As the weather turns colder, Jen Forman will do what she's always done to get her runs in: She'll go to her treadmill in her home, press start and run until she's done.
And she will hate every moment of it.
"I will continue to press the speed button to get a treadmill workout done as quickly as possible," said Forman, 38. "But I can't live without it because if it's snowing outside or I have my kids at home, I can't leave and go for a run."
In its 2016 survey, the Sports & Fitness Industry Association (SFIA) found that more than 50 million Americans said they used a treadmill at least once in the previous year. Yet if the monotonous motion feels like torture, well, that shouldn't come as a surprise. The tread wheel, a variation of what we know as the modern treadmill, was used in the 1800s to keep British prisoners from idleness but more so for hard labor.
"I can't get my head around the fact that we now pay to run on machines that were the harshest form of punishment, short of the death penalty, for about 100 years," said Vybarr Cregan-Reid, a senior lecturer at the University of Kent in England and author of "Footnotes: How Running Makes Us Human." The British outlawed the tread wheel as a punishment device near the start of the 20th century after outcries of it being seen as cruel and unusual.
Nevertheless, machines that evolved from those accounted for almost 40 percent of an estimated $3.5 billion in fitness equipment retail sales in North America, ranging from the $300 home products to the more than $10,000 commercial-grade treadmills.
The journey of the treadmill is an exercise in how work, leisure and technology evolved in the past 200 years.
Reinventing the (tread) wheel
The treadmill's evolution is emblematic of the shift in how humans work and work out that occurred because of the Industrial Revolution, Cregan-Reid said.
Before that time, most people had agrarian jobs that required constant physical labor so there was no reason to work out. Any sort of "exercise," Cregan-Reid said, stemmed from an upper-class understanding of leisure. To most aristocrats, exercise was a break from being sedentary, which was part of being elite.
With the rise of factory jobs and later with office jobs, work life became compartmentalized, and corporate culture spawned perhaps the most consequential move: We sat down to work. A sedentary life became the standard for most with some means, and specialized machines cropped up to improve on what became an activity of leisure: exercise.
The changes started by the Industrial Revolution took root in the 20th century, which paved the way for treadmills to become machines meant for privilege instead of punishment.
In the 1920s, photos of beautiful Gatsby-era women in high heels standing on wooden treadmills portrayed the machine as fashionable and luxurious.
Thirty years later, medical researchers used metallic treadmills with rubber belts to test heart and lung disease, finding the treadmill's capabilities to measure heart rate and VO2 max levels useful for diagnosis. One researcher, Kenneth Cooper, published his book "Aerobics" in 1968, encouraging readers to find ways to improve their cardiovascular fitness.
The late '60s were the unofficial start of the fitness era and of using the treadmill for recreational runs. President John F. Kennedy inspired Americans to improve the national state of physical fitness, and a decade later, runners strapped on their newly invented running shoes to join the running boom.
Inspired by Cooper's book, engineer Bill Staub founded Aerobics Inc. in 1968 and launched the PaceMaster, convinced that an affordable treadmill had a place in the home. According to his New York Times obituary, Staub sold 2,000 units a year during the 1980s, and by the mid-1990s, 35,000 PaceMasters were sold per year.
Companies saw opportunities to make the treadmill more comfortable and easier to use. In 1991, Life Fitness invented the 9500HR, with wide springs and a bouncier running surface.
"We went from not having a treadmill to being No. 1 in market share two years later," said Chris Clawson, former president of Life Fitness.
Treadmill usage grew as gyms became more popular in the 1990s and 2000s and as treadmills gained music, television and eventually Wi-Fi. On today's treadmill, one can walk, dance, watch television, listen to music and read. One can shop online, write emails and read some more.
"This machine really is the foundation of a lot of people in their lives and their physical activity," SFIA director Tom Cove said.
Boutique health clubs are using the treadmill's capabilities for more specialized workouts. Florida-based Orange- theory Fitness offers high-intensity interval workouts that are based on using the treadmill and its heart rate monitor.
RunSocial chief executive Marc Hardy said his augmented-reality programs are on most major treadmill lines, including Life Fitness and Nautilus, while other companies are creating their own virtual simulations of racecourses and scenic routes for users to engage while using a treadmill.
Some treadmill makers are hoping "green treadmills" take flight, by enabling energy offsets from the console or the treadmill motor. Wisconsin-based Woodway offers products such as the Curve, a self-propelled, bean-shaped treadmill that provides speed but no incline. The company sells the Curve at starting prices near $5,000.
At this time, the Curve doesn't come with a built-in TV.
Run to work, work to run
It's important to note that a treadmill is not necessary to run or walk successfully.
Treadmill makers and the fitness industry as a whole profit in large part because of the belief that technology can and should make people's lives easier - if they have the means.
For runners, treadmills are the conduit to run at a time and environment of their choosing. It allows a sense of control.
"Treadmills became a solution to a problem of 'I can't get out because it's too crowded, the traffic, I can't get out because it's too dark," Clawson said. "It gave you predictability. Whenever you needed it, it was available."
That sense of availability and convenience is why treadmills are still popular. And treadmill makers continue to innovate to make the device feel more than just a motorized belt.
Of course, not all of those innovations catch on. (Remember the folding treadmill?) Clawson attributes a recent drop in home-treadmill sales to users' lack of interest in those fancy added features - such as TVs - that make treadmills more expensive but that already exist in homes. And more concerning is lackluster interest among millennials and the even younger Gen Z users.
Both generational groups said in the SFIA survey that they'd rather run outside than on a treadmill.
Ultimately, while the treadmill might no longer be considered an official torture device, it still serves its original purpose: not of leisure but of work.
"No one says: 'I'm going to be a great treadmill runner. I'm going to break records this year,'" Cove said.
Said Forman: "I've got a purpose for getting on the treadmill. I want to execute that workout and want to be done."