Healthy adults navigate hills as well as the transitions between level and hill surfaces while maintaining a safe and stable walking pattern. It is important to understand how healthy adults safely navigate changing terrains and how this ability may be modified through rehabilitation interventions such as motor development or footwear type. Therefore, the purpose of this study was to characterize the temporal-spatial gait parameter and muscle activity changes that occur during uphill and downhill walking and the transitions between level and hill walking. We hypothesized that during hill walking and hill transitions, participants will alter gait parameters to achieve greater anteriorposterior and medial-lateral stability. Additionally, we hypothesized that these observed differences will be less in textured insole footwear worn during locomotion and that, compared to healthy adults, children age 3 – 6 will present greater differences in temporal-spatial gait parameters between the level and hill walking tasks. Results showed that the level to downhill transition poses the greatest challenge to both anteriorposterior and medial-lateral stability. Compared to level walking, speed and step length were significantly less during the L-DN stride and speed, step length, and stance time variability, step width, and base of support area significantly increased. During the same stride, wearing textured insoles resulted in less lower limb muscle activity and improved response to medial-lateral stability as measured by step width. Finally, during level, uphill, and downhill walking, gait variability is significantly greater in children as compared to adults and this variability significantly increases from level to downhill walking in the child group only. Combined, these results further the current knowledge of how humans adapt to terrain changes during locomotion.