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Race IntelligenceVieux-Boucau-les-Bains, France

Challenge Vieux Boucau

Know your day before you race it.

Enter four numbers you already train with. You get a likely finish range, target paces and watts, and how I would race this course.

Race day
10 October 2026
Swim
1.9 km
Bike
90 km
Run
21.1 km

Published route evidence. Final 2026 route pending. Checked 15 Sept 2026.

01 Race Card

Build my Race Card

Your first range uses conservative assumptions. Add optional evidence to make it more specific. It is calculated in your browser and saved only on this device.

Your numbers
Distance unit
Weight unit
You and this race
Sharpen your range with more detailOptional. Recent swim, bike and run results, equipment and transitions.

Add only the evidence you have. Every control changes a discipline range, its uncertainty, or an execution-risk explanation.

Swim evidence

Replaces the broad pool-to-open-water assumption.

Bike and equipment

These replace broad mass, aerodynamics, tyre, and power-to-speed assumptions.

Run evidence

A recent effort and honest durability/acclimation answers refine the post-bike run.

Race execution

Transition proficiency changes the T1/T2 range and how wet conditions are treated.

02 The course

What Vieux Boucau actually gives you

You start with a wave-free swim in the Lac Marin de Port d'Albret, ride a single fast loop through the open roads of the Landes, then run four laps around the lake and through Vieux-Boucau's streets and pine forest. The course removes the excuses. The question is whether you can hold your own effort while the coastal wind and a repeating run course try to talk you out of it.

Show distances in

Swim

1.9 km

Sea Inlet / Marine Lake

Layout
1 loop with an Australian exit
Setting
Lac Marin de Port d'Albret

A wave-free, current-free marine lake removes the ocean-swim variable while the Australian exit still asks you to settle back into rhythm mid-loop.

Source: current course description

Bike

90 km

Fast, Mostly Flat Coastal Roads

Layout
1 loop
Setting
the Landes region's open roads
Elevation
290 m published profile difference

A flat course reduces climbing cost, while high exposure on the Landes' open roads makes wind management the real variable.

Source: current course description

Run

21.1 km

Flat Lakeside, Town and Pine Forest

Layout
4 loops
Setting
around Lac Marin de Port d'Albret and through Vieux-Boucau
Elevation
5 m published profile difference

Low elevation and shaded pine-forest sections favour rhythm; four repeated laps give you constant feedback on pace and fuelling.

Source: current course description
Where these course facts come from

These facts come from the organiser’s latest published material: swim, current course description; bike, current course description; run, current course description. They describe the character of the course. They do not confirm the final 2026 route.

03 Race plan

How I’d want you to race it

One job for each part of this course. The distance markers tell you when the job changes. The course tells you why.

Swim

Use the calm water

  1. 0–1900 m

    The loop and the exit

    Settle before the Australian exit resets you

    The marine lake has no waves and no current, so the swim rewards a settled, repeatable rhythm more than raw power. The Australian exit interrupts that rhythm partway round; treat it as a brief reset, not a race move.

    • Find your rhythm early, the water will not disrupt it for you
    • Use the exit to check form, then get straight back in

Bike

Ride the wind, not against it

  1. 0 km–30 km

    Leave the lake

    Settle into the Landes before the wind asks questions

    The opening kilometres take you out onto the region's fast, open roads. Use them to find position and start fuelling before exposure becomes the deciding factor.

    • Start drinking before the open roads
    • Check effort before average speed

  2. 30 km–70 km

    Hold the loop

    Let the wind move the speed, not the effort

    A mostly flat single loop with only a few small hills will feel fast in places and hard in others, purely because of Atlantic wind. Ride the same effort in both.

    • Ride the plan by power or perceived effort, not the number on the screen
    • Bank nothing on a tailwind stretch

    Do not repay a headwind by digging a hole

  3. 70 km–90 km

    Return to the lake

    Arrive ready for four laps, not one hard finish

    As the loop closes back towards Vieux-Boucau, stop chasing speed. Finish your planned nutrition and get the legs turning over faster before you rack the bike.

