Low-back pain is one of the most common injuries in competitive swimmers. Therefore, the prevention of low-back pain would contribute to improved performance of swimmers. A biomechanical analysis is necessary to prevent the sports-related injuries. However, only lumbar movement has been analyzed in swimmers with low-back pain. Lumbar spine movement is closely associated with the pelvis and hip joint. Thus, not only the lumbar joint but also the pelvis and hip joint should be analyzed to determine the cause of low-back pain.The aim of this study was to investigate the relationship of the effect of underwater movement on the motion characteristics of the lumbar, lumbosacral, and hip joints with trunk flexion-extension in the standing position.Fourteen male competitive swimmers were recruited for this study. Trunk flexion-extension motion in the standing position and underwater dolphin kick motion were captured in the saggital plane on a digital video camera. A 2D motion analysis was performed to determine the lumbar, lumbosacral, and hip joint angles during these motions.The results demonstrated that the lumbar angle during the dolphin kick motion was associated with the angle in the standing position when the trunk was extended; and the lumbosacral angle during the same motion was associated with the angle in the standing position when the trunk was flexed.Additionally, the subjects who tilted their pelvis anteriorly while swimming exhibited a bit of pelvis motion during trunk movement in the standing position. Thus, the anterior tilting of the pelvis during swimming leads to low-back pain in swimmers.

The purpose of this study was to determine the muscle activity during cutting in female basketball player. Eight female basketball players participated in this study. Each subject was instructed to do two steps of approach run, and change direction to the right laterally. Cutting motion is divided two into a phase: knee joint flexion phase and extension phase. Bipolar surface EMG electrodes, spaced 30 mm apart and oriented parallel to the muscle fascicles were secured over the muscle bellies of the Vastus Medialis (VM), Vastus Lateralis (VL), Biceps Femoris (BF), and Semimembrasosus (SM) musculature. EMG recordings were employed to measure the ratio of activation between the medial-to-lateral Hamstring and Quadriceps, and Hamstring and Quadriceps. All the subject had 10-15 degrees knee angle during cutting. In flexion phase, Quadriceps acted more significantly than Hamstring (p<0.05). Moreover, VM activity acted larger than VL, and BF activity acted larger than SM in each phases (p<0.05) All the subject reveal a similar pattern: Quadriceps act largely in flexion phase, which may increase anterior tibial shear forces, strain on the anterior cruciate ligament. Moreover, medial muscle activity acted larger than lateral muscle in Quadriceps, and lateral muscle activity acted larger than medial muscle in Hamstring in each phase. All the subject had 10-15 degree knee angle during cutting, therefore, a variation in lateral and medial muscle may trigger knee valgus.

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.

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.

Injuries of the cervical spine occur in contact sports. Generally, muscle strengthening training of the neck is performed to prevent injuries of the cervical spine. Isometric resistance training with chin-in posture exercise is recommended for strengthening the neck. However, muscle strength and electromyography(EMG)date for chin-in posture have not been reported. The purpose of this study was to validate muscle strength and EMG testing during chin-in posture. Subjects were fifteen healthy men without pathological conditions in the neck. Muscle strength date and EMG measurements were taken for maximal voluntary isometric contraction(MVIC)flexion and extension actions during normal and chin-in posture. Subjects performed MVIC using a handheld dynamometer and surface EMG was recorded sternocleidomastoid, scalenus, upper trapezius, and splenius muscles. Results of chin-in posture showed a significant increase in muscle strength and EMG of all muscles. These results indicate the beneficial effect of chin-in posture which can increase muscle strength and prevent injuries of the neck.

The purpose of this study was to identify the angles of the shoulder complex which consist of glenohumeral joint, scapulothracic joint, and thoracic joint at the maximum external rotation (MER) of the shoulder complex during throwing in baseball players, and to analyze the correlation of each angle.The subjects were 19 collegiate baseball players. Throwing motion data was collected by three high-speed cameras and the three-dimensional (3D) coordinates of the shoulder complex were established by direct leaner translation method for the MER calculation. A 3D analysis was performed to obtain the external rotation (ER) angle of the glenohumeral joint, the posterior tilt angle of the scapula, and the extension angles of thoracic at MER of shoulder complex. The mean (±SD) value of the MER was 145.5±10.3°. The mean (±SD) values of the glenohumeral ER, the scapula posterior tilt angle and the thoracic extension angle at MER were 105.3±16.0°, 24.3±15.0°, and 9.1±7.2°respectively. Multiple linear regression analysis was used to relate the MER angle to each joint angle. The final linear regression model included the posterior tilting angle of scapula ( r=0.56, p＜0.05), and external rotation of the glenohumeral joint ( r=0.40, p＜0.05). Significant negative correlation was observed between the posterior tilting angle of the scapula and external rotation of the glenohumeral joint ( r=-0.52, p＜0.05). This finding suggested that scapula motion could be very important for the prevention of throwing injuries.

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.

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 (P<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.

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.

Purpose: 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.Method: 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: landing, silent landing and raise up landing. 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.Result: In the raise up landing, 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.Conclusion: The impact on the lumbar during raise up landing was less in dancers. In raise up landing, 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.