ABSTRACT
The aim of the present study was to investigate whether personal hamstring muscular activation increased by landing with the trunk bent forward. First, 14 healthy female university students were instructed to perform normal drop landing from a 40 cm-high box on both legs. Second, subjects were directed to perform drop landing with the trunk bent forward. Using images obtained from a high-speed video camera, the upper center of mass was calculated in the sagittal plane for determining the differences in these landings. For 0.1 second after toe contact, the muscular activation of quadriceps femoris and hamstring muscles was analyzed using an electromyogram (EMG), and these findings were compared between the 2 types of landings. There was no significant difference in the activation of quadriceps femoris, but the activation tended to decrease during landing with the trunk bent forward. However, the activation of hamstring muscles increased significantly during landing with the trunk bent forward compared with that during normal landing. During landing with the trunk bent forward, the activation of hamstring muscles increased, and the activation of quadriceps femoris tended to decrease. Because contraction of hamstring muscles decreases tension in the anterior cruciate ligament, the findings of this study may help in the prevention of anterior cruciate ligament (ACL) injury.
ABSTRACT
Purpose: Our aim was to investigate if such trunk muscular activation at standing could have an effect on their trunk muscular activation at leaning backward and forward and the strength of trunk isometric flexion and extension. Methods: The Electromyography (EMG) of lumbar paraspinals (LP) and rectus abdominis (RA) were recorded for 18 healthy volunteers at three positions (standing, leaning backward and leaning forward). In addition, the strength of maximum isometric of trunk flexion and extension were measured at sitting position. Then the flexion/extension (F/E) ratio was calculated. Results: 18 healthy volunteers were classified into Flexor group (n=5) and Extensor group (n=13). The RA-EMG of Extensor group was significantly larger than that of Flexor group at leaning backward position. Extensor group, also, had a higher strength of trunk isometric extension than that of Flexor group. Flexor group had a higher F/E ratio than that of Extensor group. Conclusion: A meaning of this study was to investigate that there were subjects who were higher paraspinals or rectus abdominis activation. Such difference was caused from muscular activation at working upper body and demonstrating of muscular strength, and this study may be helpful to develop study of physical therapy from now on.