IEEE Transactions on Neural Systems and Rehabilitation Engineering
Although studies on terrain identification algorithms to control walking assistive devices have b... more Although studies on terrain identification algorithms to control walking assistive devices have been conducted using sensor fusion, studies on transition classification using only electromyography (EMG) signals have yet to be conducted. Therefore, this study was to suggest an identification algorithm for transitions between walking environments based on the entire EMG signals of selected lower extremity muscles using a deep learning approach. The muscle activations of the rectus femoris, vastus medialis and lateralis, semitendinosus, biceps femoris, tibialis anterior, soleus, medial and lateral gastrocnemius, flexor hallucis longus, and extensor digitorum longus of 27 subjects were measured while walking on flat ground, upstairs, downstairs, uphill, and downhill and transitioning between these walking surfaces. An artificial neural network (ANN) was used to construct the model, taking the entire EMG profile during the stance phase as input, to identify transitions between walking environments. The results show that transitioning between walking environments, including continuously walking on a current terrain, was successfully classified with high accuracy of 95.4 % when using all muscle activations. When using a combination of muscle activations of the knee extensor, ankle extensor, and metatarsophalangeal flexor group as classifying parameters, the classification accuracy was 90.9 %. In conclusion, transitioning between gait environments could be identified with high accuracy with the ANN model using only EMG signals measured during the stance phase.
DISCUSSION Results of this study show that TF contact area calculated using 3D-SPGR and FSE seque... more DISCUSSION Results of this study show that TF contact area calculated using 3D-SPGR and FSE sequence are strongly correlated, though measured contact area using FSE images underestimated values by 28% compared to that using 3D-SPGR. These results suggest that both imaging sequences could be used to measure cartilage-to-cartilage contact area but the direct comparison of cartilage contact from different sequences should consider the fact that FSE images lead to underestimation of cartilage-to- cartilage contact compared to 3D-SPGR images. This study has shown that acute loading on the tibiofemoral joint resulted in significant increase of TF contact area both at the medial and lateral compartments. It is also interesting to note that the contact area in the medial compartment was twice as large as that in the lateral compartment under loaded condition. These results suggest that the in vivo articular contact environment in the medial compartment changes dramatically under acute loadi...
The purpose of this study was to determine the knee and ankle joint kinematics and kinetics by co... more The purpose of this study was to determine the knee and ankle joint kinematics and kinetics by comparing downhill walking with valley-shape combined slope walking. Method: Eighteen healthy men participated in this study. A three-dimensional motion capture system equipped with eight infrared cameras and a synchronized force plate, which was embedded in the sloped walkway, was used. Obtained kinematic and kinetic parameters were compared using paired two-tailed Student's t-tests at a significance level of 0.05. Results: The knee flexion angle after the mid-stance phase, the mean peak knee flexion angle in the early swing phase, and the ankle mean peak dorsiflexion angle were greater during downhill walking compared with valley-shape combined slope walking (p < 0.001). Both the mean peak vertical ground reaction force (GRF) in the early stance phase and late stance phase during downhill walking were smaller than those values during valley-shape combined slope walking. (p = 0.007 and p < 0.001, respectively). The mean peak anterior GRF, appearing right after toe-off during downhill walking, was also smaller than that of valleyshape combined slope walking (p = 0.002). The mean peak knee extension moment and ankle plantar flexion moment in late stance phase during downhill walking were significantly smaller than those of valleyshape combined slope walking (p = 0.002 and p = 0.015, respectively). Conclusion: These results suggest that gait strategy was modified during valley-shape combined slope walking when compared with continuous downhill walking in order to gain the propulsion for lifting the body up the incline for foot clearance.
The purpose of this study was to investigate the relationship between muscular parameters of quad... more The purpose of this study was to investigate the relationship between muscular parameters of quadriceps/hamstrings and knee joint kinetics in gait. Muscle architecture (thickness, pennation angle, and fascicle length), and quality (echo intensity) of individual quadriceps and hamstrings of 30 healthy participants (16 males and 14 females) was measured using ultrasound. Peak knee flexion moment (KFM), KFM impulse, peak knee adduction moment (KAM), and KAM impulse during walking were obtained at preferred speed. Pearson’s correlation coefficient and multiple regression analyses were performed at significance level of 0.05, and Cohen’s f2 values were calculated to examine the effect sizes of multiple regression. The hamstring-to-quadriceps muscle thickness ratio (r = 0.373) and semitendinosus echo intensity (r = − 0.371) were predictors of first peak KFM (R2 = 0.294, P = 0.009, f2 = 0.42), whereas only vastus medialis (VM) echo intensity was a significant predictor of second peak KFM ...
