Yes, There Is Such a Thing as Too Much Exercise—Here's What to Watch Out For

How much is too much?

https://www.menshealth.com/health/too-much-exercise-heart-risk

Love exercise? Turns out, too much of it may actually put your heart at risk. According to a new study in the Mayo Clinic Proceedings, people who exercise well above the current recommendations—150 minutes of moderate intensity activity a week—may actually be at higher risk of early heart disease.
In the study, researchers recruited 3,175 young adults, and asked them to report on their physical activity on eight separate occasions over the next 25 years. At the end of that time period, they used CT scans to check the buildup of calcium in their arteries, which can be a marker of early coronary heart disease. Plaque buildup is bad news, since it can hamper the flow of blood to heart.

They discovered that people who exercised at three times the recommended guidelines, which would come out to at least 450 minutes of moderate physical activity per week, were 27 percent more likely to show significant levels of coronary artery calcium than those who exercised less than 150 minutes per week.

But those who simply met the exercise guidelines were at no increased risk, though, the study found.

When the researchers broke the groups down further, they discovered something interesting: Only white participants had an increased risk of coronary artery calcium levels when they exercised above the recommended guidelines—there was no spike seen for black participants who met that physical activity benchmark. In fact, white men who exercised at three times the recommended amount were 86 percent more likely to have significant levels of coronary artery calcium.
This isn’t the first study that showed super-high amounts of exercise can be harmful, either. For instance, a 2015 study from Denmark found that people who jogged a lot, and at a greater intensity, actually had a higher risk of dying over the course of the study than those who jogged less frequently or less intensely. In fact, their risk was similar to those who were sedentary.
Other research has linked long-term, vigorous exercise to higher levels of a protein associated with heart muscle damage, irregular heartbeat, and other heart issues, too, according to the current study.
But what does this mean for your exercise routine? Well, there are a few things to keep in mind. First, the study didn’t look at whether the buildup of calcium actually caused more heart attacks.
So it's possible that even though they do have more buildup, that may not necessarily put them at any increased risk of any actual heart issues. Exercise also causes helpful adaptations to your plumbing, such as an increased ability for your vessels to dilate, improving blood flow, the authors write. It's possible that can offset the risk.
Plus, only eight percent of the study’s population (268 people) met the extreme exercise benchmark, giving them a relatively small sample size to work with.
There are a lot of uncertainties here that require further research to delve into further—including why race played a role in the findings, the researchers say. But a bottom line for now: “It does not suggest that anyone should stop exercising,” study author Deepika Laddu, Ph.D., said in the statement.