While it’s not necessarily everyone's favorite part of sex (the top spot very much going to the sex part of the sex), the afterglow has been found to play a pretty important role in relationships, having positive influence on satisfaction and keeping relationships intact.
In 2017, a team looked at data collected from newlyweds. Every day for 14 days, spouses reported their sexual activities as well as sexual and marital satisfaction.
The study then repeated, next looking at couples' sex diaries and satisfaction scores four or six months after the initial fortnight.
"Results demonstrated that sexual satisfaction remained elevated [for] approximately 48 hours after sex, and spouses experiencing a stronger afterglow reported higher levels of marital satisfaction both at baseline and over time," the team wrote in their study that was published in the journal Psychological Science.
Essentially, the strength of the afterglow (how satisfied participants were in the 48 hours following sexual activity) was positively associated with marital satisfaction at that point, as well as continued marital satisfaction over time.
"We interpret these findings as evidence that sexual afterglow is a proximal cognitive mechanism through which sex promotes pair bonding," the team concluded.
A limitation to the study, the authors point out, is that it looks at only newlyweds, and does not account for (nor look at) non-heterosexual couples, which is something they'd like to rectify in future research.
For now, the team puts the afterglow effect down to biology - which is where it all gets a bit spermy.
"We contend that sexual afterglow emerges because these biological changes remain and continue to be decoded as sexual satisfaction for an extended period of time after the act of sex," they wrote in the study.
"This functional role is consistent with the finding that sexual afterglow appears to last approximately the same length of time (a) that it takes for peak sperm concentrations to be restored, (b) that sperm remain maximally viable in the female reproductive tract, and (c) that elapses between acts of sex among newlyweds."
Something romantic to stew on the next time you find yourself glowing.