Photo: Wikimedia Commons (CC BY-SA 2.5) / Source (opens in a new tab)Saint-Leu-la-Forêt
Les 40 Bosses
Saturday, 5 December 2026
Le Monstre 120K
120km D+ 5500m
La Belle 75K
75km D+ 3300m
L'Historique 45K
45km D+ 2100m
La Classique 20K
20km D+ 900m
Le Sprint 10K
10km D+ 400m
Race data
Terrain
Trail
Difficulty
Advanced
Distance
5 modalities
Le Monstre 120K
- Distance
- 120 km
- Elevation Gain
- D+ 5500m
- Max Time
- -
La Belle 75K
- Distance
- 75 km
- Elevation Gain
- D+ 3300m
- Max Time
- -
L'Historique 45K
- Distance
- 45 km
- Elevation Gain
- D+ 2100m
- Max Time
- -
La Classique 20K
- Distance
- 20 km
- Elevation Gain
- D+ 900m
- Max Time
- -
Le Sprint 10K
- Distance
- 10 km
- Elevation Gain
- D+ 400m
- Max Time
- -
| Modality | Distance | Elevation Gain | Max Time | Price |
|---|---|---|---|---|
| Le Monstre 120K | 120 km | D+ 5500m | - | - |
| La Belle 75K | 75 km | D+ 3300m | - | - |
| L'Historique 45K | 45 km | D+ 2100m | - | - |
| La Classique 20K | 20 km | D+ 900m | - | - |
| Le Sprint 10K | 10 km | D+ 400m | - | - |
Will your watch battery last the ~28 h of Les 40 Bosses?Worked out for the longest course (120 km). See which watches reach the finish with GPS on and which die on the way.Check my watch Check my watchYour checklist for Les 40 Bosses
What you need, category by category, with our #1 pick for this race. Tick what you already have.
0 of 7 ready
GPS watch
Done, you already have it
View on Amazon →(se abre en una pestaña nueva)Coros Pace 3
38 h battery life in full GPS mode
Downside: No touchscreen (buttons only)
Gear
Test shoes and pack on long training runs before race day
Done, you already have it
View on Amazon →(se abre en una pestaña nueva)
Salomon Speedcross 6
Agarre excepcional en barro y terreno técnico
Downside: Durabilidad media en asfalto
Nutrition
Take a gel every 30-45 minutes from the start
Done, you already have it
View on Amazon →(se abre en una pestaña nueva)
Maurten Gel 100
Tecnología de hidrogel: excelente tolerancia gástrica
Downside: Precio elevado respecto a otros geles
Sun Protection
Sweat-resistant SPF 50 before the start
Done, you already have it
View on Amazon →(se abre en una pestaña nueva)
Sun Bum Sunscreen Lip Balm SPF 30
Stick format easy to apply mid-race
Downside: SPF 30 may fall short at extreme altitude
Body Care
Anti-chafe balm on feet, armpits and groin before the start
Done, you already have it
View on Amazon →(se abre en una pestaña nueva)
BodyGlide Original Anti-Chafe Balm
Easy-to-apply stick format, even with sweaty hands
Downside: Higher price than traditional petroleum jelly
Accommodation
Look for a place within 15 minutes of the start
Done, you already have it
View on Amazon →(se abre en una pestaña nueva)
SleepDreamz Tapones de Silicona Moldeable 32dB
32 dB noise reduction
Downside: Don't block noise completely
Car Rental
Pick up the car at the airport on arrival
Done, you already have it
View on Amazon →(se abre en una pestaña nueva)
DRIVALIA Alquiler de vehículos por Suscripción CarCloud Country Plus
Trip logistics
Registration, travel and insurance: what you should have sorted before race day.
Affiliate links: if you buy, we earn a commission at no extra cost to you.
9 weeks to Les 40 Bosses: get your kit ready
Buying guides with the best value for money, picked for this kind of terrain.
Swipe to see all 4 comparisons
Historical weather
What to wear at 5 °C: guide and kit →
Typical weather for the race date (10-year average)
Temperature
2°C – 7°C
Average 5°C
Rain
50%
2.9 mm avg
Wind
19 km/h
max. average
Sunshine hours
3h
daily average
Gear recommendations
Bring a waterproof jacket (50% chance of rain)
Asics
Asics Gel-Trabuco 14 GTX
A best-selling beginner trail shoe: GEL cushioning, good stability and a waterproof GORE-TEX membrane. Versatile and reliable for training on mixed terrain in any weather.
Berghaus
Berghaus Paclite 2.0 GTX
Waterproof jacket with a Gore-Tex Paclite membrane (around 330 g). Fully waterproof with taped seams, fixed adjustable hood, storm flap behind the zip and cuff adjustment. Packs down small in a vest. Heavier than a pure running hardshell, but it meets the waterproof-breathable membrane requirement in race rules and is the affordable route into Gore-Tex.
