10 Myths That Will Make You Rethink Your Relationship With Cardio

If you’re a fitness novice starting a new workout routine—or a pro returning after a hiatus with a beginner’s mindset—you might immediately want to enlist cardio as your number one way to see results fast. It wouldn’t necessarily be a bad idea: Not only can regular cardio sessions make you healthy and strong, but they're also a fantastic way to relieve stress during hectic times. And according to a recent report published by the American Heart Association, adults should get at least 150 minutes per week of aerobic exercise to lower the risk of heart disease, type 2 diabetes, high blood pressure, and dementia. 

But while it’s true that logging regular cardio sessions on the Peloton Bike or Tread regularly will help you go a long way toward your fitness goals, there are plenty of misconceptions out there. Here, we explore 10 of the most common myths surrounding cardio exercise.

Myth #1: Cardio Is the Only Workout You Need

Truth: Completing hundreds of rides or runs is an impressive feat, but don't forget to add recovery days in between to meet your fitness goals. “Most people turn to cardio as an upfront strategy,” says Dr. Jared Bunch, a Salt Lake City, Utah, cardiologist and member of the American College of Cardiology’s Sports and Exercise Cardiology Section & Leadership Council. “However, many people become frustrated when they reach a plateau.To keep the muscle mass healthy, it is also critical to stretch and consider activities like yoga that can help with mind and body as a means to keep blood pressure lower and the heart healthier.”

Myth #2: It Doesn't Count Unless You Do Cardio for at Least One Hour

Truth: Maybe you have back-to-back work meetings or a sick child at home. Either way, squeezing in a quick workout—just 15 or 20 minutes—is still well worth the effort on busy days. “Most people really need to just start moving,” Bunch says. “If you are inactive, start with 15 minutes a day. When you can do that, do it twice a day with a goal to increase to 60 minutes over time. I think a lot of people get discouraged if they don’t reach an idealized standard of 60 minutes a day, but every bit of activity counts.”

Myth #3: High Intensity Workouts Are the Best Way to Become Healthy

Truth: You don't always need to PR to garner lifelong health benefits. Low impact classes are extremely beneficial too. “In my practice, we often discuss exercising for a sustained period up to 60 minutes per day,” Bunch says. “In some athletes this is not acceptable and they want to exercise one to two hours or more a day and three to four or more hours on the weekend. Endurance athletes that spend long periods in the day cycling, running, swimming, cross-country skiing, or a combination of any of these sports experience much higher rates of abnormal heart rhythms. The people that are the highest risk are the fittest or those that participate and have the lowest personal times and greatest amount of races. Transitioning to enjoying the exercise performed at a moderate intensity and not always at a level to achieve a personal best can be helpful in lowering risk.”

Myth #4: Always Do Cardio First, Then Strength

Truth: You don't need to do cardio first for your workout to, well, actually work. While you can do both on the same day, “the order is less critical than what makes you feel comfortable and what is sustainable over time,” Bunch says. “The critical aspect to weight-lifting and cardio is to adequately prepare to do the exercise, which should include a warm-up. For some people who weight lift, their cardio is that relatively less intense warm-up. However, in others, resistance training becomes the warm-up for extended cardio.”

Myth #5: Cardio Will Reduce Muscle Mass Gains

Truth: Does cardio kill gains? Ask any lifter and you’ll likely hear that they don’t do much of it out of fear of losing bulk. But while muscle atrophy and loss is associated with aging, chronic disease, and a sedentary lifestyle, cardio can actually help you gain and retain muscle mass. Because you’re performing an activity for an extended period of time, activities like walking, running, and biking all increase your level of endurance, giving you the capacity to withstand more effort. This means your next resistance training session will feel easier, giving you the power to lift heavier and grow stronger. According to the Physical Activity Guidelines for Americans 2015-2020, adults should engage in strengthening exercises at least twice a week. 

Myth #6: There’s No Such Thing As Too Much Cardio

Truth: Sometimes, it is actually possible to get too much of a good thing. The increased popularity of distance running—and endurance races like ultramarathons—has made it easy to buy into the myth that superhuman amounts of cardio will also make you incredibly healthy. In truth, pushing yourself beyond your limits can have detrimental effects on your mental and physical health: A 2021 Healthcare study surveyed 200 adults in their mid-30s and found that some heavy exercisers considered themselves “mentally tough,” but also reported more mental health issues and stress than light exercisers—a red flag for any coaches, parents, or sports associations that value quantity and intensity of workouts over all. What counts as too much? According to a 2018 UCLA study, three 45-minute sessions a week is ideal for optimum health results; the authors found that exercisers who preferred sessions longer than three hours reported worse mental health than people who don’t exercise. 

Myth #7: Doing Tons of Cardio Is Always Beneficial for Your Heart

Truth: Cardio helps keep your heart healthy, but no matter how fit you think you are, it’s important to consult your doctor first before starting any new workout routine. “When the body is constantly stressed—in particular the heart—it will adapt to that stress and often dilate and develop small areas of scarring that can cause both mechanical and electrical problems over time,” says Bunch. “In addition, when someone is exercising and highly engaged in activity, they may not feel ill or like someone they perceive that has health problems. When we realize that, it becomes easier to get appropriate screening for common diseases like high blood pressure, high cholesterol, cancer, and diabetes.” Research published in the European Heart Journal in 2024 found that workouts containing both resistance and cardio provide the same cardiovascular benefits as those that are cardio only, so consider that a green light to mix up your routine.

Myth #8: Cardio Is the Best Way to Burn Fat

Truth: Cardio can help you burn fat, if that is a goal of yours—but if you’re looking to get the biggest bang for your buck, strength training is your best bet. Strength training means more muscle gains, which increases your body’s metabolism and allows it to burn more fat long-term. A 2023 Diabetologia study found that workout participants who followed strength training regimens for nine months lost more body fat and had more stable blood sugar levels than those who only did cardio. The bottom line: There are major benefits to cardio and strength training, so including both in your routine can amp up your fat-burning potential.

Myth #9: Walking Isn’t “Real” Cardio

Truth: Maybe it’s because we do it without thinking during our non-workout time, but many frequent gym goers don’t consider walking cardio when building their workout plans. Although it’s a simple activity, two 2022 JAMA neurology studies found that 30 minutes of walking each day lowers your risk of cancer, cardiovascular disease, and dementia. The studies found that 10,000 steps a day was the threshold for the greatest benefit—great incentive to wear your Fitbit and celebrate fitness wins while completing errands and other daily tasks.

Myth #10: More Cardio Will Help You Break Through a Fitness Plateau

Truth: Sure, having a cyclist or marathoner’s endurance and stamina are worthy bragging rights: It takes focus, consistency, and hard work to reach any workout milestone. But if you’ve hit a wall with your training—or just want to be cautious of getting your heart pumping in ways that aren’t exactly healthy—don’t constantly increase your mileage on runs or bike rides. Instead, adjusting the frequency, intensity, time, and type (F.I.T.T.) of your workouts—according to the American Heart Association’s target heart rate for your age—can keep you challenged and excited to move, even if you’ve already achieved your original fitness goals. That way, you’ll reap the benefits of exercise and cultivate a routine you’ll be happy to stick with, instead of one you feel obligated to do.