Training for the GR20: What 16 Stages Actually Demand

Why the GR20 wears fit people down

The GR20 is a waymarked path with wardened refuges, meals and basic supplies, and no permit. That is where its resemblance to other long-distance paths ends. The ground is graded T2 to T4 on the SAC scale, with frequent easy scrambling on granite, exposed ridge sections on stages 2, 4, 7 and 12, loose scree on the stage 4 diversion and long stretches without water. People read 184 km in 16 days as 10.6 km a day and train for a long walk. They arrive at 12,994 m of ascent and 13,014 m of descent on rock, carried on their own back, at a pace of about 1.8 km an hour against the Tour du Mont Blanc's 2.6.

Three things do the damage. The first is the vertical in the northern half: the first nine stages, Calenzana to Vizzavona, carry 7,995 m of the 12,994 m of ascent, stage 1 alone goes up 1,572 m from Calenzana at 289 m, stage 3 takes 5.5 to 6.2 hours for 5.0 km, and stage 4 needs 8 hours for 8.3 km over the Pointe des Éboulis. The second is the pack and the water: there are no porters, the 8 to 12 kg is yours on every step, the refuges are the only resupply, and on the waterless stretches (stages 2, 3, 11, 12 and 14; the longest gap between water points is 10.0 km on stage 11) you carry the day's water too. The third is the descent: 13,014 m in total, five stages drop 1,000 m or more, 1,359 m on the 25.0 km stage 6 from Ciottulu di i Mori to Manganu, and the last two stages fall 1,169 and 1,229 m to Conca at 245 m on legs that have done fourteen. Add summer thunderstorms on the exposed ridges, heat in July and August and snow on the northern passes in early June, and a slow walker gets caught out high.

The stage profile: the official 16 refuge stages from Calenzana to Conca, day by day

Training for a trek starts with its shape. The table is the official 16-stage refuge split published by the Parc Naturel Régional de Corse, which runs the refuges, north to south from Calenzana to Conca: what the plan is built from, and what you can check your own version against. Since 2015 stage 4 follows the diversion over the Pointe des Éboulis instead of the closed Cirque de la Solitude; fit walkers merge the short stages; and many people with one week walk the northern half only, Calenzana to Vizzavona, where the railway station makes the finish easy and operators sell it as a nine-day trip. All of it changes individual days, not the shape.

Read the table as a training brief. The route is front-loaded: stages 1 to 4 are all over five hours, stage 1 carries the biggest ascent (1,572 m from Calenzana) and stage 4 is the longest (8 hours for 8.3 km, 1,199 m up and 955 m down over the Pointe des Éboulis), so the hardest days come before your legs have adapted to the ground. Stage 6 is the long one (25.0 km, 1,359 m down, 8 hours), stages 10 and 11 reopen the vertical after Vizzavona (1,134 and 1,172 m up), and the last two stages drop 1,169 and 1,229 m to Conca. The consecutive-day structure, the slow rocky ground, the pack and the descents are what the plan is built around. Altitude is not: the high point is about 2,600 m and the highest night is 1,991 m.

What a trek asks that a summit does not

A single high mountain has one big day and a walk out. The GR20 has sixteen days on rock in a row, with your own pack and the day's water on, and the hardest ones first. That is a different physiology, and a plan built for one big day misses it.

• Consecutive days, not one day. 16 stages, no rest day, 4 in a row over five hours to open. Fatigue accumulates faster than fitness recovers, so the plan trains back-to-back long days, not a single rehearsal.
• Slow ground, not long distance. About 10.6 km and 726 m of ascent on a typical stage take about 5.8 hours, because the path is granite, scrambled and exposed in places. The weekend long days are sized in hours and gain on rough ground, not to a flat distance target.
• Descent is spread across the route and arrives tired. 13,014 m of descent in total, five stages over 1,000 m, two of them the last two days. Eccentric leg strength is not an add-on; it is what keeps the second week walkable.
• Your own pack and your own water, every step. No porters: 8 to 12 kg refuge to refuge for fifteen nights, plus the day's water on the waterless stages (the longest gap is 10.0 km on stage 11). Train with the weight from the middle of the plan, not in the last fortnight.
• Weather, heat and ground, not altitude, are the mountain risk. Summer thunderstorms on the exposed ridges, heat and dry springs in July and August, loose scree on the stage 4 diversion, snow on the northern passes in early June, and chains on the high-level Bavella variant. Fitness buys the margin to be off the ridge before the afternoon weather.

