The standard recommendation for heart health is 150 minutes of moderate-intensity cardio per week, or 75 minutes of vigorous-intensity cardio. That’s the threshold endorsed by the WHO, the CDC, and the American Heart Association. But there’s meaningful nuance beneath that headline number, including how little you can do and still benefit, how much more helps, and where returns start to diminish.
The 150-Minute Standard
The most common way to hit 150 minutes is 30 minutes a day, five days a week. Moderate intensity means activities like brisk walking, cycling on flat ground, or swimming at a casual pace. A simple way to gauge it: you can carry on a conversation but couldn’t sing a song. If you prefer harder workouts like running, vigorous cycling, or rowing at a challenging pace, you need only 75 minutes per week. At vigorous intensity, you can get out a few words at a time but need to pause for breath between them.
You can also mix the two. A rough rule: one minute of vigorous activity counts as two minutes of moderate activity. So 20 minutes of jogging plus 60 minutes of brisk walking in a week gets you to about 100 “moderate-equivalent” minutes. There’s no requirement to do it all in one session or on specific days.
Less Than 150 Minutes Still Helps
If 150 minutes feels out of reach right now, even a fraction of that amount provides real protection. A large prospective study found that people who exercised just 15 minutes a day (about 90 minutes per week) had a 14% lower risk of dying from any cause and gained roughly three years of life expectancy compared to people who were inactive. That held true even for people already at elevated cardiovascular risk.
Daily step counts tell a similar story. Among adults with high blood pressure, cardiovascular mortality risk dropped steadily as step counts increased up to about 9,700 steps per day. For overall mortality, the threshold was around 8,250 steps. Beyond those numbers, the additional benefit flattened out. If you’re currently sedentary, simply walking more each day is one of the most accessible ways to protect your heart.
Why 300 Minutes Offers More
The WHO notes that doubling the target to 300 minutes of moderate activity per week (or 150 minutes vigorous) provides additional health benefits. This is where improvements in cholesterol, blood pressure, and body composition become more pronounced. A meta-analysis of aerobic exercise programs lasting 12 weeks or longer found that, on average, HDL (“good”) cholesterol increased by 4.6%, LDL (“bad”) cholesterol dropped by 5%, and triglycerides fell by 3.7%. Higher-volume, higher-intensity programs produced the largest improvements. In one study, participants doing high-intensity aerobic training saw their triglycerides drop from 167 to 139 mg/dL and their HDL rise from 44 to 49 mg/dL.
Blood pressure responds to cardio as well. Across dozens of randomized trials, regular aerobic exercise lowered systolic blood pressure by about 4 points and diastolic by about 2.5 points on average. That may sound modest, but at a population level, even a 2-point systolic reduction meaningfully lowers the risk of stroke and heart attack.
Moderate Cardio vs. High-Intensity Intervals
High-intensity interval training, where you alternate short bursts of hard effort with recovery periods, improves cardiovascular fitness more than steady moderate-intensity exercise. A meta-analysis of cardiac rehabilitation programs found that HIIT was significantly better at boosting VO2 peak, which is the gold standard measure of how efficiently your heart and lungs deliver oxygen during exertion. The advantage was most pronounced in programs lasting seven weeks or longer. HIIT also produced greater improvements in the heart’s pumping efficiency, the function of blood vessel walls, and the heart’s ability to fill and contract.
That said, moderate-intensity cardio is better at raising HDL cholesterol. And for people who are new to exercise, older, or managing a heart condition, steady-state cardio is easier to sustain and carries less injury risk. Higher intensity seems to matter most for directly lowering LDL cholesterol and triglycerides. One controlled study found that only the high-intensity group, not the moderate group, achieved significant drops in total and LDL cholesterol. The practical takeaway: moderate cardio is the reliable foundation, and adding some higher-intensity work amplifies the benefits if your fitness level supports it.
When You’ll Notice Changes
The earliest measurable change is usually your resting heart rate. A systematic review of exercise interventions found that it takes about three months of training, at roughly three sessions per week, to see a consistent reduction. A lower resting heart rate reflects a stronger, more efficient heart that pumps more blood per beat and doesn’t have to work as hard at rest.
Cholesterol and blood pressure changes follow a similar timeline, with most studies documenting significant shifts after 12 to 16 weeks of consistent training. Fitness improvements can begin sooner, sometimes within the first few weeks, but the cardiovascular risk factors that really matter for long-term heart health need at least two to three months of regularity before they budge.
When More Isn’t Better
For most people, more cardio means more protection, up to a point. But at extreme volumes, the curve flattens and potential risks appear. Endurance athletes who train for hours daily, accumulating five to ten times the recommended weekly dose, show a higher prevalence of atrial fibrillation (an irregular heart rhythm) by up to fivefold. Some research has also identified small areas of scar tissue in the heart muscle of lifelong ultra-endurance athletes, though the long-term consequences of this finding aren’t fully understood.
This is relevant to marathon runners, ultra-cyclists, and competitive triathletes, not to someone doing 30 to 60 minutes of cardio most days. For the vast majority of people, the risk of doing too little far outweighs the risk of doing too much. If you’re consistently hitting 150 to 300 minutes of moderate cardio per week and feel good, you’re in the range where the evidence for heart protection is strongest.