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Objectives: Iliotibialis syndrome is one of the most common types of running injury of the lateral knee. Earlier studies have mainly focused on the relationship between iliotibialis syndrome and hip muscle forces, since the latter are often the target of intervention during rehabilitation. The results suggest that a curved shoe sole may affect lower limb mechanics during running. The main purpose of this study was to assess the effects of different curves of rocker shoes on activation of the musculus gluteus medius and maximus under various running conditions. Equipment and methods: Fifteen recreational runners (1.77 ± 0.44 m height, 74.25 ± 6.68 kg weight, 23.73 ± 1.79 kg/m2 BMI) were recruited to test three rocker shoes with different forefoot curvatures on a flat laboratory floor and a treadmill at flat, uphill, and downhill gradients. Surface electromyography data were collected for musculus gluteus medius and maximus, resulting in a three-way within-subject design (running condition (4) x shoe (3) x muscle (2)) with 24 measurement combinations for each runner. A linear mixed model was fitted to the data to quantify running condition, shoe curve and muscle effects. Results: The main effects of running condition, shoe and muscle were estimated. While running uphill, significant decreases were observed in both peak (P = 0.021, log%MVC) and duration (P = 0.015, log%MVC) compared to running on a flat laboratory surface. Both average (0.033 log%MVC) and peak muscle activation (0.069 log%MVC) were increased with a smaller radius of shoe curvature. Conclusion: In conclusion, the study shows that rocker shoes appear to affect gluteal muscle activation and could potentially assist in stabilising the pelvis during running. This knowledge might be of interest for runners with an increased risk of ITBS and may therefore gain health benefits from wearing rocker shoes.