Mending a Broken Heart by Nicolas Raymond on Flickr
High-Intensity interval training (HIIT) is tough.
Going “all-out” for 30 a second burst of activity stimulates the heart to intensities that may make you worried your heart will jump our of your chest . . .
or simply explode . . .
or maybe the “big one” will happen on the third Tabata interval.
Have you ever wondered whether your heart could handle such exertion?
Maybe you have a prior heart condition such as a previous heart attack or a “full metal chest” where several coronary arteries are lined with stents.
Maybe you have a new heart from a transplant or have a history of “heart failure.”
Can patients with the sickest hearts really do high-intensity interval training? Would this even benefit them?
The answer seems to be “yes!”
Studies have found that patients with “heart disease” are able to complete high-intensity interval training and may benefit from HIIT (also known as “aerobic interval training” or “sprint interval training”).
Here are 7 reasons that HIIT is good for your heart.
#1 HIIT improves fitness in heart disease
If you eat a “Western Diet” you likely have atherosclerosis or “hardening of the arteries.”
This is akin to rust and debris in your plumbing. This pugging-up of the arteries in your heart is termed “coronary artery disease.”
The process of plaque buildup begins at a young age and accumulates over time.
You may not feel plaque buildup or even get symptoms (such as chest pain).
Your job is to prevent this process from getting worse. A healthy diet of fruits and vegetables can help to decrease inflammation and possibly reverse coronary artery disease.
We know that exercise can help as well.
The exact type of exercise and the intensity is a subject of debate and actively studied, but HIIT may be king.
A study from the European Journal of Preventive Cardiology looked at HIIT versus moderate intensity continuous exercise in patients with stable coronary artery disease.
Twenty-one stable coronary artery disease patients were randomized to treadmill walking at either high intensity (80–90% of VO2peak) or moderate intensity (50–60% of VO2peak) three times a week for 10 weeks.
VO2peak (a measure of aerobic fitness) increased by 17.9% in the high intensity group but only 7.9% in the moderate intensity group.
HIIT on the treadmill appears to be safe and possibly more effective than moderate exercise in stable heart disease patients (at least in this one small study).
We obviously need larger, more robust studies to confirm this, but it shows us that your heart can withstand HIIT even if you have plaque buildup. It also shows us that HIIT may be more beneficial than the typical continuous treadmill exercise.
#2 HIIT is good for the metabolic syndrome (a major risk factor for heart attacks)
Metabolic syndrome is a condition defined by increased blood pressure, a high blood sugar level, abnormal cholesterol and body fat around your waist.
If you are like millions of Americans you may have just diagnosed yourself.
If you do have metabolic syndrome you are 3 times more likely to die of heart disease.
Maybe you should read that again.
This is why it is so important to reverse this condition (which can be done with a better diet and some exercise. Are you seeing a theme here?).
Turns out studies have looked at patients with the metabolic syndrome and whether they would benefit from HIIT.
In the journal Circulation thirty-two middle aged patients in their 50’s with metabolic syndrome were randomized to either moderate continuous moderate exercise (70% of highest measured heart rate) or aerobic interval training (HIIT with 90% of highest measured max) 3 times a week for 16 weeks or to a control group.
V̇O2max increased 35% in the aerobic interval training group and only 16% in the continuos moderate exercise
The aerobic interval training also did a better job removing risk factors of the metabolic syndrome such as improving insulin resistance, reducing blood sugar and decreasing fat storage.
This study shows us that HIIT can help improve the metabolic syndrome an important risk factor for heart disease and once again show us that it is safe even for metabolically unhealthy middle aged adults.
#3 HIIT helps get rid of plaque buildup in stents
When a heart attack occurs a plaque essentially burst open and a blood clot formed. This blood clot pugs up the artery that is supposed to give the heart blood to function.
The heart muscle is now dying . . .
. . . unless you unplug and and prop it open with a stent.
This procedure is called “angioplasty with stent placement” or “percutaneous coronary intervention with implantation of a stent.”
This procedure is life saving if you are having “the big one.” The “big one” often refers to ST-segment Elevated Myocardial Infarction (STEMI). The ST elevation refers to the EKG changes that occur during this heart attack. This signals the paramedics and emergency room providers to act quick and get you to the “angioplasty suite” to have a stent placed.
