Human-powered devices are tools or machines that rely on human energy to operate, rather than electricity or fuel. Examples include bicycles, hand-cranked generators, and manual water pumps. These devices harness the physical effort of individuals to perform tasks, making them sustainable and environmentally friendly. Many human-powered devices are designed to promote fitness and reduce reliance on fossil fuels. For instance, bicycles not only provide transportation but also encourage exercise. Similarly, hand-cranked generators can produce electricity in remote areas, showcasing how human energy can be effectively utilized in various applications.