Exercise for heart health - the ultimate guide
It’s well known that we should be engaging in some form of physical activity - whether it’s hitting the gym or heading to yoga class. But it’s less well understood exactly how much we should be getting, why, and what types are best for heart health. The consequences of physical inactivity are immense - linked with increased risk of basically all types of chronic disease including diabetes, hypertension, obesity, cholesterol issues, coronary artery disease, stroke, heart failure - this list goes on and on. When done correctly, exercise training can be one of the most powerful medications around. If you’ve ever wondered how to create the best exercise program for heart health, longevity, and wellness, read on!
Why exercise?
Exercise and regular physical activity is one of the biggest levers we can pull for improved heart health and longevity. A wealth of meta-analyses compiling observational data and systematic reviews support the recommendations for aerobic physical activity to lower risk of heart disease.
Unfortunately about half of all United States adults do not get an adequate amount of exercise
There is a well established dose-response relationship between exercise and risk of cardiovascular disease and death. It is curvilinear - meaning that the most significant improvement occurs when those who are currently engaging in little to no aerobic exercise begin to obtain the recommended amount of moderate to vigorous activity.
How does exercise effect the heart?
The benefits of exercise on the heart is due to several adaptive mechanisms in the heart and vasculature that occur as a direct results of exercise as well as a reduction in several traditional and emerging risk factors.
Cardiorespiratory fitness
Probably the greatest benefit of exercise is due to the improvements in cardiorespiratory fitness (CRF) - essentially how “in shape” you are. CRF is one of the strongest predictors of cardiovascular disease and death. Exercise improves CRF by
Improving cardiac output (how much blood the heart can pump out). Exercise programs are associated with changes in cardiac morphology - literally how big (end-diastolic volume) and strong the heart is. It’s also typically better at relaxing. All of these changes allow the heat to pump more blood out per heart beat.
Vascular adaptations, both structurally and functionally - The arteries also undergo remodeling! In those who exercise, arteries increase in size and number. They are also better able to dilate due to increases in nitric oxide production.
Skeletal muscle efficacy in oxygen uptake and utilization - Muscles become better at extracting the oxygen delivered to them with regular exercise
Reduction in risk factors
Exercise is closely correlated with a reduction in risk factors, namely
Blood pressure - both cardio and resistance training result in blood pressure reductions independently, which are clinically similar to that of blood pressure medication. This is likely due to the vascular adaptations and reductions in sympathetic activity
Diabetes and glycemic control - cardio and resistance training reduce HgbA1c by 0.6-0.8%, which is similar to the reductions seen with metformin. Contracting muscle takes up glucose via an insulin-independent mechanism
Body weight - although exercise does not result in massive reductions in weight loss, it does significantly impact the amount of visceral fat (the most cardiometabolically active)
There are also changes in autonomic tone (decreased heart rate, increased vagal tone), decreased endothelial dysfunction, decreased inflammation, and effects on stress and depression.
How much exercise is best?
The American College of Cardiology recommends at least 150 to 300 minutes of moderate intensity exercise OR 75 to 150 minutes of vigorous intensity exercise a week.
Moderate intensity exercise is defined as around 3-6 METs or 64-75% of your maximum heart rate. Effort is about a 5-6 out of 10. This includes activities like fast walking, yardwork, active yoga, recreational swimming, and light biking
Vigorous intensity exercise is defined as around 6-9 METs or 77-93% of your maximum heart rate. Effort is about a 7-8 out of 10. This includes jogging or running, cycling, hiking, or swimming laps.
Additionally, strength training or resistance training should be done twice per week. You can read more about that here.
This amount of exercise is associated with a 23-40% reduction in cardiovascular disease
Importantly
Even if you can’t hit these recommended amounts, science support that you should do what you can. In fact, the most significant benefit occurs when you go from being physically inactive to even moderately active.
Short durations of exercise (as short as 10 minutes!) seem to be as beneficial as longer ones, so the focus should be on the total accumulated amount per week. If you’ve only got time for 10-20 minutes, just do it! Don’t forgo just because you can’t fit in your typical 30 or 45 jog.
The benefits of exercise are independent of weight loss! Not hitting your target weight is not a reason to stop your exercise program! You may want to consult with a trainer to see if there are tweaks you can make to help you hit this goal as well, but you are still getting the cardiovascular benefit!
But can you get too much exercise?
We don’t know. Some epidemiological research does reflect a U-shaped curve in relation to exercise and mortality - meaning that at the very highest ends of exercise we no longer see a benefit, and instead a plateau effect with even some suggestion of harm. However, these studies are limited by the very small numbers of individuals in these highest echelons of exercise.
Why might too much exercise be an issue? Studies have demonstrated accelerated coronary artery calcification (CAC), a marker of atherosclerosis, in marathon runners and extreme runners. One study found a higher CAC in those individuals compared to both the general population and submarathon runners. Structural changes have also been observed including cardiac dilation, increased fibrosis, and post-exercise cardiac dysfunction as well as reports of increased rates of atrial fibrillation.
That said, benefits do seem to continue to accrue even past the current recommendations (ie > 300 minutes of moderate intensity exercise per week). One recent study found continued benefit (albeit with diminishing returns) all the way up to 10 times the current recommended amount. The maximal cardiac risk reduction in one analysis was around 41 MET hours per week (which is about 547 min/week of moderate-intensity exercise or 289 min/week of vigorous-intensity exercise).
So the vast majority of us are likely at no risk of getting to much exercise, but if you are getting over 10 times the current recommended amounts, speaking with your doctor about screening and possibly pre-participation risk stratification is wise.
What about high intensity interval training (HIIT)?
While clearly getting the recommended amount of aerobic exercise is important, there is evidence that getting higher intensity exercise may have additional benefits above and beyond continuous moderate intensity exercise
High intensity interval training (or HIIT) is exercise in which you engage in brief intermittent bursts of vigorous activity (usually around 90-95% of maximal heart rate) followed by active recovery. Research has shown that HIIT type training results in better improvement in VO2 max (a measure of cardiorespiratory fitness). Vigorous activity may also result in superior risk reduction - one study found that compared to no vigorous activity, those who reported some (<30% of their physical activity) or more (>30% of their total physical activity) had lower risk of death. Similar studies have also found vigorous intermittent exercise to be superior than moderate continuous exercise in patients with coronary artery disease.
It’s also very time efficient!
Is exercise safe in heart disease?
Yes! In fact some data suggest that exercise has a stronger beneficial impact on those with heart disease than without.
There is a strong body of evidence that cardiac rehab results in significant reduction in risk of death in those with coronary artery disease. Benefits can also be seen in those with heart failure, peripheral arterial disease, and atrial fibrillation.
As with all patients, it’s particularly important for those with heart disease to check in with their doctor prior to starting a new exercise program. Disease should be stable, medications should be optimized, and patients may benefit from pre-exercise testing depending on the clinical scenario.
The right exercise prescription
When it comes down to it, exercise is better than any medication on the market. It lowers blood pressure and glucose equivalent to available medications, and also has innumerable other beneficial impacts on the vasculature, muscles, body composition, and inflammation.
The primary focus should be on getting enough throughout week if possible, and breaking it up however you need to in order to make that happen. Thereafter, if you’re mostly getting moderate exercise at the moment, consider trying to mix in some short bursts of vigorous intensity exercise as well. Prescriptions for how to do this vary, but it appears at a minimum, achieving 4 mins of vigorous activity per day about 3 times a week can help you get there.
Exercise because you love your body, not because you hate it. Find movement that brings you joy, and find ways to fit it in to your life in a way that is sustainable.
