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What Is Marathon Running?

A marathon is a long-distance running race covering 26.2 miles (42.195 kilometers). It’s the signature endurance event in athletics — the race that closes every Olympic Games, the centerpiece of major city running events from Boston to Tokyo, and a bucket-list challenge that roughly 1.1 million people worldwide complete each year.

Running 26.2 miles is a deeply unreasonable thing to ask of the human body. That’s precisely why so many people are drawn to it.

The Origin Story

The marathon gets its name from the legend of Pheidippides, an Athenian messenger who supposedly ran from the battlefield of Marathon to Athens in 490 BCE to announce the Greek victory over the Persians, gasped “We have won,” and dropped dead. Great story. Probably not true — the historian Herodotus describes Pheidippides running from Athens to Sparta (about 150 miles) to request reinforcements, not to deliver a victory message.

The modern marathon was created for the 1896 Athens Olympics, the first modern Games. The race covered about 25 miles, from Marathon to Athens. The distance varied at subsequent Olympics until 1908, when the London course was set at 26 miles and 385 yards — the extra 385 yards added so the race could start at Windsor Castle and finish in front of Queen Alexandra’s royal box. That arbitrary distance became the official standard in 1921.

What 26.2 Miles Does to Your Body

Running a marathon is a full-body stress test. Here’s what happens physiologically:

Energy depletion. Your body stores about 2,000 calories of glycogen (stored carbohydrate) in your muscles and liver. Running a marathon burns roughly 2,600 calories. When glycogen runs out — typically around mile 18-20 — your body shifts to burning fat, which is less efficient. This is “the wall” or “bonking,” and it’s as unpleasant as it sounds.

Muscle damage. The repetitive impact of 40,000+ steps causes microscopic tears in muscle fibers. This is why marathon runners can barely walk stairs for days afterward.

Dehydration. Runners lose 1-2 liters of sweat per hour, carrying away water and electrolytes. Even with aid stations, most runners finish somewhat dehydrated.

Core temperature rise. Exercise generates heat. In warm conditions, core temperature can rise to 102-104°F. Heat stroke is a genuine risk.

Immune suppression. In the hours and days after a marathon, immune function drops temporarily, making runners more susceptible to upper respiratory infections.

None of this is permanent. The body recovers fully, usually within 2-4 weeks. And here’s the remarkable part: with proper training, the human body adapts to handle all of this quite efficiently. We evolved as persistence hunters, and our physiology is unusually well-suited to long-distance running compared to other mammals.

Training

Most marathon training plans follow similar principles:

Build a base. Before starting a specific marathon program, you should be running 15-25 miles per week consistently. Jumping straight from the couch to marathon training is a recipe for injury.

Progressive long runs. The centerpiece of marathon training is the weekly long run, which gradually increases from 10-12 miles to 18-22 miles over the course of the program. These teach your body to burn fat, condition your legs for sustained impact, and build mental toughness.

Easy runs. Most training miles should be run at an easy, conversational pace. This builds aerobic capacity without excessive stress. The biggest mistake beginning marathoners make is running too fast on easy days, which prevents recovery and leads to injury.

Speed work. Intervals, tempo runs, and progression runs build speed and lactate threshold. These make up maybe 20% of total training volume.

Rest days. Recovery is when your body actually gets stronger. Most plans include 1-2 rest days per week. Skipping rest is as counterproductive as skipping runs.

A typical plan runs 16-20 weeks and peaks at 35-55 miles per week for recreational runners. Elite runners train 100-140 miles per week. The final 2-3 weeks involve “tapering” — reducing mileage to let the body recover and store energy for race day.

The Major Marathons

The six World Marathon Majors are the most prestigious races:

• Boston (1897) — the oldest annual marathon, requiring a qualifying time for entry
• New York City (1970) — the world’s largest, with 50,000+ finishers
• Chicago (1977) — known for its flat, fast course
• London (1981) — the world’s largest fundraising event (over $1 billion raised for charity)
• Berlin (1974) — the fastest course, where most world records are set
• Tokyo (2007) — the newest Major, with an extremely competitive entry lottery

Beyond the Majors, thousands of marathons take place worldwide each year, from small trail races to massive city events.

The Demographics

Marathon running has changed dramatically. In 1980, about 143,000 people finished a U.S. marathon. In 2019 (pre-pandemic), about 509,000 did. The average runner has gotten slower — median finish times have increased from about 3:32 in 1980 to about 4:30 today — because the sport has expanded from elite and serious athletes to a much broader population.

Women now make up about 45% of marathon finishers, up from about 10% in the early 1980s. The average age of a marathon finisher is about 40. And the fastest-growing age segment? Runners over 60.

The democratization of the marathon is one of the more interesting cultural shifts in sports. Finishing a marathon — in any time — has become a widely respected achievement.

Should You Run One?

Honestly, running a marathon isn’t for everyone. It requires 4-5 months of consistent training, carries real injury risk (roughly 50% of marathon trainees experience a running-related injury during preparation), and the training consumes significant time — 6-10+ hours per week.

But if the idea excites you, the barrier to entry is lower than most people think. You don’t need to be fast. You don’t need to be young. You don’t need special genetics. You need decent health (get a medical clearance), patience, consistency, and the willingness to run when you’d rather not.

The finish line of your first marathon is one of those rare experiences where the reality matches the hype. All the months of training, the early morning runs, the sore legs and self-doubt — they compress into a single, overwhelming moment when you cross that line. Most people cry. Almost everyone smiles.

Then they sign up for another one.

Frequently Asked Questions

Why is a marathon 26.2 miles?

The marathon distance was standardized at 26 miles and 385 yards (42.195 km) at the 1908 London Olympics. The course was extended from the planned 26 miles so the race could start at Windsor Castle and finish in front of the royal box at the Olympic stadium. That arbitrary addition stuck, and the distance was officially adopted in 1921.

How long does it take to train for a marathon?

Most training plans span 16-20 weeks, assuming you already have a base fitness level of running 15-20 miles per week. Complete beginners should allow 6-12 months, building up gradually from shorter distances. The key is progressive overload — increasing weekly mileage by no more than 10% per week to avoid injury.

What is the average marathon finish time?

The average finish time in U.S. marathons is about 4 hours and 30 minutes. Men average around 4:22, women around 4:48. Elite runners finish in just over 2 hours — the men's world record is 2:00:35 by Kelvin Kiptum (2023), and the women's record is 2:09:56 by Ruth Chepngetich (2024). About 95% of finishers complete the race between 3 and 6 hours.

Further Reading

• World Athletics: Marathon
• American College of Sports Medicine
• Runner's World Marathon Guide