Could you provide us with some actual data that you are working with. If you say you only have one variable (hours of sport), how do you link this to the age of the person? I assume that data is stored somewhere else, or in the same data frame?
Please use the reprex guide to share some data and code. A reprex consists of the minimal code and data needed to recreate the issue/question you're having. You can find instructions how to build and share one here: