Bottom Line: The 12-3-30 workout (12% incline, 3 mph, 30 minutes) went viral on TikTok, but the concept is just structured incline treadmill walking. A 2025 study found it burns roughly the same calories as a self-paced run, with a significantly higher percentage of fat used as fuel. It's low-impact, accessible, and easy to stick with. The biggest benefit might be the one nobody talks about: it's a workout people actually do consistently.
The 12-3-30 is a viral workout, promising real results for people who want to trim fat and lose weight.
I know what you’re thinking: another ‘viral workout’. That’s my first thought too. But the workout itself isn’t some flashy, ‘hype over substance’ thing - it’s simply incline treadmill walking, something people have been doing in gyms for decades.
But with the hype comes the question: does it actually work?
Short answer: the science is on its side. Let’s dive deeper and see what exactly the research says, and whether the 12-3-30 workout is something you should add to your routine.
What is the 12-3-30 Workout?
The 12-3-30 is a treadmill workout with three settings:
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12% incline
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3 mph speed
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30 minute duration
That's the whole thing. You set the treadmill, start walking, and keep going for half an hour.
No intervals, no speed changes, no complicated programming. It's steady-state incline walking.
At 12% grade and 3 mph, you're walking at a brisk pace on a steep hill. It's harder than it sounds. Most people will feel their heart rate climb into a moderate training zone within the first few minutes, and by the halfway point, your glutes, hamstrings, and calves are doing real work.
Where It Came From
The workout was created (or at least, popularized) by social media influencer Lauren Giraldo, who first shared it on YouTube in 2019 as part of her wellness routine. It exploded on TikTok in 2020 and has been a staple of fitness social media ever since.
Here’s how she landed on those specific numbers: 12 was the highest incline on her gym's treadmill, 3 mph felt like a comfortable brisk walk, and 30 minutes came from her grandmother's advice to exercise at least half an hour a day.
That's worth noting, because the numbers aren't magic. They're one person's starting point that happened to go viral. And Giraldo wasn’t the first person to figure out you could walk on a treadmill for 30 minutes at a 12/3 incline/speed combo.
This is important to note because, once you realize the fundamental concept behind the workout is very straightforward, you’ll stop seeing it as clickbait and more as a viable way to get fitter.
What Does the Research Say About the 12-3-30 Workout?
There's one peer-reviewed study that directly tested the 12-3-30 protocol: a 2025 paper in the International Journal of Exercise Science that compared it head-to-head against self-paced treadmill running.
In short, it found that the 12-3-30 workout burned calories less efficiently than running, but it burned fat at a higher rate.
The setup: 14 recreationally active adults (7 male, 7 female, average age ~25) did both the 12-3-30 and a self-paced run on separate days. The running session was matched so participants burned the same total calories as their 12-3-30 session.
Here's what they found:
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The run took less time. Running burned the target amount of calories (~300) in about 24 minutes vs 30 minutes for the incline treadmill workout.
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Fat utilization was significantly higher with 12-3-30. Roughly 41% of energy came from fat during incline walking, compared to 33% during running (p < 0.001, large effect size). The remaining energy came from carbohydrates.
This doesn’t give us the full picture – it was a small study, with young, active participants, it only measured a single session (no long-term data), and it didn't track heart rate, perceived exertion, or VO2.
It’s far from a scientific consensus, and there’s a lot we don’t learn from the study. But the results are still interesting to note.
Research on Incline Walking
There’s little research specifically on the 12-3-30. But there’s a lot of research on incline walking – which is all this workout really is.
Here are a few highlights:
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It burns significantly more calories than flat walking. Research shows metabolic cost increases by roughly 23% at a 10% grade and 44% at a 16% grade compared to walking on flat ground.
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It's easier on your knees. A 2024 biomechanics study found that at inclines of 10% or higher, the internal knee abduction moment (a force linked to osteoarthritis progression) decreased compared to level walking.
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It works your posterior chain harder. Compared to flat walking, incline walking significantly increases activation in your glutes, hamstrings, and calves. The steeper the grade, the more these muscles are working to push you uphill.
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It pushes your heart rate into a productive training zone. Heart rate climbs roughly 10-15 bpm for every 2% increase in grade. At 12%, most people will land in Zone 2 or Zone 3 (60-80% of max heart rate), which is the range associated with improving aerobic fitness and fat oxidation.
Benefits of the 12-3-30 Workout (and Incline Walking in General)
There are plenty of reasons to like this workout, and why we can safely say it’s more than just another viral fad.
Here are the top reasons to try it (or something similar).
Meaningful Calorie Burn Without Running
Thirty minutes of steep incline walking burns roughly 250-350 calories depending on your body weight, which puts it in the same neighborhood as a moderate jog.
A lot of people struggle to get themselves to run. An incline walk could deliver similar benefits, but in a form you’ll actually stick to.
