Riding the Étape or the Marmotte: what the profile doesn't show

Two events dominate the amateur Alpine calendar, and in 2026 they shared a finish line. The Marmotte Granfondo Alpes, on 28 June, ran 177 km with 5,000 m of climbing from Bourg d'Oisans over the Glandon, the Télégraphe and the Galibier before the 21 bends of Alpe d'Huez. Three weeks later, on 19 July, the 34th L'Étape du Tour de France covered 170 km and 5,400 m from Le Bourg-d'Oisans over the Croix de Fer, the Télégraphe and the Galibier, then reached Alpe d'Huez the hard way, via the Col de Sarenne, tracing stage 20 of that year's Tour. Both organisers publish a profile. Both profiles are accurate. Neither tells you the things that end most riders' days.

What the profile shows

The published figures are worth having exactly, because the estimates that circulate on forums are often wrong. The Alpe d'Huez tourist office measures the classic 21-bend climb at 14.454 km from Bourg d'Oisans at 717 m to the resort at 1,860 m: 1,121 m of gain at an average of 7.9%, with a maximum of 14%. The Marmotte's organisers note that the first two bends average 13%, which is why the climb feels much harder than 7.9% suggests. Savoie Mont Blanc's figures for the Galibier from Valloire are 17 km from 1,430 m to 2,642 m, 1,212 m of gain at 7.2% average and 12% maximum; the Marmotte's own page rounds the summit to 2,645 m, which tells you something about how much to trust any single number to the metre. The Marmotte describes the Télégraphe and Galibier together as 2,000 m of climbing over 35 km, which is the day's central problem: a long, unbroken ascent starting at the Maurienne valley floor and ending at the highest point of either event.

Read the profile for those facts, then read our guide to reading a route profile for how the compression of a 170 km day into a chart hides the steep bits. Then put the profile down, because the rest of this post is about what is not on it.

Altitude: the Galibier is not just long

The top of the Galibier is at 2,642 m. Wehrlin and Hallén measured trained endurance athletes at altitudes from 300 m to 2,800 m and found maximal oxygen uptake fell linearly by around 6% per 1,000 m, and endurance performance by considerably more than that. A rider whose threshold is 250 W at sea level does not have 250 W at the top of the Galibier; something in the low 220s is a reasonable estimate, and the effect starts to bite from about 1,500 m, which is roughly the Télégraphe summit. In practice this means the last 5 km of the Galibier, which are also the steepest part of the climb, are ridden with less engine than the first 5 km, and a power target set in the valley is wrong by the time it matters. Ride the upper Galibier by breathing and feel, and expect the number to drop. Our post on altitude for amateurs covers what a few days at height before the event can and cannot do about it.

Temperature: three climates in one day

The profile is drawn at a constant temperature. The day is not. A late-June or mid-July start in the Romanche valley can be cool at 06:30 and hot by the time you reach the base of the Alpe in the afternoon; the Galibier summit, 1,900 m higher than the start, can be near freezing with wind on the same day the valley is in the thirties. Descending 30 km at 50 km/h in a wet jersey through cold air is the point at which riders who packed for the valley start shaking, and shaking riders brake badly. We are not going to give you a figure for the temperature drop, because it depends on the day; what we will say is that a gilet and arm warmers stuffed in a pocket at the start, and put on at the Galibier feed rather than halfway down, are the cheapest insurance in the event. Read racing in the heat for the afternoon and cold-weather riding for the summit.

The descents are longer than they look

On the profile, a descent is a thin downward line. On the road, the Marmotte's feed at the Galibier summit is at km 115 and the next one, at Bourg d'Oisans at the foot of the Alpe, is at km 162. That is 47 km, almost all of it downhill through the Lautaret and the Romanche gorge, and by the organisers' own placing it is the longest gap between feeds on the course. Riders who treat it as rest arrive at the Alpe cold, stiff and under-fuelled for the hardest hour of the day. Riders who treat it as part of the race eat and drink on the way down, pedal on the false flats to keep the legs warm, and arrive at Bourg d'Oisans ready. The Étape's route via the Col de Sarenne adds a different problem: the organisers describe the Sarenne as rarely used, and rarely used Alpine roads are narrow, rough and technical on the way down. Check the current year's route for where the Sarenne descent falls and treat it with respect.

