THE impact of his charity work hit home to Saddleworth's Kevin Sinfield when a pensioner asked to donate all the money from her 80th birthday to his latest fund-raising challenge.

The former Leeds Rhinos captain, now with Premiership rugby union pacesetters Leicester, is preparing for The Extra Mile Challenge, a 101-mile run from his new club in the midlands to Headingley inside 24 hours starting next Monday.

The money raised will be divided equally between the Motor Neurone Disease (MND) Association and the campaign to establish an MND Care Centre in Leeds in the name of his close friend and former Rhinos team-mate Rob Burrow, who was diagnosed with the disease almost two years ago.

Sinfield, who underwent testing for the event on Wednesday at Leeds Beckett University, set an initial target of £100,000 but told a press conference that he has been overwhelmed by the response so far.

"I had a quick look this morning and we're at about £70,000 with an extra £10,000 in gift aid and then there's a significant amount in sponsorship which takes us to about £150,000," he said.

"There's fans down there who are stopping me and handing me tenners and twenties and it's really kind.

"There's one guy whose former business partner died of MND who has given almost £33,000 which is absolutely incredible.

"You just don't know who's out there and who's challenged and affected by the disease. Some of the letters and the cards that we have all received have been mind-blowing and inspirational.

"I got one last week from a 79-year-old who wanted to donate all her money from her 80th birthday to this run."

Last December Sinfield helped raise over £2.7m for the MND Association by running seven marathons in seven days.

The latest challenge from the former England skipper, who is now 41, is to run just short of four marathons back-to-back.

The run will be split into 7km segments, each of which must be completed within an hour before the next one starts on the hour.

Originally, the journey was planned to cover a distance of 100 miles but the actual final distance covers 101 miles with Sinfield once again proving he will always go the "extra mile" for his friend and former team-mate.

Burrow hopes to be at the finishing line and Sinfield admits his presence would be a fitting motivation.

"Whether Rob is going to be good enough to be there on Tuesday, we'll have to wait and see," he said.

"If he is, I'll be absolutely made up. If he's not, I'll understand. I'm sure there'll be a couple of text messages en route where he's laughing and taking the mickey out of us.

"But I absolutely know he will be with us every step of the way."

Asked if he has considered failing to complete his latest challenge, Sinfield said: "Yes. It crossed my mind at the start of October that I might not finish London.

"It crossed my mind last year I might not do seven in seven. It crossed my mind when I was sitting in the dressing room waiting for big games, Grand Finals, that I might not be good enough, I might not get there.

"I think self-doubt is part of life and part of being in sport. It's part of facing challenges.

"I think my experiences in rugby as a player have given me the best prep for this mentally. But absolutely, we all have self-doubt.

"A lot of people don't want to admit to it but we all have it and we all understand but what I would say is I'm determined to get it done and if I have to crawl, I will crawl."

Sinfield, who took part in a 12-hour run comprising 52 miles last week to prepare him, says the toughest part of the challenge will be mental.

"My wife thinks I'm crackers when I say I'm going for a 12-hour run at 3am but she gets it, she understands it," he said.