It’s one of the questions people ask most often, especially those about to debut in a marathon. Do long runs of up to 30 kilometers really prepare you better for the marathon? The key isn’t only how far you can run, but how well you can sustain your performance when fatigue sets in.
1. Durability matters
A study involving 82,303 marathoners observed that the decoupling between heart rate and pace began, on average, around kilometer 25.
Runners with lower decoupling experienced this later (33 km versus 19 km among those with higher decoupling) and achieved faster times. In other words, not only does your initial aerobic capacity matter, but how well you manage to preserve it throughout the effort.
2. Accumulated volume also counts
A meta-analysis of 85 studies found associations between better times and higher weekly volume, training frequency and length of runs. But association does not mean causation: it does not prove that reaching a specific distance is indispensable. You can delve into this question with our article on how many weekly kilometers you need to prepare for a marathon.
3. What happens when we prolong a session too long?
Demands increase on different systems:
No universal physiological threshold exists beyond which a run ceases to be beneficial. Therefore, it is important to tailor the distance to each runner and their plan. In this sense, you can also consult our article on the distance the longest run should have when preparing for a marathon.
The question we should ask ourselves is not how much a runner can endure, but what stimulus they need and what recovery cost it implies. Because a good session is not necessarily the one that generates the most fatigue, but the one that contributes to improvement without compromising subsequent training.
The key is to find the balance between load and recovery: piling up kilometers makes sense when it fits into the plan and allows maintaining the continuity of training.
