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.
ABSTRACT
<b>Purpose:</b> The purpose of this study was to determine whether the impact on the body during landing in dancers is less than in non-dancers by using accelerometers and motion analyzer.<b>Method:</b> Eleven ballet dancers and 11 non-dancers participated in this study. Each subject was instructed to perform 3 types of landing from a height of 30cm: <i>landing, silent landing</i> and <i>raise up landing.</i> Markers were put on the iliac crest, greater trochanter, knee joint, lateral malleolus. The peak vertical and horizontal accelerations of the lumbar, peak vertical acceleration of the greater trochanter and the peak flexion angles of the hip and knee joints were measured after the trials.<b>Result:</b> In the <i>raise up landing,</i> the peak vertical acceleration of the lumbar region in dancers was less than that in non-dancers (p < 0.01), and the peak knee-flexion angle in dancers was greater than that in non-dancers (p < 0.01). There were no differences between the peak hipflexion angles of dancers and non-dancers.<b>Conclusion:</b> The impact on the lumbar during <i>raise up landing</i> was less in dancers. In <i>raise up landing,</i> the trunk tends to be fixed when the dancer stands upright. Moreover, dancers attenuated the shock to the lumbar region by increasing the knee-flexion angle to a greater extent than the non-dancers did. This result may indicate the importance of the knee joint flexion in attenuating the shock during landing and show that dancers excel in using their knees flexibly.
ABSTRACT
Decrease in the hip extension range of motion (HE-ROM) can cause lumbar hyperlordosis. Hyperlordosis is one of the mechanisms underlying low back pain. A diagnosis of low back pain from hyperlordosis can be used to detect the area in which hyperlordosis occurs more easily—the upper or lower lumbar spine. Twenty-one men were recruited for this study. HE-ROM was measured manually. Lumbar alignment was measured on a bed in a prone position. We extended the subject's hip by bending the bed at 4 angles (0°, 10°, 15°, 30°) and measured the spinal alignment by using a SpinalMouse. The results showed that lumbar lordosis increased at the bed angles of 15°and 30°. Only when the bed angle was changed from 0° to 30°, the increased angle of the lumbar spine was negatively correlated to the HE-ROM (r=-0.46, p<0.05), particularly that of the lower lumbar spine (r=-0.47, p<0.05). These findings suggested that lower lumbar lordosis tends to increase in individuals with poor HE-ROM. Additionally, increase in lower lumbar lordosis is attributed to the tendency to have low back pain in the lower lumbar spine.
ABSTRACT
Purpose: To determine whether performing a feint in team handball with a wide foot stance leads to a greater knee valgus angle and/or knee valgus moment.Methods: Eight women handball players performed a feint with 4 different foot stances (free and 30%, 40%, and 50% of their body height). Three-dimensional kinematics and ground reaction forces were measured during the feints. Hip abduction angle at first contact, peak vertical ground reaction force, peak knee valgus angle, and peak external knee valgus moment during the first 20% of the feint cycle were compared among the stances at 30%, 40%, and 50% of body height (ANOVA, P<0.05). In the free feint, we investigated intrasubject correlations among foot stance and hip abduction angle at first contact, peak knee valgus angle, and peak external knee valgus moment were then conducted (<i>P</i><0.05).Results: When performing a feint with foot stances at 40% and 50% of body height, the subjects had significantly greater peak external knee valgus moment. Hip abduction angle at first contact was significantly correlated to peak knee valgus angle and peak external knee valgus moment.Conclusion: Training athletes to avoid wide foot stance and large hip abduction angle may reduce the risk of sustaining noncontact anterior cruciate ligament injuries.
ABSTRACT
Purpose: The aim of the present study was to make an ankle destabilization device and investigate the effect of exercise with this device on peroneal muscles.Methods: Seventeen healthy subjects were instructed to undergo step movement exercise with the lower extremity 150 times on the spot using the ankle destabilization device. Before and after stepping, the reaction time and mean frequency of the peroneus longus and the peroneus brevis muscles were compared. While stepping with the device, muscular activity of the peroneus longus and the peroneus brevis was compared under both stable and instable conditions.Result: The results showed that peroneal reaction time didn't change after stepping with the device; but the frequency of peroneal muscle activity increased after stepping. While stepping, muscular activity of the peroneal muscles increased in an instable condition.Conclusion: The results suggested that stepping exercise with the device could be beneficial for peroneal muscles.
ABSTRACT
In this study, we investigated whether a difference in the angular velocity has an effect on proprioceptive sensibility in 30 healthy subjects. Knee detection of passive motion at five angular velocities (0.1°/s, 0.2°/s, 0.3°/s, 0.4°/s, and 0.5°/s) was carried out from a starting position of 15° knee flexion for extension using a proprioception testing device. At 0.1°/s, the elapsed time was longer than that of the other angular velocities and the angular displacement was bigger as well. There were no significant differences among the remaining angular velocities (0.2～0.5°/s). Therefore it is suggested that a healthy knee has less proprioception at an angular velocity of 0.1°/s.