Biomechanics and Modeling in Mechanobiology, Nov 24, 2018
Damage to the acetabular labrum has been associated with cartilage degeneration. Because conventi... more Damage to the acetabular labrum has been associated with cartilage degeneration. Because conventional pressure measurement devices were unable to examine the sealing function of the acetabular labrum on cartilage contact mechanics, we used an image-based computational method to examine how labrectomy affects articular cartilage contact area and strain patterns in porcine hips. Cyclically loaded hip samples were continuously imaged in a CT scanner every 3 min to trace the positions of the femur and acetabulum. Image-based displacement-controlled finite element analysis was used to calculate articular cartilage contact area and nominal strain at different time points. No changes in cartilage contact area were found after labrectomy. Compared to the labrum intact condition, average nominal strain in labrectomized hips was elevated at early time points after load application. The areas of 'high' strain in labrectomized hips were found to be increased by approximately 7% after 30 min of cyclic loading, while the changes in the areas of 'low' strain were minimal. Our result showed that changes in articular cartilage strain following labrectomy were concentrated on locally overloaded areas where the degenerative process of articular cartilage may be initiated. Keywords Acetabular labrum • Articular cartilage • Biomechanics • Medical imaging • Hips • Osteoarthritis 1 Introduction Osteoarthritis of the hip is known to have various predisposing causes. One factor which may increase the risk of developing hip osteoarthritis is damage to the acetabular labrum. Various cadaveric and clinical studies have sug-Choongsoo S. Shin and Yongnam Song have equally contributed.
International Journal of Precision Engineering and Manufacturing, Dec 1, 2015
Military personnel suffer from musculoskeletal injuries during military operations and training. ... more Military personnel suffer from musculoskeletal injuries during military operations and training. Military training is often performed with military boots in challenging outdoor environments where the ground surface is not leveled. Thus, this study aimed to determine the hip, knee, and ankle joint kinematics and kinetics during valley-shaped slope walking (VSW). Eighteen Reserve Officer Training Corps cadets walked on a valley-shaped slope wearing military boots. Three-dimensional kinematic and kinetic data of the lower extremity were obtained using a force plate and motion capture system. Kinematics changed to control the lowered and raised body during VSW. Anterior-posterior ground reaction forces (GRF) and vertical GRF were significantly increased during VSW compared with that during level walking. Furthermore, compared with level walking, both the knee extension moment and ankle plantarflexion moment were significantly increased during VSW. Joint kinematics and kinetics changed in response to the shape of the ground surface. During VSW, the changes in the pattern and magnitude of the joint kinematics and kinetics demonstrated that different movement strategies are required to provide soldiers the necessary stability and mobility.
International Journal of Precision Engineering and Manufacturing, 2020
The movement pattern during stair descent differs by gender, and this difference may be associate... more The movement pattern during stair descent differs by gender, and this difference may be associated with gender differences in muscle strength or activation. The purpose of this study was to determine whether a gender difference in muscle activation exists by comparing the muscle activation amplitude and co-activation of lower extremity muscles during the stair-to-ground descent transition. Fifteen men and thirteen women descended stairs and the muscle activation was measured. Women showed a significantly lower peak normalized electromyography amplitude of the vastus lateralis (women: 171.7% peak EMG activation amplitude for level walking (PEALW), men: 297.0%PEALW, p < 0.05). Additionally, women showed significantly elevated co-activation of the vastus lateralis and biceps femoris compared to men (p < 0.05). The lower amplitude of the vastus lateralis in women indicates lower recruitment of knee extensor. In conclusion, the significantly higher co-activation of the vastus later...
