The long run is the most ritualized session in distance running. Every weekend, millions of amateur runners lace up for their 'long one', ticking off the distance they're supposed to hit according to the training plan they found online. It's the session that earns the most Strava uploads, the most conversation at run clubs, and the most emotional weight in a training block.
It's also the session that's most often wasted by running it the same way every week. The long run should not be a single thing — it should be a session whose purpose, structure, and intensity change across the training cycle, designed to build the specific adaptations the runner needs at that moment in the plan. Pure time on feet in the base phase is not the same session as a progressive long run with a marathon-pace finish in the late build. Both are called 'long runs' and both matter, but confusing them or doing the wrong one at the wrong time is one of the most common ways amateur training stalls out.
What is the long run actually supposed to do?
The long run has four distinct jobs, and each of them matters in different proportions across the training cycle.
- Aerobic base building. Extended time at easy intensity drives mitochondrial density, capillary growth, fat oxidation capacity, and the slow structural adaptations that determine how much aerobic work you can sustain. This is the dominant purpose during base phase, and it only happens with duration — no other session replaces it.
- Durability and fatigue resistance. Long runs specifically train the body's ability to hold running economy, form, and output as the hours accumulate. A runner with good fresh-leg fitness and poor durability collapses in the last 10 km of a marathon; a runner with good durability holds pace when others fall apart. This is increasingly discussed in elite coaching as the single most important adaptation distance running demands.
- Fueling and hydration rehearsal. Long runs are the only training context that lets you practise race-day fueling — gels, drinks, timing, stomach tolerance — under realistic conditions. The race is not the time to discover your gut can't handle three gels per hour.
- Mental preparation. Running for two or three hours is a different psychological experience from running for 45 minutes, and the long run is where the brain learns to manage discomfort, boredom, and the quiet negotiation between 'I could stop' and 'I'll keep going'. Elite marathoners describe the long run as the session where you build the mental model of what race day will actually feel like.
Different training phases emphasize different jobs. A base-phase long run is 90% about aerobic building and 10% about the other three. A late-build long run with race-pace segments is 40% aerobic work, 40% durability under fatigue, 15% fueling rehearsal, and 5% mental prep. The structure changes because the purpose changes.
How long should your long runs actually be? (Peak duration by race)
The right length scales with your target race and where you are in the training cycle. The table below gives reasonable peak-week long-run durations for most amateur runners.
| Race goal | Peak long run | Typical structure | Notes |
|---|---|---|---|
| 5K / 10K | 60–90 min | Single run | Long run is aerobic base, not race distance |
| Half marathon | 90–140 min (16–22 km) | Single run | Full half distance is not required in training |
| Marathon | 2.5–3.5 h (28–36 km) | Single run | Cap at 32 km. Running full 42.2 km is almost always a mistake |
| 50K–100K ultra | 4–6 h total | Back-to-back weekends | e.g. 3 h Sat + 2 h Sun |
| 100-mile ultra | 5–8 h total | Back-to-back weekends, regularly | Adaptations come from accumulated volume, not one huge run |
A useful cross-check: your peak long run duration should not exceed 30% of your weekly volume. If your peak long run is 3 hours and your weekly total is 6 hours, the long run is 50% — too much. Bring other days up first. The long run is a piece of a periodized plan, not a standalone hero session.
What pace should a long run be?
The answer varies by phase, and it's one of the places where amateur runners most commonly go wrong.
- Base phase — pure easy pace. Zone 2, conversational, nothing that feels like work. The classic 'long slow distance' training philosophy lives here. For most amateurs this means 60 to 90 seconds per kilometre slower than marathon pace — considerably slower than feels like 'running'. Fight the urge to speed up.
- Early build phase — still mostly easy, but with a few short pickups (strides) at the end to prime the legs for faster work ahead. 4 to 6 × 20 second strides in the final kilometre of an easy long run is a common addition.
- Mid build phase — first introduction of race-pace segments inside the long run. A classic session is a long run of 2 hours with the final 20 to 30 minutes at goal marathon pace. The body is still warm, still aerobic, but learning to hold goal pace under accumulated fatigue.
- Late build phase — longer race-pace segments, or progressive long runs where each third of the run is faster than the previous. A 2.5-hour long run with 3 × 20 minutes at marathon pace in the second hour is a classic late-build session.
- Race-specific phase — a shorter long run (roughly 75–80% of peak) with significant race-pace work, e.g., 90 minutes easy + 30 minutes at marathon pace + 5 minutes easy. The goal is to rehearse the feel of race pace on pre-fatigued legs.
The cardinal sin is running every long run at medium pace — not truly easy, not truly fast, somewhere in the middle. Medium pace long runs produce medium gains at high fatigue cost, and the standard advice of distance coaches is to keep easy days easy and hard days hard, never both.
