Chiltern Hills 100K.
The Chiltern Hills 100K is an anticlockwise loop from Chesham through the Chiltern Hills, taking in the Ashridge Estate and Coombe Hill. These are low hills, and the course barely gets above 250 metres, yet the climbing adds up to around 1,900 metres. There is no big mountain to prepare for, only a long series of short climbs on tired legs.
Chiltern Hills 100K 2027: Course, Elevation & Route Profile
Start and finish are at Chesham Guides HQ in Buckinghamshire, a little under 120 metres above sea level. The first 13 kilometres rise gently to just over 220 metres before the course drops back to the valley by kilometre 18. From there the day's pattern sets in: up to around 240 metres, down to about 130, with barely a fifth of the loop properly level.
The second half is the harder one. Between kilometres 49 and 82 six climbs arrive five to seven kilometres apart. The steepest starts at kilometre 69: 800 metres averaging 14 percent, passing 20 at its sharpest point. Five kilometres on comes the next, shorter but barely any gentler. From kilometre 80 comes the longest way up, almost 120 metres of gain to the last high point. Even that is not the end of it: the course rises twice more before heading down into Chesham.
Landmarks on the loop include the Ashridge Estate and Coombe Hill. It is fully marked with GPS as a backup, and the checkpoints offer water, food and toilets. The field is limited to 250 runners and the time limit is 19 hours. With the race in early October, anyone using most of that limit will cover part of the course in the dark.
| Start | Length | Ø | Max. | Gain | Cat. |
|---|---|---|---|---|---|
| km 19 | 1 km | 6.7 % | 13.3 % | +65 m | — |
| km 38.1 | 1.5 km | 5.1 % | 15.5 % | +73 m | — |
| km 49.6 | 1.9 km | 6.1 % | 11.5 % | +114 m | Cat. 4 |
| km 56.7 | 1 km | 9 % | 16.2 % | +87 m | Cat. 4 |
| km 62.7 | 0.9 km | 7 % | 18 % | +65 m | — |
| km 69.2 | 0.8 km | 14.1 % | 21.7 % | +112 m | Cat. 4 |
| km 74.2 | 0.6 km | 11.8 % | 22 % | +68 m | — |
| km 80.1 | 1.8 km | 5.7 % | 17.6 % | +99 m | Cat. 4 |
Climb categories follow the road-cycling convention and rate the terrain itself (length and gradient) regardless of sport: Cat. 4 marks the easiest rated climbs, Cat. 1 the hardest, and HC (hors catégorie, “beyond categorization”) is reserved for the most brutal ascents. Short climbs below the Cat. 4 threshold stay unrated.
How to pace Chiltern Hills 100K 2027.
Start under control
The work is unevenly spread: the first half rolls, while the steep sections gather between kilometres 49 and 82. So run the gentle first 13 kilometres deliberately below what feels right. There is little time to be won there that will help you later, and plenty of strength to waste.
Hold your rhythm
The race is decided between kilometres 69 and 75, where the two steepest climbs arrive after a good two thirds of the distance. At 14 percent a strong walk is the faster option. Plan it from the outset, so you can break straight back into a run at the top rather than needing to recover first. Still moving rhythmically here, you control the final 25 kilometres.
Spend what is left
The real trap is downhill. More than a third of the course descends, and every short drop invites free speed. Racing into the valleys is paid for in the quads, and the bill arrives at kilometre 80 when the last long ascent begins. Let it run only as far as you can without braking.
Training plan for Chiltern Hills 100K 2027: 12-week build
Build the base
Age-group athletes can expect roughly 12 to 18 hours on their feet, with the 19-hour limit setting the ceiling. The effort is aerobic throughout, broken by a long chain of short spikes: every climb lifts the heart rate, every descent loads the quads, and calm level running is rare.
Train race pace
The critical phase comes beyond kilometre 65, when you have to power-walk gradients above ten percent after many hours on your feet. Build your long runs so that the steepest hills fall in the final hour, and practise a brisk uphill walk as a skill in its own right.
Rehearse the course
What separates this from preparing for an alpine ultra is repetition. Long climbs are not needed, since no hill here gains much more than 100 metres in one go. A session of many repeats on a short, steep slope fits the demand better: walk up, run down under control. Add strength work for the quads and downhill running on tired legs, because all that descending ends up costing more than the climbs do.
Arrive fresh
An early October date puts your longest sessions in late summer. Take at least one of them into darkness, so that headtorch, pace and eating all work at night. Use it to practise planning your fuelling from checkpoint to checkpoint, as 250 starters spread out quickly over 100 kilometres and you may run long stretches alone. Rehearse following the markings and your GPS while tired, too.
Courses
Download the Chiltern Hills 100K 2027 course as a GPX file for your watch or bike computer.
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Everything about Chiltern Hills 100K.
How long is Chiltern Hills 100K 2027?
Chiltern Hills 100K 2027 is 100 km long. That distance shapes how much aerobic endurance, pace durability, and race-specific work belong in the training plan.
How much elevation gain does Chiltern Hills 100K 2027 have?
Chiltern Hills 100K 2027 has around 1,910 m of elevation gain over 100 km. That affects pacing, muscular load, and preparation for late-race sections.
What is the route profile of Chiltern Hills 100K 2027?
Chiltern Hills 100K 2027 is classified as Hilly, averaging 19.2 vertical metres per kilometre. 19% of the route is flat, 33% climbs moderately (2 to 6%) and 6% is steeper than 6%.
What climbs does Chiltern Hills 100K 2027 have?
The hardest climb of Chiltern Hills 100K 2027 starts at kilometre 49.6, runs for 1.9 km at an average of 6.1% and gains 114 metres. Cycling-convention rating: Cat. 4. 8 climbs are mapped in total.
Is Chiltern Hills 100K 2027 a loop course?
Yes, Chiltern Hills 100K 2027 is laid out as a loop: start and finish are in the same place.
Is there a GPX file for the Chiltern Hills 100K 2027 course?
Yes. The Chiltern Hills 100K 2027 course is on this page as a free GPX download — ready to import into Garmin, Wahoo, Komoot, Strava or any other app that reads GPX.
How should I prepare for Chiltern Hills 100K 2027?
Preparation for Chiltern Hills 100K 2027 should account for 100 km, 1,910 m of elevation gain, current training load, and available training time. An adaptive plan helps place key sessions without ignoring recovery and real life.
What pacing strategy works for Chiltern Hills 100K 2027?
The pacing strategy for Chiltern Hills 100K 2027 should reflect 100 km, 1,910 m of elevation gain, and your current fitness. Start controlled and keep margin for sections where the profile or fatigue makes target pace harder.
When does Chiltern Hills 100K 2027 take place?
Chiltern Hills 100K 2027 takes place on October 2, 2027.
Where does Chiltern Hills 100K 2027 take place?
Chiltern Hills 100K 2027 takes place in Chesham, United Kingdom.
How do I register for Chiltern Hills 100K 2027?
Registration runs through the organiser: runawayracing.com. YOUB shows you the course, elevation profile and training plan for your preparation.
