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).
Having anal or vaginal sex with someone who has HIV without using a condom or taking medicines to prevent or treat HIV. For the HIV-negative partner, receptive anal sex (bottoming) is the highest-risk sexual behavior, but you can also get HIV from insertive anal sex (topping). Either partner can get HIV through vaginal sex, though it is less risky for getting HIV than receptive anal sex.