The 12-3-30 treadmill workout gained popularity a few years ago, when influencer Lauren Giraldo credited it with helping her lose 30 pounds. If you’ve been living under a fitness rock, so to speak, the workout involves setting your treadmill to an incline of 12%, at a speed of 3 miles per hour, and walking for 30 minutes. I tried it for a month, and found it to be a great, low-impact workout, but as a marathon runner, it couldn’t replace the joy I get from a slow, steady run outdoors.
Fast forward a few years, and researchers have looked into the workout and how it compares to running. It turns out Giraldo wasn’t wrong — according to the study, published in the Journal of Exercise Science, the incline treadmill workout burned more fat than running did.
The goal of the study was to look at how the body fuelled each workout, not how many calories participants burned. Specifically, the researchers wanted to look at whether the body used carbohydrates or fat as fuel. To do this, they used 16 healthy young adults, 7 female, 9 male, and got them to complete two workouts — the 12-3-30 treadmill workout, and one session of running at a steady pace for 20-25 minutes.
The researchers adjusted both workouts to burn the same total number of calories. They found that the 12-3-30 workout took longer to achieve this calorie burn. Running burned calories faster than walking at an incline — an average of 13 calories per minute, compared to 10 calories per minute when incline walking.
Interestingly, however, walking at an incline used more fat as a fuel source — 41% compared to 33% when running. The study noted that running relied more heavily on carbohydrates, which is why you’ve probably heard of marathon runners ‘carb loading’ in the days before a race.
Obviously, it’s important to recognize that this study was conducted on a very small sample size, and that burning calories isn’t the only reason we work out. As a fitness editor, I’m a big believer that to see changes in your body, or to make long-term improvements to your overall health, you need to find a workout routine you enjoy. If walking on the treadmill is for you, then great, but if you’re a runner, a cyclist, a swimmer, or someone who enjoys hiking, you’ll still get a great cardio workout.
