"There's a little snobbery about running on a treadmill," said David Siik, a track and field sprinter turned treadmill class fitness instructor at Equinox, the upscale chain of fitness centers. "Most racers are a little ashamed of running indoors."
Siik, who is now based in Los Angeles, turned reluctantly to treadmill running after a post-college stint in New York City.
"I was sick of running into cars trying to get to Central Park," he explained, "and New York in January is not always the friendliest place to run."
Now the humble treadmill has him hooked.
"I still really enjoy running outside, but there is nothing better than the ability to calculate and monitor your goals on a treadmill," he said. "You're running on this computer."
Siik, 33, believes too many people get on the treadmill without knowing what to do.
"They hit âon' and then they're clueless," said Siik, who tries to bring the energy of a spin class to his 45-minute treadmill workout class, which includes three runs, each progressively harder, after an initial warm-up.
The treadmill is by far the most popular cardio machine, accounting for 58 percent of home fitness sales in 2012, according to the National Sporting Goods Association, a percentage that has stayed consistent over the past years.
The elliptical trainer, at eight per cent, is a distant second.
Melanie Douglass, a Utah-based dietitian and trainer with ICON Health and Fitness, whose products include cardio equipment, has also taught classes on the treadmill, which she calls her preferred piece of equipment.
"People always work more efficiently (on the treadmill), because the motor and belt help you maintain a consistent pace," said Douglass.
She said people err when they go too slow, or do the same thing day after day.
"Exercise is not supposed to be comfortable," she explained. "You have to challenge your body."
Dr. Michele Olson, professor of exercise physiology at Auburn University at Montgomery in Alabama, said besides teaching proper running and walking form, classes help the exerciser learn "the bells and whistles" of the modern machine.
And unlike outdoor running, training on a treadmill ensures you are running at your intended pace, she said. Simply varying the grade, or incline, every minute will push up the calorie burning.
But that's just the beginning.
"We've researched and studied walking and running on treadmills in all directions," Olson said. "You burn more calories moving sideways and backwards, particularly at walking speeds."
She even likes to see people with their feet on the floor behind the treadmill walking on it with their hands.
"After a set of push-ups, treadmill walk with your hands," she suggests. "Your shoulder girdle will become a beast providing you with both upper body strength and endurance in those under-aerobically used upper body muscles."
Siik said using a treadmill is the best 30 to 45 minutes of cardio anyone can get inside a gym.
"The beautiful thing about a treadmill is that it will never lie to you. It's a brutally honest machine," he added.
(Editing by Patricia Reaney and Sandra Maler)