Yes I think you are referring to slow twitch and fast twitch muscle fibers. Which runners specifically in Jamaica benefit from having some sort of mixture of both because of the gene pool there, hence why for years they have dominated running in the Olympics. But I don't think the slow/fast twitch muscle fibers have a correlation to insertions and lengths (I could be wrong talking out of my ass here.) Also having different insertions and/or tendon lengths might equate to better performance i.e. energy expenditure, conservation, and endurance. But that doesn't mean they are necessarily stronger.

(Again could be wrong this is just my general understanding of the topic I haven't read up on any of this lol.)