• Journal of the Korean Society of Physical Medicine
• /
• v.8 no.4
• /
• pp.647-653
• /
• 2013

PURPOSE: The purpose of this study was to compare the lower extremities muscle activation between squatting exercise with gym ball and wall for improving muscle strengthening in lower extremities. METHODS: Participants were 21 university students (males 10, females 11) who didn't have any problem with orthopedic surgery. Participants performed squatting exercise with gym ball and wall. Squatting exercise with gym ball were performed using by gym ball behind back, and the gym ball were fixed in back and wall. We asked participants to push back the gym ball slightly to prevent fall of ball. Wall squatting exercise, we ask participants to contact their back in wall slightly in order to prevent trunk flexion during performed squatting exercise. Each squatting exercise had performed until knee joint were flexed at 60 degree, and maintained five seconds. We collected data from E.M.G of Biceps femoris, Gastrocnemius, Vastus medialis and lateralis, Tibialis anterior of lower extremity in isometric phase of knee joint angle 60 degree of each squatting exercise. We analysed data using by ANOVA and independent t-test of SPSS PC ver.20.0 in order to compare the muscle activation between squatting exercise with gym ball and wall. RESULT: All of lower extremities muscle activation showed more higher value in squatting exercise with gym ball than squatting exercise with wall, especially there was significantly difference of muscle activation in vastus medialis, tibialis anterior between squatting exercise with gymball and with wall. CONCLUSION: On comprehensively considering the results of the present study, we suggested that squatting exercise with gym ball was more effective method improving lower extremity muscle strengthening.

• Korean Journal of Applied Biomechanics
• /
• v.34 no.2
• /
• pp.81-92
• /
• 2024

Objective: The purpose of this study was to analyze the impact acceleration, shock attenuation and biomechanical variables at various running speed. Method: 20 subjects (height: 176.15 ± 0.63 cm, weight: 70.95 ± 9.77 kg, age: 27.00 ± 4.65 yrs.) participated in this study. The subjects ran at four different speeds (2.5 m/s, 3.0 m/s, 3.5 m/s, 4.0 m/s). Three-dimensional accelerometers were attached to the distal tibia, sternum and head. Gait parameters, biomechanical variables (lower extremity joint angle, moment, power and ground reaction force) and acceleration variables (impact acceleration, shock attenuation) were calculated during the stance phase of the running. Repeated measures ANOVA was used with an alpha level of .05. Results: In gait parameters, decreased stance time, increasing stride length and stride frequency with increasing running speed. And at swing time 2.5 m/s and 4.0 m/s was decreased compared to 3.0 m/s and 3.5 m/s. Biomechanical variables statistically increased with increasing running speed except knee joint ROM, maximum ankle dorsiflexion moment, and maximum hip flexion moment. In acceleration variables as the running speed increased (2.5 m/s to 4.0 m/s), the impact acceleration on the distal tibia increased by more than twice, while the sternum and head increased by approximately 1.1 and 1.2 times, respectively. And shock attenuation (tibia to head) increased as the running speed increased. Conclusion: When running speed increases, the magnitude and increasing rate of sternum and head acceleration are lower compared to the proximal tibia, while shock attenuation increases. This suggests that limiting trunk movement and increasing lower limb movement effectively reduce impact from increased shock. However, to fully understand the body's mechanism for reducing shock, further studies are needed with accelerometers attached to more segments to examine their relationship with kinematic variables.

• Journal of rehabilitation welfare engineering & assistive technology
• /
• v.4 no.1
• /
• pp.53-61
• /
• 2010

In this paper, We investigated the characteristic analysis of flexibility and muscle strength for exercise to verify capacity in rehabilitation exercise of lumbar using lumbar strengthen exercise instrument. We have experiment in 20th years man and woman who are 20 subject with no medical history, we divided subjects into control group with no exercise and training group with lumbar strengthen exercise. We used Hi-Spine(Medicalscience.korea) also, provided exercise 40 minute a day, three days a week and progressed total four weeks. Moreover in our experiment, subjects exercised four postural position as lay down, sit, stand and stretch each ten minute. We measured trunk extension backward, trunk flexion forward, evaluation of based physical fitness and lumbar joint torque. The reults have shown that there more improved all for flexibility, based physical fitness and lumbar joint torque in training group than control group. We indicated that by rotating 3-D axis movement flatform of exercise instrument, muscle spindle in subject have been stimulated and these rotation direction and angle caused muscle tonus and contraction that makes muscle, flexibility and based physical fitness improve more. Our study can be used rehabilitation exercise program to aged people and patient with lumbar injury.

• Korean Journal of Applied Biomechanics
• /
• v.31 no.4
• /
• pp.308-313
• /
• 2021

Objective: The purpose of this study was to investigate the effect of different kettlebell mass (30%, 40%, and 50% of the body mass) on kinematics and kinetic variables of kettlebell swing. Method: Total of 16 healthy male who had at least 1 year of kettlebell training experience were participated in this study (age: 31.69 ± 3.46 yrd., height: 173.38 ± 4.84 cm, body mass: 74.53 ± 6.45 kg). In this study, a 13-segments whole-body model (upper trunk, lower trunk, pelvis, both side of forearm, upperarm, thigh, and shank) was used and 26 reflective markers were attached to the body to identify the segments during the movement. A 3-dimensional motion analysis with 8 infrared cameras and 4 channeled EMG was performed to find the effect of kettlebell mass on its swing. To verify the kettlebell mass effect, a one-way ANOVA with a repeated measure was used and the statistical significance level was set at 𝛼=.05. Results: Firstly, in all lower extremity joints and thoracic vertebrae, a statistically significant change in angle was shown according to an increase in kettlebell mass during kettlebell swing (p<.05). Secondly, in both the up-swing and down-swing phases, the knee joint and ankle joint ROM showed a statistically significant increase as the kettlebell mass increased (p<.05) but no statistically significant difference was found in the hip joint and thoracic spine (p>.05). Lastly, the hamstrings muscle activity was statistically significantly increased as the kettlebell mass increased during up-swing phases (p<.05). Also, as the kettlebell mass increased in P4 of the down swing phase, the gluteus maximus showed a statistically significantly increased muscle activation, whereas the rectus femoris showed a statistically significantly decreased muscle activation (p <.05). Conclusion: As a result of this study, hip extension decreased and knee extension increased at 40% and 50% of body mass, and the spine also failed to maintain neutrality and increased flexion. Also, when kettlebell swings are performed with 50% of body mass, synergistic muscle dominance appears over 30% and 40% of body mass, which is judged to have a risk of potential injury. Therefore, it is thought that for beginners who start kettlebell exercise, swing practice should be performed with 30% of body mass. In addition, even in the case of experienced seniors, as the weight increases, the potential injury risk may increase, so it is thought that caution should be exercised when performing swings with 40% and 50% of body mass. In conclusion, it is thought that increasing the weight after sufficiently training with 30% of the weight of all subjects performing kettlebell swing is a way to maximize the exercise effect as well as prevent injury.