Every step you take in FitFlop sandals helps tone and trim your legs, while reducing strain on your feet, knees and back. Developed by biomechanists at the Center for Human Performance at London's Southbank University, the FitFlop has been scientifically proven in independent studies to boost overall leg and calf muscle activity as you walk. The secret is the multi-density EVA foam midsole that generates a Micro-Wobbleboard effect to significantly increase core muscle strength and encourage better posture. The result: your legs work harder than they do in standard sneakers or shoes and you burn more calories. A soft patent leather upper keeps feet comfy.