Alto de Serna

Overview

Alto de Serna is a long, category 1 haul: 22.7 km of continuous climbing that carries you from 608 m at the base to 1705 m at the summit. The headline average is a moderate 4.82%, but that figure hides the real story. Over its full length the road delivers 1097 m of net elevation gain, while the total ascent tallies 1186 m — the difference of 89 m tells you there are dips and false flats where the road briefly gives back before clawing upward again. At category 1, this is one rung below the hardest hors catégorie climbs, and the challenge here is duration as much as steepness.

How the Gradient Unfolds

Do not let the 4.82% average lull you. A climb this long almost never holds a single pitch, and Serna is no exception. The presence of 1186 m of total ascent against 1097 m of net gain confirms the profile rolls: short recovery sections and even brief descents punctuate the ascent, meaning the climbing pitches are steeper than the average implies. The gradient peaks at 12.37% — more than double the average — so somewhere on this road you will hit a ramp that bites hard after the legs are already deep into a 22.7 km effort. Expect the toughest sections to feel disproportionately savage precisely because they arrive late, on tired legs.

Pacing Notes

On a climb of 22.7 km, discipline beats bravado. Anchor your effort to your sustainable power rather than the terrain: aim to hold a percentage of your FTP that you can carry for the better part of an hour or more. Because the average sits at 4.82% but the road spikes to 12.37%, resist the urge to surge on every steep pitch — those 12.37% ramps will spike your power well above threshold, and repeated matches burned early will cost you dearly before the 1705 m summit. Let the gradient come to you, and use the flatter recovery sections to bring your heart rate back down. If you are unsure what your threshold actually is, run the numbers through the FTP estimator before you plan your target power.

Gearing

With 1097 m of net gain packed into 22.7 km and pitches touching 12.37%, gear conservatively. A compact 34-tooth inner ring paired with a wide-range cassette is the sensible starting point. A 34×32 will get most fit riders up the steady 4.82% stretches, but on the 12.37% ramps — hit late, after 20-plus kilometres — you will be grateful for the extra relief of a 34×34. If you have the option, fit the 34×34: spinning a lower gear preserves your legs across the full length far better than grinding a bigger cog and blowing up before the summit.

Summary

Alto de Serna rewards patience. It is a long category 1 climb where the moderate 4.82% average masks a rolling profile and a stinging 12.37% maximum. Pace to your threshold, gear low, and respect the distance.

Length: 22.7 km
Average gradient: 4.82%
Max gradient: 12.37%
Start: 608 m
Summit: 1705 m
Net gain: 1097 m
Total ascent: 1186 m
Category: 1