This guy was really skinny and maybe some of that had to do with the fact he was a runner but most people would have said it was genetic. 

If you know for a fact you haven't been blessed with "muscle friendly" genetics, then I STRONGLY suggest you check out the below link: 

"28-Day Secret" to OVERCOME "muscle-unfriendly" genetics

After a few years of lifting it's normal to hit a plateau despite your most intense efforts 
. 
This brand new method is a PROVEN "plateau crusher"!  

If your gains have slowed, have a look at this muscle building system you haven't tried and that can't even be stopped by the worst genetics... and it works extremely fast. 

Take a look yourself: 

"28-Day Secret" to OVERCOME "muscle-unfriendly" genetics