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Increasing the incline

How the 12/3/30 treadmill trend took over the internet and what exactly people hope to get from it.

by Lauren O’Connell
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As someone who spent the majority of their childhood and adolescence in dance classes, the cartilage in my knees has seen some damage and my joints creak a little more than the average 20-something’s. When I’m doing cardio workouts, my focus is on finding exercises that avoid pressure on my knees (aka: squats, burpees, and running are my natural enemies). So, after weeks of seeing the 12/3/30 treadmill workout trend all over my TikTok and Instagram in October 2021, I was intrigued. The workout is fairly straightforward and simple (set the incline to 12, speed to 3 miles per hour, and walk for 30 minutes), so when I hopped up on the treadmill, started my usual gym playlist, and began hiking the invisible mountain I had placed in front of myself, I was (naively) confident. This is essentially how it went:

Minute 3: My face is sweating, my breathing is becoming a little uneven, and I notice on my Fitbit that my heart rate is higher than I thought it would be at this point. Before starting my workout I noticed my “Daily Readiness Score” — which is calculated by your activity levels, recent sleep, and heart rate variability — was at 71. Despite having an “excellent” score (a “low” readiness score is 0-29 and both “good” and “excellent” scores vary from 30-100) I realized I was perhaps a bit too confident in my ability to go from a 0-to-12 incline in seconds with ease.

Minute 5: The machine’s clock must be broken, I think. There’s no way I’ve only been at this for five minutes.

Minute 10: I can’t even stand to look at the machine’s clockface anymore. I focus on the blank tv screen in front of me and move my hands from the hip-level bar to the top of the machine. I’m essentially holding on for dear life. My Charge 5 watch buzzes to let me know that my heart rate is in the cardio zone (when your heart rate is between 70-80 percent of

your maximum heart rate, which is recommended for aerobic exercises) and I catch myself wondering how I’m going to make it 20 more minutes.

Minute 20: I’m actively pep-talking myself into not stopping and fleeing the scene. I’m not the only person in the gym doing 12/3/30 but I am somehow the only one looking like they’re fighting for their life.

Minute 30: I hit the “cool down” button as fast as I can and feel my soul begin to reenter my body as the speed slows and I’m brought back down to a standard incline.

A few minutes later, as I was starting my walk back to my apartment, I realized something: 12/3/30 might have put me in a (metaphorical) chokehold, but I kind of loved it. My watch showed me that 22 of the 30 minutes I was on the treadmill was spent in the cardio heart-rate zone and I had burned an estimated 421 calories. For the first time, I had stepped off the treadmill feeling like I had achieved something more than a casual walk, but without feeling the dreaded joint pain running brings me. I was hooked.


Trend cycles don’t just impact fashion, art, and music they also play a role in fitness. Over the years people have traded in their stationary bike shoes for pilates socks, dance cardio classes for hot yoga, boxing gloves for tennis rackets, and high-intensity interval training (HIIT) for lower-impact alternatives. The most recent star of the cycle? The low-impact treadmill workout that some say will make you want to break up with high-intensity cardio: 12/3/30.

Originally made popular by a social media influencer in 2020, the exercise has piqued the interest of millions since. NYC-based personal trainer and group fitness instructor, Alexis Dreiss, says she understands the appeal of the trend and thinks it’s a great way to get people moving. “If you’re somebody who doesn’t like to go to the gym and kind of wants to do a mindless activity, it’s a great way of getting yourself to get your day going,” she says. “I feel like it’s a good intro into doing other forms of cardio, too.”

Studies show that low-impact cardio like walking, swimming, and yoga can be fantastic alternatives for those looking to achieve a strong cardiovascular workout without the joint pain and stress often associated with high-impact cardio. So something lower-impact, like 12/3/30, is a natural swap. “It is a great way to get the heart rate up without having that eccentric overload on your joints,” Dreiss explains. “Because if you’re going to jog or you’re going to run on the treadmill and your whole body weight is landing onto each foot, individually, every single time...that is a lot of stress on your knees and your joints.” That additional stress from running or jogging can also increase soreness in your quadriceps and calf muscles, so replacing running with an inclined walk will give you a hard workout without the overload.


Curious to know who else I know has given 12/3/30 a shot, I made an Instagram story asking my friends and followers to message me their thoughts. As I scrolled through the responses, it became clear that the secret intensity of the exercise is what drew many of them in. “I only feel good leaving the gym if I’m profusely sweating,” my friend Sarah typed in response. “12/3/30 makes me feel the same as I did after doing an intense HIIT workout, but without having to do a burpee.” Another friend, Alex, said she enjoys watching her progress on her Fitbit. “Seeing where my heart rate is at, and if I’m actively in a cardio heart-rate zone, during the workout makes me feel good about the challenge.”

While the general health benefits of cardio exercise is well known, skeptics might wonder what exactly a 30-minute walking routine could do for you. In an interview with Well + Good about the benefits of incline walking, physical therapists discuss the different impacts it can have on your body. It turns out these pros all felt that treadmill exercises can have both musculoskeletal and cardiovascular benefits. When you walk at an incline your quadriceps (the front of the thigh) and your gluteus maximus (the large buttock muscle) have to work harder than while on a level-surface stroll. Your legs also get a greater stretch and your calf muscles carry a heavier load due to gravity’s impact on your body. Cardiovascularly, walking at an incline can spike your heart rate, which then can increase your metabolic burn.

The benefits of something like 12/3/30, or any regular workout, can go even deeper than the known physical benefits of regular exercise and increasing your heart rate (although, making your heart race isn’t necessary to experience the cardiovascular benefits of walking). And it’s no secret that staying active can positively impact your mental health as well, but researchers are making progress in understanding exactly how exercise can do this. While all of these are true, it’s more than just a dopamine rush, serotonin boost, or the known spike-then-fall of cortisol levels; it appears physical exercise can have a strong effect on the brain’s structure. According to the American Psychological Association, recent studies suggest physical activity benefits white and gray brain matter, which is closely tied to “cognitive processes like thinking and memory, attention span, and perception.”

And while these long-term benefits have their appeal, some of the 12/3/30 regulars enjoy the immediate moments the workout gives them. “I try to do 12/3/30 three or four times a week because it’s a great opportunity for me to clear my head,” Jade, a woman at my gym tells me. “It’s hard enough that I have to just focus on my breathing, making it feel almost meditative.” Spencer, a 30-something man a couple of treadmills down, says he started it as a way to decompress with his girlfriend. “We live together and both work from home, so we try to keep separate during the work hours. Once we log off for the day, we come to the gym and walk off our frustrations from the day together,” he says. “It’s a nice routine.”


Now, six months into doing 12/3/30 roughly three times per week, that 0-to-12 incline climb is a very doable feat. I know I’ll break a sweat without committing to lingering joint pain or feeling my knees crack as I hit mile one (and that I’ll easily hit Fitbit’s recommended 150 Active Zone Minutes each week). Most days I mix in additional strength and weight training,

but even when I can only squeeze in that 30-minute climb, I feel good. For maybe the first time in my life I actually look forward to going to the gym. I know that as time keeps moving, the trend cycle will continue to spin, and we’ll keep seeing people try their hand at new-to-them sports, techniques, and exercises. However, 12/3/30 will stay a constant in my gym routine. It might be nearly impossible to predict the next fitness trend that will flood our screens and gyms (Dreiss’s prediction? She thinks it’ll be combat sports) but one thing’s for sure: it’ll get people moving.

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