• Journal of Life Science
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• v.18 no.1
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• pp.30-37
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• 2008

The purpose of this study was to investigate the effect of Isotonic Training and Isotonic isometric complex Training to Knee joint Isokinetic muscle function in the high-school Taekwondo athlete. This subjects were randomly divided into two groups; a Isotonic Training group (n=7) Isotonic isometric complex Training group (n=7), Taekwondo athletes share each, 12 weeks between executes a motion. peak torque, H/Q ratio, bilateral muscular ratio muscular endurance of knee joint measured. For this study, two-way ANOVA with repeated measure were used. The result of this study presents between groups was not plain difference expressed. H/Q ratio, bilateral muscular ratio, muscular endurance was plain difference expressed after 12 weeks point of time (p>0.05) and peak torque was plain difference expressed (p<0.05). Conclusion each group did not appear all but one (peak torque), but point of view exercise was effect H/Q ratio, bilateral muscular ratio, muscular endurance, peak torque plain difference expressed.

• The Journal of Korea Robotics Society
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• v.8 no.1
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• pp.8-19
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• 2013

One of the important issues for structural and electrical specifications in developing a robot is to determine lengths of links and motor specifications, which need to be appropriate to the purpose of robot. These issues become more critical for a gait rehabilitation robot, since a patient wears the robot. Prior to developing an entire gait rehabilitation robot, designing of a 1DOF assistive knee joint of the robot is considered in this paper. Human gait motions were used to determine an allowable range of knee joint that was rotated with a linear type actuator (ball-screw type) and links. The lengths of each link were determined by using an optimization process, minimizing the stroke of actuator and the total energy (kinetic and potential energy). Kinetic analysis was performed in order to determine maximum rotational speed and maximum torque of the motor for tracking gait trajectory properly. The prototype of 1 DOF assistive knee joint was built and examined with a impedance controller.

• Korean Journal of Applied Biomechanics
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• v.31 no.2
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• pp.140-147
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• 2021

Objective: The purpose of this study is to identify the mechanism of changes in maximum voluntary torque with the magnitude and duration of pre-activation torque during voluntary isometric knee extension. Method: 11 male subjects (age: 25.91±2.43 yrs., height: 173.12±3.51 cm, weight: 76.45±7.74 kg) participated in this study. The subjects were required to produce maximal voluntary isometric torque with a particular pre-activation torque condition. The properties of pre-activation torque consisted of the combinations of 1) three levels of magnitude, e.g., 32 Nm, 64 Nm, 96 Nm, and 2) two levels of duration, e.g., 1 sec, and 3 sec; thus, a total of six conditions were given to the subjects. The force and EMG data were measured using the force transducers and wireless EMG sensor, respectively. Results: The results showed that the maximum voluntary torque increased the most with relatively large and fast (96 Nm, 1 sec) pre-activation condition. Similarly, with relatively large and fast (96 Nm, 1 sec) preactivation, it was found that the integrated EMG (iEMG) of the agonist muscles increased, while no significant changes in the co-contraction of the antagonist muscles for the knee extension. Also, the effect of pre-activation conditions on the rate of torque development was not statistically significant. Conclusion: The current findings suggest that relatively larger in magnitude and shorter in duration as the properties of pre-activation lead to a larger magnitude of maximal voluntary torque, possibly due to the increased activity of the agonist muscles during knee extension.

• Korean Journal of Applied Biomechanics
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• v.31 no.1
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• pp.64-71
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• 2021

Objective: This study investigated the different in isokinetic peak strength of the knee joint, and kinetics and kinematics in drop landing pattern of lower limb between the patellofemoral pain syndrome (PFPS) patients and normal. Method: 30 adult females were divided into the PFPS (age: 23.13±2.77 yrs; height: 160.97±3.79 cm, weight: 51.19±4.86 kg) and normal group (age: 22.80±2.54 yrs, height: 164.40±5.77 cm, weight: 56.14±8.16 kg), with 15 subjects in each group. To examine the knee isokinetic peak strength, kinematics and kinetics in peak vertical ground reaction force during drop landing. Results: The knee peak torque (Nm) and relative strength (%) were significantly weaker PFPS group than normal group. In addition, PFPS group had significantly greater hip flexion angle (°) than normal group. Moreover, normal group had significantly greater moment of hip abduction, hip internal rotation, and left ankle eversion than PFPS group, and PFPS group had significantly greater moment of knee internal rotation. Finally, there was significant differences between the groups at anteroposterior center of pressure. Conclusion: The PFPS patients had weakened knee strength, and which can result in an unstable landing pattern and cause of more stress in the knee joints despite to effort of reduce vertical ground reaction force.

• Korean Journal of Applied Biomechanics
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• v.29 no.2
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• pp.79-88
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• 2019

Objective: The aim of this study was to determine the peak torques of the knee and ankle joint and local stability of the lower extremity's joints, and muscle activation patterns of the lower extremity's muscles between fallers and non-fallers in the elderly women during walking. Method: Four elderly women (age: $74.5{\pm}5.2yrs.$; height: $152.1{\pm}5.6cm$; mass: $55.3{\pm}5.4kg$; preference walking speed: $1.19{\pm}0.06m/s$) who experienced falls within six months since experiment had been conducted (falls group) and thirty-six subjects ($74.2{\pm}3.09yrs.$; height: $153.6{\pm}4.9cm$; mass: $56.7{\pm}6.4kg$; preference walking speed: $1.24{\pm}0.10m/s$) who had no experience in falls (non-falls group) within this periods participated in this study. They were measured torque peaks of the knee and ankle joint using a Human Norm and while they were walking on a treadmill at their natural pace, kinematic variables and EMG signals were collected with using a 3-D motion capture system and a wireless EMG system, respectively. Lyapunov Exponent (LyE) was determined to observe the dynamic local stability of the lower extremity's joints, and muscles activation and their co-contraction index were also analysed from EMG signals. Hypotheses between falls and non-falls group were tested using paired t-test and Mann-Whitey. Level of significance was set at p<.05. Results: Local dynamic stability in the adduction-abduction movement of the knee joint was significantly lower in falling group than non-falling group (p<.05). Conclusion: In conclusion, muscles which act on the abduction-adduction movement of the knee joint need to be strengthened to prevent from potential falls during walking. However, a small number of samples for fallers make it difficult to generalize the results of this study.

