Motivation = Genetics? Dafuq
More like genetics means how muscular you can get without needing equal effort. Some black people and slavs, for example, tend to become insanely ripped and strong without much effort compared to others. I've heard hispanic and white fitness/bulking friends rage at how ripped black people get compared to them and how it made no sense. I've had 5'6 unathletic but thick and tough black dudes lift me feet off the ground (6'1 180 pounds) like I was a baby just to prove how pro they were which was real funny.
I'm half Polish and have had "retard strength" my whole life, effortlessly shitting on dedicated people's records for lifting weights and stuff. I even got the most pullups for a year in my highschool's gym class by doing 27 or so and not even thinking it was a big deal but my gym teacher getting all pissed that I was a slacker non-athletic druggie dude owning everyone.
I wrestled before highschool too and had to laugh at some of the people in my "heavyweight division." One puerto-rican talented basketball player type dude wasn't as strong as me but real agile and fast, athletic, and gave me real good training by kicking my ass. Some other was a black dude 6'4 220+ pounds who looked real intimidating but he had some weak fucking genes and had the strength of a child. I tossed him around like nothing and probably got worse at wrestling by his pathetic lack of power.
Slavs dominate strength-based international sports, and African-Americans are almost across the board the star-athletes in American sports that require a combination of agility and power. Currently Kenyans are like the Gods of the Marathon as well.
People get all awkward talking about it cuz its kind of racist/eugenic type talk and leads to bad stereotypes but you have to be fucking ignorant to think that your genetics and ethnic heritage do not influence your physical shape.