Having sex doggy-style is the best position for men suffering back pain, according to a new study.
After documenting exactly how the spine moves during love-making sessions, researchers at the University of Waterloo in Ontario, Canada, discovered certain positions are more effective than others when it comes to avoiding back pain.
A group of scientists analysed information, gathered by infrared and electromagnetic motion-capture systems, based on 10 couples who were told to adopt a range of different sexual positions.
Results from the study, published in the journal Spine, found that contrary to popular belief doggy-style was better than spooning and men with back problems benefited better from a "hip-hinging motion rather than thrusting with their spines".
It also revealed that doggy-style was the most "spine-sparing of the positions" while the safer spooning may trigger pain.
"Before now, spooning was often recommended by physicians as the one position that fit all. But as we've discovered, that is not the case," lead author Natalie Sidorkewicz explained.
"Sex positions that are suitable for one type of back pain aren't appropriate for another kind of pain.
"For the first time ever, we now have very solid science to guide clinicians on their recommendations for patients, who suffer debilitating back pain, but still want to be intimate. This has the potential to improve quality of life - and love-life - for many couples."
They have since created a new set of guidelines recommending that men with flexion-intolerant lower-back pain change their techniques in the bedroom.
Professor Stuart McGill, of the university's faculty of applied health sciences, added: "Many couples will remain celibate because one night of lovemaking can lead to months of back agony.
"Until now, doctors have never had any hard science to base their recommendations upon."