• Journal of Advanced Technology Convergence
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• v.1 no.1
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• pp.33-42
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• 2022

The flexors and extensors of the knee joint are essential for maintaining body stability. The purpose of this study was to investigate the correlation between the isokinetic parameters of the knee flexor and extensor muscles and the function of the lower extremity muscles. Twenty-two healthy adults participated in this study. The time to peak torque (TTP), acceleration time (AT), and peak torque (PT) of the knee flexor and extensor muscles were measured. A 20m sprint, Sargent jump, one leg hop test, and side shuffle were measured to evaluate lower extremity function. The correlation between each variable was analyzed using Pearson correlation coefficient. PT of the knee flexor showed a significant correlation with single leg hops and 6M hops in a single leg. PT of knee extensors was found to be significantly correlated with Sargent jumps and triple hops. Based on the results of this study, we suggest that the strength of the knee flexor and extensor muscles has the potential to be used to predict lower extremity function.

• Journal of Biomedical Engineering Research
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• v.22 no.3
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• pp.293-301
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• 2001

A patient-specific musculoskeletal model, whose parameters can be identified noninvasively, was developed for the automatic generation of patient-specific stimulation pattern in FES. The musculotendon system was modeled as a torque-generator and all the passive systems of the musculotendon working at the same joint were included in the skeletal model. Through this, it became possible that the whole model to be identified by using the experimental joint torque or the joint angle trajectories. The model parameters were grouped as recruitment of muscle fibers, passive skeletal system, static and dynamic musculotendon systems, which were identified later in sequence. The parameters in each group were successfully estimated and the maximum normalized RMS errors in all the estimation process was 8%. The model predictions with estimated parameter values were in a good agreement with the experimental results for the sinusoidal, triangular and sawlike stimulation, where the normalized RMS error was less than 17%, Above results show that the suggested musculoskeletal model and its parameter estimation method is reliable.

• Physical Therapy Rehabilitation Science
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• v.13 no.3
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• pp.304-314
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• 2024

Objective: This study aimed to investigate the association of explosive strength with muscle mass and muscle function measured using traditional methods such as peak torque (PT) and joint angular velocity (PAV). Design: Cross-sectional study Methods: Twenty-nine healthy adults (14 males and 15 females) participated in this study. Body mass index and appendicular skeletal muscle index (ASMI) were measured using bioelectrical impedance analysis. The explosive strength of the knee extensors was evaluated by measuring the rate of torque development (RTD) and rate of velocity development (RVD). RTD was analyzed by dividing it into early (0-50 ms) and late (100-200 ms) muscle contraction phases. In addition, PT and PAV were measured as traditional methods for assessing muscle function. Results: According to regression analysis, PAV accounts for 24.7% and 66.9% of the variance of RTD 0-50 (p=0.006) and RVD (p<0.001), respectively. On the other hand, ASMI (p=0.035) and isometric PT (p=0.001) explained 49.2% of the RTD 100-200. Conclusions: Early RTD is mainly predicted by PAV, which is thought to be a result of muscle fiber type. Therefore, PAV presents the possibility of an alternative method to evaluate explosive performance. Late RTD seems to be related to ASMI or isometric PT. The findings of this study are expected to contribute to musculoskeletal rehabilitation and evaluation in that they revealed factors contributing to early and late muscle contraction.

• Korean Journal of Applied Biomechanics
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• v.17 no.3
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• pp.23-29
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• 2007

The purpose of this study were to investigate the differences between female and male basketball players in knee neuromuscular biomechanical factors during basketball rebound jump. Twelve high school female ($17.9{\pm}0.8years$) and twelve male ($19.0{\pm}1.6years$) basketball players rebound jumped for maximal vertical height to sufficiently stress the anterior cruciate ligament. Kinematic and ground reaction data were collected and combined with inverse dynamics to estimate the knee extensor and abductor torque. The EMG data from the biceps femoris and rectus femoris was used to estimate the ratio of quadriceps muscle activity. Female athletes showed more reduced knee flexion at foot contact, more increased knee abduction, extensor and abductor knee joint torque at foot contact, and quadriceps ratio at stance phase than those of male athletes. In conclusion, Female athletes showed differences in knee neuromuscular biomechanical factors than male athletes during basketball rebound jump.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.339-347
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• 2014

The purpose of this study was to investigate joint torques of lower body segments on professional golfers. Three dimensional swing analysis was conducted on the seven subjects. Each subject was asked to swing with 45 inches of Callaway driver, where two force plates (9286AA, Kistler, Switzerland) were built, with his normal speed and tempo. The resultant joint moments of the lower extremities were computed using the kinematic variables of the segments, anthropometric measures and the ground reaction force data by inverse dynamics method. Based on the results of this study, the following conclusions were drawn; It was found that the left ankle joint torque at 3rd phase was increased toward extension on the X-axis and abduction on the Y-axis. The left knee joint torque was alternated from flexion to extension direction in order to lower down the body weight at the beginning of the downswing. The lumbar joint torque was alternated from flexion to extension in order to speed up the upper body rotation which could increase the club head speed ultimately.