• Journal of Korean Physical Therapy Science
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• v.8 no.2
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• pp.967-976
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• 2001

The purpose of the present study was to the investigate the effect of aging in men and women on muscle strength of knee extensor and flexors by using the cybex 6000 isokinetic dynamometer. A total of 100 volunteers participated in this study and were divided into five groups according to their chronological age as follows: 20s, 30s, 40s, 50s, 60s, 10 men and 10 women in each decade respectively. Isokinetic ($60^{\circ}{\cdot}s-l$) knee extensor and flexor peak torque, peak torque to body weight ratio, opposing muscles(flexor/extensor) peak torque ratio, deficit of peak torque between dominant and non-dominant were measured. The results obtained were as follows: 1) In men, While the aged increased. the peak torque of the knee flexor and extensor statistically sig nificant decreased in the dominant and non-dominant side. 2) In women, Statistically significant difference of knee extensor peak torque was found as the aged increased in the dominant and non-dominant side, but significant difference of knee flexor peak torque did not that. 3) In men, No significant difference in the peak torque of knee flexor to body weight ratio was found as the aged increased in the non-dominant side, but statistically significant difference in the peak torque of knee flexor to body weight weight ratio was found as the aged increased in the dominant side. 4) In women. No significant difference in the peak torque of knee flexor to body weight ratio was found as the aged increased in the dominant side, but statistically significant difference in the peak torque of knee flexor to body weight ratio was found as the aged increased in the non-dominant side. 5) In men and women, While the aged increased, statistically significant difference was found the dominant and non-dominant side in the peak torque of knee extensor to body weight ratio. 6) Peak torque of hamstring to quadriceps ratio of dominant and non-dominant side in men and women were not significantly different as the age increases. 7) Mean deficit of peak torque between dominant and non-dominant side in men and women were not significantly different as the age increases. From these results we conclude a proper exercise program is need before 50s decade to preserve in muscle strength of knee flexors and extensors.

• Physical Therapy Korea
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• v.13 no.3
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• pp.75-83
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• 2006

The purpose of this study was to examine the isokinetic moment of quadriceps and hamstring strength ratio among women of different ages. The study population consisted of 1,184 women referred to the Health Promotion Center at the S district. All subjects were aged 20 to 69 years old and divided into 5 groups; 20s (n=248), 30s (n=255), 40s (n=248), 50s (n=228), and 60s (n=205). The strength of the knee extensor and flexor, quadriceps, and hamstring of all the participants were assessed at 60 degrees/second with an isokinetic machine. We calculated the peak torque, peak torque %BW (%Body Weight), deficit of peak torque and hamstring/quadriceps ratio of the knee. The data were analyzed by one way ANOVA to investigate statistical differences in strength variation between different age groups and were computed by ${\Delta}%$ difference from women in their 20's. The results were obtained as follows: 1. Peak torque of the knee extensor, quadriceps, were significantly reduced in women older than 30, but peak torque of the knee flexor, hamstring, were significantly reduced in women older than 50 compared to women in their 20's. (p<.05). 2. Peak torque %BW of the knee extensor, quadriceps, were significantly reduced in women older than 20, but peak torque %BW of knee flexor, hamstring, were significantly reduced in women older than 40 compared to women in their 30's (p<.05). 3. Compared to the women in their 20's, there was no significant difference among any of the age groups in the deficit of peak torque of the knee extensor and flexor, but the deficit of peak torque of knee extensor among women between 30 and 50showed significant difference within the normal range of deficit. 4. Compared to the women in their 20's, there was no significant difference among any of the age groups in the hamstring/quadriceps ratio These results showed that peak torque, peak torque %BW, deficit of peak torque, and hamstring/quadriceps ratio of the knee were reduced in each age group, but especially among the women over 50. Further longitudinal study may be needed to see if volume of muscle mass and intervention of exercise affect knee strength in spite of aging.

