ulna larger of the two forearm bones, articulating at the elbow with the humerus and at the wrist with the carpal bones. ulnar adj in descriptions of forearm structures: on or towards the side of the ulna, i.e. the fifth finger side. See appendix 1.2 fig 1.
ultrasound sound frequencies above the limit of human hearing (20 kHz). ultrasonography imaging technique for body structures by reflection of ultrasound waves (up to 20 MHz). Used in sports medicine as a diagnostic tool in both cardiovascular and musculoskeletal assessment, e.g. cardiac screening, muscle tears. Ultrasound equipment is portable and accessible, costs less than MRI scanning but requires a skilled operator. It also allows dynamic imaging, e.g. of rotator cuff during shoulder movement. ultrasound treatment (ultrasonics) (1–3 MHz) is used especially for soft tissue injuries, to reduce swelling and inflammation and to encourage the healing process. The vibratory effect has been suggested to increase local blood supply, relieve pain, produce local heat and reduce sensory stimulation. One of the key treatments for sports injuries. See also echo cardiography.
unconditioned response in classical conditioning, a response to an unconditioned stimulus that is naturally evoked by that stimulus. For example, in Pavlov’s experiments with dogs, salivation at the presentation of food is the unconditioned response. See also conditioning.
unconditioned stimulus in classical conditioning, a stimulus that automatically evokes a particular reflexive response. For example, in Pavlov’s experiments with dogs, the presentation of food is the unconditioned stimulus that automatically evokes the salivatory response. See also conditioning.
underperformance syndrome (UPS) an enduring deficit in performance which persists despite a period of rest or reduced training load and is not explained by any major diagnosed pathology. Characterized by a wide range of symptoms including fatigue, frequent minor infections and disturbed mood. It differs from chronic fatigue syndrome in that the symptoms do not have to last at least 6 months. See also overtraining.
underwater weighing an accurate method for the measurement of body density from which the percentages of body fat and lean body mass can be determined using standard equations. Weight in air is compared with weight in water during brief immersion, holding the breath after full expiration (at residual lung volume which is separately measured). Density is calculated from the volume of water displaced according to the Archimedes principle, which states that an object submerged in water is buoyed up by the weight of water displaced. syn hydrostatic weighing. See also body composition.
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