In men, postorgasmic illness syndrome (POIS) is a rare disease characterized by severe muscle pain throughout the body and other symptoms immediately following ejaculation. The symptoms last for a few hours to several days. POIS is listed on the "Rare Diseases" website of the NIH: https://rarediseases.info.nih.gov/gard/10809/postorgasmic-illness-syndrome/resources/1 .
https://en.wikipedia.org/wiki/Talk:Postorgasmic_illness_syndrome