Stents are made of metal and are essentially a foreign body. Your body wants to re-pug the stent, which is called in-stent restenosis.
A study from the American Heart Journal shows us that this plaque and debris build-up in stents can be reversed by HIIT.
Forty patients after stents were randomized to a 6-month supervised high-intensity interval exercise training program or to a control group.
At six months, restenosis was significantly smaller in the high-intensity interval training group compared to the control group. Peak oxygen uptake was also better in the HIIT group (16.8% versus 7.8%).
This shows us again that HIIT is safe in heart patients (now those that had a heart attack and received stents) and that HIIT may prevent the stent from plugging up.
#4 HIIT helps after heart bypass surgery
If you get heart disease that is severe enough, you may need heart bypass surgery.
This is where the cardiothoracic surgeon takes veins (such as from your leg) and bypasses the diseased and plugged-up coronary arteries to supply the heart muscle with blood again.
This is technically called “Coronary Artery Bypass Graft” or by the acronym “CABG.”
Often a CABG is described by the number of vessels bypassed . . . such as a “3-vessel bypass” or “3-vessel CABG” (CABGx3 for short).
After a heart bypass surgery you need to exercise again and will go through cardiac rehabilitation.
HIIT has been studied in patients after heart bypass surgery and found to be beneficial.
Fifty-nine CABG patients were randomized to either aerobic interval training at 90% of maximum heart rate or moderate continuous exercise at 70% of maximum heart rate, 5 days per week for 4 weeks at a rehabilitation center.
After six months, but not immediately, the aerobic interval training group had a significantly higher Vo2peak than the moderate continuous exercise group.
This study once again demonstrated safety in heart patients and that HIIT in the long term may improve aerobic fitness compared to continuous exercise.
#5 HIIT helps older patients with heart failure
Over time the heart gets old and riddled with heart disease. Maybe it has had a few heart attacks causing damage to the heart muscle. When this aging and cumulative damage occurs the effectiveness of its pump action dwindles.
This pump function of the heart is obviously very important and its primary job. The pump circulates the blood.
We measure the pump function of the heart with a number called the Ejection Fraction (EF), which is usually measured with an ultrasound of the heart called an echocardiogram.
The EF is a percentage of how much blood is pumped out of the heart with each beat. The heart normally pumps about half of the blood out with each pump (not all of it). So, a normal EF is a about 50% or better (generally speaking).
When the EF goes under 50% a constellation of symptoms can occur (such as shortness of breath and leg swelling) that well call “heart failure” or “congestive heart failure.”
Because heart failure is generally cumulative (not always as their multiple types of heart failure) it tends to be more present as we age and fairly common in the elderly. In fact, if you have a grandparent their is a significant chance they may have heart failure at some point.
It turns out that even these older end-stage heart patients (in their 70’s and 80’s) can benefit from HIIT!
In the journal Circulation twenty-seven patients (average age about 75 years +/- 11 years) with heart failure were randomized to either moderate continuous training (70% peak heart rate) or aerobic interval training (95% of peak heart rate) 3 times per week for 12 weeks or to a control group that received standard advice regarding physical activity.
V̇O2peak increased by 46% in the aerobic interval training and only 14% in the moderate continuous training.
Aerobic interval training was also associated with reversal of left ventricular remodeling. Left ventricular remodeling is a complex process that occurs in the heart after damage that leads to worse heart function and heart failure. This is what we are trying to reverse.
HIIT (aerobic interval training) improved the ejection fraction in the participants by an overall 10% (a relative 35% improvement). This is like taking an EF of 30% and making it 40%!
A marker of heart failure called the Pro-brain natriuretic peptide decreased 40% in the aerobic interval group.
This study shows us that even older patients in their 70’s and 80’s with heart failure can benefit significantly from HIIT. In this small study there were significant improvements in aerobic fitness, left ventricular remodeling, pro-BNP levels, and most importantly ejection fraction (pump function).
#6 HIIT is safe and effective in heart transplant patients
But what if it’s not even your own heart?
