With this partnership, Raidlight offers you special GRR advice for you to prepare as well as possible for this major event in the trail running calendar.

The mythical North to South traverse of Reunion island is a bucket list event in the world of Ultra running, which for a week puts the whole island in a state of excitement. The beauty and fame of this jewel in the Indian Ocean brings competitors from all over the world, but for the locals it is simply the event of the year, everyone has a relative or friend who takes on this formidable challenge with a very fitting nickname: The Diagonal of Fools!


Physical and mental preparation



The Grand Raid de la Reunion or the Diagonale des Fous, is the experience of crossing a beautiful island with magnificent landscapes. It is important to set off with confidence in your equipment. That's why it's important to test everything during training. Wear clothes that make you feel good. Keep what you need on hand so you don't have to search in your pack. Be careful what you put in your pack, you have to carry it and extra weight will increase your fatigue over the km. Food is your fuel and allows you to continue over the long hours of effort. The recommendation is to drink and eat little and often according to your feelings of thirst and hunger. For my part, I eat and drink very regularly. I always have a time when it is difficult for me to eat (20th hour of the race), so I take a bottle of liquid food. Throughout the race, I diversify the flavours, the textures and I alternate sweet and salty to keep my taste buds interested. I hydrate with water and an energy drink that allows me to compensate for the loss of mineral salts.
Crossing the finish line of the Grand Raid will remain an unforgettable moment for all. Once you reach the La Redoute stadium, everything collapses: you let go, you let yourself go. Nerves crack and the pre-raid Superman's varnish cracks. There is the immense happiness of having finished; there is also, and above all, the pain, the suffering, the cracks in the soul... one thing is certain: from this ordeal, you come out of it changed.
I don't know if this race deserves to be called "the hardest race in the world" but it is the most difficult (especially because of the almost permanent danger) of the races I have taken part in and also the most rewarding. Because this Grand Raid was, above all, the occasion for exceptional encounters, whether with exuberant nature, the mountains so steep, the tormented landscape, the competitors united in effort and suffering, friends found on the island and even fear, a surprise guest.
In my head the memory of the magnificent journey through the cirque of Mafate remains present, making this final part a little dull. It's 10:30 pm on Saturday and I "ran" 48:30hrs, I survived one more time, and with a lot of luck.
ERIC, NOELLE and CYRIL Team Raidlight athletes

The physical

The GRR is a race that physically demands to be in full possession of one's ability. Physically of course, but also mentally, which is often neglected. It is necessary to start the year fresh, rested from its previous events. Without any worries about health, little niggles, or fatigue that could increase over the coming months.

One of the keys is general physical preparation:

This must be done regularly beforehand during the winter period with upper and lower body work, as well as Specific Physical Preparation or PPS exercises that must be done to strengthen your lower limbs in order to better support the kilometres and difficulties of the terrain that you will encounter during the GRR. These exercises will make up for the absence of poles during the whole year of your preparation. And yes!! You will have to plan to run during the year without poles. Especially for those who normally use them, because on the GRR, poles are forbidden! So you might as well start in January and not to use them at all during training and racing for the year.

The Mind

You will need your mental strength during the race; it will be put to the test in the months building up. The brain is likely to go on a loop, thinking only about the race. You have to be able to disconnect, to continue to live your life in a closed loop.

Family is one of the keys to staying grounded. It is also important to take advantage of these months of preparation to find useful mental help keys on D-Day. Some people use positive image flashes. To do this, you get used to having an image of a happy moment in your life appear, and you bring it into your mind at any time of the day, then you add a second one... Others count from 1 to 100 in moments of doubt for example, you can also listen to music, have song cues by programming active songs to boost yourself, soft music for a steady pace... During the 10 months of preparation, if you haven't done it before, start gradually and test yourself regularly in training, in build up races. And if you already have a method, perfect it so that your brain is even more efficient when the time comes. For if the risk of injury during the race is very present, very often the mind fails with fatigue. Being able to block negative thoughts by staying in a bubble where the brain won't get in the way of your performance is one of the things you need to be able to control, because if your brain thinks positively, your body is likely to carry you to the finish line despite the fatigue and difficulties. One of the things that can also be important is to have maximum fun during your race by being positive at every moment, even at the most difficult times along the way. Enjoy the landscape, the people, the applause, the silence, the rain, the mud, ... everything must be a moment of pure happiness, and all the more so on this island so far from home, because you might not come back to do this race again!

Preparatory races

There are two categories of preparatory races, those that are part of a training plan and those that serve as intermediate objectives.

The Ardéchoise can be (depending on the dates) a very good race for intermediate objectives, because of its profile, its difficulty, its distance, its D+ and its date which allows for work beforehand, a complete recovery afterwards before moving on to the next one. But it may very well be another race. The point is that its date falls on the right weekend in your annual program to optimize the smooth running of your march forward to the GRR. In the preparatory races that are integrated into the training plans, you must follow a logic of progression on the first half of the plan, then conversely on the second part of it. If it doesn't fall on the planned weekend, it is always possible to have a gap of one week, in this case you will just have to anticipate it by reversing a few sessions.

As these races are preparatory, it is not necessary to do them all at full race pace, some of them should be done at a more flexible pace <85% of maximum heart rate. There are two reasons for this: the first is that you are building yourself, and therefore you cannot be at your best during this period, so always in the mindset of incremental progress, leave time for the body and the brain to accept the training load, the sole aim is to be in shape on the day, not fifteen days before. Secondly, careful management allows you to recover better, to limit physical and mental fatigue and the risk of injury.


