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Trail Running · Chamonix

🇫🇷Marathon du Mont-Blanc 90 km:
Course Analysis & Race Readiness

An 89 km ultra with 5,660 m of climbing and 5,664 m of descent across nine climbs and ten descents. Descending dominates, but relentless steep gradients demand both strong legs and lasting durability.

CourseRecon scores your own training against the descending and durability demands that define Marathon du Mont-Blanc 90 km — the sample analysis below shows exactly how.

89.1 km
Distance
+5,660 m
Vertical Gain
−5,660 m
Total Descent
25 Jun 2027
Next Edition · 293 days out
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The Course · GPS-Measured

What 86.8 km / 53.9 mi and 5,660 m / 18,570 ft of vertical gain actually look like

Measured from the GPS track: 86.8 km / 53.9 mi and 5,660 m / 18,570 ft of vertical gain. This is the terrain you're signing up for: read it before it reads you.

Course Profile

Claimed vs GPS-Measured
Claimed · Organizer
89.1km
Distance
+6,240m
Gain
−2.3 km−580 m
GPS-Measured
86.8km
Distance
+5,660m
Gain
Climb & Gradient
+5,660 mTotal Gain
−5,660 mTotal Loss
Gradient Distribution
19%
Flat
≤3% grade
26%
Run-Climb
3–15% up
15%
Steep Climb
>15% up
40%
Descent
downhill
Steepest Sustained Sections
1
Descent
KM 39.9–43.9 · −890 m
-22%
2
Climb
KM 43.9–51.2 · +1,197 m
+16.5%
3
Climb
KM 35.5–39.9 · +717 m
+16.4%
4
Climb
KM 68.1–75.1 · +1,105 m
+15.7%
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 52% 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 output over 89 km between 1,044 m and 2,467 m of elevation.
ClimbingVertical power
21%
5,660 m of total gain across nine climbs, including a 1,424 m ascent.
DescendingEccentric / braking
52%
5,664 m of loss over ten descents, with grades reaching -22%.
DurabilityLate-race resilience
27%
Repeated 15-16% climbs and steep descents late, past 68 km, tax fatigued legs.
The Profile in One Line

Ninety kilometers of near-symmetrical up and down, weighted toward sustained, punishing descents.

Aerobic FoundationalClimbing 21%Descending 52%Durability 27%

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
58
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
100
The 89 km distance and 2,467 m high point require steady aerobic capacity, though the course rewards climbing and descending strength over pure endurance.
Climbing
80
Nine climbs totaling 5,660 m, including a 1,424 m biggest climb and sustained 16-16.5% pitches, demand strong, efficient ascending.
Descending
42
Ten descents totaling 5,664 m with a 1,158 m longest drop and grades to -22% place the heaviest load on braking control and quad resilience.
Durability
70
Alternating steep climbs and descents across nine ascents and ten descents, with hard efforts arriving past 68 km, test resistance to accumulated fatigue.
km 40–51
Plunge then Reclimb
A -890 m descent at -22% over km 40–44 immediately gives way to a 1,197 m climb at 16.5% through km 51, shredding legs on both directions.[m].[m]
km 68–75
Late Steep Climb
A 1,105 m ascent at 15.7% arriving past 68 km forces a heavy climbing effort on already-fatigued legs.
Descent load
Cumulative Downhill
With 5,664 m of loss across ten descents, including a 1,158 m drop, quad-eccentric fatigue becomes the decisive limiter over the full 89 km.
That was a sample

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