Masturbation has no known negative effects on energy, height, growth, stamina, or strength whatsoever. Myths such as this have developed throughout the ages, particularly in cultures that are highly religious and moralistic. Why? Because in many cultures masturbation and sex are seen as sinful or against God s will. Of course, some religions consider male masturbation a spilling of seed that might better be used for procreation rather than recreation. So masturbation gets a bad rap in some cultures and religions and this gets passed down through generations and winds up affecting people like you in 2012. Masturbation is a normal and healthy bodily function for both men and women. In men, masturbation leading to orgasm is extremely pleasurable and has been demonstrated to release important neurochemicals in the brain that regulate mood. The only harm you could do to yourself by masturbating is to do so excessively or perhaps too violently. The penis and scrotum are tough and can withstanding a lot of physical stimulation, but at times men are not very careful with listening to their bodies and they can damage sensitive tissue by being too rough with themselves. If your back hurts and you are an athlete, see your doctor, because you might have damaged your back from a sporting injury. I hope this answer helps you and that you feel better very soon!