{"id":203083,"date":"2026-10-30T08:33:02","date_gmt":"2026-10-30T15:33:02","guid":{"rendered":"https:\/\/www.rei.com\/blog\/?p=203083"},"modified":"2026-10-30T08:33:04","modified_gmt":"2026-10-30T15:33:04","slug":"is-cardio-bad-for-you","status":"publish","type":"post","link":"https:\/\/www.rei.com\/blog\/run\/is-cardio-bad-for-you","title":{"rendered":"Is Cardio Bad for You?"},"content":{"rendered":"\n

Spend enough time on TikTok or Instagram and you\u2019ll find someone telling you to stop jogging, step away from the stationary bike or swap your weekend trail runs for a lower-impact activity. The argument usually goes something like this: Steady cardio spikes your cortisol, inhibits muscle growth, makes you too<\/em> hungry and might even contribute to faster aging. Depending on the social media platform or influencer, the advice might be to lift heavy instead, try Pilates or just take a nice slow walk\u2014whatever will keep your heart rate low. <\/p>\n\n\n\n

If you love to run, hike or cycle, this can be an unsettling message. But does it hold up? And if some cardio is fine, how much is too much?<\/p>\n\n\n\n

We talked to two experts<\/a>\u2014Tamanna Singh, MD, FACC, a sports cardiologist and director of the Sports Cardiology Center at Cleveland Clinic, and Kylee Van Horn, a trail runner, podcaster and endurance sports dietitian based in Carbondale, Colorado\u2014about what’s driving the trend, what cortisol actually does and why the healthiest approach to exercise usually sits somewhere between the extremes commonly found online.<\/p>\n\n\n\n

Where the anti-cardio trend comes from<\/strong><\/h2>\n\n\n\n

Van Horn is all too familiar with the anti-cardio messaging many of us have stumbled upon, and she most often sees it aimed at people experiencing signs of aging. “There is an idea that steady-state cardio spikes cortisol, burns muscle and ‘ages’ you faster than it helps you,” she says. \u201cIt is usually presented as ‘lift heavy’ and avoid intense cardio.\u201d<\/p>\n\n\n\n

There’s a kernel of truth to this suggestion. Strength training becomes more important as we age, particularly for people going through perimenopause or menopause. Van Horn notes that there is research showing a connection<\/a> between the estrogen decline experienced during these phases and muscle and bone loss. \u201cThis gave strength training a boost that shifted the message from ‘strength training will make you bulky’ to one that was about preserving muscle mass,\u201d she says. Singh has seen this shift in her clinic, where she says her patients are more likely to be strength training than they were even five years ago.\u00a0<\/p>\n\n\n\n

The trouble, Van Horn explains, is what happened next. The findings of these studies have \u201cgotten twisted,\u201d according to Van Horn, who says that a small body of research “has been extrapolated and blown up out of proportion.”<\/p>\n\n\n\n

What cortisol actually does<\/strong><\/h2>\n\n\n\n
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Photo credit: Dustin Kingman | REI Co-op<\/em><\/figcaption><\/figure>\n\n\n\n

It\u2019s almost impossible to spend time online as a fitness enthusiast and not come across the word \u201ccortisol.\u201d And if you don’t know what it does, it’s easy to assume it’s nothing but bad news. But cortisol is just the stress hormone. While it\u2019s true that it rises when you exercise, what that means for your health takes more nuance. <\/p>\n\n\n\n

When you exercise, cortisol increases because exercise stresses the body. How high your cortisol rises depends on how long and hard you train, but it should return to baseline one or two hours after you finish. Even more importantly, the cortisol increases you get from exercise can have long-term health benefits. As Signh explains, \u201cthis stressor leads to positive adaptation over time, which includes reduction in baseline cortisol levels.\u201d In other words, engaging in cardio exercise makes your body more resilient to all types of stress. <\/p>\n\n\n\n

Van Horn puts it more bluntly. According to her, a cortisol \u201cspike\u201d is \u201cnormal.\u201d What’s not normal, and what Van Horn says doesn’t get talked about enough, is chronic stress that dysregulates the hypothalamic-pituitary-adrenal (HPA) axis, your body’s central stress-response system. That usually stems from \u201ctraining too much or too hard without proper fueling and recovery.\u201d If you\u2019ve ever embarked on a cardio training plan for running, hiking or biking without having a clear sense of how allostatic load<\/a>\u2014the accumulation of wear and tear on organs and tissues\u2014works, what your heart rate zones are, how much fuel you need or how to build in enough time for rest or recovery, you may have experienced a version of this. But that\u2019s not a reason to avoid cardio exercise entirely.<\/p>\n\n\n\n

Singh says it\u2019s all about balance: Cortisol bumps from exercise aren’t harmful when training is balanced with recovery. But overtraining, where load and recovery are out of whack, becomes \u201ca big stressor in a negative way,\u201d increasing the risk of injury and more.<\/p>\n\n\n\n

It’s not the cortisol blip from a run that does damage. It’s a pattern of piling on stress without enough rest and food\u2014and cardio exercise is only one way you can incur that type of damage. Lifting, work and even enjoyable life events like planning a big party can all add to the total. But that\u2019s not a reason to skip out on any of those activities, either.<\/p>\n\n\n\n

