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London 2012 organisers have announced alterations to the Olympic mountain bike course, after feedback from competitors in last year's test event.

Parts of the course, set in the grounds of Hadleigh Castle in Essex, will be widened to allow more opportunities for athletes to pass.

New features have been added to further increase the course's difficulty.

The main climb has been extended and a new feature has been added with an extended climb to reach it.

Several parts of the course, including the switchback climbs, have been widened and a new climb has been added into the start loop which will be used on the first 4.7km lap of the races.

The changes came after feedback from the mountain bike test event last July.

London 2012 organisers, Locog, gave the riders a questionnaire to complete after the test event, and said amendments would be made after criticims that the course was too flat and narrow.

Debbie Jevans, Locog's director of sport, said she was confident the largely man-made course would be one of the most technically challenging courses at an Olympic Games, and as competitive as possible due to the increased number of places where competitors could pass each other.

"It is wider and higher than for the test event and with the stunning setting of Hadleigh Farm we are looking forward to a world-class Olympic event," she said.

Some 36 nations are expected to take part in the London 2012 mountain bike competition; the men's race on 12 August will have 50 riders, and the women's race a day earlier will have 30 competitors.

Other test events have also elicited complaints. At the Greenwich Park equestrian test event, while the cross-country drew praise, the surface inside the dressage and show jumping arena was criticised by some riders.

Show jumper David McPherson, who tested the arena, said the waxed sand and fibre surface was "nowhere near good enough", with British colleague Nick Skelton adding: "The ground is a little bit dead and dense at the moment."

And in BMX, concerns were raised at August's test event over the lack of protection from the elements on the straights, where BMX riders perform the majority of their jumps.

British medal hopeful Shanaze Reade said windy conditions made the Olympic Park course particularly hard for female riders.

Mariana Pajon of Colombia, the 2011 world champion, fell victim to the course at the test event, suffering a hard fall in the women's final and leaving on a stretcher.