• Journal of Korean Physical Therapy Science
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• v.7 no.2
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• pp.711-725
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• 2000

The purpose of this study was to determine the effects of knee flexor isokinetic training on the mean peak torque of knee muscles and hamstrings-to-quadriceps ratio(H/Q ratio) in hemiplegia able to walk independently for more than 10 meters, to analyze the effect of torque increasing on functional aspects; fatigability and ambulation times, also. Forty-one adult subjects with hemiplegia secondary to a stroke partipated in this study. All participants were in/out patients at the College of Medicine, Pocheon CHA University, Pundang CHA General Hospital. The patients were allocated to two groups: one group exclusively for isokinetic maximal voluntary knee flexor training at $150^{\circ}$/sec(n=20) and the other exclusively for isokinetic maximal voluntary knee flexor training from $30^{\circ}$/sec to $150^{\circ}$/sec (n=21) gradually. The allocation was performed according to patient age, sex, affected side to minimize imbalance between the two training groups. Training was carried out from February 14th, 2000 to April 15th, 2000. Analysis of the data was done by means of t-test, x2-test, paired t-test, ANOVA, and multiple regression analysis. The results of this study were as follows: 1. There were no significant differences between the two groups in mean peak torque of knee muscles and relative decreases in knee extensor mean peak torque with increased knee flexor velocities before training (P<.05). 2.There was no significant differences between the two groups in the H/Q ratio, and no relative increases with increased knee flexor velocities before training. 3. there were significant changes in mean peak torque in group A after training(P<.05), but no significant differences as the velocity increased 4.there were significant changes in mean peak torque in group B after training(P<.05), but no significant differences as the velocity increased 5.there were no significant differences between the two groups, and no significant differences in mean peak torque increase rate between the groups with increased knee flexor velocities after training 6.H/Q ratio increased with increased knee flexor velocities between the two groups, but not statistically And there was no significant differences between the groups with increased knee flexor velocities 7.After training, Ambulation time and its decreasing rate decreased significantly in group B (P<.05) 8Before and after training, there was no significant differences between the groups in the fatiguability 9. In the multiple regression analysis, mean peak torque increase rate of the knee extensor and flexor were higher in group B than A(P<.05), and significantly higher with increased knee flexor velocities (P<.05) Also, training method influenced on Ambulation times decreases significantly(P<.05). Results indicated that knee flexor isokinetic training was effective to knee extensor and flexor mean peak torque increase in the hemiplegia able to walk independently for more than 10 meters. Therefore, we were able to conclude that gradual training from low to high velocity was more effective in the increase of mean peak torque of knee joint and decrease of Ambulation times than training only at high velocity.

• Physical Therapy Korea
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• v.14 no.3
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• pp.23-31
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• 2007

The purpose of this study was to determine the influence of high-heeled shoes on walking of obese women as it was already proven an extrinsic factor of knee osteoarthritis in women with normal weight. In this study the aimed therefore in particular was to utilize high-heeled shoes in proving it's causal influence on knee osteoarthritis by measuring the angle and torque of the knee joint. Fifteen obese women (BMI>25 $kg/m^2$) were measured in their twenties. Each angle and torque of their knee joints during walking on 6.5 cm high-heeled shoes and with a bare feet, were compared with each other and analyzed with a 3D motion analysis system. There was no significant difference in walking speed, cadence and stride length between the two conditions. However, there was a significant increase in a double limb support time and the stance phase when walking on high-heeled shoes as when walking with bare feet. The peak knee flexion angle and peak knee varus torque was higher when walking on high-heeled shoes than with bare feet. On the contrary, the peak knee flexion angle in the swing phase was not statistically different. The prolongation of peak knee varus torque was also proven. There was a significant increase in peak knee varus torque in the initial and last stance phases during walking on high-heeled shoes as compared to walking on bare feet. Through the above results, it was proven that when obese women walked on high-heeled shoes, rather than with bare feet, peak knee flexor and varus torque increased along with the changes of the in knee joint angle. Therefore, the influence of high-heeled shoes might be a significant intrinsic factor in knee osteoarthritis of obese women.

