According to the Britain's NHS Direct website, "sexercise" can lower the risk of heart attacks and helps people live longer.
Sexercises are exercises done during sex, sexual foreplay or exercises in preparation for sexual activity designed to tone, build, and strengthen muscles. Sexercises are often performed as part of a Sex Diet, a lifestyle which maximizes the health benefits of regular sex that does not involve a food-based regimen. While normally this is a partner-assisted exercise, masturbation might also be considered a form of sexercise, if done athletically with a mind for health and fitness.
The nervous system sends electrical messages to control and coordinate the body. The endocrine system uses hormone chemicals to communicate with target cells. A hormone is a specific messenger molecule synthesized and secreted by a group of specialized cells called an endocrine gland. These glands are ductless, which means that their secretions (hormones) are released directly into the bloodstream and travel to elsewhere in the body to target organs, upon which they act. Note that this is in contrast to our digestive glands, which have ducts for releasing the digestive enzymes.
Each hormone’s shape is specific and can be recognized by the corresponding target cells. The binding sites on the target cells are called hormone receptors. Many hormones come in antagonistic pairs that have opposite effects on the target organs. For example, insulin and glucagon have opposite effects on the liver’s control of blood sugar level. Insulin lowers the blood sugar level by instructing the liver to take glucose out of circulation and store it, while glucagon instructs the liver to release some of its stored supply to raise the blood sugar level. Much hormonal regulation depends on feedback loops to maintain balance and homeostasis.
Endorphins released during orgasm stimulate immune system cells, which also helps target illnesses like cancer, as well as wrinkles.
'Sexercise' yourself into shape. BBC News. 11 February 2006.