Cardio is essential for general health and fitness. As the American Heart Association notes, aerobic exercise keeps your heart, lungs and circulatory system healthy, which helps reduce your risk of developing a chronic disease like diabetes, heart disease and stroke. Everyone should aim to log at least 150 minutes (2.5 hours) of cardio every week.
IS TOO MUCH CARDIO POSSIBLE?
You can get too much of a good thing — cardio included. While most of us don’t get enough physical activity (only 22.9% of U.S. adults actually met physical activity guidelines between 2010–15), there are people who fall at the other end of the spectrum — namely, people who are exercise-addicted and/or those who regularly participate in endurance events (e.g., marathons, triathlons, trail races).
“We tend to have this mindset where, if a little is good, more is better,” says Shawn Arent, PhD, certified strength and conditioning specialist, associate professor of kinesiology and director of the Center for Health and Human Performance at Rutgers. “And I’ve seen this over the years, especially working with athletes at the college and professional level, where the natural response when you start to see a performance drop-off is to train harder, when in fact it might be you’ve been working too hard for too long.”
SIGNS IT’S TOO MUCH
So, how do you know when you’re doing too much cardio? The answer will be different for every person, but in general, it’s when your body starts to break down. That is, your body can’t fully recover from your cardio routine anymore, Arent says.
There are a few ways you can tell if you need to cut down on cardio. Hopefully, you’re already tracking your workouts (type, duration, intensity, etc.), but if you’re not, start now. Tracking makes it easier to notice if you’re no longer making progress, when an “easy” pace suddenly feels challenging or if you need more rest between workouts than usual.
Also, if you’re constantly sick, sore or injured, or notice changes in sleep (e.g., you have a hard time getting to sleep and/or waking up), your body could be telling you you’re doing too much cardio, Arent says.
Granted, there will be days when workouts feel harder than usual, or you feel extra sore from bumping up your mileage or intensity, so don’t worry too much about the occasional “off” day. Instead, pay attention to trends. That is, do your “easy” days consistently feel harder than usual? Do you always feel sore and sluggish after a workout?
If you suspect you’re overdoing it, you can also track your resting heart rate for added insight. If you notice your resting heart (taken first thing in the morning before you get out of bed or drink coffee) continues to creep up over the course of four or five days, you may need to back off mileage or intensity or take an extra recovery day, Arent says.
Exactly how much cardio is too much also depends on your training goal. For example, if you’re trying to gain muscle, doing a ton of aerobic exercise cuts into your ability to add mass, because your body will be too busy recovering from the cardio to dedicate resources for building muscle. “But it doesn’t mean you have to avoid cardio like the plague,” Arent says, “it just means that you may do a little bit less of it.”
Finally, keep in mind that other life stressors (work, family, relationships) can impact how well you recover from exercise. So, if you’re having an unusually stressful week, an “average” amount of cardio could be too much for you in that moment. “Don’t stop training,” Arent says. “[Exercise] helps you handle the stress.” However, you may need to cut down on the mileage and/or intensity.
