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.
Safe sex and sexually transmitted diseases. All sexually active people should consider safe sex because of the risk of contracting a sexually transmissible infection. STIs include conditions such as genital herpes, HIV, hepatitis B, gonorrhoea, syphilis, chlamydia, crabs and genital warts.