Sitting down to interview a human performance expert who’s trained “around 30” celebrities to complete the most gruelling of endurance challenges for Comic Relief, I wanted to know which star had impressed Professor Greg Whyte the most.

Would it be Eddie Izzard, who ran 43 marathons in 51 days with Greg’s coaching? Maybe it was Gary Barlow, Cheryl Cole and Chris Moyles for climbing Mount Kilimanjaro, or perhaps Davina McCall for completing a 506 mile ultra-triathlon.

There was also Dermot O’Leary and Olly Murs’ trek across the driest desert in Africa, John Bishop’s cycle, row and run from Paris to London, and BBC Radio 1’s Greg James’ five triathlons in five days.

But, when pushed to answer, Greg said it was “probably David Walliams”.

The comedian swam across the English Channel in 2006, the Strait of Gibraltar two years later, before completing the length of the Thames in 2011.

“Cold open water swimming is the nadir of misery.

“There is nothing tougher,” he told me in HealthHackers episode 25.

Greg is familiar with tough. 

He’s been an Olympic athlete (twice competing in the modern pentathlon), he won silver at the World Championships in 1994 (his proudest moment - because his father was there to see it).

Since retiring from athletics, he’s completed the famously punishing Marathon des Sables (running the equivalent of more than six marathons over seven days in the Sahara desert). He’s also swum from Europe to Africa, across the Channel and the length of the Thames. 

One of Greg’s books is called Achieve the Impossible.

I asked him if he thought anybody could achieve the impossible.

“Yes,” he said, without hesitation.

If you’re wondering how - Greg summed up his methodology in three key steps for us.

Firstly, commit; “I always say to people, look, tell as many people as you can.

“That actually creates quite a nice motivation because people are engaged in what you’re trying to do.”

Next, get a good team who will support you on your journey.

“Nothing great is achieved alone,” he said.

“The world’s greatest explorers have got an incredible team that sit behind them, you may not see them.”

And finally, “planning is absolutely crucial.”

According to Greg, it’s not just about setting one long-term major goal but breaking that down into “short and medium term goals.”

“Effectively you are creating flags along the way of whether you are on track.”

You can understand now why one of his favourite sayings is: “Success is not a chance event, it doesn’t just happen.”

Greg’s a big believer in a customised and targeted approach, profiling each of his clients to find their strengths and weaknesses, so that coaching can focus on the weaknesses while maintaining the strengths. 

When he started training Davina McCall for her ultra-triathlon, he said she was only a holiday swimmer.

“She could swim 25 metres and would have to recover before going again.”

“I remember the first time I took her open water swimming… it took us about three hours to get her into the water because the fear of open water is real.”

He wrote her a training plan with a heavy focus on swimming - five times a week. Then cycling and running on top, getting faster or further each week.

She would train, on average, six days a week, he told me. And within 8-12 weeks she was able to swim 2500m across Lake Windermere in her ultra-triathlon.

When he’s not busy training celebrities or pushing himself through gruelling challenges, Greg works with professional athletes, like boxer Anthony Joshua, to optimise their athletic performance.

He also sees a range of people with different needs at London’s Centre for Health and Human Performance - which he co-founded, including cancer patients undergoing chemo.

“What chemotherapy does is it reduces muscle mass dramatically,” he explained.

“Some of the things we work on very hard with cancer patients is optimising protein intake, the right type of protein which targets muscle regeneration combined with strength training.”

In doing so, he’s seen some muscle-loss cases reversed, he told me.

After 30 years of working in sport and exercise science, I asked Greg what his most fascinating discovery has been during that time.

“I think what we should always do is challenge dogma.”

He speaks from experience; in his early career he turned a long-held scientific belief on its head by proving it was wrong. 

“If you ever read a textbook up until the nineties it would say the heart doesn’t fatigue.”

“I remember doing sessions thinking, ‘it must fatigue’ because I’m fatiguing.”

Through his research, and going against the widely held view at the time, he was able to demonstrate that the human heart does indeed fatigue.

He went on to publish many more scientific papers - around 200, in fact. That’s alongside his eight books.

And there’s another important lesson Greg says he’s picked up over the years.

“Einstein, for me, coined it beautifully… ‘genius is the ability to explain the complex in simple terms.’

“It’s very easy to sound very intelligent and bamboozle people. 

“But I think the genius is the ability to take what is incredibly complex and make it understandable by all.”

Find out more about Greg on his website here.

You can also follow him on Twitter and Instagram.

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