You’re standing on a treadmill, staring at the little red numbers, wondering if this is actually doing anything or if you're just punishing your knees for no reason. It’s the million-dollar question. How often should you do cardio? If you ask a marathon runner, they’ll say "every day." If you ask a powerlifter, they might tell you that walking to the fridge counts as their zone 2 for the week.
The truth is messier.
Most people are overthinking it while simultaneously under-doing the right kind of work. We’ve been fed this idea that more is always better, but your heart and your central nervous system don't always agree with your New Year's resolutions.
The Baseline: What the Science Actually Says
The American Heart Association and the CDC generally land on 150 minutes of moderate-intensity aerobic activity per week. Or, if you’re short on time, 75 minutes of vigorous stuff. That’s the "don't die early" baseline. But let’s be real—most of us aren’t just trying to avoid a heart attack at 80; we want to feel good, look decent, and be able to climb a flight of stairs without sounding like a broken vacuum cleaner.
When you're trying to figure out how often should you do cardio, you have to look at your "Minimum Effective Dose." For a total beginner, three days a week of 20-minute brisk walks is a massive win. For someone training for a Spartan Race, three days isn't even a warm-up.
Dr. Kenneth Cooper, the guy who basically coined the term "aerobics" in the 60s, famously shifted his stance later in life. He started realizing that excessive distance running was causing massive oxidative stress and joint decay in his patients. He eventually pivoted toward the idea that if you’re running more than 15 to 20 miles a week, you’re doing it for something other than health. You're doing it for sport. There is a distinction.
The Problem With "Every Day" Cardio
Consistency is great, but your body isn't a machine. It's a biological system that adapts to stress. If you do high-impact cardio like running seven days a week, you aren't just burning calories; you're inviting repetitive stress injuries. Shin splints, plantar fasciitis, and IT band syndrome are basically the "participation trophies" of people who don't know when to take a day off.
If you must do something every day, you have to vary the modality.
- Monday: Run (High impact)
- Tuesday: Swim or Bike (Low impact)
- Wednesday: Walk (Very low intensity)
This keeps the engine humming without snapping the suspension.
Why Your Goals Change the Answer
If you're trying to lose weight, cardio is a tool, but it's a fickle one. Your body is incredibly efficient. It wants to survive on as few calories as possible. After a few months of the same 30-minute jog, your body gets "better" at it, meaning it burns fewer calories to do the same amount of work. This is the "cardio plateau" that kills most people's motivation.
For fat loss, the frequency of your cardio should probably be lower than you think, provided you’re lifting weights. Three sessions a week of Zone 2 cardio—that’s the pace where you can still hold a conversation but you're definitely sweating—is often the sweet spot. It aids recovery by flushing blood through the muscles without adding so much fatigue that you can't hit your squats the next day.
Heart Health vs. Performance
Are you training for a 5k or just trying to lower your resting heart rate?
For heart health, frequency matters more than intensity. Getting your heart rate up four or five times a week, even for just 10 or 15 minutes, keeps the arteries flexible. It’s about vascular compliance. On the flip side, if you're training for performance, you need "polarized training." This is a concept popularized by exercise physiologist Dr. Stephen Seiler. He found that elite endurance athletes spend about 80% of their time at low intensity and only 20% at very high intensity.
Most amateurs make the mistake of living in the "grey zone." They go too hard on their easy days and can't go hard enough on their hard days. They end up stuck in the middle, tired but not faster.
The "Zone 2" Obsession: Is It Overrated?
Lately, everyone in the longevity space—from Peter Attia to Andrew Huberman—is talking about Zone 2. Basically, this is cardio at roughly 60-70% of your max heart rate. It's the pace where you're "huffing a bit" but not gasping.
How often should you do this specific type of cardio?
If longevity is the goal, the consensus is leaning toward 3 to 4 hours a week. That sounds like a lot. But you can break it up. Two 45-minute sessions and one long 90-minute hike on the weekend gets you there. Zone 2 is magical because it builds mitochondrial density. Think of it as upgrading the battery in your car. It doesn't beat you up, so you can do it more frequently than HIIT (High-Intensity Interval Training).
The Dark Side of HIIT
We’ve been told for a decade that HIIT is the holy grail. "Burn fat in 4 minutes!" "The Afterburn Effect!"
Honestly? Most people aren't actually doing HIIT. They’re just doing "Hard Cardio." True HIIT requires you to go at 90-100% of your max capacity. It’s painful. It’s vomit-inducing. If you can do it more than twice a week, you’re probably not going hard enough.
Doing "pseudo-HIIT" four or five times a week is a recipe for burnout. It spikes cortisol. High cortisol over long periods leads to water retention and sleep issues. If you’re wondering how often should you do cardio that’s high intensity, the answer is usually: less than you think. Once or twice a week is plenty for most mortals.
