So for a young runner in England, the practical answer is quite clear.

But the question of whether a teenager should run a marathon is more interesting.

What does England Athletics say?

England Athletics has taken a deliberately developmental approach to youth endurance running.

Its Youth Endurance Resource emphasises long-term athlete development and late specialisation. It is aimed at coaches, athletes, clubs and parents and covers subjects including wellbeing, physiology, strength and conditioning, road running and training. Importantly, England Athletics cautions against a prescriptive approach to generic training schedules for young endurance athletes and says that sample schedules should be individualised according to need.

That philosophy is also reflected in England Athletics’ broader guidance on junior training: it recommends considering long-term athlete development, growth and maturation, puberty, physical preparation and the athlete’s individual circumstances, rather than applying a single mileage figure to every junior of a given age.

The message is consistent.

The objective is not to get a young runner through as many miles as possible.

It is to develop the athlete gradually so that they remain healthy and capable of improving as they get older.

What are the current age limits?

England Athletics introduced new youth age groups from 1 April 2026.

The current groups are U12, U14, U16, U18 and U20, replacing the previous U13, U15 and U17 categories.

For off-track events, England Athletics publishes both maximum permitted distances and recommended distances. Within each two-year age band, the maximum distance is higher for the older age and lower for the younger one:

The U20 maximum reaches marathon distance at 18 and 45km at 19. The U18 maximum tops out at 25km, well short of a marathon.

These are competition rules and guidance, not a table of how far young people should train each week.

That distinction matters.

A 17-year-old being permitted to race 25km does not mean that running 25km regularly is an appropriate training session.

Why does England Athletics take this approach?

The organisation’s stated objectives for the new age-group structure include supporting long-term development, providing a clearer progression through the sport and providing more age- and stage-appropriate competition.

Its youth endurance material goes further.

It describes endurance running as a long-term journey and emphasises late specialisation. It also discusses wellbeing, underfuelling and overtraining.

That is particularly relevant to marathon training.

Training for a marathon isn’t simply a matter of being able to run for a long time. It involves building up training volume, recovering from that training and maintaining sufficient energy and other resources to support both the training and normal development.

For a developing athlete, those demands need to be considered together.

Can teenagers physically run a marathon?

Yes.

That is one of the important distinctions in this debate.

A young person being capable of completing 26.2 miles does not establish that marathon training is appropriate for them.

Research has documented substantial numbers of adolescent marathon runners.

The largest study we found followed participants in the Students Run Los Angeles marathon programme, published in the Clinical Journal of Sport Medicine. Of 1,927 students enrolled in the 2017–18 programme, 583 injuries were reported among 18% of the runners during the 28-week training period. Knee injuries were the most common type. Almost all of the participants who entered the marathon completed it, with 99% finishing.

Interestingly, the runners who reported injuries had run more miles per week on average than those who did not. The injured group averaged 14.6 miles per week compared with 12.0 miles in the uninjured group.

That does not prove that running 14.6 miles a week causes injury.

The study was observational, and many factors can influence injury.

It does, however, provide useful evidence that marathon training in adolescents is not simply a question of whether they can physically cover the race distance.

What do we know about injury?

The evidence is limited compared with adult marathon running.

A 2024 narrative review examining children’s participation in marathon races, published in the Journal of Functional Morphology and Kinesiology, concluded that there was relatively little evidence on either the risks or benefits of youth participation in long-distance events. It identified overuse injuries, stress fractures and psychological burnout as legitimate concerns.

That lack of evidence is important.

It means we should be wary of two equally confident claims:

“Marathons are dangerous for teenagers.”

and

“Marathons are perfectly safe for teenagers.”

Neither is adequately supported by the evidence.

What we can say is that young athletes have additional considerations because they are still growing and developing.

Growth changes the equation

Adolescence isn’t simply a period in which an adult runner becomes fitter.

Height, muscle mass, bone development, coordination and other physical characteristics can change considerably.

England Athletics specifically highlights growth and maturation when discussing appropriate junior training. Its guidance refers to peak height velocity, puberty and physical preparation as factors that should be considered when deciding how much training an individual young athlete should undertake.

This helps explain why two runners of exactly the same age may not have identical training needs.

Chronological age is only one part of the picture.

What about the psychological side?

Marathon training can also change the role running plays in a young person’s life.

A structured programme can involve several months of training, regular long runs, targets and expectations around performance.

For some young athletes that may be enjoyable and motivating.

For others it may turn something they enjoy into a source of pressure.

England Athletics’ Youth Endurance Resource deliberately considers the young endurance athlete as a whole person, including mental wellbeing and the risks associated with underfuelling and overtraining.

That broader perspective is useful.

The question isn’t simply whether a teenager can complete the training.

It is whether the training fits sensibly into their life.

