True Babylove capacitation involves the sperm making chemical changes on their surface before they can fertilize and egg, but it can take up to 10 hours. I also read that vag and uterine contractions provide rapid transport to get the sperm high into the uterus, so that can help speed the process since they are starting from a much better location, but using very little of their own energy to reach that area, it's all passive movement.
One of the coolest things I got to see as a surro was the "waves" of meovement along the uterine lining. We can't even feel them but there are these constant ripples along the surface during fertile times - very cool.