Most adults need at least 150 minutes per week of moderate-intensity cardio for meaningful heart health benefits. That’s the baseline recommendation from both the American Heart Association and the U.S. Department of Health and Human Services, and it translates to about 30 minutes on five days a week. If you prefer harder workouts, 75 minutes of vigorous cardio per week delivers comparable benefits.
The Weekly Targets That Matter
The 150-minute moderate or 75-minute vigorous threshold isn’t arbitrary. A pooled analysis of four international cohort studies covering more than 2 million people found that meeting these guideline levels was associated with a 22% reduction in mortality. Studies using wearable activity trackers to measure movement (rather than relying on people remembering what they did) found even stronger effects.
You can also mix intensities. Each minute of vigorous activity counts as roughly two minutes of moderate activity, so 20 minutes of running plus 60 minutes of brisk walking in a week gets you to the equivalent of 100 moderate minutes. And you don’t need to do it all at once. Breaking exercise into 10- or 15-minute blocks throughout the day still counts toward your weekly total.
Going beyond the baseline brings additional protection. Doubling the target to 300 minutes per week of moderate activity provides even greater cardiovascular benefits. That said, the biggest jump in risk reduction comes from moving out of the sedentary category altogether. If you’re currently doing nothing, even a fraction of the guideline amount is a significant upgrade.
What Counts as Moderate vs. Vigorous
Moderate intensity means you can talk but not sing during the activity. Brisk walking, casual cycling, water aerobics, and doubles tennis all qualify. Vigorous intensity means you can only say a few words before needing a breath: running, swimming laps, singles tennis, cycling uphill, or a fast-paced group fitness class.
If tracking minutes feels tedious, step counts offer a simpler proxy. Research from the National Heart, Lung, and Blood Institute followed more than 14,000 women aged 62 and older for up to nine years and found that logging around 7,000 steps per day provided benefits comparable to getting a 30-minute brisk walk most days of the week. Women at that activity level had roughly a one-third lower risk of premature death or developing cardiovascular disease compared to the least active participants.
How Cardio Changes Your Heart
Regular aerobic exercise physically remodels the heart over time. The left ventricle, which pumps oxygenated blood to your body, grows slightly larger and stronger. This allows the heart to push out more blood with each beat, a measurement called stroke volume. With a larger stroke volume, the heart doesn’t need to beat as often to circulate the same amount of blood, which is why fit people tend to have lower resting heart rates. Highly trained endurance athletes can have resting heart rates as low as 30 to 40 beats per minute while maintaining normal blood flow.
These structural changes can begin after as little as three months of training and roughly three to four hours of exercise per week. At that threshold, measurable adaptations start showing up in resting heart rate, the heart’s electrical activity, and the heart’s capacity to deliver oxygen to working muscles (a metric called VO2 max).
Beyond the heart itself, regular cardio lowers systolic and diastolic blood pressure by an average of 3 to 4 mmHg and reduces LDL (“bad”) cholesterol by 3 to 6 mg/dL. Those numbers sound small on their own, but at a population level, even modest reductions in blood pressure significantly cut the risk of stroke and heart attack.
HIIT vs. Steady-State Cardio
High-intensity interval training, where you alternate short bursts of all-out effort with recovery periods, delivers cardiovascular improvements comparable to longer steady-state sessions in less time. A study published in the British Journal of Sports Medicine found that HIIT nearly doubled improvements in cardiorespiratory fitness compared to moderate continuous training in patients with conditions like coronary artery disease, heart failure, hypertension, and diabetes.
HIIT also tends to improve VO2 max more than moderate-intensity exercise, meaning the heart and lungs get better at delivering oxygen under demand. For people short on time, this makes interval training an efficient option. A few 25-minute vigorous sessions per week can replace five 30-minute moderate ones and still meet the guidelines. That said, steady-state cardio is easier to sustain, gentler on joints, and more accessible for beginners. The best type is whichever one you’ll actually do consistently.
Can You Do Too Much?
There’s been growing interest in whether extreme amounts of endurance exercise can backfire. A systematic review and meta-analysis found that endurance athletes do show a higher prevalence of coronary atherosclerosis (plaque buildup in the arteries) compared to sedentary controls. But the nature of that plaque matters. Athletes tend to develop more stable, calcified plaques rather than the soft, lipid-rich plaques that are most likely to rupture and cause a heart attack. Athletes in the studies did not show a greater prevalence of high-risk or obstructive plaques.
In practical terms, this means that people training at very high volumes (think marathon and ultramarathon runners logging many hours per week for years) may accumulate some arterial plaque, but it appears to be the less dangerous kind. There’s no established threshold where exercise definitively becomes harmful for the heart, and the overwhelming evidence still favors more activity over less for nearly everyone. The risk of being sedentary dwarfs any theoretical risk from doing too much.
Practical Ways to Hit Your Target
If 150 minutes feels like a lot, start by reframing it. Three 10-minute walks per day, five days a week, gets you there. A 20-minute bike ride to work and back covers 40 minutes in a single day without setting foot in a gym. Weekend hikes, pickup basketball, or swimming with your kids all count.
For people who already exercise regularly, pushing toward the 300-minute-per-week mark or adding one or two higher-intensity sessions can unlock additional cardiovascular benefits. Mixing in some interval work, even something as simple as alternating between a fast and slow pace during a jog, can boost VO2 max more effectively than staying at one speed.
Spreading your activity across the week matters more than cramming it into one or two days. The American Heart Association specifically recommends distributing exercise throughout the week rather than concentrating it. This keeps blood pressure and blood sugar regulated more consistently and gives the heart a regular training stimulus rather than occasional spikes of demand.