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.
CHICAGO (AP)  A study of heterosexual couples in Africa concludes that the chance of catching the AIDS virus from a single sexual encounter with an infected person is one in 588. This risk is calculated for people who do not use condoms and who have sex regularly with one infected partner.