TikTok's Viral 12-3-30 Treadmill Workout Is Accessible, But Is It Safe? Here's What We Know

If you're at all into fitness and trying new workouts, the algorithms of Instagram and TikTok have probably shown you some of the viral #12330 workouts where influencers swear by the treadmill hack. 12-3-30 isn't some kind of Morse code; it's actually a treadmill workout that many influencers are saying is low impact, but still has all the benefits of an extreme HIIT or cardio workout. As Instagram coach Healthy Happy Olivia describes it, you "set your treadmill to an incline of 12 and a speed of 3 miles per hour, and then you simply walk for 30 minutes. Sounds easy but that 12 incline gets hard fast." She says this gets her into the "fat-burning sweet spot" and she's not alone. The tag on TikTok has more than 410 million views, and that's due to TikTok influencer Lauren Giraldo who coined the term in 2020. Her original video that spawned the trend has already been viewed more than 2.8 million times.

Giraldo credits the 12-3-30 treadmill hack as the reason for her 30-pound weight loss, and for bringing joy to her workouts. "I can go, I can feel good about myself, plus I feel like I look snatched!... I look forward to it, it's my 'me' time," she says. Is this truly the exercise game-changer the influencers are touting it to be? Is the workout more difficult than it purports to be? We investigate.

Have you ever heard of LISS cardio? It stands for Light Intensity Steady State cardio, and Everyday Health reports that this fairly new concept in exercise offers newbies an incentive to work out because the exercise isn't intimidating or too hard. According to exercise influencers on Instagram and TikTok, LISS and 12-3-30 go hand-in-hand, making the treadmill exercise a great start for those new to the gym. Instagram influencer FitByNlo swears by 12-3-30 not as magic, but as an example of a LISS workout, and TikTok user @vvgymmy says 12-3-30 is a beginner workout accessible to everyone. "There are immense health benefits of doing consistent LISS for all fitness goals like weight loss, strength training, and just maintaining cardiovascular and overall health," certified personal trainer Anna Victoria told PureWow about the intersection between LISS and 12-3-30. Easy on the joints, Victoria adds that "You can do LISS several times a week with minimal injury risk when compared to high intensity or high impact cardio." Osteopathic sports medicine specialist Dr. Dennis Cardone agrees, telling Today.com that when doing 12-3-30, "People are getting more of a workout in a shorter period of time; the muscles are working harder."

But some influencers are raising the red flag. TikToker @sujanpang says 12-3-30 is definitively not a beginner workout, finding that it was only "bearable" for her after doing it for five weeks. It turns out that there are some safety concerns you should consider before jumping on the 12% incline.

Dr. Dennis Cardone told Today.com that 12-3-30 treadmill workouts aren't something you should just jump into if you haven't worked your way up to the 12% incline. "The problem is people don't think that walking is a stressor. They think 'What's the big deal using an incline? I'm only walking.' But it really is a big stressor: low back, hamstring, Achilles tendon, knee, plantar fascia ... these are the areas where we see some significant injury related to inclining a treadmill," he told the outlet. 

Personal trainer Anna Victoria agrees, telling PureWow that "such a high incline" can result in injury and that you can probably get the same results if you do 10-3-30 or 8-3-30. "I don't think the steep incline of 12% is necessary," she explains, "but it also isn't harmful. You can do a lesser incline and still achieve the same LISS heart rate zones and get an amazing cardio workout in."

If you're just jumping on the treadmill for the first time, maybe start flat and progressively increase the incline each week to see gains, exercise physiologist Katie Lawton, MEd told the Cleveland Clinic. "Or put the incline at 5% to see how you do. Maybe slow down the pace or go for less time. See what your body can tolerate and build from there."