Introduction: We investigated the reliability of a novel Fatmax protocol on a treadmill, and if exercising at Fatmax in the cold would increase fat oxidation and energy expenditure.

Methods: On separate days, five participants performed two identical Fatmax tests. They then exercised at Fatmax, in cold (~0°C) and thermoneutral (~22°C) environments for 30 min.

Results: Excellent reliability (ICC >.9) was found for the Fatmax protocol, and a non- significant increase in fat utilization was observed during cold exercise at Fatmax. Conclusions: Our novel Fatmax protocol on a treadmill is reliable and its impact on fat utilization in the cold should be further studied.