• The Journal of Korean Physical Therapy
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• v.21 no.2
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• pp.97-101
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• 2009

Purpose: This study examined how the direction of carrying a load affects the foot stability and kinesiology while walking. Methods: The heel rotation, Hallux stiffness, foot balance, metatarsal load, toe out angle, subtalar joint flexibility were measured in 40 adults (men and women) who carried a load back and forth, walking on a 2-meter-long board. The measurement was carried out three times and the mean of the measurements was used to compare the difference between the front, back and the condition without a load. Results: While walking, heel rotation and hallux stiffness occurred most when a front load was applied compared to a back load or no load condition (p<0.05). A metatarsal load also appeared to be the highest with the frond load, but there was no significant difference in the balance of the whole foot. Both the toe out angle and subtalar joint flexibility appeared to increase significantly (p<0.05). Conclusion: Applying the front load causes subtalar joint instability and increases the plantar foot pressure imbalance during walking.

• Korean Journal of Applied Biomechanics
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• v.19 no.4
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• pp.663-669
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• 2009

The purpose of this study was to investigate the functional role of foot effectiveness when humans execute running turn maneuvers. Foot rotation angle at the starting turn and body angle at the vertical axis were analyzed through three-dimensional image analysis and ground reaction force analysis. Then, we created a simple equation: foot effectiveness = total foot rotation angle/total body rotation angle at the vertical axis. This equation made it possible to explain the dynamics of angular running turns. We analyzed data from running turns(0, 30, and 60) at average initial running velocities of 4.5, as well as rotations around the vertical axis during the running turns. As a result, the stance time, foot placement, and left and right force increased.

• Journal of muscle and joint health
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• v.17 no.2
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• pp.142-150
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• 2010

Purpose: The purpose of this study was to examine EMG activities and VMO/VL ratio of the vastus medialis oblique, vastus lateralis, and rectus femoris during squat exercise (knee angle: 15, 45, and 60 degrees; tibial rotation: internal rotation, neutral, and external rotation). Methods: Twelve subjects performed squat exercise at each knee angle and tibial rotation while electromyographic (EMG) activity was collected. Statistical analysis consisted of two-way repeated measures analysis of variance with post hoc analysis. Results: There were significant main effects of knee angles and foot positions and interaction effect on EMG activities of vastus medialis oblique and vastus lateralis. VMO/VL ratios were significantly different by tibial rotations and there was an interaction effect. A neutral position produced significantly more VMO/VL activity ratio than that from internally rotated position and externally rotated position at 60 degrees. Conclusion: Considering the interaction effects for EMG activity across quadriceps muscles tested, the 60 degrees knee angle with a neutral foot position may provide the most effective condition for patients with acute patellofemoral syndrome.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.143-149
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• 2018

Objective: This study aimed to investigate the influence of landing foot orientations on biomechanics of knee joint in order to identify vulnerable positions to non-contact knee injuries during single-legged landing. Method: Seventeen men (age: $20.5{\pm}1.1 years$, height: $175.2{\pm}6.4cm$, weight: $68.8{\pm}5.8kg$) performed single-leg drop landings repeatedly with three different landing foot orientations. They were defined as toe-in (TI) $30^{\circ}$ adduction, neutral (N, neutral), and toe-out (TO) $30^{\circ}$ abduction positions. Results: The downward phase time of TI was significantly shorter than those of N and TO. The flexion and valgus angle of N was greater than those of TI and TO at the moment of foot contact. At the instance of maximum knee flexion, N showed the largest flexion angle, and TO position had the largest varus and external rotation angles. Regarding ground reaction force (GRF) at the moment of foot contact, TO showed the forward GRF, while others showed the backward GRF. TI indicated significantly larger mediolateral GRF than others. As for the maximum knee joint force and joint moment, the main effect of different foot positions was not significant. Conclusion: TI and TO might be vulnerable positions to knee injuries because both conditions might induce combined loadings to knee joint. TI had the highest mediolateral GRF with a shortest foot contact time, and TO had induced a large external rotation angle during downward phase and the peak forward GRF at the moment of foot contact. Conclusively, N is the preferred landing foot orientation to prevent non-contact knee injuries.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.6 no.1
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• pp.69-79
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• 2008

