Mess with an ordinary mathematician and you'll likely be on the receiving end of a dirty look.
Mess with mathematician-slash-author-slash-boxer Keith Liddell, however, and you might be on the wrong end of a world record-setting punch.
"Chicago has the record for the fastest hands," he said. "That's what I want people to see."
The 26-year-old Logan Square resident has etched his name in the Guinness Book of World Records as the owner of the world's fastest martial arts punch. On Oct. 6, Liddell threw a punch traveling 44 mph at Body Tac Karate Dojo in South Shore.
Last month, Guinness alerted Liddell that he indeed had broken the record. The previous mark was 43.3 mph, achieved by John Ozuna in 2008 in San Jose, Calif. Manu Gautam, records manager at Guinness, confirmed that Liddell is now the puncher to beat.
"[My coach] said if I hit somebody in the windpipe with that move, it could possibly kill them," he said. "We didn't know it was that powerful. We thought it was just speed."
Liddell set his sights on breaking world records after a double hernia derailed his Olympic boxing dreams in 2009.
"My coach [Larry Tankson] was being facetious," Liddell said. "He said 'you got a little bit of speed on you. Why don't you try and break a world record?' That's how it all got started."
Measuring the speed of a punch is a lot different from measuring the speed of a car, however. Liddell said it's more complicated than merely having someone train a radar gun on his fists.
"They analyzed a lot of my work that I had done," he said. "There's a lot of precision. It has to be on contact. It has to be a 44 mph on contact. It can't just be thrown at a speed instrument."
He said Tankson noticed something unusual when the two were working on his side jab.
"We had a shield, a punching bag shield and I demonstrated the side jab," he said. "When I did that, [Tankson] said to stop because it felt like his arm was going to break."
Liddell, who says he's hoping to qualify for the 2016 Olympics, said throwing punches that are both swift and destructive involves just as much brain as brawn.
"It's moving your whole body into one motion fluidly," he said. "You have to generate something called torque, basically based upon full rotation on an axis point. With that movement, that's how you generate velocity."
Building that velocity in the gym isn't a matter of being able to lift a ton of weight, either. Liddell said the average person can develop fast fists by doing basic exercises.
"What you want is lean body tone; that will allow you to go quick," he said. "Pushups, situps, even possibly chin-ups. One-, two-hand pushups, pushups on the knuckles."
As for getting hit by a 44 mph punch, Liddell said he isn't exactly sure how it would feel, and would rather avoid the experience if at all possible.
"I hope it never happens, buddy, but I've been hit a lot," he said.
Matt Lindner is a RedEye special contributor.
With his 44 mph punch, Chicagoan Keith Liddell joins these Guinness Book of World Records all stars.
Fastest time typing the alphabet on an iPad
Chase Samuel in Osler, Saskatchewan, in February 2013.
Fastest 100 meters on a skateboard by a dog
Tillman the English Bulldog during X Games XV in L.A. in July 2009.
Set by a motorcycle and sidecar hidden under a bathroom set consisting of bathtub, sink and laundry bin, in Milan, Italy, in March 2011.
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