Couples can't synchronise Image: Could not subscribe, try again laterInvalid Email Why is it that a man feels at his sexiest when he wakes up in the morning but a woman wants to go back to sleep? And why, late at night, when a woman is in the mood for love, is her man just lying there, snoring?
It all comes down to hormones. It is also kept in balance by oestrogen and progesterone. A good kip is another reason a man may feel even more amorous in the morning. Studies found the longer and deeper a man has slept, the higher his testosterone levels. As both sexes get ready for the day, levels of the stress hormone cortisol rise to help them wake up — and help dampen the effect of sex hormones.
After this initial surge, if the body keeps producing too much in response to stressful events over the day, studies have found it lowers the sex drive of both men and women.
The hormone is also needed to trigger muscle growth and sperm production. Sex hormones take longer to increase. However, when confronted with a sexy person, a man who naturally already has higher testosterone levels is likely to be more flirtatious with them.
Men with more testosterone are also more likely to be found attractive by women, according to researchers at Wayne State University in Michigan, US. The tests were given two weeks before they saw their partners, the day before, before sex, the day after sex and three days after the pair were separated. However, an after-work gym session can boost the libido of both genders.
Research by scientists at the University of California, San Diego, found men who exercised had a boosted libido. Levels of sex hormones also spike in women after exercise. According to a study by the University of Texas, women who had 20 minutes of cardio exercise were more aroused by seeing an erotic film than women who had not exercised. Researchers believe the reason is that music may make women feel more relaxed, bonded and in turn more sexual, while in men it calms their aggression and in turn reduces their levels of testosterone.
Not good news for England fans, then! By contrast, women are more likely to be affected by actually playing sport rather than watching it. In one study of women athletes, their testosterone levels significantly increased after long runs. But the more attractive a woman feels, the more likely it is that she will want to jump into bed with him.
When the levels are lower, her climaxes are less intense and centred mainly around the sexual organs. In males, the bonding hormone helps make the prostate and seminal glands to contract. In women, it helps to spark uterine contractions that move the sperm towards the ovaries. The release of oxytocin after sex also explains why men are notorious for falling asleep after making love.
In one study, Swiss researchers gave 47 couples a nasal spray containing either oxytocin or a placebo. The pairs were then videotaped, discussing subjects that they usually rowed about.
The partners who were given oxytocin were more reasonable and less aggressive with each other.