What the long run is and why it matters

The most important workout of the week

The long run is the longest run of the week, done at a comfortable pace. It develops deep aerobic endurance: more capillaries in the muscles, more mitochondria, more ability to use fat as fuel and more mechanical tolerance to repeated impact. It's the base every other workout rests on.

For 5K and 10K runners, the long run is what makes the race feel short. For half and full marathoners, it's the workout that decides whether you finish well or "crack" at the end — no other stimulus replaces the hours on your feet.

How far to run

Practical references: for a 5K, a long run of 6 to 8 km; for a 10K, 10 to 14 km; for a half marathon, 14 to 19 km; for a marathon, 28 to 34 km. In every case, the long run makes up between 25% and 35% of weekly volume — beyond that, the week becomes unbalanced and injury risk climbs.

It grows slowly: 1 to 2 km a week, with a step back every three or four weeks. A runner doing 30 km a week shouldn't do an 18 km long run, even if they "can handle it"; the math doesn't add up and the injury shows up two weeks later.

At what pace

Conversational. If you can't say a full sentence, you're going too fast. In numbers, that usually means 45 to 90 seconds per kilometer slower than your 10K pace. Running the long run fast is the most common mistake of intermediate runners: it feels productive, but it turns the workout into a race and eats the whole week's recovery.

There's room for variation in peak phase: a progression long run (the last 3 to 5 km slightly stronger) or one with race-pace segments. But that's an occasional tool, not the default — and only after months of well-executed easy long runs.

Before, during and after

Before: a light, carbohydrate-rich meal one to two hours ahead. During: from 75 minutes on, some carbohydrate (gel, chews, dried fruit) and water. After: eat within the next two hours, with protein and carbohydrate, and don't schedule anything intense for the next day — the day after the long run is easy or rest.

Choose routes with little traffic and an even surface, avoid doing the long run on extremely hot days, and start slowly even if you feel great: the first 2 km dictate how the last 5 will go.

How PaceOn helps

The long-run distance is computed from your real weekly volume and the race distance, with a safety ceiling — the plan warns if the window is too short for the long run to reach the ideal and suggests alternatives. After every imported long run, the system compares the pace with the range and comments on whether you hit it or went too fast.