Journal of Mechanical Science and Technology, 2016
We investigated 3D kinematic and kinetic changes of knee and ankle during downhill walking as the... more We investigated 3D kinematic and kinetic changes of knee and ankle during downhill walking as the slope angle increased and evaluated biomechanical injury risk factors related to non-contact ACL injury. Fifteen male subjects performed level walking and 15° and 25° downhill walking. For the kinetic and kinematic parameters, one-way ANOVA and post-hoc tests were performed at a significance level of 0.05. This study revealed significant differences in 3D knee and ankle kinematics and kinetics among 0°, 15° and 25° downhill walking. The peak posterior ground reaction force, the peak knee anterior force and the knee valgus moment (0° vs. 15°: p < 0.05; 0° vs. 25°: p < 0.05) in the early stance phase increased as the slope angle increased. The peak knee internal tibial rotation moments in the late stance also increased (0° vs. 15°: p < 0.05; 0° vs. 25°: p < 0.05; 15° and 25°: p < 0.05) as the slope angle increased. These results showed the risk for ACL injuries may be increased during downhill walking with a greater slope angle.
Background: Muscle thickness can influence the joint kinematics and/or kinetics during dynamic ac... more Background: Muscle thickness can influence the joint kinematics and/or kinetics during dynamic activities. The relationship between the muscle thickness of individual quadriceps and hamstrings or medial-to-lateral thigh muscle thickness ratio and the knee kinematics/kinetics with respect to anterior cruciate ligament (ACL) injury risk remains unclear. Hypothesis: Higher medial-to-lateral thigh muscle thickness ratio would be associated with lower knee valgus angle/moment and lower tibial internal rotation angle/moment during single-leg landing. Study Design: Cross-sectional. Level of Evidence: Level 4. Methods: Muscle thickness of the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) of 30 healthy participants (16 males and 14 females) were measured using ultrasound. Knee joint kinematics and kinetics during single-leg landing were obtained. Stepwise multiple regression analysis, a follow-up Fisher’s r to z test to examine the sex as a moderat...
The purpose of this study was to examine whether there is a sex difference in the effect of ankle... more The purpose of this study was to examine whether there is a sex difference in the effect of ankle plantar flexion at the contact angle, ankle range of motion (ROM), and ankle plantar flexion moment on knee valgus loading during single-leg landing. Twenty-five females and twenty-four males performed a single-leg landing. Joint kinematics and kinetics of the lower extremities were measured. Correlation coefficients were used to assess the relationship between ankle biomechanics in the sagittal plane (ankle plantar flexion angle at contact, ROM, and peak ankle plantar flexion moment) and peak knee valgus moment. In males, the larger ankle plantarflexion angle at contact and ROM were significantly associated with lower peak knee valgus moment (r = − 0.46, p < 0.05; and r = − 0.42, p < 0.05). In addition, in males only, a greater peak ankle plantar flexion moment was significantly associated with a lower peak knee valgus moment (r = − 0.83, p < 0.001) and greater peak ankle inve...
The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculosk... more The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculoskeletal model, which enables the adjustment of ligament length and implant alignment; validate the model; and evaluate the effects of varus/valgus alignment adjustment and unbalanced medial/lateral ligament laxity during gait. A cruciate-retaining total knee arthroplasty musculoskeletal model was constructed and validated against the in vivo contact forces. This model was transformed to 2° varus/valgus alignment of femoral or tibial replacement models and 2° medial/lateral laxity models. The contact forces and ligament tensions of the adjusted models were calculated. The contact forces in the model showed good agreement with the in vivo contact forces. Valgus replacement alignment with balanced ligament models showed a lower contact force at the medial compartment than at the neutral alignment model, whereas the varus replacement alignment with balanced ligament models showed a greater co...
The metatarsophalangeal (MTP) joint is not considered in most current walking assistive devices e... more The metatarsophalangeal (MTP) joint is not considered in most current walking assistive devices even though it plays an important role during walking. The purpose of this study was to develop a new MTP assistive device and investigate its effectiveness on the muscle activities of the lower extremities during walking while wearing the device. The MTP assistive device is designed to support MTP flexion by transmitting force through a cable that runs parallel with the plantar fascia. Eight participants were instructed to walk at a constant speed on a treadmill while wearing the device. The muscle activities of their lower extremities and MTP joint kinematics were obtained during walking under both actuated and non-actuated conditions. Paired t-tests were performed to compare the differences in each dependent variable between the two conditions. The muscle activity of the MTP flexor was significantly reduced during walking under actuated conditions (p = 0.013), whereas no differences we...
