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Bear Grylls//Digital Spy

Yesterday, Is ultra-running bad for the heart. Everything you need to know about fell running.

1/ Athlete selection

No matter how perfectly everything else is planned, there are probably only a few people on earth who have a chance of breaking two hours.

The team started with a pool of the hundreds of Nike-sponsored distance runners - a large group, but one that notably omits the three most recent marathon record-setters, Kimetto, Wilson Kipsang and Patrick Makau, who are all sponsored by Adidas. Nike further narrowed the field by looking for sub-2:05 marathoners and sub-60-minute half-marathoners, and then examining their recent performance profiles. Over the past few years, 18 of the most promising candidates visited Nike HQ for a few days of physiological testing. One of the elements: a two-mile run at sub-two-hour marathon pace - 4:34 per mile - to see how the athletes looked, followed immediately by an all-out 400-meter lap.

It wasn’t just numbers and PBs. The team also spent lots of time with each athlete, considering who had the most room to improve and searching for the intangibles in attitude and outlook that might make the difference between success and failure. The three athletes who were finally selected are quite different from one other. Read more about them here.

2/ Course and environment

It’s no secret that the details of the race will make a big difference. Temperature, hills, turns, drafting and pacing all play a role, and each can be optimised beyond what’s typically seen in big-city marathons. Just getting the drafting right could shave 100 seconds off an elite marathon time, according to wind-tunnel estimates.

Exactly how Nike will choose to organise the race remains to be seen, but the company has the resources to create circumstances that are as conducive as possible to success.

3/ Training + 4/ Nutrition and hydration

These are the basic areas that most of us worry about when preparing for a marathon. Nike has a huge scientific staff ready to offer every possible support in these areas; still, over the coming months, each of the three athletes will continue to train with his own coach and in his own environment. Getting this balance right, so that the athletes benefit from extra support without disrupting what has worked so well for them in the past, will be a delicate task.

5/ Equipment

Shoes and apparel, of course, are Nike’s bread and butter. Plans in this area remain very much in progress, and aren’t yet public.