I did the 12

Spoiler: It's harder than it sounds

As a runner, I rarely 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 millions of times on TikTok. But what is the 12-3-30 treadmill workout, what are the benefits, and what would happen if I tried it every day for a week?

Giraldo 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 looking for a running alternative that still counts as cardio, Giraldo has found it. If you prefer running, find the best treadmill workouts here.

The 12-3-30 workout involves walking at an incline, which has been proven to provide benefits like increased weight loss (Giraldo credits it for helping her lose 30 pounds), as you'll burn more calories and work your core, glutes, hamstrings, and calves harder. Compared with running, power walking is lower impact which is perfect for anyone returning from injury or suffering from hip, knee, or ankle pain.

Looking for more walking inspiration? Here's everything you need to know about walking for weight loss and what happens to your body if you walk 30 minutes a day, or read on for the full workout.

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

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%.

To caveat, I first tried this workout and wrote about it for Tom's Guide when I was ten days away from running my fourth marathon. Being in a taper, I was paranoid about pulling my calves walking up hill, so I've revisited this workout recently to give it a proper try over the course of a month — read on to find out what happened.

During this month, I did the 12-3-30 workout three times a week, in place of my running workouts.

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.

Over the month, I definitely got used to walking at this incline, but I could feel it down the back of my legs for the first few walks. I can see how doing this several times a week would increase your fitness levels. I definitely felt my calves working harder than they would on a treadmill run.

That said, due to the tough incline, if you do suffer from upper or lower back pain, you should be careful, as it can put more pressure on your spine.

The first few times I tried this workout, I found myself staring at the ticking clock on the treadmill, willing it to go faster. Again, 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, or press pause on the treadmill should you need.

After a month, I'd gotten used to my strolls up hill on the treadmill, but I really missed running outside. I definitely prefer to exercise outdoors, and as much as I enjoyed the challenge of the 12-3-30 workout, I struggled with boredom strolling on the treadmill.

As mentioned, the first time I did this workout I was a few days out from running 26.2 miles, and I noticed about 20 minutes in that I was working muscles I wasn't used to targeting. Doing the workout every day for a week, my hips and calves really felt the effects of hiking up a hill, even if that hill was in a gym. After a week, I could also 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.

On most days, I hiked around 948 feet over 30 minutes. On some days, I continued walking until I'd hit 1000 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.

Like all good workouts, this one is easy to adapt should you need to — you can easily break up the workout with minute breaks where you lower the incline, build up to walking at 12% over a number of weeks, or reduce the speed of the treadmill as you get fitter.

Alternatively, as you get fitter, you can speed the belt of the treadmill up, walk at a steeper incline, or like I did, challenge yourself to hike up a little higher each session.

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.

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.

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.

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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.

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