This study investigated how spatial projection systems influences body balance including postural stability. Analyzing precisely defined frequency bands of movements of the center of pressure makes it possible to determine the effectiveness of the balance system’s response to disruptions and disorders and may be used as an indicator in the diagnosis of motor dysfunction. The study involved 28 participants for whom the center of pressure was assessed in a test with open eyes, closed eyes and with virtual reality projection. Percent distributions of energy during wavelet decomposition were calculated. Changes in body stability were determined for the virtual reality tests and these changes were classified as an intermediate value between the open-eyes test and the closed-eyes test. The results indicate the importance of using safety support systems in therapies involving Virtual Reality. The results also show the necessity of measurements times in stabilographic evaluations in order to conduct a more thorough analysis of very low frequencies of the center of pressure signal.

The objective of the work was to determine biomechanical parameters influencing loads affecting the musculoskeletal system and shock absorption during the landing phase in Grand Jeté, Entrelacé and Ballonné. Methods: Motion kinematics measurements of the landing phase in GrandJeté, Entrelacé and Ballonné were carried out using the optical APAS system, and measurements of the GRF components-using Kistler platform. The research was carried out for three professional dancers. Kinematic and kinetic parameters of the landing were analysed. Results: The mean maximum GRF value in relation to the classical dancer amounted to 8.16 ± 1.37 N/BW. During landing, the joints of the lower limb are affected by external force moments of high values (ankle-3.04 ± 0.54 [Nm/BW], knee-7.56 ± 5.53 [Nm/BW], hip-10.97 ± 6.80 [Nm/BW]). The maximum value of the external force moments in the joint were strongly negatively correlated with the value of the angle in the hip joint at the moment of the first contact with the ground. It was noticed that the obtainment of maxGRF was preceded by a decrease in kinetic energy of approximately 50%. Conclusions: Factors affecting loads present in the musculoskeletal system during the shock absorption of a leap are: GRF values, the values of external force generated inside the joints and a change in the value of kinetic energy. The safe shock absorption after landing is influenced by properly positioned limb at the moment of the first contact, a greater range of movements in the joints and longer time from the moment of the first contact to the obtainment of maxGRF.

BackgroundThis paper presents a case study of kinematic analysis of the modern dance movement known as the “stag jump”. Detailed analysis of the kinematic structure of this movement as performed by the dancers, accompanied by measurements of impact forces during landing, will allow the authors to determine, in subsequent model-based research phases, the forces acting in knee joints of the lower landing limb.Material/MethodsTwo professional modern dancers participated in the study: a male and a female. The study consisted in recording the values of ground reaction and body motion, and then determining and analyzing kinematic parameters of performed movements.ResultsThe results of measurement of joint angles in the landing lower limb, pelvis, and foot position in relation to the ground, as well as the level of vertical components of ground reaction, provided insight into the loading response phase of the “stag jump”. The measurements and obtained results show differences between the man and woman in ground reactions and kinematic quantities.ConclusionsThe results obtained during the research may be used in the development and teaching of dancing movements. Training sessions, carried out in the biomechanical laboratory, with active participation of dancing teachers, could form a basis for a prevention model of injuries and physical overloads occurring within this occupational group.Primary differences in the “stag jump” performance technique probably result from the different educational path the man and the woman went through.

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