Search

[Purpose] This study investigated the characteristics of postural control following postural disturbance in elite athletes. [Subjects] Ten elite ski jumpers and ten control subjects participated in this study. [Methods] Subjects were required to maintain balance without stepping following unexpected horizontal surface perturbation in a forward or backward direction. [Results] A lower and reproducible peak magnitude of the center of mass velocity was shown in the athlete group compared to the control group. Cross-correlation analyses showed longer time lags at the moment of peak correlation coefficient between trunk flexor and extensor muscle activities, and shorter time lags and higher correlations between ankle flexor and extensor muscle activities were shown in the athlete group than in the control group. [Conclusion] The elite ski jumpers showed superior balance performance following surface perturbations, more reciprocal patterns in agonist-antagonist pairs of proximal postural muscles, and more co-contraction patterns in distal postural muscles during automatic postural responses than control individuals. This strategy may be useful in sports requiring effective balance recovery in environments with a dynamically changing surface, as well as in rehabilitation.

[Purpose] The purpose of this study was to compare the upper, middle, and lower trapezius muscles' activity in the different planes of shoulder elevation. [Subjects] Twenty male subjects volunteered for this study. [Methods] Surface electromyographic (EMG) activity for each of the three regions of the trapezius muscles in the three different planes of elevation were collected while the participants maintained 30, 60, and 90 degrees of elevation in each plane. The EMG data were normalized with maximum voluntary isometric contraction (%MVIC), and compared among the planes at each angle of elevation. [Results] There were significantly different muscle activities among the elevation planes at each angle. [Conclusion] This study found that the three regions of the trapezius muscles changed their activity depending on the planes of shoulder elevation. These changes in the trapezius muscles could induce appropriate scapular motion to face the glenoid cavity in the correct directions in different planes of shoulder elevation.

[Purpose] The aim of this study was to quantitatively investigate gender differences in trunk muscle strength and activity and to verify the two proposed field tests for screening the muscle strength of trunk flexors by use of surface EMG (sEMG). [Subjects and Methods] Fifty-four healthy young volunteers participated in this study and RA strength was evaluated using the curl-up (CU) and double-leg-lower (DLL) tests. All muscle activity that occurred in the upper and lower RA sites during the two tests was recorded using sEMG. The sEMG data were then normalized using the maximum voluntary contraction. To investigate the validity of the two tests, the ratio of muscle activity between the upper and lower RA sites was calculated. [Results] The reliability of the CU and the DLL tests were estimated using the intraclass correlation coefficient and the values ranged from 0.84?0.96 and 0.93?0.98, respectively. Muscle activity was significantly higher in females than in males in all tests except one of the DLL tests. The activity ratio with respect to each muscle grade was constant between the CU and the DLL tests. [Conclusion] Our results indicate that trunk muscle activity is affected by gender, and the tests should be selected according to purpose.