Surely one of the most demanding and extreme forms of human endurance is that experienced by the Kaihigyo, or so-called 'Marathon Monks' of Mount Hiei in Japan who attempt a special 1,000-day challenge in pursuit of spiritual enlightenment.

These monks are members of the Tendai Sect of Buddhism based at temples on Mount Hiei, to the north east of the historic ancient capital city of Kyoto. The 1,000-day challenge takes seven years to complete, as it must be undertaken alongside a monk's other religious duties and meditations, and since 1885 (the time I assume records go back to) only around 50 monks have completed it.

During the first 300 days, a participating monk begins to condition his body, a regime which includes running 40km per day for 100 consecutive days. During the fourth and fifth years he will run the 40km per day for 200 consecutive days, in the sixth year he runs 60km per day for 100 consecutive days, and in the final year he will run an astonishing 84km per day (the equivalent distance of two Olympic marathons combined!) for 100 consecutive days.

These runs are undertaken wearing a white robe, straw sandals and a straw hat, and the routes follow poorly marked, uneven mountain paths which are unlit at night and frequently icy or snow-covered during winter months. The monks must also carry spare sandals (they can wear out three or four pairs a day on the longest runs), books containing directions and mantras to chant, food to make offerings en-route, and candles for illumination.

They must stop at temples of worship, of which there can be as many as 260 on the 84km course and consequently each of these runs can take up to 20 hours to complete, leaving the monk precious little time for rest or recouperation before he sets off again. There is a saying that 'ten minutes sleep for a marathon monk is worth five hours of ordinary rest'.

And, on top of all this, the participating monk carries a knife and wears a rope belt (known as the 'cord of death') to remind him to take his own life either by self-inflicted disembowelment or hanging, should he fail to complete any part of the challenge. Although there have been no recorded suicides since the nineteenth century, there are said to be simple shallow graves at points alongside the route which remind the runners of the fate of their unsuccessful predecessors.

Another aspect of the 1,000 day challenge is the 'doiri', a period of seven days in which the monk is allowed no food, drink or sleep, but must spend the entire period in the temple reciting chants and mantras. These extreme feats of endurance are designed to take the human body beyond the bounds of mundane experience and into a state of suspended reality in which spiritual enlightenment may be found.

It is a central tenet of Buddhism to pursue a path to enlightenment - commonly referred to as 'The Way'.