Exercise as it relates to Disease/Effectiveness of high-intensity interval training for the rehabilitation of patients with coronary artery disease

This is a critique of a journal article 'Effectiveness of High-Intensity interval training for the rehabilitation of patients with coronary artery disease' Darren E.R Warburton, Donald C. McKenzie, Mark J. Haykowski, et al.

What is the background to this research?
Coronary artery disease (CAD) can be described as the narrowing or blockage of the coronary arteries (blood vessels that carry blood and oxygen to the heart). It occurs when plaque builds up, it narrows your coronary arteries, decreasing blood flow to your heart.

Research into the effects of high intensity interval training (HIIT) on individuals rehabilitating from coronary artery disease is imperative. This is a result of the large scale affect CAD has globally as it is one of the leading causes for mortality and morbidity in both men and women. In 2008 it was estimated that 1 in 13 Americans over the age of 18 had CAD. The morbidity and mortality rates of this disease make timely accurate diagnosis and cost-effective management of CAD of the utmost importance. Current studies have shown the positive benefits aerobic fitness and other forms of exercise have on the rehabilitation of CAD patients. Due to this the implication of the HIIT on rehabilitating CAD patients must be investigated and researched in order for adaptations and progressions that could help in treating the disease.

Where is the research from?
The research was supported by the Natural Sciences and Engineering Council of Canada, the Canada Foundation for Innovation, the British Columbia Knowledge Development Fund, and the Michael Smith Foundation for Health Research, Canada. The research was published in the American journal of cardiology a very reputable source for health and sciences. It was published by Elsevier, a information and analytics company that focuses on technology and science. The main author Darren E.R Warburton has an significant publication record in leading peer-reviewed journals. His work includes publications in journals such as the Canadian Medical Association Journal, the American Journal of Physiology, the American Journal of Cardiology, and the Journal of Physiology. One article published by Darren Warburton in the Canadian Medical Association Journal has already been cited more than 2400 times since its publication in 2006. This article is used a required reading for many agencies, medical training programs, and certifications from around the world.

What kind of research was this?
Darren Warburtnon et al, conducted a randomized control trial (RCT). RCT is considered the gold standard for research testing. This study shows low levels of bias as the patients are apart of one population group and were all asked to perform the same test. However this article has a large bias as only men were asked to complete this study. For this reason the study is mostly not applicable to females as it is unknown if females would have the same adaptations as the males

What did the research involve?
This study involved fourteen men with CAD who had undergone bypass surgery or angioplasty, were stratified and randomly assigned to traditional or interval training. All individuals were chosen from a group of patients who had a negative stress test and a VO2peak >9 METs.

The traditional cardiac rehabilitation model and interval training model were carried out over a 16-week period. Both groups were given specific instructions on the task they would be completing and were made to perform the same standardized 10-minute warm-up, resistance training and cool-down. The individuals completing the traditional training performed 30 minutes of continuous aerobic exercise at 65% of heart rate/VO2 reserve. The Interval training group exercised using 2-minute, high-intensity work phases (90% of heart rate/VO2 reserve [range 85% to 95%]) followed by 2-minute recovery bouts (40% of heart rate/VO2 reserve [range 35% to 45%]). Both groups were required to train for 30 minutes/day, two days/week for 16 weeks.

All participants were assessed on two separate days after 16 weeks of aerobic training. The first day of testing involved individuals performing a symptom-limited, incremental to maximal exercise treadmill test (Bruce protocol) to assess VO2peak. During the second day of testing, the participants completed a high-intensity time to exhaustion test on a treadmill at 90% of heart rate reserve. Each participant had previously engaged in 1 familiarization time to exhaustion test.

What were the basic results?
According to the authors, the key finding of this study was that high-intensity interval training results in similar improvements in aerobic fitness and a greater tolerance to an anaerobic challenge in comparison to traditional continuous aerobic exercise training.

The study found, sixteen weeks of cardiac rehabilitation (both traditional and interval training) did not result in significant changes in resting measures of heart rate, systolic blood pressure, diastolic blood pressure, pulse pressure, and rate–pressure product, and maximal exercise measures of heart rate, systolic blood pressure, and rate–pressure product. However, there were extensive improvements in resting and maximal exercise oxygen pulse, VO2peak, Bruce treadmill time, and time to exhaustion after both training programs.

The study showed that it was important to maintain the average training intensity of 65% of VO2 reserve between the traditional and interval training groups. As both intensity and duration have independent effects on cardiovascular function.

What conclusions can we take from this research?
This research provides evidence that shows high-intensity interval training can be completed with limited risk to highly functional male patients with CAD. However, the research conveys there are no significant benefits of conducting a HIIT program over traditional program in the rehabilitation of male patients with CAD. Studies that have been conducted recently have displayed evidence that shows HIIT is not superior to other forms of endurance training.

Practical advice

 * HIIT has been proven to provide an effective means to improve the cardiovascular fitness and health status of highly functional patients with coronary artery disease.
 * However, HIIT has been proven to have many positive benefits for the rehabilitation of male CAD patients, recent studies have shown that endurance based training incites adaptations that are more beneficial.

Further readings

 * What is Coronary artery disease? http://www.heart.org/HEARTORG/Conditions/More/MyHeartandStrokeNews/Coronary-Artery-Disease%E2%80%94Coronary-Heart-
 * What is HIIT? http://www.popsugar.com.au/fitness/What-HIIT-41016932