Higher Fat Oxidation
The 2025 study showed a clear and statistically significant advantage for fat utilization during incline walking vs running.
This makes sense physiologically: moderate-intensity exercise relies more on fat for fuel than higher-intensity work does.
A quick caveat: higher fat oxidation during a workout doesn't automatically mean more fat loss over time. Total calorie balance across your entire day still matters more than what fuel source you're using during any single session. But if you're already in a calorie deficit, training in a zone that prioritizes fat as fuel isn't a bad thing.
Improved Cardiovascular Fitness (VO2 Max)
Thirty minutes of sustained Zone 3 cardio is a solid stimulus for your cardiovascular system.
A 2022 overview of systematic reviews found that moderate-intensity continuous training reliably improves VO2 max, the gold standard measure of aerobic fitness and one of the strongest predictors of longevity.
High-intensity interval training (HIIT) can improve VO2 max faster, but the difference is smaller than you'd expect. For people who aren't already doing regular cardio, research suggests the gap between moderate and high-intensity training for VO2 max gains is small to trivial.
In other words, if you're choosing between incline walking you'll do four times a week and intervals you'll do once, the walking wins.
Low Impact, Joint-Friendly
Walking is inherently lower-impact than running. There's no flight phase (both feet off the ground), which means less force through your ankles, knees, and hips on every step.
The 2024 biomechanics data supports this finding, making it a decent choice for people with pre-existing joint problems, or people with more mass (thus exerting more joint stress from stronger impact).
Posterior Chain Work
Your glutes and hamstrings work harder on an incline. It's not a replacement for squats or deadlifts, but you'll feel it in your legs, especially during the last 10 minutes. Think of it as a cardio session that also gives your posterior chain some volume.
Is the 12-3-30 Workout Safe?
The 12-3-30 workout is generally safe and doable for people at a wide range of fitness levels.
If you’re a complete beginner, you may find it difficult at first; but there’s no rule saying you can’t start a little less intense, and build your way up.
In general, the 12-3-30 workout is safer than faster-paced, flat running, because there’s less impact with each stride. That can make it a better choice if you’re returning from an injury or dealing with existing joint problems (but, as always, get a medical professional’s advice on this if you do have a pre-existing condition).
There are some situations where incline treadmill walking may be less safe than other forms of cardio:
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If you have lower back issues. A steep incline can increase lumbar extension, especially if you lean back. Start at a lower grade (6-8%) and see how your back responds.
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If you have Achilles or calf tightness. The constant uphill angle keeps your calves under tension for 30 straight minutes. If you're prone to calf or Achilles problems, build up gradually.
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If you have balance concerns. A 12% incline is steep. If you feel unsteady, start lower and progress as you get comfortable.
So, again, check with your physician if you have any concerns.
How to Do the 12-3-30 Workout (Tips for Getting Started)
Here's the thing: there's nothing magical about 12% incline, 3 mph, and 30 minutes.
Those are fine numbers to start with, but the core principle is just incline treadmill walking at a moderate, sustained intensity. How you dial that in should be based on your body, not a viral formula.
The great thing about the treadmill is that it’s easy to program speed and incline up and down, to match the intensity you’re able to maintain.
If you’re struggling to keep up at 12 and 3, start slower and lower. If you have a wearable to track your heart rate, a good rule of thumb is to aim for whatever keeps you in mid-zone 3. From there, slowly push the intensity, but dial it back if you’re getting too close to your HR threshold (90%+ of your max HR).
In summary, here are some general tips to take on board:
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If 12% feels too steep, start at 8-10% and build up over a few weeks. The principle works at any challenging incline.
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3 mph is a brisk walk for most people, but stride length varies. Adjust so you're walking with purpose, not shuffling or overstriding.
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Don't hold the handrails. This is a big one. Gripping the rails significantly reduces the workload and changes your posture. If you need to hold on, lower the incline until you can walk hands-free.
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30 minutes is a target, not a requirement. If you can only do 15-20 minutes at first, that's fine. Build up.
This works well as a primary cardio option 3-5 times per week, or as a 1-2 session supplement alongside other training.
It's low-impact enough that daily use is manageable for most people, though listening to your calves and lower back is smart, especially early on.
The Bottom Line on the 12-3-30 Workout
If you’re wondering if the 12-3-30 workout is another viral, clickbait social media fad, or a real way to burn calories and improve your fitness, the answer is: a bit of both.
The 12-3-30 is just incline treadmill walking, with a catchy name.
But the workout (and incline walking in general) burns comparable calories to running with significantly higher fat utilization, it's easier on your knees than flat walking or running, and builds real cardiovascular fitness over time.
Don’t get too caught up in the naming. Just understand that there are real benefits to working out on the treadmill at higher inclines. And if a workout like this gives you a form of cardio you’re able to stick with and do consistently, then it’s absolutely worth the hype.