The purpose of this study was to investigate the effect of load carriage on the kinematics and ki... more The purpose of this study was to investigate the effect of load carriage on the kinematics and kinetics of the ankle and knee joints during uphill walking, including joint work, range of motion (ROM), and stance time. Fourteen males walked at a self-selected speed on an uphill (15°) slope wearing military boots and carrying a rifle in hand without a backpack (control condition) and with a backpack. The results showed that the stance time significantly decreased with backpack carriage (p<.05). The mediolateral impulse significantly increased with backpack carriage (p<.05). In the ankle joints, the inversion-eversion, and dorsi-plantar flexion ROM in the ankle joints increased with backpack carriage (p<.05). The greater dorsi-plantar flexion ROM with backpack carriage suggested one strategy for obtaining high plantar flexor power during uphill walking. The result of the increased mediolateral impulse and inversion-eversion ROM in the ankle joints indicated an increase in body...
International Journal of Precision Engineering and Manufacturing
Upslope-walking is more challenging and therefore has a greater fall risk than level-walking. The... more Upslope-walking is more challenging and therefore has a greater fall risk than level-walking. The current study aimed to investigate the difference in control strategy for stability between level and upslope walking using the center of pressure (COP) and the ratio of three sub-phases in stance phase (loading-response, mid-stance and push-off). Two hypotheses were tested: the excursion, range, and speed of the COP increases in the mediolateral and anteroposterior directions with slope grade; and the duration of the midstance phase increases with slope grade. Eleven male subjects walked on a level (0°) surface and upslope at 15° and 25°. The duration of the mid-stance phase was significantly greater in the 25° upslope-walking condition than that in the level and 15° upslope-walking conditions (both p<0.05). This result implies that the subjects adopted a different control strategy when walking upslope at 25° than when walking level and upslope at 15°. The range and speed of the mediolateral COP were larger in the 25° upslope-walking condition than those in the level and 15° upslope-walking conditions (p<0.05). This result indicates that a change in control strategy during upslope-walking at 25° can improve mediolateral stability. These findings imply that a transition grade exists between 15° and 25° where one can alter their control strategy to improve stability during upslope-walking.
IEEE Transactions on Neural Systems and Rehabilitation Engineering
Although studies on terrain identification algorithms to control walking assistive devices have b... more Although studies on terrain identification algorithms to control walking assistive devices have been conducted using sensor fusion, studies on transition classification using only electromyography (EMG) signals have yet to be conducted. Therefore, this study was to suggest an identification algorithm for transitions between walking environments based on the entire EMG signals of selected lower extremity muscles using a deep learning approach. The muscle activations of the rectus femoris, vastus medialis and lateralis, semitendinosus, biceps femoris, tibialis anterior, soleus, medial and lateral gastrocnemius, flexor hallucis longus, and extensor digitorum longus of 27 subjects were measured while walking on flat ground, upstairs, downstairs, uphill, and downhill and transitioning between these walking surfaces. An artificial neural network (ANN) was used to construct the model, taking the entire EMG profile during the stance phase as input, to identify transitions between walking environments. The results show that transitioning between walking environments, including continuously walking on a current terrain, was successfully classified with high accuracy of 95.4 % when using all muscle activations. When using a combination of muscle activations of the knee extensor, ankle extensor, and metatarsophalangeal flexor group as classifying parameters, the classification accuracy was 90.9 %. In conclusion, transitioning between gait environments could be identified with high accuracy with the ANN model using only EMG signals measured during the stance phase.
DISCUSSION Results of this study show that TF contact area calculated using 3D-SPGR and FSE seque... more DISCUSSION Results of this study show that TF contact area calculated using 3D-SPGR and FSE sequence are strongly correlated, though measured contact area using FSE images underestimated values by 28% compared to that using 3D-SPGR. These results suggest that both imaging sequences could be used to measure cartilage-to-cartilage contact area but the direct comparison of cartilage contact from different sequences should consider the fact that FSE images lead to underestimation of cartilage-to- cartilage contact compared to 3D-SPGR images. This study has shown that acute loading on the tibiofemoral joint resulted in significant increase of TF contact area both at the medial and lateral compartments. It is also interesting to note that the contact area in the medial compartment was twice as large as that in the lateral compartment under loaded condition. These results suggest that the in vivo articular contact environment in the medial compartment changes dramatically under acute loadi...