What are progressive long runs?
A progressive long run is one where pace gets gradually faster across the session. The classic structure divides the run into thirds: the first third at easy base pace, the middle third at marathon pace or slightly slower, and the final third at goal race pace or slightly faster. The intensity climbs across the session so the last kilometres are run on tired legs at the fastest pace.
The specific adaptations are excellent for race preparation. Progressive long runs train the body to accelerate when already fatigued, teach pacing discipline (you cannot go out fast or you can't finish), and closely simulate the negative split a well-paced marathon actually requires. They're also psychologically useful — running your fastest kilometre at km 30 of a long run builds confidence that your legs will still work when they need to.
A typical progressive long run for a marathoner: 60 minutes easy, 40 minutes at marathon pace, 20 minutes at 10–15 seconds per km faster than marathon pace. Total time roughly 2 hours. These are harder than pure easy long runs and should be limited to one per 1–2 weeks in the late build phase.
How should you fuel a long run?
Every long run beyond about 90 minutes should be a full rehearsal of your race-day fueling strategy. This is one of the places where amateur runners leave enormous amounts of performance on the table, because they train fueled with whatever's convenient and then panic on race day when they realize they don't know what 60 or 90 grams of carbs per hour feels like.
The practical rules:
- Eat what you'll eat in the race. Same gels, same drink, same brands, same flavors. Switching products in the final taper is how race-day GI disasters happen.
- Practise the full target intake. Your race-day target might be 60 or 90 g/h. Training long runs with that exact intake is what gut training is for. Arriving at race day having never taken 90 g/h is the leading cause of stomach failure in marathons.
- Drink like you'll drink in the race. Fluid volume, sodium content, and carrier (bottle, hydration pack, aid stations) should all match what you'll actually do.
- Eat breakfast before the long run if your race has an early start. Running long runs fasted or on coffee alone tells you nothing about how your body will handle the race-day breakfast.
- Test everything. Weird sensations, bloating, cramps, and bathroom stops during a long run are data. Long runs are the laboratory where you find out what your body tolerates and what it doesn't.
Should you do long runs on consecutive days for ultras?
For runners training for events longer than a marathon, back-to-back long runs are a well-established technique. The structure is a long run on Saturday followed by another long run on Sunday, often with the second one at a similar or only slightly shorter duration. The total weekend volume is what matters — a 3-hour run Saturday plus a 2-hour run Sunday produces adaptations similar to a single 5-hour run, with lower total stress and faster recovery.
Back-to-backs build the specific durability needed for multi-hour events. Running on tired legs the day after a long run simulates the second half of an ultra in a way that a single long run cannot. For 50K and shorter ultras, a single long run still works for most runners. For 100K and 100-mile events, back-to-backs become essential — you simply can't accumulate enough single-day running without destroying recovery.
The tradeoff is that back-to-backs use up a full weekend of recovery. Midweek training after a back-to-back weekend is lighter, and the overall weekly plan has to account for the fatigue. They're not a free addition — they're an alternative structure for accumulating race-specific volume.
What are the most common long-run mistakes?
Five mistakes catch most amateur runners at some point in a training block.
- Running every long run at the same medium pace. The single most common mistake. Medium-pace long runs produce medium gains and high fatigue cost. Easy should be truly easy; hard should be actually hard.
- Extending distance too aggressively. Adding 15 minutes per week to your long run for 8 weeks is how athletes end up with Achilles tendinopathy and ITB syndrome. Progressive overload for long runs follows the same 10% rule as weekly volume.
- Running the full race distance in training. Almost always a mistake for marathons. The recovery cost eats into the final 2–3 weeks of training, and the adaptations are no better than a 32 km run.
- Fueling with unfamiliar products or skipping fueling entirely. Long runs are the rehearsal. Athletes who train fasted 'to burn fat' and then try 90 g/h of gels on race day almost always regret it.
- Treating every long run as the same session. The purpose changes across the training cycle. Base-phase long runs are pure aerobic time; late-build long runs have race-pace segments; peak-phase long runs are race rehearsals. Using the same structure all year loses the specific adaptations each phase is supposed to produce.
Key takeaways
- The long run has four jobs: aerobic base, durability under fatigue, fueling rehearsal, and mental preparation. The weight of each changes across the training cycle.
- Peak long run duration: 60–90 min for 5K/10K, 90–140 min for half, 2.5–3.5 h for marathon, 4–6 h for 50K+ ultras, often as back-to-backs for 100+ milers.
- Pace depends on phase: pure easy in base, easy plus strides in early build, easy plus race-pace segments in mid/late build, race-rehearsal pace in specific phase.
