I wanted to make a mutation suggestion for a while but I didn't know what to make for the longest time, but after seeing a repost about the Whippet with the odd muscle growth, I thought that it might be pretty interesting as a mutation on here.

Human - http://www.lolwot.com/wp-content/uploads/2015/07/20-of-the-most-shocking-physical-mutations.jpg
Whippet - https://blogmuscle.files.wordpress.com/2007/07/wendy1.png
Cow - https://i.pinimg.com/736x/dc/1f/ef/dc1fefe3d670dbb02fcfd1ed9eea993c--belgian-blue-beef-cattle.jpg

It would be non-lethal and wouldn't affect hunting or patrolling as much (the lions that have it could gain less stats as the larger muscles slow the affected lion/lioness down).

If a king has it, however, I think it would affect exploring where energy could be consumed at a higher rate due to it being slowed by the extra muscle mass.