Spanking during sex might be stressful at first but it helps bring couples closer together, according to a study.
According to scientists from Northern Illinois University in DeKalb, sadomasochistic (S and M) activities like spanking, bondage, and flogging increase relationship closeness.
During the study, lead researcher Brad Sagarin looked at 13 men and women at an S and M party in Arizona, and measured the levels of the stress hormone cortisol during and after participating in activities.
The researcher found a significant increase in cortisol levels in those receiving stimulation, but dropped back to normal within 40 minutes if the scene went well.
However, there was no change in those inflicting the activity.
For further analysis, the scientists again studied an S and M event in Colorado, and found that testosterone was measured in 45 men and women.
There was a significant increase in receiving women only.
Donatella Marazziti of the University of Pisa, Italy, said that the boost might help women cope with the aggressive nature of S and M activities, or that it could be another sign of stress.
The researchers found that couples who said that the party went well also reported increases in relationship closeness.
"When sexual intercourse is consensual it is not stressful - even if it is extreme sex," New Scientist magazine quoted Marazziti as saying.
Richard Wiseman, a psychologist at the University of Hertfordshire in Hatfield, UK, also said that any shared activity was likely to promote interpersonal closeness.