    • Finish the bottle you planned
    • Let cadence rise before T2

Run

Make four laps work for you

  1. 0 km–5.3 km

    Lap 1

    Find running legs before you trust them

    The first lap around the lake and into town will feel quicker than it is. Use the shaded pine-forest sections and the first two aid stations to convert bike legs into running legs.

    • Shorten your stride out of T2
    • Take the km 2 and km 4 aid stations deliberately

  2. 5.3 km–15.8 km

    Laps 2 and 3

    Use the repetition, don't fight it

    Two more laps past the same lake, town streets and pine forest give you regular checkpoints. Use each pass to check posture and fuelling rather than letting a familiar stretch tempt you into a faster split.

    • Assign a check to each lap landmark
    • Keep taking the aid stations even when you feel fine

  3. 15.8 km–21.1 km

    The last lap

    Earn the last move on the fourth pass

    Only on the final lap should you decide whether the day has given you permission to race. If it has, change one thing at a time: cadence, posture, then pace.

    • Look for a genuinely strong final lap before committing
    • Keep the finish decision yours, not the crowd's

04 Race week

What I would keep an eye on

There is no useful 2026 forecast this far out. For now, past race dates give us a point of reference. Closer to the race, the forecast will tell us whether the plan needs changing.

Forecast statusToo early for a forecast

A race-day forecast is not meaningful yet; check back closer to the event.

Temperature
13.5–24.4°CDew point centred on 13.5°C
Wind and gusts
10.0 km/hGusts up to 43.6 km/hPrevailing direction W
Rain likelihood
Up to 85%Wet-surface uncertainty retained

Historical baseline, 2019–2025 · Open-Meteo historical archive · Updated 2026-09-15.Historical comparison only. This is not a forecast for 2026.

05 Method

What goes into your range

Your CSS, FTP, weight and run threshold create the first range. Open-water, bike, run and execution evidence can replace broad assumptions. Course data and the historical conditions baseline shape every simulation.

  1. Your numbersCSS · FTP · weight · run threshold
  2. This raceDistance · water type · elevation · exposure
  3. Your Race CardFinish and discipline ranges, with target paces and watts

Confidence is built from four inputs

Athlete evidence
Builds with recent open-water, bike and run efforts
Bike setup
Builds with equipment, mass, aero and tyre detail
Course evidence
Partial while the 2026 route is unconfirmed
Race-week conditions
Historical baseline until a forecast is useful
How the model works

It starts with the targets in your Race Card, then samples the parts of a 70.3 that vary: open-water pace, transitions, bike speed at the planned power, and the drop in run performance after the swim and bike. Repeating that calculation produces a likely range rather than a single heroic number.

The current time calculation uses this race’s published distances, or standard 70.3 distances where none are published, with the available course headings, elevation and exposure evidence. Weather scenarios vary temperature, dew point, wind, gusts, rain and water conditions together. Unknown route detail stays visible as uncertainty rather than false precision.

It is not predicting your exact finishing time, placing, or race-day weather. It answers a narrower question: given the plan and the information we have, what range of day is plausible, and where is the uncertainty coming from?

Confidence is not a permanent “low”. It is recalculated across four separate inputs:

  • Your evidence: consistent inputs and recent race-like swim, bike, and run results.
  • Bike setup: measured or specified aerodynamics rather than a broad prior.
  • The course: verified distance and route character, including elevation and technical sections.
  • The conditions: a current forecast is more useful than a historical comparison.

It starts low when those inputs are broad. It can become moderate or high as the evidence improves. A narrower range means better information, not a guarantee.

06 Next steps

If Vieux Boucau is your race

Your range is built on today’s numbers. The months of training before race day decide what those numbers become.

The work from here.

Self-guided routeHalf-distance training plansTraining plans for the fitness and durability this course asks for.See the plans Personalised routeWork with me on the whole buildCoaching when you want the plan, feedback and race decisions joined up.See coaching

Further reading

ArticleHow to pace a 70.3 so you can still runThe longer version of the swim-bike-run pacing logic behind this Race Card.ArticleOpen water swimming tacticsUseful for settling into the marine lake and recovering rhythm after the Australian exit.

Evidence

Sources and verification

Course status: Partially verified. The organiser’s descriptions and latest published route profiles are in use. The final 2026 route is not yet confirmed. Last checked 2026-09-15.