There are many interesting phenomena and mysteries surrounding sex. The US "Medical Daily" published an article on July 21, listing 10 facts about sex that you may not know yet.

1. The penis follows the "use it or lose it" rule. A complete absence of sexual activity may lead to penile atrophy. Sexology expert Dr. Tobias Kohler said that if no activity is done to maintain a normal erection, the penis will slowly shorten by 1 to 2 centimeters.

2. A study by the National Bureau of Economic Research found that sex brings as much pleasure as earning $100,000.

3. Showgirls make more money during ovulation because women release more sex hormones during ovulation to attract the opposite sex.

4. During sex, it is very rare for couples to climax at the same time. 42% of couples said it was almost difficult to reach orgasm at the same time.

5. Studies have found that 51% of women have an orgasm while doing sit-ups.

6. Some people will have a strong sexual interest in mannequins and statues. This phenomenon is called "sculpture fetishism" (or sculpture worship).

7. If a man is left-handed (or right-handed), his testicles on the same side will be relatively tall.

8. It's easier to orgasm when you have sex with socks on because the warmth of your feet helps promote orgasm.

9. Although sperm is small, it is extremely fast. Sperm swim toward the egg at speeds of up to 28 miles per hour.

10. Sex is a great workout, burning an average of 144 calories per session.