The Marmotte also requires lights: its rules make a personal light kit and a visibility vest mandatory because of the run of poorly lit tunnels on the approach to the Galibier. That is a rule, not advice, and riders without lights have been turned back at the start. Our descending guide covers the technique; the tunnels are simply a matter of packing.

Cut-offs: the clock runs from the start, not from your start

The Marmotte's organisers publish two cut-offs: the Galibier summit at 15:30 and the foot of Alpe d'Huez at 17:45, with a start from 06:30. That is nine hours to cover 115 km and three passes, which sounds generous until the profile reminds you the three passes contain roughly 3,900 m of climbing, if you subtract the Alpe from the organisers' total, and the day started with a 36 km run-in to the first feed. Riders in the later start waves have less time than the headline. Work out your realistic climbing speed from a training ride, add feed stops and the descent, and see whether the cut-off is comfortable or close before you are on the Galibier looking at your watch. The Étape publishes its own limits each year; the figure changes with the route, so read the current year's rider guide rather than an old one.

Feed stations are a queue, not a buffet

The Marmotte lists four feeds: Col du Glandon at km 36, Valloire at km 98, the Galibier summit at km 115, and Bourg d'Oisans at km 162. Between Valloire and the Galibier feed there is nothing but the climb, and between the Galibier and Bourg d'Oisans there is 47 km. Two things follow. First, carry enough to ride between feeds without them, so that a queue at Valloire is an option rather than a necessity. Second, plan the carbohydrate by the hour, not by the feed. Jeukendrup's review of carbohydrate intake during exercise supports intakes of up to around 90 g per hour from mixed sugars for efforts over two and a half hours, provided the gut has been trained to accept it; on a day that will take most riders eight to eleven hours, under-eating in the first three is the commonest mistake and the one that shows up on the Alpe. We set out the hourly detail in fuelling long rides and the week before in carb loading.

Pacing a day with the hardest climb last

Abbiss and Laursen's review of pacing strategies concludes that for very long events the best outcomes come from an even or slightly negative distribution of effort, and that an aggressive start is reliably punished. The Marmotte and the Étape are designed to punish it more than most, because the Alpe comes last and is the steepest climb of the day. Maunder and colleagues' work on durability adds the physiological reason: after several thousand kilojoules of work, the power a rider can hold at a given effort drops, and it drops more for riders who have not trained for it. The Glandon, or the Croix de Fer on the Étape, is a long, uneven first climb by the organisers' own description; it is where fresh riders go too hard because the gradient is irregular and the bunches are still big. Ride it a step below the effort you would choose, and treat the Télégraphe as a warm-up for the Galibier rather than a climb in its own right. The number to remember is not any single gradient but the order: your fourth climb is the hardest, and it arrives after seven hours. Our gran fondo pacing guide gives the power framework.

Gearing, and honesty about it

The Alpe's first two bends average 13% by the organisers' figure, and the top of the Galibier holds 12% in places by Savoie Mont Blanc's. After seven hours, a compact chainset and an 11–34 cassette is not a beginner's setup; it is the setup most riders wish they had. Our post on gearing for climbing runs the numbers on cadence at 12% for a given power-to-weight, and if yours comes out below 60 rpm, change the cassette before the event, not after it.

Preparing for the specific day

You cannot rehearse the altitude at home, but you can rehearse the shape: a long day with the hardest work at the end. The plan wizard takes an event date and builds backwards, with long-ride days you choose and a taper at the end. If your local roads have no 14 km climbs, the Alpe and the Galibier can both be loaded as real routes in Moveee Indoor, rebuilt in 3D from map and elevation data, so a smart trainer can give you the gradient sequence of the final climb with the fatigue of a long indoor session already in your legs. It will not give you the thin air, the heat, the queue at Valloire or the view from bend 7, and we would rather list those than imply otherwise. Read underprepared for a hilly sportive if the event is closer than your fitness, and event-week logistics for the travel, the bike box and the registration queue.

The profile is the easy part. The people who finish comfortably are the ones who planned for what is not on it.