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 The presence of STDs in an HIV infected person can increase the risk of HIV transmission. This can be through a genital ulcer which could bleed or through genital discharge.  An HIV negative person who has an STD can be at increased risk of becoming infected with HIV through sex. This can happen if the STD causes breaks in the skin (e.g. syphilis or herpes), or if it stimulates an immune response in the genital area (e.g. chlamydia or gonorrhoea).