US Patent 7077790 Adjustable weight exercise methods and apparatus

An exercise dumbbell system includes a handle and weight plates maintained in spaced relationship at opposite ends thereof. Weight selectors are movable laterally into and out of engagement with respective weight plates to secure them relative to the handle. Each weight plate is provided with a pathway having at least one notch that opens upward, and at least one groove that is bounded above by a lip. The selectors have respective weight engaging portions that travel along respective pathways to alternatively underlie different combinations of the weights.