• The Journal of Korean Physical Therapy
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• v.16 no.4
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• pp.1-10
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• 2004

The purpose of this study was to investigate the effects of treadmill aerobic exercise training on isokinetic muscle strength in students with cerebral palsy. The subjects consisted of 9 female students with cerebral palsy between the ages of 10 to 22. The subjects performed treadmill aerobic exercise training with $0\%$ grade by free speed with three times a week for 20 minutes a session and 12 weeks. Concentric peak torque of knee flexors and knee extensors was measured before training and after training at $30^{\circ}/sec$ and $60^{\circ}/sec$ by isokinetic dynamometer. Paired t-test was used to assess changes in variables of isokinetic muscle strength. The results of analysis are as followings. 1) After training, concentric peak torque of the least affected knee flexors(p<.01) and the most affected knee flexors (p<.01) and concentric peak torque of the least affected knee extensors(p<.01) and the most affected knee extensors(p<.01) at $30^{\circ}/sec$ significantly increased. 2) After training, concentric peak torque of the least affected knee flexors(p<.05) and the most affected knee flexors(p<.01) and concentric peak torque of the least affected knee extensors(p<.05) and the most affected knee extensors(p<.01) at $60^{\circ}/sec$ significantly increased. These findings provide evidence that treadmill aerobic exercise training improves isokinetic muscle strength in students with cerebral palsy.

• Korean Journal of Applied Biomechanics
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• v.13 no.2
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• pp.1-12
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• 2003

This study was performed to provide normative isokinetic strength of knee muscles of middle school non-athletic and athletic populations for rehabilitation and pre-season screening for injury prevention. Seven non-athletic subjects and 8 hockey players participated in this investigation. Each subject was tested at speeds of $60^{\circ}/sec$, $180^{\circ}/sec$, and $300^{\circ}/sec$. The free weight of lower leg was measured at speed of $60^{\circ}/sec$ to take gravity effect Into consideration when peak torque of knee muscles occurred. The results showed that the relative peak torque production of knee flexors did not change but the relative peak torque of knee extensors decreased significantly. Mamstring/quadriceps ratios increased mainly due to significant decreases in knee extensors torque production. No significant differences were found between groups. The hamstring/quadriceps ratios for both groups were significantly lower when the gravity effect was not eliminated.

• Korean Journal of Exercise Nutrition
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• v.24 no.4
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• pp.28-33
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• 2020

[Purpose] This study aimed to investigate the effects of branched-chain amino acid (BCAA) supplement on delayed onset muscle soreness (DOMS) by analyzing the maximum muscle strength and indicators of muscle damage. [Methods] Twelve men with majors in physical education were assigned to the BCAA group and placebo group in a double-blinded design, and repeated measurements were conducted. DOMS was induced with an isokinetic exercise. Following BCAA administration, the changes in the knee extension peak torque, flexion peak torque, aspartate aminotransferase (AST), creatine kinase (CK), and lactate dehydrogenase (LDH) concentrations were analyzed. The maximum knee muscle strength was measured at the baseline (pre-D0) following BCAA administration for 5 days before exercise (-D5, -4D, -3D, -2D, -1D). In contrast, the post-treatment measurements (D3) were recorded after BCAA administration for 3 days (post-D0, D1, D2). Blood samples were obtained before (pre-D0), immediately after (post-D0), 24 h (D1), 48 h (D2), and 72 h (D3) after the exercise to analyze the indicators of muscle strength. BCAA was administered twice daily for 8 days (5 days and 3 days before inducing DOMS and during the experimental period, respectively). [Results] There was no difference in the flexion peak torque between the groups. However, the BCAA group showed a significantly higher extension peak torque at D3 (second isokinetic exercise), compared to the placebo group (p<.05). There was no difference in AST changes between the groups. Nonetheless, the CK and LDH were significantly reduced in the BCAA group, compared to the placebo group. There was no correlation between the extension peak torque and flexion peak torque. However, the CK and LDH increased proportionately in DOMS. Moreover, their concentrations significantly increased with a decreasing peak torque (p<.01). [Conclusion] An exercise-induced DOMS results in a decrease in the peak torque and a proportional increase in the CK and LDH concentrations. Moreover, the administration of BCAA inhibits the reduction of the extension peak torque and elevation of CK and LDH concentrations. Therefore, BCAA might be administered as a supplement to maintain the muscle strength and prevent muscle damage during vigorous exercises that may induce DOMS in sports settings.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.8 no.2
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• pp.31-43
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• 2002

