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This workout is popular on TikTok — but is it healthy?

Lauren Giraldo in her home gym in 2020 ((Courtesy of Lauren Giraldo))

When social media personality and content creator Lauren Giraldo began experimenting with the settings on her treadmill, she could never have predicted how many people would follow her example.

But today, interest in the workout she created has surged. The video she shared in 2020 has now been liked by more than 2.8 million people. Fitness influencers and regular exercisers are sharing results and raving about how the workout has changed their bodies.

What is the ‘12, 3, 30’ workout?

The workout, called “12,3,30” was created after Giraldo realized that running on a treadmill didn’t suit her. So she started experimenting with its settings, eventually settling on a 12 percent incline — the equivalent of a steep hill — and walking at a speed of three miles an hour for 30 minutes.

“That’s where I kind of found my groove,” Giraldo said. She started promoting “12, 3, 30” in videos shared to YouTube, where she has more than 1 million subscribers, and on her other social media pages.

Giraldo has credited the routine, which she said she does about five times a week, with helping her become active and maintain her improved physical and mental health.

The workout appears to resonate with many viewers, who have posted on social media about adding the workout to their routines. Some before and after videos on YouTube with titles like “I Tried Lauren Giraldo’s Treadmill Workout for One Week *surprising results*” have racked up thousands of views, and Giraldo has said she often receives messages from people who say the workout has helped them become more confident.

What experts say

But when asked about “12, 3, 30,” experts took a more cautious approach, saying it’s important for exercisers to listen to their bodies, protect themselves against potential injuries and be realistic about results.

“For the average person starting out, a 12 percent incline is really high and 30 minutes can be a really long time,” said Michele Stanten, co-author of “The Walking Solution” and a fitness instructor certified by the American Council on Exercise (ACE). “It could be an effective part of an overall exercise program but with the caveat that you have to build up to it.”

Arnold Ravick, a podiatrist who specializes in sports medicine and an assistant clinical professor of surgery at George Washington University Medical School, suggested starting at a lower incline and walking for a shorter period of time.

Giraldo, who has described herself as being “in a very unhealthy place” when she started the routine, said at first she felt “out of breath the whole time” and needed to take frequent breaks. An exercise shouldn’t be “super hard on yourself if you can’t get through the 30 minutes without stopping,” she said.

But within a couple of months of consistently doing the routine, Giraldo added, she started noticing positive changes. She has publicly talked about losing weight as a result of “12, 3, 30,” although she emphasized that wasn’t her main goal. “Primarily what I was looking for was to just be more fit and feel healthier,” she said.

“12, 3, 30” has probably worked so well for Giraldo because it is an aerobic exercise that falls within the ideal range of energy expenditure for most healthy young adults, said David Bassett, an expert in exercise physiology. Given its intensity, the workout may not be suitable for older people or those who are overweight or have chronic conditions, Bassett noted.

Weight loss and health benefits

Bassett estimated a person who weighed 150 pounds would burn 283 calories per “12, 3, 30” workout. In comparison, walking at that speed for 30 minutes without the incline would burn 113 calories, he said.

“Putting the incline on there is really what gets the calorie cost up a lot,” said Bassett, head of the department of kinesiology, recreation and sport studies at the University of Tennessee at Knoxville. “It’s not as vigorous as most runners would be doing, but it’s still well into the vigorous zone, so that’s definitely a benefit.”

Over time, people should expect to improve their heart and lung function, Stanten said. “You would notice things like you’re not as winded climbing stairs; you have more endurance for other activities that you’re doing.”

While losing weight is also possible, Bassett emphasized that it takes time. “You may also be putting on muscle at the same time as you’re burning fat, and so don’t expect huge changes when you’re looking at the scale,” Bassett said. But, he added, people may see their waistline getting trimmer or their legs getting toned. Try not to hold onto the hand rails which can decrease the energy expenditure, core engagement and calorie burn.

12, 3, 30 workout modifications

Experts also urged people to consider modifying the workout to fit their abilities and incorporating a variety of exercises into their routines, such as interval or strength training. “Your body is going to experience a level of a plateau in the changes that you see take place, not just with this type of workout, but any activity that’s the same thing over a long period of time,” Ewunike Akpan, an ACE-certified personal trainer, said. “You have to vary it because the body is so adaptive.”

Doing the same high-intensity exercise frequently could also become boring or result in overuse injuries such as Achilles tendinitis, plantar fasciitis, knee pain or shin splints, experts said.

“You’re using the same joints and muscles and tendons repeatedly like that, and that’s really not the object of exercise,” Ravick said. “That’s why you want to cross train, that’s why you want to use interval training, so that you don’t strain the same thing because that’s how you get hurt.”

He noted that he wouldn’t do any one specific workout more than three or four days a week. “That’s the sweet spot for exercise.”

Giraldo said she has not encountered physical problems doing the workout frequently, and varies what she’s watching or listening to prevent boredom. But she has added other exercises to her routine, including strength training like weights and squats, and is no longer intimidated at her gym. “Getting on the treadmill was a really great entryway for me,” she said.

Reducing your risk of injury

To reduce the risk of injury during an incline treadmill workout, you should wear proper shoes, drink water and stretch before and after the workout, experts said. Be sure to stretch the leg muscles likely to feel the most strain, such as calves, Achilles, hamstrings, glutes, quads and hips.

Good posture while walking can also help reduce risk of injury and increase the benefits of the workout, several experts noted. “You want to roll your shoulders back, stand up tall, don’t bend at the waist,” Stanten said. “When your body’s aligned like that, number one, you can breathe better when your chest is open, and you’re using all of your core muscles to hold yourself up.”


If you don’t have a treadmill, you can get a similar cardiovascular effect through interval training. Geoffrey Burns, a biomechanics and sport science researcher at the University of Michigan, suggested alternating running for one minute and walking for several minutes.

For those looking to avoid running, experts suggest walking up outdoor inclines such as hills or stairs, or walking with hand weights or a weighted backpack. “What it comes down to is just making walking harder on yourself,” Burns said.

Whatever the workout is, consistency is key, Stanten said. People need to find exercises they enjoy and are able to do on a regular basis.

Giraldo agreed. “I’ve learned that it’s less about what exact workout you’re doing but more about getting your foot in the door and implementing something into your routine,” she said.

For Giraldo, “12, 3, 30” also has become an opportunity for “me time,” she said. “I can hop on the treadmill, watch my videos, get one thing done. Just one simple thing done, and I can feel accomplished and confident.”

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