More than 45 miles into the race, Kate Jenkins felt euphoric. On a hazy, sunny day she ran through birch-wood glades and over bubbling streams before careering into Glen Orchy in the Grampian Mountains. The formidable Ben Dorain towered over her path as she climbed steeply towards Loch Tulla, where the track headed north to Glen Coe.
Fifteen miles later, she was in desperate trouble. Her stomach was cramping, she felt faint and dizzy. Dehydration was setting in, she was losing her balance and she felt scared. In the middle of the desolate Rannoch Moor – a sombre expanse of peat bog covering 20 square miles – she started to panic. She had 35 miles still to run, and she didn't know if she could manage five.
Kate, 27, who works for Scottish Forest Enterprise, was running the West Highland Way, from the suburbs of Glasgow to Fort William. For most fit people, it is a formidable 95-mile walk. For an élite few, it is an awe-inspiring hill run. In 18 years of races, fewer than 150 runners have finished; the West Highland Way is at the extreme end of a tough sport.
But hill and fell running involves more than extreme distance. Hundreds of events are organised in the UK every year. Most are races between five and 15 miles long. They are pitched at all levels of experience, and while most fell runners (Scotland has no fells, only hills, but both terms are used) are painstakingly fit, the sport is not exclusive to svelte athletes.
"I'm 15 stone and 46," says Dick Wall, an enthusiast since 1981. "If I can get up and down some of those hills I bet most people could." More people are trying. Fell running associations report a rising membership, and individual races can attract hundreds of entrants.
Most fell runners will tell you they are glad their days of road-running are over. Tired of pounding busy pavements and stretches of dull suburban road, most only turn to tarmac reluctantly when they can't get on a hill. "In road running you can settle into a pace, switch off and plod through a marathon," says Coventry-based Bill Waine, a committee member of the Fell Running Association (FRA). "In fell running you have to focus every minute."
Oliver Gero has completed three New York marathons. Keen to try fell running in the North West Highlands, he set off on a rough 10-mile route with two local hill runners. He threw in the towel after about seven. "The level of fitness you need for fell running is one or two notches higher than for a marathon," he says.
On steep ascents, runners will burn twice as many calories as on a flat road. They expect rough paths or no paths at all, boggy ground, vast stretches of open moorland and ferocious descents. If a fell runner describes a descent as "rough", it is likely to be a treacherous drop over loose, rocky outcrops, where one badly timed step would mean a bruising fall, a broken leg or worse. "In a fast descent you need the same levels of concentration as a downhill skier," says Waine.
That said, hill running over rocky, undulating ground is one of the sport's biggest thrills. Fell runners can slip into periods of calm, almost hypnotic, rhythm while running on the most precarious trails. Ridge running at heights of 3,000 feet is common. It's no coincidence that one of the most popular fell running shoes is called the Felldancer.
A growing number of "mountain marathon" events reflect an interest in fell running and adventure racing. The Lowe Alpine Mountain Marathon, held in Scotland each year, caters for novices through to élite runners. Entrants must carry enough food and gear to spend two days safely in the mountains.
The training necessary to compete at any level of fell running is a big commitment. Some runners train every day in the winter and spring to prepare for the next season. Notching up 30 or 40 miles each week training is no big deal. To get any pleasure from fell running, you need to be fit. It will be painful and sometimes dangerous. So why do it?
"First of all you have to like running," says Dick Wall. "That simply depends on the way you're born. After that, it's about the finer things in life – brought to you by nature." All fell runners will tell you they like open spaces, the wind in their hair and the rain on their faces. But for some the motivation goes deeper still.
"Many of these people are seeking out incredible personal challenges. Challenges we don't have in our daily lives," says Joan Duda, a professor of sports psychology at Birmingham University. "Even if you run the odd 10km, the average person will never have a clue what it feels like to run 95 miles."
Kate Jenkins did eventually finish the 95 punishing miles of the West Highland Way in a record time of 17 hours 37 minutes. Holding off the dehydration, she fought through "a long silent spell of despair where I was convinced I had reached the limit".
"It changed my life," says Kate, who only began hill running seriously in 1996. "It makes you realise you are something you never knew you were. I wanted to spend more time with people who have experienced the same emotions. It is a high I will never experience again."
For more information on fell running in general and up-to-date race details, visit the Fell Running Association's website at www.fellrunner.org.uk. As a guide, beginners should start on routes less than half the length they normally run on the road.
For races in Scotland, see the Scottish Hill Runners website, www.hillrunner.com Both this and the FRA site carry links to running clubs all over the country.
For informal challenges, visit the Scottish Hill Running Records website: http://alastair-matthewson.freeyellow.com/index
In England, the Bob Graham Round is a 74-mile route involving 28,500 feet of ascent. Visit: www.bobgrahamround.co.uk
Naiad Discovery offer a range of weekend and week-long courses in trail and hill running in Scotland. Contact them on 01337 831 196, or check their website: www.naiaddiscoveryscotland.co.uk, email: NAIAD13@hotmail.com
Some race organisers will allow you to just turn up and run, but always check races are still on before you go. Many races have been cancelled this year due to foot and mouth disease and some hill areas are still out of bounds to walkers and runners.
Do and don't
Drink plenty of fluid before, during and after every run.
Tell someone where you are going when you take to the hills on training runs.
Take emergency food and equipment.
Try fell running on your own unless you can navigate in the hills.
Be too ambitious. Try shorter routes first that are well under your normal road running distance.
Rely on mobile phones to raise an alarm. Network coverage is poor in many hilly areas.
Think fell running is confined to mountainous areas. There are regular fell runs in many other areas.