'Ultra' athlete Shane Finn has completed one of the most extraordinary charity treks ever undertaken by an Irish athlete.

Five weeks and 5,000km after leaving San Francisco to run and cycle across America, the 26-year-old Dingle man ran across the finish line in New York. 

His first hug went to the woman who inspired his 'American Ultra', his first cousin Mary Evans, 37, from Celbridge, Co Kildare.

Ms Evans has Spina Bifida and Hydrocephalus and Mr Finn undertook his mammoth adventure to underline the difficult struggle she faces every day.

She had never been to the US before but flew out especially to greet the Kerry man in Brooklyn Bridge Park.

Mr Finn crossed 11 American states during his 36-day feat, over mountains and across deserts and kept going through every possible weather, from snowstorms to searing heat.

"It's a big country Mary and I'm never again going back to Nevada!" he joked. "We actually got lost an hour into the first day, I have lots of stories to tell you!

"I'm pretty shattered but fatigue has really been the biggest difficulty," he said.

He did it by using a steady six-day rotation of cycling 270km for each of three days, followed by three consecutive days of running 60km, a pattern he repeated six times.

Mr Finn's only major set-back was a bad Achilles injury in the second week and some nerve damage to one of his fingers from having to grip the handlebars so hard while climbing peaks of up to 11,000ft.

"We played down the Achilles injury but really, it was a miracle that we got through it because I couldn't walk with it at one point," he said, praising the work of physiotherapist Ali McCann who kept him on the road.

"Ali said you would usually need to rest such an injury for three weeks and then rehab it for another few but we just had no alternative and got through it. When you think you have no more to give you'll always find something extra in the bottom of the tank."

Ms McCann was part of a small crew that accompanied Mr Finn and his trip during which he consumed 8,000 calories a day.

His small support group also included his father Tim and drivers Martin Fahey and Anthony O'Gorman who all travelled together.

They were hit with a snowstorm at one point but managed to get the schedule back on track.

"Towards the end the fatigue was tough, it was just a case of staying upright on the bike at times," he said.

"But whenever I had tough times I always thought of Mary and everyone I know at SBHI. Any struggles I had were nothing compared to the uphill battles they have every single day.

Mr Finn ran his first marathon at 17 as a fundraiser for SBHI. 

He raised nearly €150,000 previously by running 24 marathons in 24 days and hopes his latest feat of endurance will raise €250,000.