- Never run all long runs at medium pace. Easy days easy, hard days hard.
- Progressive long runs (first third easy, middle third marathon pace, final third faster than marathon pace) are excellent race-specific preparation.
- Every long run over 90 minutes is a fueling and hydration rehearsal. Train with exactly what you'll race with.
- Back-to-back long runs are a powerful structure for ultra training, simulating cumulative fatigue without a single exhausting session.
- Peak long run should not exceed 30% of weekly volume. Bring other days up first if it does.
Frequently asked questions
Should I ever run the full marathon distance in training?
For almost every amateur, no. The recovery cost of a 42 km training run is disproportionate to the adaptation benefit — the body has already adapted to the aerobic stimulus by the time you've run 32 km, and the extra 10 km adds muscle damage, glycogen depletion, and fatigue that eats into your final training weeks. The classical 32 km cap exists for good reason. Exceptions: very experienced runners preparing for multi-day events, or athletes returning to running after a long layoff who need to build confidence. For a first or standard marathon, don't run the full distance.
How slow is a Zone 2 long run?
For most amateur marathoners, Zone 2 pace is 60 to 90 seconds per kilometre slower than marathon pace. A runner whose marathon pace is 5:00/km should be running easy long runs around 5:45–6:15/km, sometimes slower. This usually feels frustratingly slow and triggers the instinct to speed up — which is exactly the trap that turns productive Zone 2 long runs into medium-intensity grey zone runs that produce less adaptation. Resist the urge. The slowness is the point.
How often should I do long runs?
Once a week in base and build phases, scaling down to every 10–14 days in the race-specific and peak phases. During race week itself, the long run drops to a short 'dress rehearsal' of 60–90 minutes with some race-pace work, or is skipped entirely for shorter races. The consistent weekly long run is the anchor of the training week for most runners.
Can I replace a long run with a long bike ride?
For runners, partially. A long bike ride captures some of the aerobic adaptation and fatigue exposure, without the impact cost of long running. It's a reasonable substitute for an injured runner who can't run long, or a recovery week where you want aerobic stimulus without running volume. But it is not a full substitute — the running-specific adaptations (musculoskeletal loading, gait efficiency, impact tolerance) come only from running. For triathletes, the bike long run is a separate session entirely, not a substitute.
Should I eat breakfast before a long run?
For race-simulation long runs, yes — eat what you'll eat on race morning. For pure base-phase Zone 2 long runs, fasted is an option for some runners and produces modest adaptations for fat oxidation, but it's not required and isn't necessarily better. The harder the long run's intensity, the more important pre-run fueling becomes. A progressive long run with race-pace segments should always be fueled; a flat easy long run can be done either way depending on preference.
What's the difference between a long run and a marathon-pace run?
A long run is a duration-focused session, usually mostly at easy pace, built around time on feet. A marathon-pace run is an intensity-focused session where the goal is specific time at your target race pace. A long run can include marathon-pace segments (and probably should in the late build phase), but the two sessions are distinct. The long run's job is the aerobic base and durability; the marathon-pace run's job is specificity and pacing confidence. Most training plans include both, on different days of the week.
How CoreRise structures long runs across your plan
Long runs in CoreRise plans are not a single weekly session repeated at the same distance. The structure, length, and pace progression are built into the macrocycle based on your race distance, your current fitness, and where you are in the phase. Your first long runs in a marathon build might be 90 minutes of pure Zone 2. Three months later, they've grown to 2.5 hours with the final 30 minutes at marathon pace. Two weeks before the race, they shrink back to 90 minutes with a race-pace rehearsal. The coach is managing both the duration and the structure to produce the right adaptation at the right time.
Your coach also monitors how you handle each long run. If you report that a 2.5-hour run at easy pace felt unexpectedly hard, the next long run is adjusted. If you nail a progressive long run and feel good afterward, the coach can push the next one slightly further. And crucially, every long run is explicitly paired with a fueling and hydration plan tied to your race-day target — so by the time race day arrives, you've rehearsed 60, 80, or 90 grams per hour dozens of times in your own training, not for the first time under race pressure.
- Long run length, pace, and structure are matched to your macrocycle phase — they change across the block, not just extend.
- Race-pace segments, progressive runs, and back-to-backs are introduced when they're appropriate for your goal.
- Every long run comes with a fueling and hydration plan tied to your race-day target, not generic advice.
- Your coach tracks how you recover from each long run and adjusts the next one based on your feedback.
- Peak long run is scaled to your weekly volume and race distance, not a universal 'run 32 km' rule.
Antoine Boudet is the founder of CoreRise. He finished Ironman 70.3 Oceanside in 2026 and writes the evidence-based Learn hub articles for runners, cyclists and triathletes, drawing on the research literature and his own training.