Pain experienced during periods may not be relieved with exercise, say researchers.
Birmingham University researchers, who studied more than 650 university students, said they found no link with the amount of exercise the participants did.
The study reported in BJOG found 28 percent had moderate to severe period pain, reports The BBC.
According to study boffins, beliefs about exercise being an effective treatment for bad period pain had persisted for years.
Researcher Dr Amanda Daley said: "Anecdotal beliefs that exercise is an effective treatment have prevailed for many years and while it might seem intuitively appealing to promote exercise as a treatment for menstrual disorders, the findings from this study, along with many others, would not support such a view.
"Of course there are many other important health reasons for encouraging women to be physically active and exercise performed in moderation is unlikely to be harmful."