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I tried the viral TikTok 12-3-30 treadmill workout — does it work?

Feet walking on a treadmill, trying the 12-3-30 TikTok treadmill workout
(Image credit: Shutterstock)

As a runner, it’s not often that I turn to TikTok for inspiration, but the viral "12-3-30" treadmill workout caught my attention. The workout made famous by former actress and social media star, Lauren Giraldo, has been shared over 154 million times on TikTok, with users raving about it. But what is the 12-3-30 treadmill workout, and what are the benefits? 

When Giraldo spoke about the workout online, she said, "I used to be so intimidated by the gym, and it wasn’t motivating. But now I go and do this one thing, and I can feel good about myself." If you're not a fan of running, but you're looking for a cardio workout to get you moving, Giraldo has found it. (If you are a runner, we've found the best treadmill workouts here). 

Rather than running, the workout involves walking at an incline, which has been proven to have some serious benefits, such as increased weight loss (Giraldo credits the workout for helping her lose 30 pounds) as you’ll burn more calories walking at incline than on the flat and working the core, as well as the glutes and calves. Compared to running, power walking also has less impact on the joints, so it’s a good option for those who find running too intense.

You can also read what happened when I tried the viral 25-7-2 workout for a week, when I added 30 sit-ups a day to my workout for 30 days, and when I did 100 dead bugs a day for a week

How do you do the 12-3-30 workout? 

Don’t panic, it’s much, much easier than it sounds. To follow this treadmill workout, you simply: 

  •  Warm-up for 5 minutes, either walking on the flat or at a slight incline 
  •  Set the treadmill incline to 12%  
  •  Set the treadmill speed to 3mph 
  •  Walk for 30 minutes  

There's no firm guidance on whether or not to hold on to the bars of the treadmill. Giraldo says she holds the bars about 30% of the time and goes hands-free the other 70%.

What is the 12-3-30 workout like? 

To caveat, I was ten days away from running my fourth marathon when I tried this workout, so I considered myself to be at a pretty good level of fitness. On average I run four to five times a week, with an average mileage of around 30 miles, but aside from going out with the dog, power walking isn’t part of my daily routine. 

The first thing that struck me when I set up this treadmill was that 12% is pretty high. We’re talking about hiking up a steep hill for 30 minutes, not the gentle stroll in the park I’d expected when setting out to test this workout. I’d suggest that those not used to walking or running regularly might start a little lower, as it was a bit of a shock to the system for the first few minutes.

It’s also worth noting, 30 minutes is on the longer side of a workout for beginners. Giraldo herself said it took her a while to build up to walking for the full 30-minutes and had to take breaks when she first started, so don’t be afraid to lower the incline should you need.

A screenshot of an Apple Watch 6 following the TikTok 12-3-30 treadmill workout

(Image credit: Future/Tom's Guide)

Next up, power walking at incline uses different muscles to running. As mentioned, I was a few days out from a marathon, so I didn't want to put too much strain on my calves, hamstrings, or my lower back muscles, as I was supposed to be tapering, but I definitely felt my calves working harder than they would on a treadmill run. (If you do suffer from upper or lower back pain, you should be careful walking or running at an incline, as it can put more pressure on your spine).

Finally, in terms of calorie burn, this workout is not on par with a HIIT workout or a run. According to my Apple Watch 6, I burned 159 active calories in the 30-minutes, which is a lot less than I’d burn if I ran for 30-minutes, but more than if I walked on a flat surface. Of course, calories are very specific to the stats of the user, and according to the tread, which I hadn’t programmed my data into, I’d burned 323 calories in 30 minutes.

In total, I walked 1.5 miles and climbed 948 feet. While I’ll definitely stick to running outside as my exercise of choice, this was a brilliant, low-impact way to get my heart rate up. What’s more, when I stepped off the tread, I could feel that I’d really worked my glutes and my hamstrings, which are areas runners often neglect, so this would be a great form of cross-training a couple of times a week. 

According to her TikTok, Giraldo does this workout five times a week and while I’d say that’s probably a little much for most gym-goers, it’s definitely a great treadmill workout to try if you’re not keen on running.

Are there any risks with the 12-3-30 workout?

Of course, no workout is 100% injury-proof, but are there any risks associated with the 12-3-30 workout, and is it better than other forms of cardio? In a word, no. While walking at incline definitely targets different muscles to when walking on the flat, there are plenty of other forms of cardio that will work you just as hard. 

The workout isn't without drawbacks either, walking at an incline can put more pressure on your lower back, so it's a good idea to pair this with these back strengthening exercises. You'll also be working your hamstrings and calves harder when walking at an incline, so it's a good idea to ensure you've done a proper warm-up before jumping on the treadmill and increasing the incline. 

Like all forms of exercise, it's a good idea to mix the 12-3-30 workout up with strength training, stretching, and other forms of cardio to work the entire body, and keep you from getting bored. 

Jane McGuire
Fitness editor

Jane McGuire is Tom's Guide's Fitness editor, which means she looks after everything fitness related - from running gear to yoga mats. An avid runner, Jane has tested and reviewed fitness products for the past five years, so knows what to look for when finding a good running watch or a pair of shorts with pockets big enough for your smartphone. When she's not pounding the pavements, you'll find Jane striding round the Surrey Hills, taking far too many photos of her puppy.