Hog-tying and the prone position alone do not cause death; obesity, acute alcohol or drug intoxication, and violent struggles prior to being restrained can be additional factors. Police officers should learn the body's physiological dynamics to ensure that problems do not arise during transport. They should control violent persons as quickly and humanely as possible, using handcuffs and restraints. Improperly applied or old and poorly maintained handcuffs can permit the arrestee to escape. Arrestees transported with standard handcuffs should be carefully searched, closely watched, handcuffed with hands behind their backs, and seated with the seatbelt securely fastened. Hinged and chainlink cuffs have different advantages and disadvantages. The National Institute of Justice tests and certifies police equipment and lists five companies with models passing the test. Nylon and plastic restraining straps are often used during nonviolent mass-arrest situations. Several companies make back seats built especially for transporting prisoners. Training police officers in the lower use-of-force skills such as cuffing techniques is essential to police effectiveness. Reference notes and list of suppliers of police handcuffs and restraints