The subjects of this study were 15 woman soccer players and 15 untrained woman students at H-Cheju University. Each subject was measured on the muscle strength and peak torque of knee extensors and knee flexors with isokinetic load ($60^{\circ}$/sec, $180^{\circ}$/sec). The results were as follows: 1. There was no significant difference between right and left leg strength measured isokinetically in each group. 2. The peak torque of knee extensors and flexors was significantly higher in scoccer players than untrainded students (p<0.001). 3. For the angle of knee joint showing the highest peak torque, there was significant difference between soccer players and untrained students in knee extensors(p<0.05) and right flexors (p<0.01). 4. For knee H/Q ratio, there was significant difference between two groups(p<0.05). 5. For the total work and average power at $180^{\circ}$/sec, there was significant difference between two groups in knee extensors(p<0.001) and flexors(p<0.01). 6. In soccer players at $60^{\circ}$/sec, there were significant correlations between peak torque and height and between peak torque and weight.(p<0.001). 7. For the muscular contraction velocity at $60^{\circ}$/sec, there was significant difference between two groups in flexors (p<0.01). 8. For the muscular indurance at $180^{\circ}$/sec in extensors and flexors, there was no significant difference between two groups(p<0.05). In conclusion, there were significantly higher in peak torque, contraction velocity, knee joint's angle with the highest peak torque, H/Q ratio, total work and average power in woman scoccer player than general students. But there was no significant difference in muscular endurance. Soccer performance is based on the various components including muscular endurance that is one of the most important components. So it is necessary that the training method to improve the various components (especially including muscular endurance) should be done.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.8 s.197
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• pp.130-137
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• 2007

The optimized prosthetic mass distribution was a controversial problem in the previous studies because they are not supported by empirical evidence. The purpose of the present study was to evaluate the effect of prosthetic mass properties by modeling musculoskeletal system, based on the gait analysis data from two above-knee amputees. The joint torque at hip joint was calculated using inverse dynamic analysis as the mass was changed in knee and foot prosthetic components with the same joint kinematics. The results showed that the peak flexion and abduction torque at the hip joint were 5 Nm and 15 Nm when the mass of the knee component was increased, greater than the peak flexion and abduction torque of the control group at the hip joint, respectively. On the other hand, when the mass of the foot component was increased, the peak flexion and abduction torque at the hip joint were 20 Nm and 15 Nm, greater than the peak flexion and abduction torque of the control, respectively. The hip flexion torque was 4.71-fold greater and 7.92-fold greater than the hip abduction torque for the knee mass increase and the foot mass increase on the average, respectively. Therefore, we could conclude that the effect of foot mass increase was more sensitive than that of knee mass increase for the hip flexion torque. On the contrary, the mass properties of the knee and foot components were not sensitive for the hip abduction torque. In addition, optimized prosthetic mass and appropriate mass distributions were needed to promote efficiency of rehabilitation therapy with consideration of musculoskeletal systems of amputees.

• Physical Therapy Korea
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• v.11 no.4
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• pp.31-41
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• 2004

The purpose of this study was to examine the effect of the angle of a wedged insole on knee varus torque during walking. Fifteen healthy subjects were recruited. Knee varus torque was measured using three-dimensional motion analysis (Elite). Knee varus torque was normalized to gait cycle (0%: initial contact; 100%: ipsilateral initial contact) and stance phase (0%: initial contact; 100%: ipsilateral toe off). The average peaks of knee varus torque during the stance phase of the gait cycle according to the different insole angles (10 or 15 degrees) were compared using one-way ANOVA with repeated measures. The results showed that in the early stance phase, the average peak knee varus torque increased significantly for both the medial 10 and 15 degree wedged insole conditions and decreased significantly for both the lateral 10 and 15 degree wedged insole conditions as compared with no insole (p<.05). However, there were no significant differences between the 10 and 15 degree wedged insole conditions with either the medial or lateral wedged insole (p>.05). In the late stance phase, the average peak knee varus torque increased significantly for the medial 10 and 15 degree wedged insole conditions (p<.05), but not for the lateral 10 and 15 degree wedged insole conditions as compared with no insole (p>.05). We suggest that these results may be beneficial for manufacturing foot orthotic devices, such as wedged insoles, to control medial and lateral compartment forces in the knee varus-valgus deformity. Further studies of the effects of wedged insole angle on knee varus torque in patients with medial-lateral knee osteoarthritis are needed.