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.
What Increases Your Risk. Most people get HIV by having unprotected sex with someone who has HIV. Another common way of getting the virus is by sharing needles with someone who is infected with HIV when injecting drugs. You have an increased risk of becoming infected with HIV through sexual contact if you: 1  Have unprotected sex (do not use condoms). 2  Have multiple sex partners. 3  Are a man who has sex with other men.  Have high-risk partner(s) (partner has multiple sex partners, is a man who has sex with other men, or injects drugs).
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.