The long run is usually the training that provides the most confidence before tackling a half marathon or a marathon. It is also the one that raises the most questions. Should you run 18, 20, or even 22 kilometers before a half marathon? Are the famous 30 or 32 kilometers mandatory to prepare for a marathon? What happens if a runner needs more than three hours to cover that distance? The answer cannot be reduced to a single figure. The longest run must be long enough to develop the necessary endurance, accustom the muscles to withstand impacts, and allow the runner to practice fueling, hydration, and racing pace. However, extending it too long can cause a fatigue that takes several days to disappear and can jeopardize the rest of the preparation.
No existe una distancia obligatoria para todos
Two runners training for the same event may need very different sessions. One can complete 28 kilometers in two hours and another may require more than three. Although the course is identical, the physiological and muscular load will not be. For this reason, the long run should be evaluated simultaneously by distance, duration, weekly volume, and the effort expended. Kilometers relate training to the demands of the competition, while the time reveals how long the body remains subjected to that load. Experience also matters. A runner who has completed several marathons tolerates certain sessions better than someone facing the distance for the first time. The history of injuries, age, availability to rest, and weekly training frequency also modify the decision. A study published in Scandinavian Journal of Medicine & Science in Sports, conducted with recreational half-marathon and marathon runners, found an association between higher weekly volume, longer long runs, and better results. However, it was an observational study: it does not prove that adding unlimited kilometers automatically yields better times.
The longest run to prepare for a half marathon
For many recreational runners, reaching between 16 and 19 kilometers represents sufficient preparation to confidently complete the 21.097 kilometers. Beginners or those with limited weekly volume may stay around 14 or 16 kilometers, as long as they have progressed consistently and are able to maintain a comfortable effort for about 90 minutes. Experienced runners can cover between 20 and 23 kilometers. Slightly exceeding the half-marathon distance allows extending the aerobic stimulus without the pressure of maintaining race pace. However, it is not a required condition to finish the event nor to improve. In the study of Scandinavian Journal of Medicine & Science in Sports, runs longer than 21 kilometers were associated with a faster time and a smaller loss of pace among half-marathon participants. This does not mean that everyone should run more than 21 kilometers. Runners who reached those distances also tended to accumulate more training and possess a stronger preparation. When a 20-kilometer outing represents almost half of weekly mileage, its cost can be excessive. In that case, it is more beneficial to gradually increase the regularity of the other days than to turn Sunday into an oversized session.
Are 30 or 32 kilometers essential for a marathon?
Long runs of 30 to 32 kilometers have become a traditional reference in marathon plans. They are reasonable distances for many experienced runners with a sufficient weekly volume, but they are not a test that must be overcome to be prepared. In recreational runners, the longest run typically sits between 26 and 32 kilometers. Those who accumulate a lot of volume, recover well, and aim for a demanding time can approach the upper end of that range. Beginners, runners with slower paces, or those who train fewer days may find a better balance staying between 24 and 28 kilometers. The cited research observed that completing less than 25 kilometers as the maximum distance was associated with slower marathon times. Once past that point, however, the study did not establish a magical distance capable of guaranteeing a better result. Running 35 or 36 kilometers can provide confidence, but it also imposes a substantial muscular load. If it forces interruptions or reductions in training for a large portion of the following week, the cost may outweigh the benefit. The purpose of preparation is not to prove that you are already able to complete a marathon in a single training session. It is to accumulate enough stimuli to be able to do so on race day after a load reduction, with rest, fueling, and a planned strategy.
Should you stop at the three-hour mark?
The three-hour limit is frequently used to prevent slower runners from turning the long run into a too aggressive effort. It is a practical reference, not a physiological boundary from which training suddenly stops producing adaptations. A session that substantially exceeds three hours can increase muscle damage, dehydration, glycogen depletion, and recovery time. It also requires considering environmental conditions, especially during the summer. That does not mean that every minute beyond three hours is harmful. A runner who expects to take five hours to finish the marathon may need some prolonged exposure to practice fueling, gain confidence, and get used to staying in motion for a long time. This can be achieved through a combination of running and walking, a very comfortable pace, or a split session, without needing to complete four hours of continuous weekly training. For faster runners, the distance can be a useful reference. For those who need more time to cover it, it is advisable to place greater emphasis on duration and the recovery cost.
The long run should relate to weekly volume
One of the most common mistakes is to concentrate an excessive portion of kilometers in a single session. If someone runs 35 kilometers per week and completes 25 on Sunday, that run accounts for more than 70% of their volume. The distance may seem adequate to prepare for a marathon, but the distribution is highly unbalanced. There is no perfect universal percentage valid for everyone, although among recreational runners it is prudent that the long run represents approximately 25% to 35% of weekly volume. In plans of few days it can exceed that interval, but the greater its relative weight, the more careful the progression must be. A study published in British Journal of Sports Medicine, which followed more than 5,000 runners, related abrupt increases in the distance of a single session compared to the longer recent outings with a higher risk of overuse injury. The practical conclusion is not to mechanically apply another universal percentage, but to avoid sudden jumps. Going from a recent maximum long run of 16 kilometers to another of 25 kilometers represents a very different demand than reaching that same distance after having completed 18, 20, 22, and 24 kilometers in previous weeks.
No todas las tiradas largas tienen que ser iguales
Most long runs should be done at a comfortable intensity, capable of sustaining a conversation and far from competitive effort. Their main function is to accumulate running time without generating disproportionate fatigue. As training progresses, some long runs may include segments at half-marathon or marathon pace. For example, an experienced runner might complete 26 kilometers including two blocks of five kilometers at the marathon pace. That session is more specific, but also more demanding than simply covering 26 kilometers in a uniform, easy manner. It is not advisable to turn all long runs into race simulations. Alternating easy sessions, progressive runs, and workouts with specific blocks allows a better distribution of the load and prevents every weekend from becoming an exam. Moreover, these sessions provide the best setting to test gels, drinks, breakfast, clothing, and shoes. In the marathon, a slightly shorter long run in which the nutrition strategy is practiced correctly can be more useful than adding kilometers without drinking or ingesting carbohydrates.
When to perform the longest run
The final long run is usually scheduled two to three weeks before a marathon. This allows time to repair the accumulated fatigue and begin reducing the volume. In the half marathon, it can take place seven to fourteen days beforehand, depending on its difficulty and the runner’s experience. Repeating a maximum distance too close to competition rarely improves our form. Adaptations do not appear immediately, while fatigue can accompany the runner up to the start. It is also necessary to modify the session if there is localized pain, obvious technique deterioration, dizziness, chills, confusion, or symptoms related to heat. Meeting a target distance does not justify ignoring signals that advise stopping.
So, what should your maximum long run be?
As a general guideline, a half-marathon runner can set it between 16 and 19 kilometers, with the possibility of slightly exceeding 21 kilometers if they have experience, sufficient weekly volume, and good recovery. In the marathon, a range of 26 to 32 kilometers covers the needs of many recreational runners. Beginners or those who run at slower paces can follow a combination of kilometers and time, limiting the session when fatigue begins to compromise their technique or subsequent training. The best long run is not necessarily the one that contains the most kilometers. It is the one that provides the necessary stimulus, allows practice of the race demands, and leaves the runner in a position to continue training. Training is built through consistent weeks, not with a single heroic Sunday.
