What it takes to complete a 100 mile ultra race around the cornish coast?

The last weekend of January is one of my highlights of the trail running calendar. If I’m in someway not involved, that is either running or crewing, I’ll login at 1230 on a Friday and keep my browser refreshed for the next 36 hours. The initial stress of, have I got all the channel streams open, followed all my friends and coached athletes and making sure there aren’t any major commitments in the way - I’m ready to track, dot watch and get involved with the WhatsApp chat.

Scheduled in the diary for the last week of January, under new management, the now UTMB Arc of Attrition weekend is close to my heart with 3 races following the South West Path of Cornwall; that being the classic 100 & 50 milers and now with a new 50K, the Cornish trails have become more accessible to a wide range of ultra running abilities. A little disconcerting for the locals but a boost for the local economy. Especially the Eco Parks vegan café.

My obsession for the 100 is evident by completing it twice, with a sub 24 hour on one occasion, a DNF (did not start) in 2024 and perhaps even harder experiencing on the other side by crewing one of my athletes in 2023. The year of 2025 was not meant to be having to cancel my entry due to a long term injury - a DNS (did not start).

So what makes it a particular choice for the ultra runner?

Timing is important. It is in the off season. Fair weather ultra runners, if there is such a breed, are coming out of hibernation. Recovering from their past year, sitting comfortably in their base building phase hopefully with their next year ‘A’ race booked up. Why upset the ultra cart with a winter race? Factoring in recovery lag from the Arc weekend, which depending on your unique metabolic profile can take up to 6-12 weeks which potentially rules out a March / April ultra race.

You will also have to train hard in the winter. That means dark mornings and nights. Of course great for developing your pyche to endure 15 hours of darkness running over night but tough when factoring in other commitments.

Then you have the distraction of a seasonal holiday. I will assume you are like me. Partying and certain indulgences take a back seat in an ultra runners life but there is still the cheese board and family attention needed. You should also give yourself permission to decompress from the year but that week Coach Adam has prescribed some high volume training.

If you are thinking of entering you are advised to have completed some less complicated ultras. Maybe not 100 milers but at least where you have had to solve an in-race problem. Maybe sickness, cramps, tiredness, fatigue or a mid race injury. You must have that experience. It goes without saying for any entry to such a distance but take a look at the Arcs elevation profile. It is like a bed of undulating thorns. Sure there’s sections of relief - the run up to Penzance, the town section through Hayle and the stunning coastline around Godrevy. But it still comes with its challenges. It dips into bays, climbs out of coves, asserts technical terrain and the gravity pulls you to the sea. Depending on your time zone a lot of running in the dark.

Training to perform at this ultra 50 or 100 mile distance would look like this. Start at the end of August, 23 weeks out from race day. Prior to this a solid consistent base with 30-50 mile run weeks injury free should be well established. Splitting the 23 weeks into training phases - economy, VO2 aerobic power, threshold, aerobic endurance, taper, race. Depending on your unique profile, adaption and recovery speed we would split the training plan into 3-4 weeks blocks. You will need to get permission from yourself and your friends and family for a free 8-15 hours of weekly training which will include strength work, mobility, kit prep, self care and perhaps an upgrade in diet.

Having DNF’d this race before I can understand what the deterioration of a race looks like and the tough decision to hand in your bib and go home, knowing tomorrow will be full of regret. There are so many different scenarios. But most of these can be avoided if you split your training into 5 buckets - Fitness, Strength & Mobility, Nutrition, Mental and Equipment. Get these right and you are looking like being one the ‘probables’. For 2025 the stats speak volumes: For the Arc 100 there were 515 starters with 255 DNFs. That’s a whopping 50% drop out rate! The Arc 50 28% and the Arc 25 5%. There are always exceptions but I would hedge my bets if I interviewed every DNF candidate we would find gaps in their preparation.

So now we look at the race. I’m focussing more on the Arc 100 although similar principles are similar for both the 50 and 25. Each race follows the same route but have different start points. The terrain is very mixed and depending on the pre race weather very unpredictable. Expect boggy trails, road, grass, rocks, sand and yes a lot of steps. This is why I love and hate this race. It is relentless. Apart from the road sections which can come as a relief, it is very hard to get a rhythm: and ultras are all about rhythm. Lock in, focus and commit to that next aid station. The elevation, although compared to other races is quite low at 26 m/km (compared to say 66 m/1km UTMB Chamonix), the attack on the legs and knees is intense - and it never gives up with the final infamous climb to Mount Pleasant (it just isn’t).

Cornwall due to its physical geography has different pockets of weather - micro climates if you will and as you loop around you are running to the west and then at Lands End head back east effecting the overall wind direction. From what I hear the start was perfect conditions, the night gave rain storms and the following day some beautiful coastal sun. Although a winter race I’ve never really seen winter. With good kit choices combating the weather shouldn’t be a big issue but what it does do is mentally drain you.

Like all long distance efforts your mental game needs to be on point. This has been practiced in your training process. You’ve had to go out and do the prescribed 8x200m interval session early doors or after work. Yes you are building your aerobic base but what your really doing is adding blocks to your mental fortress. You will be seriously tested. You will go to depths of self administered pain with I never knew existed.

Another part of the puzzle to get you round is strength and mobility. The route offers some short but very aggressive climbs. The start out of Coverack , around Black Head towards Cadgwith can be only be described as a bit of a shocker. If you can miss the queues its a quick start with high steps, exciting turns and stunning coastline. The nerves start to settle and you should be thinking about your pacing strategy. Too fast and you’ll pay later - too slow and you may miss your race time goal. You will get a feel for the pace. This is where those glute, knee and ankle strength sessions pay dividends. You will feel the recruitment of your gluteus maximus when you push up the Minack Steps or encounter the Bitches before Porthtowan. Strength and mobility work is a game changer and missing this in your training will only lead to an early retirement. The longer you can run strong with good stability the longer you will run efficiently.

So you have the fitness, strength and the mental capability. What cannot be avoided is a nutrition plan with various bail out options. This year has changed with now a mighty 9 aid stations. Previously there were 4. The idea I think is to reduce the need for random placed crewed support and make it more equal for overseas / non local runners who run unsupported. Nutrition is one of the main reasons for DNFs. Gut training starts when the plan starts. Understanding about your gut and how fussy it is. What happens after 3-4 hours running (you will not run for 19-36 hours in training so you can never replicate). During the race there some long sections without aid which can throw up (excuse the pun) some challenges so it good to get this dialled in. The other obstacle is cost. Testing various forms during training can be costly. At £2+ per gel and electrolytes each run can make a dent. But you need to test your reaction. I guess its down to your budget and commitment. But be sure to have tried you chosen form before the race.

So with all the above to contemplate I’m sure you’ll agree it really is complex affair training and completing an ultra. Coming back to the stats it says it all. These races should be hard - very hard. The end achievement and satisfaction is, well, I’ll leave that for you to experience. Go get that buckle.