I just learned that the soleus exists, and is different to the gastrocnemius (what I used to think of as "the calf"). But the crazy thing is, the soleus is what does almost all of the work for running, because it works while your knee is bent while the gastroc works when your knee is straight. And unless you're sprinting or running up an extremely steep hill, your leg is still going to be 20-30% bent at the end of your stride.
The soleus is also mostly slow-twitch muscle fibres for endurance, while the gastroc is mostly fast-twitch fibres for immediate strength.

I've been training my calves like a bodybuilder - standing calf raises with low rep ranges. But what I actually should have been doing is SEATED calf raises with much higher rep ranges. I always thought the seated calf raise was just less efficient, but it specifically targets the soleus.

I realised after a race that my calves were sore in a different place to what I'd expected, so I did some research and this is what came up. I think this is big news, did anybody else already know this?