The Children's Health Network explains that locking the knees for an extended amount of time can cause fainting. To avoid fainting when standing for long periods of time, the knees should be kept slightly bent. Contracting the leg muscles helps to continue steady circulation.Continue Reading
According to the Children's Health Network, keeping knees locked while standing for long periods of time prevents continuous blood flow in the body; as a result, fainting occurs.
WebMD states that other causes of fainting include diseases of the autonomic nerve system, conditions that interfere with parts of the nervous system, heart problems, conditions that unusually stimulate the nerves and hyperventilation.Learn more about Fitness & Exercise