Trail Running · Chamonix

🇫🇷TDS 148 km:
Course Analysis & Race Readiness

145 km with 8,725 m of climbing and 8,904 m of descent across 16 climbs and 14 descents. Net-negative terrain that punishes the legs downhill as much as up.

CourseRecon scores your own training against the descending and durability demands that define TDS 148 km — the sample analysis below shows exactly how.

145 km

Distance

+8,680 m

Vertical Gain

−8,860 m

Total Descent

Aug 24, 2026

Next Edition · 35 days out

Check YOUR readiness

Connect Strava · No card · 2 min

The Course · GPS-Measured

What 145 km / 90.0 mi and 8,680 m / 28,480 ft of vertical gain actually look like

Measured from the GPS track: 145 km / 90.0 mi and 8,680 m / 28,480 ft of vertical gain. This is the terrain you're signing up for: read it before it reads you.

Course Profile

Terrain summary

Claimed vs GPS-Measured

Claimed · Organizer

145km

Distance

+8,730m

Gain

+0.0 km−50 m

GPS-Measured

145km

Distance

+8,680m

Gain

Climb & Gradient

+8,680 mTotal Gain

−8,860 mTotal Loss

Gradient Distribution

22%

Flat

≤3% grade

23%

Run-Climb

3–15% up

15%

Steep Climb

>15% up

40%

Descent

downhill

Steepest Sustained Sections

Climb

KM 126.0–128.0 · +552 m

+25.7%

ClimbCRUX

KM 49.3–57.8 · +1,549 m

+18.2%

Descent

KM 60.6–63.7 · −538 m

-17.4%

Descent

KM 128.0–130.0 · −405 m

-16.7%

Finish & Cutoff Times

What it takes to finish

Reference finish times from past results — use them to set a realistic goal pace.

18h 59m

Winning time

20h 45m

Top 5

21h 26m

Top 10

44h 55m

Back of pack

What This Race Demands

Four things this course asks of your body

Every course weights the four pillars of mountain-ultra fitness differently. Descending carries 51% of the scoring weight on this course — the terrain makes that the deciding factor.

Weighting shows where readiness is won or lost at this distance — not whether you need each pillar. An aerobic base is a given for a race this long, so it carries little deciding weight even though it's essential — the gaps open on the climbs, descents and the back half.

AerobicSustained engine

Foundational

Sustained ultra-length effort at altitude, climbing from 1,222 m to a 2,590 m high point.

ClimbingVertical power

20%

16 climbs totaling 8,725 m, including a single 1,549 m ascent over 8.5 km.

DescendingEccentric / braking

51%

14 descents totaling 8,904 m; 46% of the course points downhill, much of it very steep.

DurabilityLate-race resilience

29%

Repeated impact over 145 km with net-negative loss, testing leg integrity to the finish.

The Profile in One Line

A 145 km ultra where relentless descending outweighs climbing, demanding legs that survive 8,904 m of downhill loss.

Aerobic FoundationalClimbing 20%Descending 51%Durability 29%

Here's how CourseRecon reads a course and an athlete

Sample Readiness Analysis

What a readiness result looks like for this course

This is a worked example for a representative strong mountain-ultra athlete — not your score. Connect your own training and the same analysis runs on you.

Sample

OUT OF 100

QUESTIONABLE

For a representative strong mountain-ultra athlete

This is a sample — connect your Strava to see your own result.

Pillar Breakdown

Aerobic

With a start at 1,222 m rising to 2,590 m, the course demands aerobic capacity that holds across many hours of thin-air climbing.

Climbing

Sixteen climbs stacking 8,725 m of gain, headlined by a 1,549 m ascent over 8.5 km at 18.2%, require both power and pacing discipline.

Descending

The dominant demand: 8,904 m of loss over 14 descents, with very-steep grades covering 21.2% of distance and drops up to 1,437 m, hammering the quads.

Durability

At 145 km with net-negative elevation, the constant eccentric loading demands muscular resilience so late climbs and descents remain runnable.

KM 49–58

The 1,549 m Climb

A single 1,549 m ascent over 8.5 km at 18.2% grade is the biggest climb on course, demanding sustained power without redlining before the descents that follow.

Descending

8,904 m of Loss

With 14 descents including a 1,437 m drop and a 12.1 km descent, downhill loss exceeds total gain, making quad durability the decisive factor.

KM 125–128

The 25.7% Wall

Late in the race, a 552 m climb over 2.1 km at 25.7% grade tests reserves after more than 125 km of accumulated fatigue.

That was a sample