Well, if you think about it in retrospect, African Americans were brought over to America (and many other places) to work, so I'm guessing all that hard labor which was brought upon them caused their kids to have the same build...
I don't think it has much to do with heritage at all. I think genetics is the key. I am a skinny white guy. 6 foot 4. With broad shoulders. Yet my ancestor's were Scottish and Russian, and weren't slaves. So I think your assumptions are a little flawed.
well a simple explaination for a lot of this all is that Africa as well as the most of the other countries which we deem as places where typically black people originated from have different geographical conditions and climatic conditions then what we're used to. The fact that the altitude is so much higher in some of those countries and the conditions of living harsher (ie less available food) has made it so people who originated from those countries are more adapted to athleticism and such. For example, because of the mountainous regions, many africans are good runners because their lungs and muscles became adapted to having less oxygen so in comparison to americans and european countries they tire less easily.
I think just most people are too physically lazy to go all-out on sports. that and I'm sure there still remains prejudice against african-americans in upper-crust, corperate america, so gettiing there may be harder? I dunno.
*cough* If you look at the average african american in america you will find that they are MUCH more active than other races... thats why they are usually skinny tall and strong... genes also help in this... the other races... not being racist but specially the whites are very lazy... they dont go out much... and they eat ---- loads of food...
