Ben Nevis Race organizers said the decision to change course came after “many meetings and consultations” with landowners and environmental organizations including the John Muir Trust and Nature Scot.
The area near the Red Burn has been damaged by erosion and landslides and concerns have been raised about the safety of runners.
Competitors racing on Saturday September 2nd must now follow the main trail, both up and down, past four checkpoints.
Organizers, the Ben Nevis Race Association, said failure to follow the route would result in disqualification from the race and “endanger the future of the race”.
Added an additional 15 minutes to the cut-off time by which runners should have reached the half-time mark, with the new completion limit set at 3 hours and 30 minutes.
The route was changed once before in 2016, when runners were forbidden from using the grassy banks of the Ben for their ascent or descent.
The route begins and ends at the Claggan Park soccer field on the outskirts of Fort William and is 14 kilometers (8.7 miles) long with an elevation gain of 1,340 meters (4,400 feet).
The first ‘race’ was undertaken by William Swan, a Fort William barber who set out on the first recorded timed ascent and descent of Britain’s highest mountain in 1895.
A number of races were organized on an ad hoc basis in the late 19th and early 20th centuries, but it was not until 1951 that the Ben Nevis Race Association was formed with the intention of formalizing the organization of an annual race.
Today, the event features 600 runners taking on a challenge that organizers say is “not for the untrained or the faint of heart”.
The event is so popular that it is usually overbooked within two days of the registration forms being released at the end of January.
It has been held every year since, with the exception of 1980 when poor weather conditions made a last minute decision to cancel the race to ensure the safety of runners and officials on the mountain.
The record times for men and women have stood since 1984 when Kenny Stuart and Pauline Stuart (née Haworth) clocked 1 hour, 25 minutes and 34 seconds and 1 hour, 43 minutes and 25 seconds respectively.