The purpose of this study was to determine the knee and ankle joint kinematics and kinetics by co... more The purpose of this study was to determine the knee and ankle joint kinematics and kinetics by comparing downhill walking with valley-shape combined slope walking. Method: Eighteen healthy men participated in this study. A three-dimensional motion capture system equipped with eight infrared cameras and a synchronized force plate, which was embedded in the sloped walkway, was used. Obtained kinematic and kinetic parameters were compared using paired two-tailed Student's t-tests at a significance level of 0.05. Results: The knee flexion angle after the mid-stance phase, the mean peak knee flexion angle in the early swing phase, and the ankle mean peak dorsiflexion angle were greater during downhill walking compared with valley-shape combined slope walking (p < 0.001). Both the mean peak vertical ground reaction force (GRF) in the early stance phase and late stance phase during downhill walking were smaller than those values during valley-shape combined slope walking. (p = 0.007 and p < 0.001, respectively). The mean peak anterior GRF, appearing right after toe-off during downhill walking, was also smaller than that of valleyshape combined slope walking (p = 0.002). The mean peak knee extension moment and ankle plantar flexion moment in late stance phase during downhill walking were significantly smaller than those of valleyshape combined slope walking (p = 0.002 and p = 0.015, respectively). Conclusion: These results suggest that gait strategy was modified during valley-shape combined slope walking when compared with continuous downhill walking in order to gain the propulsion for lifting the body up the incline for foot clearance.
The purpose of this study was to investigate the relationship between muscular parameters of quad... more The purpose of this study was to investigate the relationship between muscular parameters of quadriceps/hamstrings and knee joint kinetics in gait. Muscle architecture (thickness, pennation angle, and fascicle length), and quality (echo intensity) of individual quadriceps and hamstrings of 30 healthy participants (16 males and 14 females) was measured using ultrasound. Peak knee flexion moment (KFM), KFM impulse, peak knee adduction moment (KAM), and KAM impulse during walking were obtained at preferred speed. Pearson’s correlation coefficient and multiple regression analyses were performed at significance level of 0.05, and Cohen’s f2 values were calculated to examine the effect sizes of multiple regression. The hamstring-to-quadriceps muscle thickness ratio (r = 0.373) and semitendinosus echo intensity (r = − 0.371) were predictors of first peak KFM (R2 = 0.294, P = 0.009, f2 = 0.42), whereas only vastus medialis (VM) echo intensity was a significant predictor of second peak KFM ...
Biomechanics and Modeling in Mechanobiology, Nov 24, 2018
Damage to the acetabular labrum has been associated with cartilage degeneration. Because conventi... more Damage to the acetabular labrum has been associated with cartilage degeneration. Because conventional pressure measurement devices were unable to examine the sealing function of the acetabular labrum on cartilage contact mechanics, we used an image-based computational method to examine how labrectomy affects articular cartilage contact area and strain patterns in porcine hips. Cyclically loaded hip samples were continuously imaged in a CT scanner every 3 min to trace the positions of the femur and acetabulum. Image-based displacement-controlled finite element analysis was used to calculate articular cartilage contact area and nominal strain at different time points. No changes in cartilage contact area were found after labrectomy. Compared to the labrum intact condition, average nominal strain in labrectomized hips was elevated at early time points after load application. The areas of 'high' strain in labrectomized hips were found to be increased by approximately 7% after 30 min of cyclic loading, while the changes in the areas of 'low' strain were minimal. Our result showed that changes in articular cartilage strain following labrectomy were concentrated on locally overloaded areas where the degenerative process of articular cartilage may be initiated. Keywords Acetabular labrum • Articular cartilage • Biomechanics • Medical imaging • Hips • Osteoarthritis 1 Introduction Osteoarthritis of the hip is known to have various predisposing causes. One factor which may increase the risk of developing hip osteoarthritis is damage to the acetabular labrum. Various cadaveric and clinical studies have sug-Choongsoo S. Shin and Yongnam Song have equally contributed.
