Kinsey delineated six types of male orgasm. In part the types vary according to the intensity of the reaction exhibited. The most common type of male orgasm supposedly characterising about 45 per cent of adult males - features some body tension. There may also be twitching or tension in one or both legs, of the mouth, of the arms, or of other particular parts of the body. There is gradual build-up to a climax which involves rigidity of the whole body and a degree of throbbing in the penis. There is orgasm with a few spasms but little after-effect. This is seen as the most common type of male orgasm (discussed in 1. Singer "The Goals of Human Sexuality") .