George Hood says he's still in "excruciating" pain after breaking the Guinness World Record for planking over eight hours on Feb. 15. 

"The soreness is very deep," Hood told CNBC Make It on Feb. 24. "The body has to heal from the inside out."

Hood broke the record for the longest time in plank position for a male by holding one for eight hours, 15 minutes and 15 seconds. (The previous record was held by 45 year-old Mao Weigdong of China, who held a plank for eight hours, one minute and one second in 2016.)

Hood, an ex Drug Enforcement Administration agent, has been exercising since completing Marine Corps officer training program in his 20s, but says he is now in the best shape of his life at age 62.

But Hood, now a two-time planking world record holder, had an inauspicious start when he got into competitive planking 10 years ago.

"When I first tried to do it, I went five minutes," Hood says.

He began to plank every day for six months and eventually had his first Guinness World Record in 2011 with a plank that lasted one hour, 20 minutes and 25 seconds.

For the 2020 plank challenge, Hood, who is mostly retired but has some fitness clients, trained seven hours a day for about 18 months to build stamina and physical and mental strength leading up to the event. 

Here's how Hood trained for the world planking record.

Mindset coaching

Despite the physical pain of planking for eight hours, Hood says the hardest part of conquering the feat is the mental challenge. So for six months leading up to the event, Hood worked with mindset coach Renae Cobley.

"There are times you get self-doubt. You get bored. You wonder if it's worth anything," Hood says. Cobley "taught me to believe [in myself] no matter what."

"Cleaning up people's mindset is a must," Cobley tells CNBC Make It, "as every human invents themselves through a figment of their imagination and their thinking."

During training, Hood (who is based in Chicago) would call Cobley (who's based in Australia) after long practice planks. For an hour or two they would discuss Hood's thoughts and any barriers he ran into. Hood, for example, often struggled with thoughts of quitting as the pain from planking intensified.

One technique Cobley used with Hood both in training and during the competition was having him visualize that he was a tree and that his roots run deep through through earth.

George Hood's mindset coach Renae Cobley talking to him during his planking challenge on Feb. 15 in Chicago, Illinois.

"A tree that has deep roots can outlast almost any condition — ferocious storms, extreme heat and cold and the sheer brutality of life and its obstacles," Cobley says.

The visualization helped to distract Hood from his own thoughts, even as his his elbows began to bleed four hours into his record-breaking plank, and to "dissociate any awareness of time," which Cobley says is key in a timed competition. 

4 to 5 hours of planking and 2,000 crunches a day

For the physical portion of the training, Hood devoted four to five hours a day solely to planking.

To build stamina, "it's done in three sets or less a day," Hood says, meaning that he planked for an hour or two at time and then took a short break (break times varied he says) to give his body some rest.

"I had a 30 hour [planking] goal to make each week," he said. 

Every day, Hood also did "at least" 700 push ups, 2,000 crunches, 500 toe squats (squats done balanced on your toes) and about 500 bicep curls using a resistance band (to strengthen his arms and shoulders).

"Then of course of my cardio, which is a minimum of 30 minutes on the treadmill a day," he says.

Eating for energy

During the eight-hour-plus competition plank, Hood says he burned 4,252 calories, according to his heart rate monitor.

Hood had only a half-cup of oatmeal, one egg and lots of water four hours before the event so that he didn't need to use the bathroom while planking, and during training, Hood's diet was also a balance of carbohydrates and proteins.

"I'm not vegan, so there, but I do eat healthy," Hood joked, referring to his friend and female Guinness world record holder for planking, Dana Glowacka, who is vegan. (Glowacka, who is from Canada, broke the record on May 18 after planking for four hours, 19 minutes and 55 seconds.)

Hood also says he has found "some success" boosting his energy in recent years by adding super foods including spirulina and moringa to his diet.

(Spirulina, a blue-green algae, is high in nutritional content and a richer source of protein than most vegetables, but no research has been done on its impact on energy levels. The moringa plant contains lots of vitamins, minerals and proteins when dried, according to studies, and it acts as an antioxidant. But more research to needed to determine its uses and effectiveness.)

But even Hood splurges. After breaking the world planking record, Hood says he treated himself to pizza at a local pizzeria.

"It was hard to lift my arms to eat, but I managed," Hood says.

As for his next move, Hood says he plans to break the Guinness World Record for the most push ups in one hour. The record is currently held by Carlton Williams from Australia, who at 52, did 2,682 push ups in 60 minutes in 2017. 

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