Brooks
Brooks Cascadia 20 GTX
The Cascadia 20 with a GORE-TEX membrane: stability and protection for rocky mountain terrain, keeping the foot dry on cold, rainy days.
Gore Wear
Gore Wear C5 GORE-TEX Glove
Glove with a fully waterproof, windproof GORE-TEX membrane and light insulation. The pick for running in snow, sleet or heavy rain while keeping your hand dry.
Gore Wear
Gore Wear M GORE-TEX Thermo Glove
Warmer variant of the Gore Wear C5 GORE-TEX: the same fully waterproof, windproof membrane, with extra thermal lining for intense cold on top of snow or rain. The pick when the problem isn't just water, but water AND hard cold at once.
Gore Wear
Gore Wear R7 GTX Shakedry
Chubasquero Gore-Tex Shakedry ultraligero (110 g). Impermeabilidad total sin membrana interior, altamente transpirable. El referente para corredores de montaña.
Nike
Nike Pegasus Trail 5 GORE-TEX
The best-selling gateway trail shoe: comfortable, cushioned and versatile for moving from road to trail. Waterproof GORE-TEX version, perfect for beginners and easy runs on mixed terrain.
Salomon
Salomon Bonatti Pro Waterproof Glove
Lightweight waterproof glove built for running, not just standing still in the snow: a waterproof membrane with more dexterity and less bulk than a thick membrane glove, for sustained rain without giving up handling gels or poles.
Salomon
Salomon Bonatti WP
Chaqueta cortavientos impermeable ultraligera (135 g). Costuras selladas, capucha ajustable y ventilación trasera. Se pliega en su propio bolsillo.
Salomon
Salomon Speedcross 6 GTX
The Speedcross 6 with a GORE-TEX membrane: the same aggressive 5 mm lugs for mud and soft ground, now waterproof for winter, rain and snow.
Sealskinz
Sealskinz Waterproof Lightweight Glove
Lightweight waterproof glove from a brand that specializes in outdoor sport waterproofing. A solid middle ground between a thin windproof glove and a thick membrane glove: genuinely waterproof without the bulk or price of the Gore C5.
TRIWONDER
TRIWONDER Polainas Impermeables Trail
Waterproof, breathable low gaiters for trail running, hiking and mountain use. Under-shoe strap and adjustable elastic band. A budget-friendly alternative to premium technical brand gaiters.
Bring thermal layers (low of 2°C)
Buff
Buff Thermonet
Buff tubular térmico con tecnología Primaloft. Retiene el calor corporal, ultraligero y polivalente: gorro, braga, cinta. Ideal para alta montaña.
Craft
Craft Pro Hypervent LS Wind Top
Thermal top with a windproof ripstop panel on the chest and a highly ventilated soft jersey back. Built for high-intensity sessions in cold, windy conditions, with long cuffs and thumb loops.
HANKER
HANKER Braga de Cuello Térmica
Unisex thermal seamless neck gaiter in Soft Air Plus fabric (97% polyester). Seamless fit designed for trail running, cycling, motorcycling and outdoor sports. A budget alternative to Buff for moderate cold.
Icebreaker
Icebreaker Merino 200 Oasis LS Crewe
Long-sleeve thermal top in 100% merino wool (200g). Natural temperature regulation, genuine multi-day odor resistance and a soft, non-itch handfeel from the fine merino yarn.
Odlo
Odlo Active Warm Eco
Camiseta térmica de manga larga con tejido reciclado y tratamiento antiolor. Regulación térmica activa, ideal como capa base en montaña.
Odlo
Odlo I-Thermic Longsleeve Mujer
Women's long-sleeve thermal top with insulating panels placed over cold-sensitive areas (lower back and kidneys). A mid-layer built for genuinely cold winter conditions, mountain outings or cross-country-style trail sessions.
ROCKBROS
ROCKBROS Pasamontañas Térmico y Cortaviento
Thermal windproof balaclava covering head, ears, cheeks and neck. Designed for cycling and motorcycling, it works just as well on windy, freezing trail runs.
Salomon
Salomon Agile LS Tee
Lightweight quick-dry polyester long-sleeve tee with underarm mesh, a side pocket and reflective details. Works as a standalone layer in mild cold or as a base layer under a windbreaker on colder days.
Salomon
Salomon Cross Run Tight
Mallas largas de trail con tejido elástico y transpirable. Cintura ajustable, bolsillo trasero con cremallera. Protección contra el frío y la vegetación.
