If you think the Comrades Marathon is tough‚ try running 250km through the Kalahari Desert.

That is what 51-year-old David Barnard is doing in a bid to raise funds for the Nelson Mandela Children's Hospital.

Barnard – who earlier this year ran 250km through Iceland – started the Kalahari Augrabie Extreme Marathon on Saturday to raise funds for the hospital. The race runs until October 26.

He said he knew the race would not be easy.

“Running 250km through the Kalahari Desert in extreme heat and sand will be a tough challenge‚ but I’m inspired by this cause and the belief that together we can achieve this target. Nothing will give me greater pleasure than honouring Madiba’s legacy and centennial birthday in this manner‚” Barnard said.

Although every racer has different goals‚ Barnard said he was inspired by a combination of personal passion for sport and raising awareness about matters close to his heart.

The 250km race in which he participated in Iceland in June served as a big part of his preparation for the Kalahari event.

“Although the conditions were different because it was very cold there‚ and here in the Kalahari it will be extremely hot‚ it prepared me physically and mentally‚” Barnard said.

To let his body to adjust to the hot conditions‚ Barnard said that for the past seven weeks he has been running through the Johannesburg streets between midday and 2pm daily – even though he doesn’t believe this heat will be as bad as he expects in the desert.

The extreme sport enthusiast said he felt well prepared for the race and said he hoped to reach his target of reaching R250‚000. His fundraising campaign will run till November 27‚ to coincide with Giving Tuesday‚ an annual global initiative aimed at encouraging social giving.

Barnard said that every year he selected an organisation which embraced and represented issues close to his heart. He has been doing so since 2013.

From developmental and social justice issues‚ to those affecting children‚ are some of the things he feels passionate about. And it was organisations that dealt with these issues that he looked for.

Speaking to TimesLIVE on Friday morning‚ a day before the marathon began‚ Barnard said the mood at the race village was electric.

“It will definitely be a tough one for all the racers and most of us here are not racing to win. We want to reach that finish line‚ which in its own right is a huge achievement‚” Barnard said.

Barnard is the first African to have run at least one ultramarathon on every continent.

Nelson Mandela Children’s Hospital CEO‚ Dr Mandisa Maholwana‚ said they were honoured by Barnard’s gesture - as well as the general public supporting his campaign.

“This state-of-the-art facility was built through a global fundraising campaign and continues to rely on the generosity of individuals like David to ensure that we are able to offer the best care to children who otherwise would not be able to afford it‚” Maholwana said.

If Barnard is successful in reaching his target of raising R250‚000‚ Moholwana said funds would go towards supporting at least five heart surgeries for their public patients. These can cost R20‚000 each. It would also go towards medication for at least one patient in the intensive care unit for three weeks.

“Some of the money raised through the campaign will also contribute towards other costs such as toys for children in physiotherapy‚ noise-cancelling earphones and welcome packages‚” Maholwana said.

Those wishing to donate to Barnard’s cause can do so on BackaBuddy.