You wouldn't know it by looking at her, but Wendy (yes, this dog is a she) is friendly and "likes nothing better than a good back scratch and isn't shy about sitting in your lap to ask for one". The Whippet's herculean appearance comes from two gene defects which cause a condition called "double muscling", which can occur in any animal species. http://www.canada.com/victoriatimescolonist/story.html?id=67f15c17-2717-4022-bb76-1b982456e793&k=94653
There's even an unnamed German boy running around with this genetic defect (the only recorded human case), who as a toddler had the strength of some adults.