[The Heart of a Swimmer vs. the Heart of a Runner](https://www.nytimes.com/2019/04/03/well/move/heart-health-swimming-running-exercise.html "The Heart of a Swimmer vs. the Heart of a Runner - The New York Times")

From nytimes.com:

In theory, those differences should allow blood to move from and back to the runners’ hearts more rapidly than would happen inside the swimmers’.

Main takeaway is that you should always mix it up.

Roberto Mateu @roberto