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.
1,2 Youth of color and young men who have sex with men continue to be most at risk. It is important to promote programs that help young people lessen risky sexual behaviors by encourag-ing condom use, delay in sexual initiation, partner reduction, and early HIV testing and treatment.