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Abstract

International Journal of Exercise Science 18(6): 56-64, 2025. The fitness movement in the United States has evolved substantially since its emergence in the late 20th century, with social media platforms like YouTube and TikTok now playing a pivotal role in disseminating fitness programs and associated claims. One program that has gained considerable popularity is the 12-3-30 treadmill workout (12-3-30), which involves walking at a 12% grade at 3 mph for 30 minutes. Despite widespread claims about its effectiveness in burning fat and calories, there is a lack of peer-reviewed scientific studies evaluating these claims. The present study investigated metabolic responses to 12-3-30 compared to self-paced treadmill running, with both sessions matched for total energy expenditure. Sixteen participants (7 female, 9 male) completed both sessions in a controlled laboratory setting, where metabolic data were collected using a metabolic analyzer. The measures recorded were completion time, total energy expenditure, energy expenditure rate, and substrate utilization (percentage of carbohydrate [%CHO] and fat [%FAT]). The results showed that, when matched for total energy expenditure, 12‑3‑30 had a significantly longer completion time, lower energy expenditure rate, higher %FAT, and lower %CHO than self-paced running. While 12-3-30 may be less time efficient than self-paced running for expending energy, it may be more advantageous for individuals aiming to increase fat utilization. The present study enhances our understanding of the metabolic demands associated with a trending fitness program and highlights the importance of scientifically evaluating such programs to provide evidence-based recommendations.

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