It is an excuse? Sex can be physically exhausting. This is trickier to explain. I will leave frustrated American women with one final thought: On the other hand, if you know that "I'm tired" is just an excuse, then it's time to talk it out. But stop pushing yourself till you drop or, if you are training for a specific reason, talk to your trainer about when to take breaks and conserve energy for better sex, itself a fitness activity. Studies evaluated the effects of phosphodiesterase-5 inhibitors PDE5i ,. In addition to oxytocin, men and women release vasopressin, prolactin, serotonin, nitric oxide, and endorphins, according to Costa. But perhaps since he cannot immediately run off with another woman anyway — damn that recovery time! See your doctor for medical treatment and remember that your sex life is flexible. The bottom line is this: One thing, however, is certain: When you have early warnings like fatigue, you could be less than five years from your first heart attack, so get it checked out. Giphy Before you worry that there's something wrong with your sex life, evaluate the nature of your lives. Abraham Myerson measured initial levels of circulating testosterone in men and exposed their various body parts to UVB light. Many women still seek the answers to these questions. Some people might feel energized after sex and ready to take on the world, while others want nothing more than to curl up and fall asleep.