Marathon season is here.
Should everyone run 42 km?

It is marathon season. Every weekend, Strava fills up with 10 km, 21 km and 42 km screenshots. Friends become runners. Runners become content creators. A finish medal appears, and suddenly 42.2 kilometres starts to look like the minimum entry requirement for being “fit.”

It is not.

A marathon is a serious and beautiful physical challenge. It can build fitness, confidence, community and a very specific kind of stubbornness. But being able to run a long way is not the same thing as building the most durable possible body.

Why marathon FOMO is a real training problem

Distance is easy to compare. That is why it is so tempting. You can post it, race it and collect it. A strong squat, pain-free ankles, healthy body composition, power, mobility and a well-recovered nervous system are less photogenic, even though they matter enormously.

The problem starts when a desk worker or a lifter sees the social proof and jumps straight into a high-volume running plan. Their cardiovascular system may improve quickly. Their feet, calves, tendons and bones adapt on their own schedule. A systematic review found that novice runners have a higher rate of running-related injury per hour of running than recreational runners. The smart move is not fear. It is gradual exposure.

Running is healthy. Marathon training is more specific.

Cardiorespiratory fitness is one of the strongest predictors we have of long-term health. Regular aerobic activity improves cardiovascular fitness, metabolic health and mood. Running is one excellent way to get there.

But marathon preparation solves a narrow problem: how to cover 42.2 km on one day. That calls for long runs, race-specific fatigue, fuelling practice and enough weekly volume to make the distance familiar. It can be absolutely worth doing if the race itself matters to you. It is simply not the same as a longevity plan.

These goals overlap. A marathoner can be very healthy. A person who never races can have exceptional healthspan. The mistake is treating one medal as proof of the other.

More mileage is not automatically more lifespan

The public-health baseline is clear: adults should aim for 150 to 300 minutes of moderate aerobic activity each week, or 75 to 150 minutes of vigorous activity, plus muscle-strengthening work on two or more days. Going above this range can bring additional benefit. There is no honest universal line where exercise suddenly becomes harmful for every person.

What changes at high marathon volume is the trade-off. Your recovery needs rise. Energy availability matters more. A poorly managed plan can crowd out strength training, sleep and family life. It can also produce overuse pain. After a marathon, studies do show temporary changes in cardiac biomarkers and function. That is a reason to respect the event and prepare properly, not evidence that a healthy, trained runner has “destroyed their heart.” The long-term meaning of these acute changes remains uncertain.

Zone 2 versus miles for the sake of miles

For health, how you train often matters more than how impressive the weekly distance looks. Many recreational runners drift into the middle: too hard to be easy, too tired to do a genuinely high-quality hard session, and too fatigued to lift well. This is often called the grey zone.

Easy aerobic work is valuable because it lets you accumulate time moving without turning every run into a test. In a lab, the upper edge of this easier range is related to your first ventilatory or lactate threshold. In real life, use the talk test: you should be able to speak in full sentences without gasping. If easy running pushes you too hard, use a run-walk format, an incline walk, cycling, swimming or rowing. Your body responds to the effort, not the social status of the exercise.

The popular 80/20 split, meaning most aerobic time easy and a small part hard, is a helpful endurance-training heuristic. It is not a longevity law. Start with consistency. Add intensity only when your body is handling the easy work well.

How much should you run? Four practical starting points

These are starting frameworks, not rules carved into a treadmill. Change the mode, duration and frequency based on your history, joints, recovery and goals.

The high-intensity piece: valuable, but not for day one

Higher cardiorespiratory fitness is strongly associated with lower all-cause mortality. Once you have an aerobic base and no contraindications, a small dose of hard work is a time-efficient way to challenge that system.

A classic option is the Norwegian-style 4 x 4: four four-minute efforts at a hard but controlled intensity, commonly targeting about 85 to 95 percent of maximum heart rate, with three minutes of easy active recovery between. This is not a first-week workout. Use hills, a bike or an elliptical if hard running beats up your joints. Warm up, cool down, and stop if you get chest discomfort, dizziness or unusual breathlessness.

Three rules that protect the long game

What a medal cannot tell you

A marathon finish cannot tell you whether your blood pressure is healthy, whether you are sleeping enough, whether you have enough muscle, whether your bones are strong, or whether you are carrying a running injury. It tells you that you completed a difficult running event. That is already impressive. It does not need to be inflated into a complete health score.

Run a marathon because the adventure calls you. Run easy because you enjoy it. Walk when walking is the sensible move. Lift because a long life needs strength. The goal is not to avoid hard things. It is to choose hard things that leave you more capable, not less.