Does marathon training interfere with other sport?

This is another reason not to look at mileage in isolation.

England Athletics encourages young athletes to participate in multi-sport and multi-event activity during the early stages of development rather than concentrating exclusively on mileage. Its coaching guidance states that young athletes should, in most cases, be training at substantially lower mileage than senior athletes, with fewer training days and lower volume per session.

A young runner who plays football, swims, cycles or takes part in athletics is therefore doing something quite different from a teenager whose entire sporting programme revolves around marathon preparation.

More running is not necessarily better athletic development.

What about a 16- or 17-year-old who really wants to run a marathon?

This is where the England Athletics position provides a practical answer.

Under the current rules, a U18 athlete cannot compete in a marathon-distance road race. Their maximum permitted distance across all terrains tops out at 25km, at age 17.

So there is no need to construct a training argument about whether they should enter a marathon.

They cannot do so within the England Athletics competition framework.

That does not prevent a young person from enjoying longer running as part of an appropriately designed training programme. But it means that the marathon itself does not need to be the immediate target.

There are plenty of opportunities to develop endurance without making 26.2 miles the objective.

What happens when they turn 18?

The position changes.

An 18-year-old moves into the U20 category, where the current maximum permitted distance is set specifically at marathon distance; that maximum rises to 45km at age 19. The recommended road and multi-terrain distance across the U20 band is 22km.

That does not mean that every 18-year-old should immediately run a marathon.

It simply means that the competition rules no longer exclude marathon-distance races on age grounds.

Whether a particular 18-year-old is ready is a separate question.

Training history, experience, injury history, development, recovery and motivation all remain relevant.

Is there evidence that marathon training can be done safely?

The adolescent marathon study provides some reassurance.

Among the 1,927 young runners who enrolled in the 28-week programme, 583 injuries were reported affecting 18% of runners during training, and 99% of marathon participants completed the race.

That is useful evidence.

But it should not be interpreted as a universal safety certificate for adolescent marathon training.

The programme had a particular structure, participants were supervised and the findings came from one organised programme in the United States.

We cannot assume that the same results would apply to every young runner following an independently designed marathon schedule.

What about the long-term effects?

This is where the evidence becomes particularly thin.

A 2007 review published in Sports Medicine noted that there were very few data on youth marathon runners and that important questions about the long-term health consequences remained unanswered. The author highlighted the need for follow-up studies to establish those longer-term effects.

A later review likewise described the evidence base surrounding long-distance running in young athletes as limited.

The absence of evidence is not evidence of harm.

But it is a reason to be cautious about making strong claims either way.

So should children run marathons?

For children, the answer is straightforward in England.

A marathon is not an appropriate competition distance within the England Athletics framework. Younger age groups have substantially shorter permitted distances, and primary-school-aged athletes are encouraged towards flexible, local and multi-event competition rather than long-distance racing.

For 16- and 17-year-olds, England Athletics currently sets the maximum off-track competition distance at 25km (reached at 17), so a marathon is outside the permitted competition distance.

For 18- and 19-year-olds, marathon racing becomes possible under the U20 rules, but that does not make it automatically appropriate for every athlete.

The research doesn’t provide a universal age at which every young person becomes “ready” for a marathon.

What it does provide is evidence that adolescents can complete marathon training, alongside evidence that injuries occur and that the long-term evidence remains limited.

A better question than “Can they?”

For a young runner, the more useful questions may be:

Why do they want to run a marathon?

Is it because they enjoy endurance running?

Are they being encouraged by a parent or coach?

Is it part of a charity challenge?

Are they comparing themselves with older runners?

And then:

What would the training require?

Would it reduce participation in other sports?

Would it interfere with school or other commitments?

Is the runner recovering properly?

Are they eating enough to support both training and normal development?

Is there an experienced coach involved?

And perhaps most importantly:

Is there any particular reason the marathon needs to happen now?

A young runner has plenty of time to become a marathon runner.

There is rarely a need to rush the process.

The verdict

A teenager can run a marathon.

That does not mean every teenager should run one.

The evidence from organised adolescent marathon programmes suggests that marathon training can be completed by young runners, but injuries do occur and the evidence about longer-term consequences remains limited.

England Athletics takes a deliberately developmental approach. Its current rules do not permit U18 athletes to compete over marathon distance, while U20 athletes can compete at distances up to 45km. Its youth endurance guidance emphasises individualisation, long-term development, wellbeing and avoiding an overly prescriptive approach to training.

So our view is fairly simple.

There is no need for a child to run a marathon.

For an older teenager, the question becomes one of individual readiness rather than simply age.

And for a young runner who loves endurance running, there is a considerable advantage in remembering that the marathon isn’t going anywhere.

There is plenty of time to get there.