Power is the fitness skill associated with the rate at which strength can be used.

Power is indeed defined as the ability to exert strength at a fast rate. It combines the elements of strength and speed, allowing a person to perform explosive movements; this is particularly important in various sports and physical activities. For instance, activities like sprinting, jumping, or throwing require a significant amount of power to achieve good performance.

The description provided in the question accurately captures this definition, affirming that power is directly related to how quickly one can use their strength. In contexts like weightlifting, measuring power is often fundamental since lifters not only need to lift heavy weights but also to do so explosively to achieve greater performance.

The other choices do not accurately reflect the true nature of power in the context of fitness. It is a key aspect of physical fitness that transcends weightlifting and applies broadly across numerous sports, making the assertion true.