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.
The top is also at risk because HIV can enter the body through the opening at the tip of the penis (or urethra); the foreskin if the penis isnât circumcised; or small cuts, scratches, or open sores anywhere on the penis. See the Prevention Q&As for information on how to lower your risk of getting HIV from anal sex.