Salomon
Salomon Cross Warm Glove
Guantes térmicos de running con palma antideslizante y puntas táctiles. Ligeros, cálidos y compatibles con bastones.
Under Armour
Under Armour ColdGear Armour Compression Mock
Compression thermal top with a dual-layer fabric: ultra-warm brushed interior and quick-dry exterior. Second-skin compression fit with stretch mesh panels at the back and underarms for ventilation without losing warmth.
Under Armour
Under Armour ColdGear Armour Compression Mock Hombre
Men's high-neck thermal compression top: brushed interior that holds heat and a quick-dry outer. Base layer for cold-weather runs.
Bring thermal gloves (low of 2°C)
Gore Wear
Gore Wear C5 GORE-TEX Glove
Glove with a fully waterproof, windproof GORE-TEX membrane and light insulation. The pick for running in snow, sleet or heavy rain while keeping your hand dry.
Gore Wear
Gore Wear M GORE-TEX Thermo Glove
Warmer variant of the Gore Wear C5 GORE-TEX: the same fully waterproof, windproof membrane, with extra thermal lining for intense cold on top of snow or rain. The pick when the problem isn't just water, but water AND hard cold at once.
Icebreaker
Icebreaker Oasis Liners
Thin merino wool glove, lightweight and breathable, with good moisture management and none of the overheating of a thick technical glove. Ideal as a liner layer or for mild winter temperatures.
LEKI
LEKI Ultra Trail Storm Shark
Glove for pole runners with the Shark system: clips straight into the grip of compatible LEKI poles, transferring force without closing your hand. Windproof and water-repellent.
Ronhill
Ronhill GORE-TEX Windstopper Glove
Running glove with GORE-TEX Windstopper fabric: blocks wind and repels light rain without the bulk of an insulated glove. Thin, close-fitting and dexterous.
Salomon
Salomon Bonatti Pro Waterproof Glove
Lightweight waterproof glove built for running, not just standing still in the snow: a waterproof membrane with more dexterity and less bulk than a thick membrane glove, for sustained rain without giving up handling gels or poles.
Salomon
Salomon Cross Warm Glove
Guantes térmicos de running con palma antideslizante y puntas táctiles. Ligeros, cálidos y compatibles con bastones.
Salomon
Salomon Fast Wing Winter Glove
Technical winter trail running glove with a windproof outer shell and warm lining. Built for long outings in intense cold, wind and some moisture in the mountains.
Sealskinz
Sealskinz Waterproof Lightweight Glove
Lightweight waterproof glove from a brand that specializes in outdoor sport waterproofing. A solid middle ground between a thin windproof glove and a thick membrane glove: genuinely waterproof without the bulk or price of the Gore C5.
Consider long tights for nighttime cold
Amazon Essentials
Amazon Essentials Mallas Active Sculpt Talla Grande
High-waisted leggings with Active Sculpt compression fabric, available in plus sizes. Wide waistband that doesn't roll down or over-compress during long mountain outings.
Izas
Izas Olimpia Mallas Largas Mujer
Women's long leggings with a shaping, push-up compression effect, stretch breathable fabric and reflective details. Originally designed for gym and yoga, but the compression and reflective details also make it usable for low-light running.
Joma
Joma Pantalones Térmicos Academy Knight Hombre
Men's thermal pants with a brushed inner lining, built for training and running in cold weather. Elastic drawstring waist and heat-retaining fabric for winter outings or cold early mornings.
Joma
Joma Vela II Shorts Mujer
Lightweight, stretch women's running shorts with a wide size range (4XS to 2XL). Breathable fabric built for training and running in summer without overheating.
Salomon
Salomon Cross Run Tight
Mallas largas de trail con tejido elástico y transpirable. Cintura ajustable, bolsillo trasero con cremallera. Protección contra el frío y la vegetación.
Forecast for 5 December
Weather forecast from Open-Meteo (may change until race day)
Les 40 Bosses: the toughest trail in Île-de-France
Nobody expects 5,500 m of climbing 25 km from Paris. Les 40 Bosses (“the 40 bumps”) finds it in the Montmorency forest by linking short, brutal climbs one after another in a maze of trails that north Paris runners know by heart.
Five formats
- Le Monstre: 120 km / 5,500 m D+
- La Belle: 75 km / 3,300 m D+
- L’Historique: 45 km / 2,100 m D+
- La Classique: 20 km / 900 m D+
- Le Sprint: 10 km / 400 m D+
Mud, leaves and cold
Early December means soaked ground, leaves hiding roots and short days. The course passes the Tour du Plumet, the Pont du Diable and the Étangs Marie, with hidden singletrack around Béthemont, Bessancourt and Chauvry. Deep-lugged shoes are the best investment for this race.
