Why Too Much Exercise May Harm Your Heart, and What Science Tells Us About the Ideal Amount and Type of Exercise

Exercise Is Good Medicine at the Right Dosage

Modern fitness research offers many potent reminders that physical activity is one of the best “preventive drugs” for many common ailments, from psychiatric disorders to heart disease, diabetes, and cancer.3

For example, one meta-review4 of 305 randomized controlled trials comparing the effectiveness of exercise versus drug interventions on mortality outcomes found “no statistically detectable differences” between exercise and medications for prediabetes and heart disease.

One of the key health benefits of exercise is that it helps normalize your glucose, insulin, and leptin levels by optimizing insulin and leptin receptor sensitivity. This is an important factor for optimizing your overall health and preventing chronic disease.

Another way in which exercise promotes good health and longevity is by forcing your mitochondria (those little “power stations” inside your cells that produce energy or ATP) to work harder, thereby producing more mitochondria (biogenesis) to keep up with the heightened energy requirement.

A side effect of this is a slowing down of your biological aging process.

However, as with other medications, there’s the matter of dosage. Too little exercise and you won’t get much benefit. (Worse yet, chronic inactivity has been shown to be an independent risk factor of chronic disease and early death.)

On the other hand, exercise too much, and you could do harm. As noted by Dr. Levine, while endurance athletes live longer than non-athletes — in general, nearly 20 percent longer than non-runners — the evidence also shows that going overboard does put your health at risk.

One of the risks of excessive high intensity cardio is you can develop enlargement of your heart that leads to something called diastolic dysfunction which can lead to heart failure and is really an epidemic in the U.S.

What’s the Ideal Dose of Exercise for Optimal Health and Longevity?

Research has shown that once you reach 40 to 50 minutes of daily vigorous exercise, or just over an hour of moderate exercise (such as walking), the benefits from your efforts plateau, and further efforts do not convey additional improvements in life expectancy.

One of the largest, longest, and most recent studies5 to shed light on this “Goldilocks zone” found that those who walked or engaged in other moderate-intensity exercise for 450 minutes per week (right around one hour per day, seven days a week) lowered their risk of premature death by 39 percent compared to non-exercisers.

Those who exercised around 3.5 hours a day only reduced their mortality risk by 31 percent — the same risk reduction as those who met the guidelines of 150 minutes per week (about 20 minutes per day).

A second large-scale study,6 which focused specifically on intensity, found that spending 30 percent of your exercise time on strenuous, high-intensity activity can gain you an extra 13 percent reduction in early mortality, compared to never picking up the pace and breaking a sweat.

When it comes to endurance cardio, previous research (discussed in the TED Talk below) has shown that to optimize the health benefits from running you’ll want to run 5 to 20 miles per week — the ideal amount being 10 to 15 miles per week. Once you reach 25 miles or more per week, the benefits again disappear.

Also, if you run too fast — over 8 miles an hour — the benefits tend to go away (note we’re talking about speed in long distance endurance running here, not interval sprinting). Lastly, if you run seven days a week, the benefits also disappear. The ideal amount was found to be a 30-minute run, two to five days a week.

So, the key really is moderation — moderation in terms of intensity, duration, and frequency. The human body simply wasn’t designed to engage in long-term extreme athletic performance, like battling ocean waves for 8 hours a day for six months straight.

Exercise Less — Move More

Some people may be a bit confused by my exercise recommendations because on the one hand, I advocate high-intensity exercise, and on the other, I’ve repeatedly pointed out that non-exercise movement may be even more important than a regular exercise routine.

It’s really not a contradiction, if you stop and think about it. The fact of the matter is that working out really hard for an hour and then spending the majority of the rest of your day sitting down is not going to do you much good, because the latter counteracts the former.

Research has demonstrated that six hours of uninterrupted sitting counteracts the positive health benefits of one hour of exercise. So the foundation for good health is relatively constant or regular movement, i.e. avoiding sitting down as much as possible, because even just standing up produces beneficial biological effects.

I firmly believe that walking say 7,000 to 10,000 steps a day is key for health and longevity. Now that I’m a full-time resident of Florida, I walk barefoot on the beach for about one hour each day. I used to do two hours but realized that the extra time was not providing any additional health benefits based on the information reviewed in this article. Balance and moderation is the key.

This lays the groundwork or foundation, so to speak, on top of which you can then build your fitness to increasingly higher levels. For maximum benefits with a minimal time investment, high-intensity interval training (HIIT) is an ideal add-on, two or three times a week — and no more than that, as your body needs to recuperate in between sessions.