Physical benchmarks to hit before the GR20

The GR20 loads five physiological systems. A real preparation plan trains all five, with the consecutive-day demand and the pack at the centre.

Altitude: what the itinerary handles and what training cannot

Altitude is the one thing the GR20 does not ask of you. The high point is about 2,600 m (8,530 ft) on the Pointe des Éboulis ridge below Monte Cintu on stage 4, the only time the route goes above 2,500 m, and the highest night is 1,991 m at the refuge of Ciottulu di i Mori. Most people feel nothing beyond a slightly higher heart rate on the passes. No acclimatisation days are needed, and none are scheduled.

What replaces altitude as the limiter is ground, heat and weather. The path is granite with frequent easy scrambling and exposed ridge sections on stages 2, 4, 7 and 12, loose scree on the stage 4 diversion and chains on the high-level Bavella variant; July and August are hot, with afternoon thunderstorms on the exposed ridges and springs that run dry, so the waterless stretches on stages 2, 3, 11, 12 and 14 are carried; snow can linger on the northern passes in early June; and the refuges are only wardened from about June to mid September. The fitter you are, the earlier you are off the ridge and the more margin you keep. Our hiking training guide covers the base, and this guide explains why a trek like this is trained differently from a single mountain.

The 12 to 16 week GR20 preparation timeline

The block runs backwards from your departure date. Six phases, each with a distinct target. The hardest training weeks land three to six weeks before you fly, not in the final taper.

• Weeks 1 to 4 · Aerobic base. Three to four Z2 sessions a week, 45 to 90 minutes. Walk, hike, run, cycle; weight on feet preferred.
• Weeks 5 to 8 · Base plus strength plus the weekend pair. Add one eccentric leg session a week and make the weekend two consecutive Z2 hikes on the roughest ground you have, with the full pack from here on.
• Weeks 9 to 11 · Muscular endurance. Weekend days grow to 4 to 5 hours with 900 to 1,300 m of gain (a typical stage is 726 m, the biggest 1,572 m), the Sunday walk stays long. Stairs and incline if you have no hills.
• Weeks 12 to 13 · Big-stage rehearsal. One 8 hour day with 1,199 m up and 955 m down on rough ground, the real pack, the real food and the day's water: the shape of stage 4.
• Week 14 · Last big weekend. One more back-to-back pair at full length, then the taper begins.
• Weeks 15 to 16 · Taper. Volume drops 30 to 50 percent, one short sharp session stays, legs arrive fresh in Calenzana.

A weekly distribution that works

The polarised principle applies: most of the week at low intensity, one hard session, and the weekend pair that makes a trek plan different from a summit plan, two long days back to back (Seiler & Kjerland, 2006). A representative week, 10 weeks out from GR20:

• Mon · easy 60 min Z2 walk or run
• Tue · threshold intervals, 4 x 4 min Z4, or hill repeats
• Wed · rest or 30 min mobility
• Thu · 60 to 90 min stairs or treadmill incline, Z2, 8 to 12 kg pack, 400 to 600 m of gain
• Fri · eccentric strength: weighted step-downs, split squats, calf and hip work, 40 min
• Sat · long Z2 hike on rocky ground, 4 to 5 hours, 900 to 1,300 m of gain, full pack
• Sun · second long Z2 walk on tired legs, 2.5 to 3.5 hours, pack on (the back-to-back day)

Roughly 80% of weekly volume sits at Z1 to Z2, with one hard intensity session and the back-to-back weekend. Vertical and hours accumulate progressively across the block. The deeper rationale is in our heart rate zones guide; the descent work is explained in eccentric descent training.

How TTM trains the plan to the GR20

When you tell TTM your trek is the GR20 and your departure date, the plan is built backwards from that date with the stage profile above engineered in, and it recalculates every week, every Sunday, against your actual training data from your watch. You do not need to assemble the pieces yourself.

GR20: quick answers

Common questions about training for the GR20

How fit do I need to be for the GR20?

Fit enough to walk about 5.8 hours a day for 16 consecutive days on scrambled granite with about 726 m of ascent on a typical day and an 8 to 12 kg pack. The benchmark that matters most is two long hill walks on a weekend, pack on, that leave you fine on Monday.

How many weeks does it take to train for the GR20?

Twelve to sixteen weeks from a base of two or three sessions a week. The hardest training weeks land three to six weeks before you go, followed by a two week taper.

What is the hardest stage?