Listening to Your Heart (Literally)
One of the best ways to determine your personal frequency is to track your Heart Rate Variability (HRV). Devices like the Oura ring or Whoop have made this mainstream, but you don't need fancy tech.
How do you feel when you wake up?
If you feel like you got hit by a truck, don't go for a run.
A simple test: check your resting heart rate in the morning. If it’s 5-10 beats higher than usual, your body is still recovering from the last session. Pushing through isn't "toughness"; it's bad math. You're digging a hole that you'll eventually have to climb out of.
Age Matters
Let’s be honest. A 22-year-old can bounce back from daily sprints in 12 hours. At 45, those same sprints might leave your Achilles tendons feeling like brittle glass for three days. As we age, the "frequency" dial usually needs to turn down while the "intentionality" dial turns up.
Older athletes should prioritize low-impact stuff. Rucking—walking with a weighted backpack—is becoming huge for a reason. It provides the bone density benefits of lifting with the cardiovascular benefits of a jog, but with way less impact on the knees. How often? You can ruck 3-4 times a week because it’s basically just "walking plus."
Common Myths That Won't Die
"Fasted cardio burns more fat."
Technically, you might burn a slightly higher percentage of fat during the workout, but over a 24-hour period, it doesn't matter. Total caloric deficit is king. If doing cardio on an empty stomach makes you miserable and eat a box of donuts at noon, it’s a net loss."You have to do 30 minutes for it to count."
Total nonsense. Research into "exercise snacks"—short bursts of 1-2 minutes of vigorous activity spread throughout the day—shows significant improvements in cardiorespiratory fitness. If you can only do 10 minutes, do 10 minutes."Cardio kills your gains."
Unless you are trying to be an elite-level bodybuilder, a few runs a week won't shrink your muscles. In fact, better cardio improves your work capacity in the weight room. You’ll be able to recover faster between sets of squats.
Building a Sustainable Schedule
So, let's put it into a real-world context.
If you are a busy professional who just wants to stay healthy and not feel winded, here is a realistic way to approach the how often should you do cardio dilemma:
The "Maintenance" Plan:
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- Daily: 8,000–10,000 steps. This is your foundation. It's non-negotiable cardio.
- 2x Weekly: 30 minutes of Zone 2 (Bike, brisk walk, elliptical).
- 1x Weekly: Something that makes you breathe hard. A hill sprint, a fast swim, or a heavy circuit.
The "Fat Loss & Fitness" Plan:
- Daily: 10,000 steps.
- 3x Weekly: 45 minutes of Zone 2.
- 1x Weekly: HIIT session (15-20 minutes).
The "Endurance Athlete" Plan:
- 5-6x Weekly: Mix of long slow distance and interval work. (Warning: This requires massive attention to sleep and nutrition).
The Hidden Variable: NEAT
We can't talk about cardio frequency without talking about Non-Exercise Activity Thermogenesis (NEAT). This is just a fancy way of saying "moving around when you aren't exercising."
If you do "cardio" for 30 minutes but then sit in an office chair for 8 hours and on a couch for 4, you are still sedentary. The frequency of your formal cardio matters way less than the frequency of your general movement. Stand up. Pace while you're on the phone. Take the stairs. It sounds cliché because it works.
What Happens If You Do Too Much?
There is a point of diminishing returns. It’s called Overtraining Syndrome. Symptoms include irritability, persistent soreness, lack of motivation, and weirdly enough, an increase in resting heart rate. If you find yourself hitting the pavement six days a week but you're getting slower and your sleep sucks, you've crossed the line.
More isn't better. Better is better.
Making It Stick
The biggest mistake people make isn't the frequency—it's the intensity. They start a program, go way too hard on day one, feel like they're dying, and quit by day ten.
If you’re wondering how often you should do cardio, start with a frequency you can actually maintain for the next six months, not just the next six days. If that’s twice a week, great. Own those two days. Once that becomes a habit, add a third.
Cardiovascular health is a long game. Your heart is a muscle, and like any other muscle, it needs a reason to grow stronger but also the space to actually do the growing.
Practical Next Steps
- Audit your current movement: For the next three days, don't change anything, but track your steps. If you're under 5,000, don't worry about "cardio" sessions yet—just get that number up to 8,000.
- Find your Zone 2: Use the "Talk Test." Go for a jog or a bike ride. If you can't speak a full sentence without gasping, slow down. Do this twice this week for 30 minutes.
- Pick a "Hard" Day: Choose one day a week to really push it. This could be as simple as finding a steep hill and walking up it as fast as you can five times.
- Listen to your joints: If your ankles or knees hurt every time you run, stop running. Switch to a bike or a rower. The "frequency" of your cardio depends entirely on your ability to stay uninjured.
Cardio doesn't have to be a grueling chore. It's just about keeping the pump primed and the pipes clear. Whether it’s three days or six, the best frequency is the one that allows you to show up again next week.