How exercise protects the heart
Physical activity works through several routes at once, which is why its effect is larger than any single mechanism suggests.
- Blood pressure — regular aerobic training typically lowers systolic pressure by around 5 to 8 mmHg.
- Lipids — triglycerides fall and HDL rises modestly; LDL changes less.
- Insulin sensitivity — improves within hours of a session and persists for a day or two.
- Endothelial function — the vessel lining becomes better at dilating, improving blood flow.
- Heart efficiency — stroke volume rises and resting heart rate falls, so the heart does the same work with fewer beats.
- Weight, inflammation, sleep, and mood — all improve, each contributing indirectly.
Cardiorespiratory fitness itself is among the strongest predictors of mortality, and unlike age or genetics it is modifiable.
How much and what kind
The targets mirror general physical activity guidance: 150 to 300 minutes a week of moderate aerobic activity, or 75 to 150 minutes of vigorous, or a mix, plus strength training on two or more days.
The benefit curve is steepest at the start. Moving from no activity to even 60 to 90 minutes a week produces a substantial reduction in cardiovascular risk. Beyond about 300 minutes, additional gains flatten, though more activity is not harmful for most people.
- Moderate — brisk walking, cycling on flat ground, water aerobics, doubles tennis.
- Vigorous — running, lap swimming, uphill cycling, singles tennis.
- Strength — two sessions covering major muscle groups.
- Frequency — spreading activity across most days is better than one long weekend session.
Using heart rate and effort to guide intensity
Estimated maximum heart rate is commonly approximated as 220 minus age. It is a rough population average with wide individual variation, so treat calculated zones as a guide rather than a rule.
- Moderate — roughly 50 to 70% of estimated maximum.
- Vigorous — roughly 70 to 85%.
Two simpler methods often work better. The talk test: at moderate intensity you can hold a conversation but not sing; at vigorous you can only manage a few words. And a perceived effort scale of 1 to 10, where moderate is about 5 to 6 and vigorous 7 to 8.
Beta blockers and some other medications lower heart rate, making heart-rate zones unreliable. If you take one, use effort-based methods and ask your clinician what intensity is appropriate.
Exercising with existing heart disease
Having heart disease is a reason for tailored exercise, not for avoiding it. Cardiac rehabilitation — a supervised programme combining exercise, education, and risk factor management after a heart attack, cardiac surgery, or with heart failure — improves outcomes and quality of life, and is consistently underused. If you are eligible, ask for a referral.
For people with stable heart conditions exercising independently, a few principles apply.
- Get individualised guidance about safe intensity before starting.
- Warm up and cool down for longer than you otherwise would.
- Know your specific stop signals as agreed with your care team.
- Adjust for heat, humidity, and illness.
- If you use nitroglycerin, know when and how to use it as prescribed.
Warning signs during exercise
Most people can exercise safely without medical clearance. The risk of a cardiac event during exercise is very low overall and is far outweighed by the risk of remaining inactive. Still, some symptoms mean stop.
- Stop and seek emergency care for chest pain, pressure, or tightness; pain spreading to arm, jaw, neck, or back; severe breathlessness out of proportion to effort; fainting or near-fainting; or an irregular, racing heartbeat that does not settle.
- Seek a prompt appointment for new breathlessness with usual activities, new leg swelling, unusual fatigue, or palpitations.
- Check before starting vigorous activity if you have known heart disease, symptoms during exertion, or have been advised to.
Take new exertional symptoms seriously even if they resolve with rest — that pattern is exactly what warrants assessment.