What about patient’s who have undergone a heart transplant? They couldn’t possibly do HIIT? Right?
Even heart transplant patients need to exercise to keep their new hearts strong and yes, HIIT has been studied in these patients as well. In fact, once again HIIT was found to be safe and significant benefits were found.
A study in the American Journal of Transplantation compared the effects of 12 weeks of HIIT versus continued moderate exercise in stable heart transplant recipients more than 12 months after transplantation in a randomized crossover trial.
They found that HIIT increased VO2peak 17% compared to only 10% in the continuous moderate exercise group.
HIIT was found to be well tolerated, had a superior effect on oxygen uptake, and led to an increase in HR peak accompanied by a faster HR recovery.
The benefits of HIIT may be a result of improved heart rate response.
HIIT was found in this study to be safe and effective at improving aerobic fitness in heart transplant patients.
#7 Systematic review of HIIT in heart disease patients shows it is effective and safe (but more research is needed)
Finally, a review of the literature from The European Journal of Applied Physiology demonstrated that interval training is beneficial in heart disease patients.
They reviewed two controlled trials and five randomized controlled trials (RCTs) with 213 participants.
Interval training was shown to improve cardiorespiratory fitness (e.g. VO2max), endothelial function, left ventricle morphology and function (e.g. ejection fraction) more than conventional moderate continuous exercise.
The review had only 213 patients, so I want to again stress that the research is small. What is needed are larger controlled studies on this form of exercise in heart disease patients.
However, it appears that HIIT is safe and possibly more effective that continuous exercise.
Finally, a study out of the journal Circulation in 2012 looked at 4846 stable cardiac patients during cardiac rehab. Participants completed either a high-intensity interval program or a moderate continuous exercise program at one of 3 Norwegian cardiac rehab centers.
One fatal death occurred from cardiac arrest in the moderate intensity group. No deaths occurred in the high-intensity interval rehab group, however, the HIIT group had 2 non-fatal cardiac arrests.
This was 1 event in 23,182 patient-exercise hours in the HIIT group.
This is the first study to directly investigate the safety of HIIT in cardiac rehab in a relatively large number of people. However, more research is needed.
Even our sickest heart patients with heart failure, coronary stents, and even transplant patients have safely completed aerobic interval training at high intensities.
If you are considering doing HIIT and have heart disease please consult with your personal physician or cardiologist.
Please remember I am NOT your physician. Neither is Dr. Oz.
I do not know your personal medical history.
You should always consult your personal physician or cardiologist before starting a workout program especially if you have heart disease.
Also, if at any time you experience chest pressure or pain in your jaw or shoulders you should seek immediate medical attention as this is a potential sign of a heart attack.
How to determine if you need to see a physician before starting an exercise program from the American College of Sports Medicine: When to see a Physician Before Exercising
The Evidence:
- Rognmo et al. High intensity aerobic interval exercise is superior to moderate intensity exercise for increasing aerobic capacity in patients with coronary artery disease. European Journal of Preventive Cardiology, 2004.
- Tjonna et al. Aerobic Interval Training Versus Continuous Moderate Exercise as a Treatment for the Metabolic Syndrome. Circulation, 2008.
- Junk et al. High-intensity interval training may reduce in-stent restenosis following percutaneous coronary intervention with stent implantation. American Heart Journal, 2009.
- Moholdt et al. Aerobic interval training versus continuous moderate exercise after coronary artery bypass surgery: A randomized study of cardiovascular effects and quality of life. American Heat Journal, 2009.
- Wisloff et al. Superior Cardiovascular Effect of Aerobic Interval Training Versus Moderate Continuous Training in Heart Failure Patients. Circulation, 2007.
- Dall et al. Effect of High-Intensity Training Versus Moderate Training on Peak Oxygen Uptake and Chronotropic Response in Heart Transplant Recipients: A Randomized Crossover Trial. American Journal of Transplantation, 2012.
- Cornish et al. Interval training for patients with coronary artery disease: a systematic review. European Journal of Applied Physiology, 2010.
- Rognmo, et al. Cardiovascular Risk of High- Versus Moderate-Intensity Aerobic Exercise in Coronary Heart Disease Patients. Circulation, 2012.