Stage 4 is the longest (8 hours for 8.3 km over the Pointe des Éboulis); stage 1 has the biggest ascent (1,572 m from Calenzana) and stage 6 the biggest descent (1,359 m to Manganu).

Is the GR20 the same as the GR 20 or Fra li Monti?

Yes. GR20, GR 20, Fra li Monti and the Corsica GR20 all name the same route down the island from Calenzana to Conca through the Parc Naturel Régional de Corse. The official split is 16 refuge stages, north to south; the northern half to Vizzavona is the more famous and more technical part and is often walked on its own.

Do I need to train with a weighted pack?

Yes. Refuge to refuge means 8 to 12 kg on every stage, plus the day's water on the waterless stretches. Carry it on every long training day.

Is altitude a problem?

No. The high point is about 2,600 m and the highest night is 1,991 m; the limiters are the slow rocky ground, the consecutive days, the pack and water, the heat and the storms.

Do I need a guide or a permit?

No permit and no guide requirement. Refuge beds and tent pitches are booked online through the park's reservation centre and the confirmation is shown to the warden; wild camping is not allowed, so nights are at the refuges, their tent areas or the gites at the road passes. The main line involves frequent easy scrambling on granite and exposed ridge sections; the chains are on the high-level Bavella variant.

When is the best time to walk it?

June to September, with the refuges wardened from about June to mid September, snow on the northern passes in early June, and heat, afternoon storms and dry springs in July and August.

Can I walk half of the GR20?

Yes. Many people with one week walk the northern half, Calenzana to Vizzavona, the first nine stages, where the railway station makes the finish easy and operators sell it as a nine-day trip. It is the more technical half and carries 7,995 m of the route's 12,994 m of ascent, so train for it as you would for the whole route.

How hard is the GR20?

The GR20 is 16 stages: 184 km, 12,994 m of ascent and 13,014 m of descent. A typical day is about 5.8 hours with 726 m of ascent; the longest, day 4, is 8 hours with 1,199 m up and 955 m down. The high point is 2,600 m. You carry your own pack, 8 to 12 kg, every day. Frequent easy scrambling on granite, exposed ridge sections on stages 2, 4, 7 and 12, loose scree on the stage 4 diversion, summer thunderstorms on the ridges and long waterless stretches on stages 2, 3, 11, 12 and 14. There is no rope work on the standard route (graded SAC T2-T4). In training terms the difficulty is consecutive days, the daily vertical, the descents and the pack, and 12 to 16 weeks from a base of two or three sessions a week covers it; the 16-week GR20 training plan is the fixed version.

How long is the GR20?

The GR20 is 184 km in 16 stages, about 92 to 95 hours of walking in all, with 12,994 m of ascent and 13,014 m of descent, from Calenzana (289 m) to Conca (245 m). Other itineraries in the trek database: 9 stages from Calenzana to Vizzavona; 7 stages from Vizzavona to Conca. The plan on this page is built for the standard version in the table above; a shorter version compresses the same vertical into fewer, longer days, so it is not easier to train for.

Can I do the GR20 without training?

Not well, and for most people not safely. The GR20 asks for 16 consecutive stages with an 8 to 12 kg pack, about 5.8 hours and 726 m of ascent on a typical day and 8 hours on the longest. Untrained walkers are the ones the later days hurt: fatigue accumulates faster than fitness recovers, the 13,014 m of descent lands on quads that have never braked for hours, and the gap shows on the longest day, not the first. Twelve to sixteen weeks from a base of two or three sessions a week is enough for most people; the 16-week GR20 training plan is the fixed version and the app builds the personalised one backwards from your departure date.

Is the GR20 exposed? Do I need a head for heights?

In places, yes. There is frequent easy scrambling on granite and exposed ridge sections on stages 2, 4, 7 and 12, with loose scree on the stage 4 diversion over the Pointe des Éboulis. The Cirque de la Solitude, the passage people fear from older accounts, is closed and no longer part of the route, and the chains are on the high-level Bavella variant, not the main line. No rope skills are needed on the standard route; comfort on steep rock with a pack is, and the training plan asks you to do your long days on the roughest ground you have.

Tools and deeper reading

Related treks

The takeaway

The GR20 is rarely a fitness problem in the abstract. It is a shape problem: the people who walk into Conca with legs to spare trained for 16 consecutive stages on slow granite, their own pack and water, and 13,014 m of descent, not for 184 km of path. Train the week, not the day, train on rock, and carry the pack from the middle of the plan.