interested in further information please see the links below:


 * Exercise & Activity After a Heart Attack
 * Physical activity after a heart attack: Heart Foundation
 * The risks and benefits of exercise after a myocardial infarction