Col du Loson cycling climb profile
The Col du Loson is not a climb that can be reduced to a single steep section or a short anaerobic test. On the numbers alone, it is an endurance problem first: 36.5 km of climbing, rising from 587 m to 3291 m, with 2704 m of net elevation gain. That places it firmly in HC territory, and the reason is obvious. A 7.41% average over that distance is not just hard - it is the kind of sustained load that exposes pacing errors long before the summit.
The key feature is the combination of length and severity. Plenty of climbs can average around this gradient for a shorter duration, but holding that demand across 36.5 km changes the physiology and the tactics. You are not managing one effort. You are managing repeated muscular strain, fueling, temperature changes, and the risk of drifting above threshold too often.
How the gradient unfolds
From the base at 587 m, the road gains steadily toward a summit at 3291 m. With a 7.41% average, the climb should be treated as consistently demanding rather than rolling or forgiving. The listed maximum gradient of 23.1% is the warning sign. Even without sector-by-sector data, that number tells you the climb contains ramps steep enough to punish anyone riding too close to the limit early.
That is the practical reading of the profile: the average is already high, and the steepest pitches are far above sustainable climbing rhythm. On a climb this long, those sharp sections matter less as isolated moments and more as fatigue multipliers. Each time the gradient kicks, torque rises, cadence can fall, and the effort can spike well above a controlled aerobic pace. Do that too often and the final part of the climb becomes damage control.
Pacing strategy
The first objective is restraint. A 36.5 km HC climb with 2704 m of net gain should be paced from the bottom as a long threshold-adjacent endurance effort, not as a climb to attack early. If using power, anchor the effort below your /glossary/ftp for the opening phase and give yourself room for the 23.1% ramps. If using feel, the correct early intensity should feel almost too calm.
Avoid chasing speed on the steeper sections. On this profile, the steep ramps are where riders will overpay. Let cadence drop only as much as necessary, keep the upper body quiet, and return to a sustainable rhythm as soon as the road eases.
Gearing and ride notes
Bring genuinely low climbing gears. The average gradient already demands efficient seated climbing, and the 23.1% maximum means a standard race setup can become a liability late in the climb. The goal is not to spin easily everywhere. It is to avoid being forced into low-cadence grinding when fatigue is already high.
Fuel early, pace conservatively, and treat the summit elevation as part of the challenge. The Col du Loson cycling climb rewards riders who keep the effort boring for as long as possible. The profile is too long, too high, and too steep in places to bluff with enthusiasm.