International Journal of Precision Engineering and Manufacturing, Dec 1, 2015
Military personnel suffer from musculoskeletal injuries during military operations and training. ... more Military personnel suffer from musculoskeletal injuries during military operations and training. Military training is often performed with military boots in challenging outdoor environments where the ground surface is not leveled. Thus, this study aimed to determine the hip, knee, and ankle joint kinematics and kinetics during valley-shaped slope walking (VSW). Eighteen Reserve Officer Training Corps cadets walked on a valley-shaped slope wearing military boots. Three-dimensional kinematic and kinetic data of the lower extremity were obtained using a force plate and motion capture system. Kinematics changed to control the lowered and raised body during VSW. Anterior-posterior ground reaction forces (GRF) and vertical GRF were significantly increased during VSW compared with that during level walking. Furthermore, compared with level walking, both the knee extension moment and ankle plantarflexion moment were significantly increased during VSW. Joint kinematics and kinetics changed in response to the shape of the ground surface. During VSW, the changes in the pattern and magnitude of the joint kinematics and kinetics demonstrated that different movement strategies are required to provide soldiers the necessary stability and mobility.
International Journal of Precision Engineering and Manufacturing, 2020
The movement pattern during stair descent differs by gender, and this difference may be associate... more The movement pattern during stair descent differs by gender, and this difference may be associated with gender differences in muscle strength or activation. The purpose of this study was to determine whether a gender difference in muscle activation exists by comparing the muscle activation amplitude and co-activation of lower extremity muscles during the stair-to-ground descent transition. Fifteen men and thirteen women descended stairs and the muscle activation was measured. Women showed a significantly lower peak normalized electromyography amplitude of the vastus lateralis (women: 171.7% peak EMG activation amplitude for level walking (PEALW), men: 297.0%PEALW, p < 0.05). Additionally, women showed significantly elevated co-activation of the vastus lateralis and biceps femoris compared to men (p < 0.05). The lower amplitude of the vastus lateralis in women indicates lower recruitment of knee extensor. In conclusion, the significantly higher co-activation of the vastus later...
Journal of Mechanical Science and Technology, 2016
We investigated 3D kinematic and kinetic changes of knee and ankle during downhill walking as the... more We investigated 3D kinematic and kinetic changes of knee and ankle during downhill walking as the slope angle increased and evaluated biomechanical injury risk factors related to non-contact ACL injury. Fifteen male subjects performed level walking and 15° and 25° downhill walking. For the kinetic and kinematic parameters, one-way ANOVA and post-hoc tests were performed at a significance level of 0.05. This study revealed significant differences in 3D knee and ankle kinematics and kinetics among 0°, 15° and 25° downhill walking. The peak posterior ground reaction force, the peak knee anterior force and the knee valgus moment (0° vs. 15°: p < 0.05; 0° vs. 25°: p < 0.05) in the early stance phase increased as the slope angle increased. The peak knee internal tibial rotation moments in the late stance also increased (0° vs. 15°: p < 0.05; 0° vs. 25°: p < 0.05; 15° and 25°: p < 0.05) as the slope angle increased. These results showed the risk for ACL injuries may be increased during downhill walking with a greater slope angle.
Background: Muscle thickness can influence the joint kinematics and/or kinetics during dynamic ac... more Background: Muscle thickness can influence the joint kinematics and/or kinetics during dynamic activities. The relationship between the muscle thickness of individual quadriceps and hamstrings or medial-to-lateral thigh muscle thickness ratio and the knee kinematics/kinetics with respect to anterior cruciate ligament (ACL) injury risk remains unclear. Hypothesis: Higher medial-to-lateral thigh muscle thickness ratio would be associated with lower knee valgus angle/moment and lower tibial internal rotation angle/moment during single-leg landing. Study Design: Cross-sectional. Level of Evidence: Level 4. Methods: Muscle thickness of the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) of 30 healthy participants (16 males and 14 females) were measured using ultrasound. Knee joint kinematics and kinetics during single-leg landing were obtained. Stepwise multiple regression analysis, a follow-up Fisher’s r to z test to examine the sex as a moderat...
The purpose of this study was to examine whether there is a sex difference in the effect of ankle... more The purpose of this study was to examine whether there is a sex difference in the effect of ankle plantar flexion at the contact angle, ankle range of motion (ROM), and ankle plantar flexion moment on knee valgus loading during single-leg landing. Twenty-five females and twenty-four males performed a single-leg landing. Joint kinematics and kinetics of the lower extremities were measured. Correlation coefficients were used to assess the relationship between ankle biomechanics in the sagittal plane (ankle plantar flexion angle at contact, ROM, and peak ankle plantar flexion moment) and peak knee valgus moment. In males, the larger ankle plantarflexion angle at contact and ROM were significantly associated with lower peak knee valgus moment (r = − 0.46, p < 0.05; and r = − 0.42, p < 0.05). In addition, in males only, a greater peak ankle plantar flexion moment was significantly associated with a lower peak knee valgus moment (r = − 0.83, p < 0.001) and greater peak ankle inve...
