A relentless Norwich teenager has completed a challenge of a lifetime.

Eastern Daily Press: Harper Sharrocks watching on as Isaac Ringwood does three pull ups a minute on the minute during an exercise marathon. Picture: Isaac RingwoodHarper Sharrocks watching on as Isaac Ringwood does three pull ups a minute on the minute during an exercise marathon. Picture: Isaac Ringwood (Image: Archant)

Isaac Ringwood, who lives off Earlham Road, spent 12 non-stop hours doing pull ups in October and managed to hoist himself up 2,304 times.

The 19-year-old did three pull ups on the minute every minute and even upped the number to six in the last ten minutes despite exhaustion.

Eastern Daily Press: Isaac Ringwood did over 2,000 pull ups in 12 hours. Picture: Dean RudlingIsaac Ringwood did over 2,000 pull ups in 12 hours. Picture: Dean Rudling (Image: Archant)

While Isaac works as training instructor at Body Transform Fitness on Delta Close, where the challenge was held, the extreme exercise was unlike anything the former Aylsham High School student had done before.

"It was nerve-wracking," he said. "I did not know what to expect as it was unknown territory. Halfway through it I knew I could do it but it was going to be tough."

Eastern Daily Press: Isaac Ringwood was raising money for Harper's Little Helpers to fund a life-changing operation in America. Picture: Isaac RingwoodIsaac Ringwood was raising money for Harper's Little Helpers to fund a life-changing operation in America. Picture: Isaac Ringwood (Image: Archant)

"It was quite boring being in the same spot for 12 hours. And it was tiring, painful and everything not nice."

He added he completely lost his appetite during the marathon session and as a result felt sick from the lack of energy.

But Isaac persevered and it was only once the 12 hours were up that he realised he was in intense pain.

He said: "I felt relieved I was done, but I was in a lot of pain. I wasn't thinking much at all during it or afterwards.

"I took a whole week to recover as I was mentally and physically done in."

He added he went home expecting to crash out but was so wired from the exercise he was unable to rest fully.

However, the gruelling challenge was all in aid for a charity campaign, Harper's Little Helpers, and Isaac raised just under £3,000.

Harper's Little Helpers wants to raise £80,000 for three-year-old Harper Sharrocks, from Sprowston, who was diagnosed with a form of cerebral palsy when she just eight months old.

Her parents have embarked on a race to get the toddler to America for an £80,000 spinal operation known as selective dorsal rhizotomy (SDR) as well as a year of physiotherapy.

SDR would give Harper the best chance of walking unaided and relieve the pain and stiffness in her legs

So far, the campaign has raised just over £40,000.

To donate to Harper's Little Helpers click here