A Paris getaway
Combine the race with a few days in Paris and its Christmas markets. Find more events among the races in Île-de-France and fit the dates with the race planner.
360Complete Pack
Les 40 Bosses 2026 registration
RegistrationPlaces are limited on every distance: secure your bib on the official website before it sells out.
Tips
- •Check deadlines and prices for each distance on the official website
- •France requires an FFA licence or the online PPS (Parcours Prévention Santé) for non-members
- •Keep your confirmation: it is checked at bib pick-up
Where to stay for Les 40 Bosses
AccommodationBook close to the start in Saint-Leu-la-Forêt: local accommodation fills up fast on race weekend.
Tips
- •Look for a place within 15 minutes of the start
- •Earplugs and eye mask if the start is before dawn
- •Microfibre towel and a duffel bag to keep your kit organised
Gear for Les 40 Bosses
GearDecember in the Montmorency forest: mud, leaves and cold. Deep-lugged or GTX shoes, a headlamp for the long distances, gloves and a waterproof layer.
Tips
- •Test shoes and pack on long training runs before race day
- •Check the mandatory gear list in the race rules
- •Always carry a waterproof jacket in autumn and winter
Which shoes for Les 40 Bosses?
Which footwear fits based on the race's terrain and weather
Which GPS watch for Les 40 Bosses?
Which watch has the battery to last based on your estimated finish time
Best Neck Gaiter (Buff) for Trail Running 2026: Comparison & Buying Guide
Comparison of the best neck gaiters for trail running in 2026: Buff Original, Midweight, Windproof, DryFlx, CoolNet UV+, Thermonet, HANKER and Salomon Merino. Which to pick based on sun, wind, cold or budget.
Best Thermal Base Layer for Trail Running 2026: Comparison & Buying Guide
The best thermal base layers for trail running in 2026: Odlo Active Warm Eco, Icebreaker Merino 200 Oasis, Craft Pro Hypervent, Under Armour ColdGear, Salomon Agile LS Tee and Odlo I-Thermic. Which to pick based on cold, sweat management, merino wool, compression or built-in wind protection.
Best Trail Running Gaiters 2026: 3-Way Comparison
Comparing the 3 best trail running gaiters in 2026: Salomon Trail Gaiters High, Salomon Trail Gaiters Low and TRIWONDER waterproof gaiters. Which to pick by terrain and budget.
Nutrition for Les 40 Bosses
NutritionPlan 60-90 g of carbs per hour on long sections and replace salts even when it is cool.
Tips
- •Take a gel every 30-45 minutes from the start
- •Electrolytes in every bottle: you sweat even in the cold
- •Recovery drink within 30 minutes of finishing
Getting to Saint-Leu-la-Forêt
TransportSaint-Leu-la-Forêt is about 25 km north of Paris with a train station (line H from Gare du Nord). Charles de Gaulle airport is around 30 minutes away by car.
Tips
- •Compare flight + car with driving
- •Arrive the day before to collect your bib calmly
Car hire for Les 40 Bosses
Car RentalPublic transport to Saint-Leu-la-Forêt is limited: a hire car gives you freedom for the start and the trip home.
Tips
- •Pick up the car at the airport on arrival
- •Book early: prices rise on race weekend
Sports insurance for Les 40 Bosses
InsuranceIf you travel from abroad, bring your EHIC/GHIC and travel insurance covering mountain sports.
Tips
- •The FFA licence includes insurance; the PPS does not cover accidents
- •Check your policy covers mountain rescue in France
Body care for Les 40 Bosses
Body CareMud, damp and long hours of effort: prevent chafing and blisters and look after recovery.
Tips
- •Anti-chafe balm on feet, armpits and groin before the start
- •Seamless technical socks and blister plasters in your pack
- •Compression socks and a foam roller for recovery
Sun protection for Les 40 Bosses
Sun ProtectionEven in autumn or winter, sun on the ridges and glare from sea or rock burn: protect face and lips.
Tips
- •Sweat-resistant SPF 50 before the start
- •Lip balm: dry wind cracks lips
- •Light sunglasses for exposed sections
Frequently Asked Questions
- When is Les 40 Bosses 2026?
- On 5 and 6 December 2026 in Saint-Leu-la-Forêt (Val-d'Oise), in the Montmorency forest.
- What distances are there?
- Le Monstre 120 km / 5,500 m D+, La Belle 75 km / 3,300 m D+, L'Historique 45 km / 2,100 m D+, La Classique 20 km / 900 m D+ and Le Sprint 10 km / 400 m D+.
- Can I get there by public transport?
- Yes: Transilien line H from Gare du Nord stops at Saint-Leu-la-Forêt.
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