The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculosk... more The purposes of this study were to develop a cruciate-retaining total knee arthroplasty musculoskeletal model, which enables the adjustment of ligament length and implant alignment; validate the model; and evaluate the effects of varus/valgus alignment adjustment and unbalanced medial/lateral ligament laxity during gait. A cruciate-retaining total knee arthroplasty musculoskeletal model was constructed and validated against the in vivo contact forces. This model was transformed to 2° varus/valgus alignment of femoral or tibial replacement models and 2° medial/lateral laxity models. The contact forces and ligament tensions of the adjusted models were calculated. The contact forces in the model showed good agreement with the in vivo contact forces. Valgus replacement alignment with balanced ligament models showed a lower contact force at the medial compartment than at the neutral alignment model, whereas the varus replacement alignment with balanced ligament models showed a greater co...
The metatarsophalangeal (MTP) joint is not considered in most current walking assistive devices e... more The metatarsophalangeal (MTP) joint is not considered in most current walking assistive devices even though it plays an important role during walking. The purpose of this study was to develop a new MTP assistive device and investigate its effectiveness on the muscle activities of the lower extremities during walking while wearing the device. The MTP assistive device is designed to support MTP flexion by transmitting force through a cable that runs parallel with the plantar fascia. Eight participants were instructed to walk at a constant speed on a treadmill while wearing the device. The muscle activities of their lower extremities and MTP joint kinematics were obtained during walking under both actuated and non-actuated conditions. Paired t-tests were performed to compare the differences in each dependent variable between the two conditions. The muscle activity of the MTP flexor was significantly reduced during walking under actuated conditions (p = 0.013), whereas no differences we...
The purpose of this study was to investigate the effect of load carriage on the kinematics and ki... more The purpose of this study was to investigate the effect of load carriage on the kinematics and kinetics of the ankle and knee joints during uphill walking, including joint work, range of motion (ROM), and stance time. Fourteen males walked at a self-selected speed on an uphill (15°) slope wearing military boots and carrying a rifle in hand without a backpack (control condition) and with a backpack. The results showed that the stance time significantly decreased with backpack carriage (p<.05). The mediolateral impulse significantly increased with backpack carriage (p<.05). In the ankle joints, the inversion-eversion, and dorsi-plantar flexion ROM in the ankle joints increased with backpack carriage (p<.05). The greater dorsi-plantar flexion ROM with backpack carriage suggested one strategy for obtaining high plantar flexor power during uphill walking. The result of the increased mediolateral impulse and inversion-eversion ROM in the ankle joints indicated an increase in body...
International Journal of Precision Engineering and Manufacturing
Upslope-walking is more challenging and therefore has a greater fall risk than level-walking. The... more Upslope-walking is more challenging and therefore has a greater fall risk than level-walking. The current study aimed to investigate the difference in control strategy for stability between level and upslope walking using the center of pressure (COP) and the ratio of three sub-phases in stance phase (loading-response, mid-stance and push-off). Two hypotheses were tested: the excursion, range, and speed of the COP increases in the mediolateral and anteroposterior directions with slope grade; and the duration of the midstance phase increases with slope grade. Eleven male subjects walked on a level (0°) surface and upslope at 15° and 25°. The duration of the mid-stance phase was significantly greater in the 25° upslope-walking condition than that in the level and 15° upslope-walking conditions (both p<0.05). This result implies that the subjects adopted a different control strategy when walking upslope at 25° than when walking level and upslope at 15°. The range and speed of the mediolateral COP were larger in the 25° upslope-walking condition than those in the level and 15° upslope-walking conditions (p<0.05). This result indicates that a change in control strategy during upslope-walking at 25° can improve mediolateral stability. These findings imply that a transition grade exists between 15° and 25° where one can alter their control strategy to improve stability during upslope-walking.
Uploads
Papers by Choongsoo Shin