Evaluation of the accuracy of the postural stability measurement with the Y-Balance Test based on the levels of the biomechanical parameters.

The study of dynamic balance involves tests that assess the muscle control of spatial changes of the position of the centre of gravity over the base of support. The purpose of this work was to determine the structure of the Y-balance test and its accuracy based on the measurements of strength performance of the muscles acting on the knee joint as well as the flexibility and balance in boys aged 14 years.The study included 43 schoolboys regularly participating in physical education lessons. The examination of postural stability was conducted with the use of the Y-balance test. The measurements of muscle strength and of resistance to fatigue of the extensors and flexors of knee joints in isometric contraction were performed on a measurement stand in a standard position with the use of tensometric sensors. The measurement of mobility range of the lower extremity joints was performed according to the SFTR. The examination of balance was performed with the use of the modified "Flamingo balance test".The factor structure of the Y-balance test results for the left and right lower extremities is similar and includes five principal independent factors that characterise the structure of analysed variables. They explain 76% and 74% of communality in total for the left and the right extremity, respectively.The extracted factor structure points to a hybrid structure of the Y-Balance Test and shows its accuracy in the measurements of the lower limb joint mobility and strength performance of knee joint extensors.