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Balance is defined as the maintenance of the center of mass of a body within its base of support. In humans, a properly functioning balance system allows the perception of body movement, identification of its orientation relative to gravity, direction, and speed, and makes more or less conscious postural adjustments to maintain stability. This complex mechanism of control and regulation occurs in various conditions and activities, whether static, semi-static, or dynamic.

Postural stability is fundamental not only in everyday life situations but in almost all sports. Static balance, for example, is essential in archery. In contrast, dynamic balance plays an important role in activities such as snowboarding, skateboarding, and windsurfing. In karate, tai chi, yoga, ballet, and gymnastics, the goal is to control balance in different positions, which can vary in difficulty depending on the specialization. Precision in controlling the center of mass (COM) is also crucial in climbing, mountaineering, figure skating, and ice hockey, where the support area becomes particularly restricted.

In sports, compromised postural stability can lead to significant compensations that may result in overloads and possible injuries to the weaker parts of the system (joints, tendons, and muscles). Therefore, it is essential to measure and train the athlete's abilities.

To assess and monitor over time the level of control and postural strategies adopted, bi- and mono-pedal balance tests (sway analysis protocols) are very useful. Gyko allows measuring the performance of these tests with objective and comparable values without interfering with the subject's abilities.

In the sway test, the parameters of major interest are (see figure below):

- Path Length: The global path of the COM during the test. It is an index of the energy expended by the system; the greater the length, the greater the energy expenditure.

- Average Length of Anteroposterior and Mediolateral Oscillations: Indicates whether the subject tends to move forward or backward, right or left.

- Ellipse Area: Represents the precision of the postural system, inversely proportional to the area's magnitude.

- Average Speed of Movements: An index of fatigue; the higher its value, the greater the effort to maintain orthostatic posture.

- Frequency of Human Body Oscillations: Obtained through Fourier transform.

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