Hyperkinesia
A tic can be defined as a repeated, individually recognizable, intermittent movement or movement fragments that are almost always briefly suppressible and are usually associated with awareness of an urge to perform the movement. These abnormal movements occur with intervening periods of normal movement. These movements are predictable, often triggered by stress, excitement, suggestion, or brief voluntary suppressibility. Many children say that the onset of tics can stem from the strong urge to move. Tics can be either muscular (alter normal motor function) or vocal (alter normal speech) in nature and most commonly involve the face, mouth, eyes, head, neck or shoulder muscles. Tics can also be classified as simple motor tics (a single brief stereotyped movement or movement fragment), complex motor tics (a more complex or sequential movement involving multiple muscle
groups), or phonic tics (including simple, brief phonations or vocalizations).
Motorcycle speedway
Speedway uses a unique type of motorcycle, governed by the FIM's "Track Racing Technical Rules". In the past, bikes with upright engines were used (the name taken from the way the engine sits in the frame), but today most professional riders use laydown bikes as it is argued that they are easier to handle. As speedway bikes do not use brakes, the clutch is used as a release mechanism at the start of races. FIM regulations state that the motorcycles must have no brakes, are fueled by pure methanol, use only one gear and weigh a minimum of . By using engine and rear wheel sprockets the gear ratio can be adjusted as required for track conditions. The use of methanol allows for an increased compression ratio to the engine producing more power than other fuels and resulting in higher speeds (approximately when cornering).
Machines used must: