Because of this tough sport--he says he's lost a lot of weight and he's nearly cut his medication down to nothing.
"It's the best thing, I could have started," Tierney said.
And it's what other riders are saying too.
"Cycling started to be important because of health reasons," Dan Joy, Tulsa Tough competitor.
This weekend, thousands of racers across the U.S. and the globe will travel right here to Tulsa to compete in a three day cycling event.
"I'm ready for it," Joy said. "I'm excited."
The course will test their endurance and provide Tulsans with the chance to see some of the strongest athletes in the world.
These guys will be hitting speeds around 40mph," said Malcolm McCollam of St. Francis' Tulsa Tough. "When they come into the finishing stretch in a pack about 125 they'll be making the turns at 30mph."
Tierney says its "mass chaos and heart rate" -- a crazy heart rate he is thankful for.
"The cardiovascular exercise definitely just has made the biggest impact on my overall health. "
And a crazy sight to see, as riders are calling this the NASCAR of cycling.
Organizers say they expect 20,000 people to come to the event throughout its three-day period.