Act as a senior product designer with 10 years of experience in wearable technology. Design a sleek, futuristic smart cuff for fitness tracking that combines [minimalist aesthetics] with [advanced health metrics]. The cuff should feature a [customizable LED display] that shows real-time data like heart rate, steps, and calories burned. Use high-quality materials like brushed titanium or ceramic, and ensure the design is waterproof for swimming. The cuff should appeal to both athletes and fashion-conscious users, with interchangeable bands for different occasions. Include subtle branding and intuitive touch controls. Render the design in a studio setting with soft lighting to highlight its premium finish.