Demi de Jussy: Course, Elevation & Route Profile

Course & Elevation

Both laps follow the same loop: out of Jussy to the southwest on Route de Lullier, over the field lanes past Lullier, then east across the plateau, into the woods above Les Fossats and through the hamlet of La Renfile, back on Chemin des Grands Bois and Chemin des Meurets and finally down Route de Juvigny into the village. The lap split and the finish are at the same spot in front of the mairie.

Because the loop is run twice, its rhythm doubles too. Twice you leave the village downhill to the low point at Lullier, twice a very even, shallow rise of around five kilometres follows up into the woods, and twice the course falls back from there into the village. None of it is steep, but the pattern repeats when you are tired, and that is a different race from the first lap.

The 20 km sets off first of the evening so that it is done by the time the course closes. That puts the second lap in the window when the 10 km runners and the walkers have already finished: less light on the course, fewer runners in sight, and on the chemins you are often alone with your lamp. The race reaches its 44th edition in 2026 and is organised by a club with more than a hundred volunteers.

Pacing Strategy

The only sensible way to divide this distance is by lap time. The first lap feels fast in a big field on fresh legs, and it costs you almost nothing to run it clearly more calmly than it feels. A race that falls apart on the second lap was decided on the first.

The decisive part is the second pass over the shallow drag, roughly kilometre twelve to seventeen. It is the same rise as the first time, but now on tired legs and without a group, and because it never turns steep there is no natural moment where you switch to pushing. That is exactly where you lose seconds per kilometre without noticing. Plan for a deliberately higher effort at the same pace through that stretch.

The trap is familiarity. Coming through the lap split in front of the mairie, surrounded by spectators and light, almost everyone starts the second lap too fast, and the next three kilometres are downhill, which amplifies the error. Let the lap start quietly and use the falling final third only if something is genuinely left.

Training plan for Demi de Jussy: 12-week build

Twenty kilometres on this loop take an age-group runner roughly 1:25 to 2:15. The demand is steady aerobic work over a long duration, with no anaerobic spikes and no technical ground, but with one very shallow rise that comes round twice. This is an endurance task with pace control, not a strength task.

The key stimulus is the long run with speed in its back half. In the two to three months before the race, sessions of 90 to 110 minutes with the last 30 to 40 minutes at marathon to half marathon pace, ideally on gently rising ground, match the second lap more closely than any interval session.

The conditions need their own preparation. The race starts late in the evening and runs into the night, so most of your effort falls at an hour you normally do not run. Move at least two long runs into the late evening, with the headlamp you will race in, and use them to work out how much you can eat across a whole day beforehand. The second lap without a group also asks for the ability to hold pace alone.

The surface question is repeatability. Around half the loop is farm track with a changing surface, and you cover it twice, the second time with tired feet. Regular long runs on field and forest paths rather than asphalt are the more concrete preparation here than extra track sessions.