And yes, you can make it look like you are not playing a game, tactics can help and change a lot of things in the end.

In order to do this, you have to accept your true self, your abilities, the weather, the worries to come

I often advise to think step by step. A race like the GRR is broken down into feed stations with supplies, so you have to use it as a strategy. At the same time you plan food, batteries for headlamps, clothing, drop bags where it is possible to have a backups of full clothing, shoes, food, equipment ... If you have support crew, prepare the same for a change of shoes, socks, clothing ...

The idea is to know, to foresee, everything you will do, free the brain from a crowd of thoughts that would disrupt you, put all the lights to green. In the same way as you have to plan your last week, you have to plan your equipment, clothes, shoes, pack, food, the number of this or that thing, make sure you use a checklist prepared beforehand. Nothing should be left to chance, you owe it to yourself to control as many things as possible for your piece of mind on D-day. Have a waterproof map of the route, easily accessible and without risk of being lost, you can attach a running schedule with a fast pace, ideal pace and a slower pace, include a margin of adaption to allow for fatigue. Some sites or Excel easily allow this kind of programming.

On D-Day, be in the right place at the start, by using the value in % of position achieved in previous races/total number on startline helps you to get started in a way that matches your abilities. Afterwards, it is absolutely necessary to concentrate on yourself, your running, your breathing, your sensations, minute after minute, hour after hour. If you run alone, don't want to follow a competitor, or accompany another runner, but know how to let them go if their pace is not yours, or go ahead if the opposite is true.

When you're in good shape, take your time, keep some in reserve, If you are in doubt, now is the time to put your brain to work, because the mind will know how to pull you out of this bad moment. If you are in a group, the most reliable one must be the group's driving force, the strongest being the guardian of the group to make sure that everyone stays positive. For the pace, if you have a heart-rate monitor, it can be very useful in the first few hours to channel you, and thus save you for the rest of the long journey that awaits you over the next 160 km. If you start too slowly, you will not be able to accelerate, and if you start too fast, you will find it very difficult to finish due to the excessive energy used, caused by your enthusiasm at the start.

I often compare a runner at the start of an Ultra to a car with a full tank of fuel. If you drive too fast from the start of your trip, you will use 15L of fuel, you will have to slow down to hope to have enough fuel to reach the destination. If you leave at the correct speed, you will use 10L of fuel and will arrive at the scheduled time. If you drive too economically, you will only use 5L of fuel, but you risk arriving after the destination is closed!

Racing without poles

If you are used to poles: you will have to leave them at home gradually to get the muscles and body used to working differently. The energy you use to carry them, put them away, fold them, adjust them... will in the end save you time and comfort when you have your hands free. Having your hands free also allows you to help yourself when going uphill by pushing on your thighs and when going downhill in technical sections (rocks) and/or to hold on to vegetation.


Do not hesitate to use your arms by pushing on the quads to help the push-off and use less force on the lower limbs. Reaching straight forward in the supporting movement of the hands also helps! In training, focus on a series of stair climbs or small steep slopes.


No secret, make the most of it in training by absorbing as much impact shock as possible.

Avoid landing on the heel first. Run as if you were running on hot coals, taking small, quick steps in succession, landing on the front of the foot.

Preparation advice


Before starting your training programme, if you use a heart rate monitor, with GPS it's even better, do a VO2 Max test to set your pace especially during specific VO2 Max(aerobic) sessions.

With your heart rate zones, set up your endurance, running, threshold training in the appropriate zones as follows: < 70 %, active recovery, 70 / 80 %, endurance, 80 / 85 % threshold, marathon effort, 85 / 90 %, threshold, half marathon effort, < 90 %, VO2 Max zone.

If you don't have a heart rate monitor, but a GPS, you can use your VO2 Max to set your pace. However, running at a % of your VO2 Max pace on trail when you have elevation and terrain to negogiate, is not logical, because if you try to maintain pace on a climb you will force the heart to do a lot of work and so you're out of the zone of efficiency. In this case, learn from fartlek style efforts. If you have no heart rate montor, no GPS, no phone... well, it is your breathing and "feel" that should be your source of information through experience and good knowledge of your abilities. You need to know the feel of your effort, for example to know if you are in endurance, threshold... This can be useful, because even though modern technology can be of valuable assistance they sometimes break down!

Training advice

Specific preparation (3-4 sessions per week)

To take part in this mythical race, it is best to be organised, to plan ahead, logically at least 2 to 3 years in advance to have progression in terms of weekly training time /km, a progression on the distances with D+ in the race. As far as we're concerned, we'll mainly talk about the current year. Here is an example of a years training plan for a runner who participated in the GRR.

The specific speed is that of the Ultra that you are going to run.

For 4 weekly sessions, you can add in the middle of the week a session of 1h30' on trail at a specific pace, with a progression of intervals at 80-85% MaxHR.

2x10' with 2' of recovery

3x10' with 2' of recovery

2x15' with 2' of recovery

50' running specific pace the week of the weekend block, 50' running specific pace the week after the weekend block 2x20' with 2' of recovery

50' running specific pace the week of the weekend block 50' running specific pace the week after the weekend block

50' running specific pace

40' running specific pace