This article is from the Neapolitan Mastiffs Breed FAQ, by email@example.com (Barry Reder).
No they do not. In fact as adults they prefer to lounge around the
house or yard most of the time. although they do not need acres of
property to run a small apartment in not well suited for a Neapolitan
Mastiff. They can reach near 200 pounds and will clear coffee tables
and move furnature if they are not provided enough room.