What a long fast run is
A long fast run is a long continuous effort at a pace close to race pace, well above easy running. For the marathon and half marathon it is the central session of the plan. It replaces the slow long run in the final weeks, because three slow hours train volume and leave your ability to hold a hard pace untouched.
Canova-style training expects you to run long and fast to beat your personal best. Intervals without a demanding long run leave a gap in your preparation.
Which percentage to use
The percentage depends on the plan’s distance and comes from race pace at that distance.
| Distance | Percentage | Typical long run distance |
|---|---|---|
| 5K | 85-88% | 8-12 km |
| 10K | 87-90% | 12-15 km |
| Half marathon | 90-95% | 16-24 km |
| Marathon | 88-95% | 24-35 km |
The 5K and 10K use lower percentages because 95% of 5K pace equals 10K pace. A long continuous run there is race effort, and you cannot hold it for long-run distance. In those events the long fast run is shorter and lower in percentage.
In the half marathon, the long run starts at 90% and climbs to 95% in the final weeks. In the marathon it starts at 88-90% and also tops out at 95%. Only one session goes higher: a specific marathon pace (MP) block late in the build, with segments at 97-100% (see the progression).
Example paces
For a 40:00 10K runner with a marathon goal of 3:08 (4:27/km):
| Percentage | Pace/km |
|---|---|
| 88% | 4:59 |
| 90% | 4:54 |
| 92% | 4:48 |
| 95% | 4:40 |
| 97% | 4:35 |
| 100% | 4:27 |
The 97% and 100% rows apply to the MP block alone.
For a half marathon at 4:12/km, 90% is 4:37/km and 94% is 4:27/km.
For the 40:00 10K (4:00/km), a long fast run at 87.5% comes out at 4:30/km. Fifteen kilometers take about 67 minutes.
Progression
Extend the distance or duration first. Raise the pace afterward. One progression for a 4:27/km marathon, with a long run every two weeks:
- 24 km at 90% (4:54), about 1:58 of running.
- 26 km at 90-92%.
- 28 km at 92% (4:48), about 2:14.
- 30 km at 92-94%.
- MP block: 28 km with the last 18 km at 97-100% (4:35-4:27). This is the only long run above 95%.
The last big long run falls 3 to 4 weeks before the race.
Duration versus distance for slower runners
Measure the load of a long fast run in minutes. Thirty kilometers at marathon pace take about 2:13 for a 3:08 runner and 2:52 for a 4:02 runner. The second runner takes on more than half an hour of extra load for the same mileage.
Cap the long run near 2:30, with 3:00 as a ceiling for the most experienced. Work at marathon pace inside the long run stays near 2 hours for intermediates.
Example with a 4:02 marathon goal (5:45/km):
- 92% comes out at 6:13/km.
- 28 km at 92% takes 2:53, close to the ceiling.
- 24 km at 92% takes 2:29 and is a more prudent dose.
The 4:02 runner covers fewer kilometers than the 3:08 runner in the same long run and takes on a similar load, matching the time of effort the body can absorb.
The calculator gives you the exact paces. If your plan prescribes a distance beyond your maximum duration, trim kilometers and keep the time.
Example for a 1:28:40 half marathon
With a half marathon pace of 4:12/km, these long fast runs work in a 16-week plan:
- Week 8: 16 km at 90% (4:37/km), about 74 minutes.
- Week 10: 18 km at 92% (4:32/km), about 82 minutes.
- Week 12: 20 km at 94% (4:27/km), about 89 minutes.
- Week 14: 22 km at 95% (4:25/km), about 97 minutes.
Distance grows every two weeks and the percentage rises 1 or 2 points. Put interval or alternation sessions between long runs.
How to run a long fast run
- Warm-up. Start with 3-5 easy kilometers, or the first 20 minutes, before settling into pace.
- Start on pace. Opening at 97% on a run planned at 92% is the common error, and it costs you over the last 10 km.
- Steady or a little progressive. Finishing 4-6 s/km faster than you started is fine. Avoid fading.
- Terrain. Flat or with small rises is best. Avoid long hills that change the effort.
- Finish. End with 1-2 easy kilometers and walk for a few minutes.
Gels and fueling
Long fast runs are the place to rehearse race-day food.
- When. Start at 40-45 minutes and repeat every 30-40 minutes.
- How much. Between 30 and 60 g of carbohydrate per hour. A typical gel gives 20-25 g.
- With water. Take the gel with about 150-200 ml of water so it digests better.
- Same product. Use the brand, flavor and timing in training that you will use on race day.
- Before. A breakfast you already know, 2 to 3 hours ahead.
If a product upsets your stomach, drop it and try another on the next long run. Finding out on race day costs you the race.
Common mistakes
- Racing it. A first long fast run at 95% can feel easy at 10 km and brutal at 25 km. Keep the first one at 90%.
- Skipping the easy days after. Without them the next quality workout suffers.
- Fixing the distance and ignoring the clock. When the plan says 28 km and you run 6:15/km, you have signed up for close to three hours. Cut kilometers before you cut pace.
- Changing fuel on race day. Race with the gel you tested in training.
Recovery and frequency
A big long fast run calls for 3 to 4 easy days afterward. Run it every 2 to 3 weeks in the support phase and every 2 in the specific phase. Do not add a quality session the next day.
To get a plan that places them for you, create one from the home page.
Frequently asked questions
What pace is the long fast run?
Between 85% and 95% of race pace, depending on the distance: 85-90% for 5K and 10K, 90-95% for the half marathon and 88-95% for the marathon. With a marathon at 4:27/km, 92% comes out at 4:48/km.
Does it replace the easy long run?
In the specific phase, yes. The very easy long run builds general base early in the plan. As the race approaches, the long run turns fast or gains a segment at marathon pace.
What is the maximum duration?
Between 2:30 and 3:00 hours for most recreational runners. For a slower pace, that limit shortens the distance: with a marathon at 5:45/km, 24 km at 92% takes 2:29.
How many gels should I take on a long fast run?
Between 30 and 60 g of carbohydrate per hour from about 40-45 minutes, which means one gel every 30-40 minutes with water. Use the same product you plan to use on race day.