What cardio does for your body<\/strong><\/h2>\n\n\n\n
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Photo credit: Dustin Kingman | REI Co-op<\/em><\/figcaption><\/figure>\n\n\n\n

Singh names a number of benefits that are specific to cardio exercise. It can improve blood pressure, cholesterol and blood sugar control, and it reduces cardiovascular risk. When it comes to the arguments that cardio will cause weight gain, Singh is, frankly, perplexed. \u201cI’m not sure where that concern comes from,\u201d she says. She believes cardio exercise can help reduce body fat and improve metabolism.<\/p>\n\n\n\n

More importantly, Singh cautions that the number you see on the scale is rarely a perfect indicator of health. For those engaging in weight training and cardio, Singh points out that their weight may increase simply due to added muscle mass. But, it can also be influenced by a number of other variables, such as diet, hydration and electrolytes. In fact, she points out that some people’s weight can swing 4 to 5 pounds in a single day just from fluid shifts. \u201cThe more valuable metric is body composition,\u201d she says.<\/p>\n\n\n\n

So, do you have to choose between ditching cardio entirely and making it the centerpiece of your exercise routine? According to Singh, \u201ccardio and weight training are complementary to one another.\u201d Cardio builds aerobic efficiency, while strength training builds the muscle and tendon capacity to generate power, protect against injury, and respond better to cardio training. Both reduce cardiovascular risk.<\/p>\n\n\n\n

Her advice is simple: \u201cBodies want to move and tend to get stiff, inflexible, and weak when they don’t.\u201d Aerobic and strength training together help build \u201ca resilient body and mindset.\u201d<\/p>\n\n\n\n

Hunger is a signal, not a problem<\/strong><\/h2>\n\n\n\n
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Photo credit: Ryan Valasek | REI Co-op<\/em><\/figcaption><\/figure>\n\n\n\n

\u201cHow did we get to the point that hunger is a bad thing?\u201d Van Horn asks. She says posts frequently frame cardio as risky because it makes you hungry, and she thinks the idea ties into broader cultural fears about weight gain. She notes that GLP-1 medications have added another layer: With a pharmacological appetite suppressant available, \u201cthere is a fear around doing too much cardio that could increase appetite because hunger is ‘bad.’\u201d<\/p>\n\n\n\n

There’s a physiological nuance here, too. Cortisol can briefly suppress ghrelin, a hunger hormone, so your appetite may dip right after hard exercise. \u201cHunger will typically return later and if someone hasn’t fueled enough, it might come in raging a bit,\u201d Van Horn says. That’s your body doing its job\u2014but it can feel confusing when you\u2019re first adjusting to it. And it can take some time to figure out how to best fuel after exercise when you don\u2019t always feel like it, so you\u2019re not falling into a pit of fatigue and extreme hunger hours later when your appetite finally returns. That practice requires embracing the fact that our bodies need food to fuel the activities we want to do, rather than treating a momentary loss of appetite as a victory.<\/p>\n\n\n\n

Van Horn emphasizes that hunger is \u201ca physiological signal, not a ‘problem to avoid.’\u201d Diet culture, however, has taught people to ignore hunger or suppress it with medication. Over time, that can erode trust in your own body’s cues, a pattern eating disorder specialists refer to as interoceptive avoidance. \u201cIn the broader cultural context, ‘I’m just never hungry anymore’ has become a status marker,\u201d Van Horn says, which \u201cnormalizes appetite suppression as a goal in itself\u201d\u2014a message that’s especially risky for people already vulnerable to eating disorders.<\/p>\n\n\n\n

The same logic applies to how people fuel for different exercise routines. Online, it sometimes seems like each type of training plan comes with its own trendy diet\u2014whether that\u2019s \u201cclean eating\u201d for Pilates, carb-loading for running or a paleo diet for lifting. And while the details of macronutrient ratios might shift a bit between lifting and endurance training, Van Horn says that \u201cno matter what you are doing, you still need to have carbohydrates, protein and fats in your diet to physiologically function well.\u201d Fueling matters, regardless of the type of exercise you\u2019re engaging in, and it\u2019s important to find balance with what you eat.<\/p>\n\n\n\n

Figuring out what you need<\/strong><\/h2>\n\n\n\n

So, how should you decide how much cardio to do? Start with your goals and be honest about what’s driving your choices. If you’re training for an event, your needs will look different from those of someone who just wants to stay healthy and strong. <\/p>\n\n\n\n

Singh points to the American Heart Association<\/a>‘s baseline: At least 150 minutes of moderate-intensity exercise or 75 minutes of vigorous exercise per week is recommended. For strength training, the AHA recommends exercising each muscle group\u2014one set of 8 to 12 repetitions per muscle group, working to fatigue\u2014at least two times a week with two days of rest between sessions. Your own goals may sit above that, whether that’s improving overall health, increasing fitness or training for a race, and they may not match anyone else’s.<\/p>\n\n\n\n

There\u2019s no one-size-fits-all number of weekly minutes that means you\u2019re on the right track. The key is getting to know your body and listening to it, as well as being honest with yourself about why you\u2019re hitting the gym or the trails in the first place. <\/p>\n\n\n\n

These questions can help guide your approach:<\/p>\n\n\n\n