What do we know about genetics and physical traits in the area of athleticism?

Genetics

what factors could contribute to this?
Breeding.

Can someone be trained to do certain tasks from an environmental influence at a young age?
Sometimes. If the genetic disposition is there for it. If we are talking about excellence not just getting by.

I don’t think I understand your question. You asked:

what factors (genetic, environmental etc) contribute to a group of people being more athletic than another group.

But I think you answered the question right there. Genes and environment contribute to one group being different from another group, both in terms of athleticism and any other trait I can think of.

And if it is mainly genetics, what factors could contribute to this?

Again, it seems like you answered your own question? If genes are contributing to athletic differences between groups… then the cause of the difference between groups is genes. Right?

@nikipedia But what makes the genes favor that group of people, lets say for example, a race.

If I understand what you’re asking, the answer is natural selection. Genes that work well for a group of people increase in the population. Genes that don’t work well for a group of people are selected out.

A race is defined by their gene pool.

@nikipedia Oh yes I understand now, that was a brain fart. But then, why would natural selection favor a certain type of gene?

“why would natural selection favor a certain type of gene?”

That gene giving an advantage.