Anna Mazurkiewicz

The relationship of muscle strength symmetry with the symmetry of dynamic activities such as vertical jump (CMJ) and with symmetry of ranges of motion is ambiguous. Therefore, the aim of the current investigation was to assess the relationship between the flexor/extensor strength ratio and the range of motion of the knee joints and VGRF during jump in a sample of young healthy men. The sample consisted of 64 healthy, active men. The flexor and extensor torques and ranges of active and passive mobility of both knee joints were measured. Vertical ground reaction force (VGRF) was measured using two platforms. There were no significant correlations between the symmetry of muscle strength and the symmetry of ranges of motion and the symmetry of the VGRF. Therefore, using the cluster analysis, 4 subgroups were distinguished due to the size of the flexor/extensor ratio (H/Q ratio). Significant differences were found in the level of strength of the knee flexors between the clusters. Detailed analysis of muscle strength symmetry and VGRF symmetry seem to confirm the Leading Joint Hypothesis theory of motion control in multi-joint systems. It was found that the process of controlling movement by the nervous system compensates for the small asymmetries in the level of muscle strength in the knee flexors and extensors, as well as small asymmetries of VGRF.

Introduction: The aim of this study was to characterize kinematic parameters of the rotational body movement during the office figure skating multi-revolution jumping exercise and to propose applications to training. Material and Methods: Six elite Polish female junior singles figure skaters were examined performing single and their respective maximum total rotation vertical jumps in off-ice conditions. Measurements of the ground reaction force were performed with a KISTLER (500 Hz) piezoelectric sensor platform with BioWare Software, synchronized with the cinematographic analysis using the Vicon T-Series motion capture system. Results: The analysis revealed positive linear relations between selected jump parameters of the pre-take-off phase and after the landing. Two moments of countering torque were also noticed: the first in the landing phase, and the second before reaching the stabilized position. Conclusions: Applications of the findings for off-ice training were discussed.