1 Isotonic -a muscle fiber contraction in which force production is unchanged when the muscle contracts causing movement of an external load.  Isokinetic -a muscle fiber contraction in which force production of the contraction is sufficient to overcome the external load.
HIV/AIDS. HIV Risk Behaviors. The risk of getting HIV varies widely depending on the type of exposure or behavior (such as sharing needles or having sex without a condom). Some exposures to HIV carry a much higher risk of transmission than other exposures.
HIV severely affects gay and bisexual menâmore than any other group in the United States. Gay and bisexual men make up about 2% of the overall population, but account for approximately two-thirds of all new HIV infections each year. Having sex with someone who has HIV. 2  In general: 3  Anal sex is the highest-risk sexual behavior. 4  Receptive anal sex (bottoming) is riskier than insertive anal sex (topping). 5  Vaginal sex is the second highest-risk sexual behavior.