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/AIDS. HIV Risk and Prevention. In the United States, HIV is mainly spread by having sex or sharing syringes and other injection equipment with someone who is infected with HIV. Substance use can contribute to these risks indirectly because alcohol and other drugs can lower peopleâs inhibitions and make them less likely to use condoms.