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Experts say the “12-3-30” treadmill routine is convenient and can provide a good workout, but it’s not for beginners. Wera Rodsawang/Getty Images
  • The viral “12-3-30” workout involves setting a treadmill to 12 percent incline at 3 miles per hour and walking on it for 30 minutes.
  • Experts say that the workout provides good exercise, but it doesn’t offer unique benefits versus other cardio routines.
  • Those who haven’t been working out should build up to the workout.
  • Cardiovascular exercise is associated with better long-term health outcomes.
  • Walking or running is excellent for cardio health, but resistance training is also recommended in order to get a complete workout.

Trend followers may have noticed that there’s a new cardio workout that’s gone viral — one that may have people dusting off their old treadmills.

Lauren Giraldo, a social media personality, first shared her “12-3-30” workout on YouTube in late 2019, and then again on TikTok last November.

The workout is elegant in its simplicity, getting its name from its core concept: set a treadmill to an incline of 12 at a speed of 3 miles per hour, and then walk for 30 minutes.

Giraldo explained in her videos that the workout is a “game changer” for her, saying that it’s a way to stay fit at home for those who aren’t motivated to go to the gym.

Now, in the midst of the COVID-19 pandemic that’s seen many gyms shut down or reduce capacity, home-based workouts are more relevant than ever.

While Giraldo’s videos have garnered millions of views, it’s important to note that she’s an influencer, not a personal trainer or a doctor.

Healthline spoke to several experts about the efficacy of the “12-3-30” workout.

The workout promises to provide good cardiovascular exercise in a relatively short period of time.

But that doesn’t mean it’s a safe place to start, particularly for someone who’s been more sedentary than usual during the winter months.

Morgan Rees, a certified personal trainer and nutrition specialist, told Healthline that there’s no doubt that walking at a 12 percent incline for half an hour will increase cardiovascular and muscular endurance.

But it comes with a caveat.

“It is definitely something you want to work up to if you do not work out on a regular basis,” she said. “That is the one major issue I have with this routine. Most people cannot just jump on the treadmill and maintain 3 miles per hour for 30 minutes at a 12 percent incline. I think there should be a system set up where one can increase their intensity over time.”

Rees suggested a beginner start out by doing perhaps 20 minutes with their treadmill at a 4 percent incline at 2.5 miles per hour.

Chris Higgins, a certified trainer who focuses on bodyweight training and running coaching, agreed.

He detailed some of the ways that a higher-impact workout can be detrimental to those who are just starting out.

“This is definitely not a beginner-friendly activity, as walking on a steep incline is very taxing on the body, especially if one is overweight, obese, or suffering from underlying muscle and joint conditions,” he told Healthline.

“Running or walking at a level 12 incline rapidly shortens the chest and pectoral muscles while lengthening the upper back and scapular muscles,” Higgins explained. “This means it is detrimental for anybody struggling with breathing. The posture will also severely suffer if done without properly pulling the shoulders back, engaging the core, and avoiding arching your back — which is difficult when you’re on a level 12 incline treadmill.”

While the workout might be too intense for beginners, there’s no doubt that it can yield positive results for those who are ready for it.

It’s important to recognize, though, that it isn’t a silver bullet that’s more effective than other workouts.

Rees points out that a solid workout routine doesn’t just include cardio.

“I will always be one to say that getting on the treadmill is simply not enough in terms of a workout routine,” she said. “Resistance training should always be included in one’s regimen. If you are looking to get a full-body toning effect, this is not the only thing you should be doing in your workout. You need to include bodyweight and resistance training routines.”

For those who are ready to start up a workout routine, a treadmill is a good place to start — assuming, of course, that they don’t bite off more than they can chew.

“I think [treadmills] are very effective for putting in a workout whether you walk or run, particularly in the cold weather months and when going to the gym is not possible,” explained Dr. James N. Gladstone, chief of sports medicine at Mount Sinai Hospital in New York City. “That being said, there are many benefits to being outdoors, and I would elect an outdoor walking routine over an indoor treadmill routine any day if that’s a choice.”

When the weather doesn’t allow for an outdoor workout, Gladstone suggests a number of indoor approaches.

“Using a treadmill is excellent for those who have the space in their homes or one available,” Gladstone told Healthline. “Walking the stairs of an apartment building can be very helpful as well. If you have a long corridor, walking up and down the corridor and getting your 10,000 steps in can be great. Finally, if the conditions are safe outside, walking around the block a few times as long as you’re well bundled up can be very invigorating.”

Ultimately, cardio workouts come down to simple exercise, whether it’s part of a viral workout trend or not.