In this paper, the effects of the external-rotation exercise on the gait of hemiplegia was investigated. 26 patients with hemiplegia due to cerebrovascular accident participated in this study. Subjects were randomly assigned to experimental group(n=12) and control one(n=14). 12 subjects of the experimental group were received the external rotation reducing exercise on the mat with seating and supine posture after the general therapeutic exercise for hemiplegia. 14 subjects of the control group were received only general therapeutic exercise. The effects of external rotation reducing exercise were evaluated by measurements of gait velocity, cadence, stride length, step length and foot angle using ink-foot prints. The collected data were analyzed statistically based on Wilcoxon, Mann-Whitney and correlation analysis. After treatment of three weeks, it turned out that external rotation reducing exercise has the significant effect on foot angle(p<0.01). However the exercise has no statistically significant direct effect on the gait velocity, cadence, stride length and step length.

• Journal of The Korean Society of Integrative Medicine
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• v.5 no.4
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• pp.41-48
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• 2017

Purpose : The purpose of this study was to verify the relationships among the knee adduction moment, hip rotation range, strength of hip rotators, and Foot Posture Index of healthy young adults. Method : Thirty-two healthy adults(24 male, 8 females) participated in this study. Subjects performed 5 walking trials to evaluate the knee adduction moments using a three-dimensional motion analysis system. Hip rotation ranges and hip rotator strengths were measured using a standard goniometer and a handheld dynamometer, respectively. The mean of three trials of clinical tests was used for data analysis. Results : The first peak knee adduction moment was significantly correlated with the hip rotation ranges and hip rotator strengths (P<.05). The second peak knee adduction moment was showed significant correlations with hip external rotation and rotation ratio. There were no correlations between Foot Posture Index and all knee adduction moments (P>.05). Conclusion : This study suggests that imbalances of the range of motion and strength of the internal and external rotation of the hip joint can affect knee adduction moments. The impact may exacerbate musculoskeletal disorders such as osteoarthritis of the knee. Therefore, further studies should be conducted to evaluate the effects of clinical interventions to correct these imbalances on the reduction of the knee adduction moments in patients with knee osteoarthritis.

• Korean Journal of Applied Biomechanics
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• v.29 no.2
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• pp.61-70
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• 2019

Objective: This study aimed to investigate the characteristics of the declination of the subtalar joint rotation axis and the structural features of the ankle joint complex such as rear-foot angle alignment and ligament laxity test between chronic ankle instability (CAI) patients and healthy control. Method: A total of 76 subjects and CAI group (N=38, age: $23.11{\pm}7.63yrs$, height: $165.67{\pm}9.54cm$, weight: $60.13{\pm}11.71kg$) and healthy control (N=38, age: $23.55{\pm}7.03yrs$, height: $167.92{\pm}9.22cm$, weight: $64.58{\pm}13.40kg$) participated in this study. Results: The declination of the subtalar joint rotation axis of the CAI group was statistically different from healthy control in both sagittal slope and transverse slope. The rear-foot angle of CAI group was different from a healthy control. Compared to healthy control, they had the structure of rear-foot varus that could have a high occurrence rate of ankle varus sprain. CAI group had loose ATFL and CFL compared to the healthy control. Conclusion: The results of this study showed that the deviation of the subtalar joint rotation axis and the structural features of the ankle joint complex were different between the CAI group and the healthy control and this difference is a meaningful factor in the occurrence of lateral ankle sprains.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.162.2-162
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• 2001

This paper presents the stability analysis of a biped robot IWR-III. We use a foot-rotation indicator(FRI) concept to reveal the degree of stability. The foot rotation can be a barometer of postural instability, which should be carefully treated in implementing a dynamically stable walk and avoided altogether in performing a statically stable walk. The conventionally mentioned zero moment point(ZMP) criterion may not be sufficient to express the stability of a biped robot. ZMP equation needs an assumption that the supporting foot is fixed firmly to the ground during the walking. Therefore, applying the FRI concept is more desirable when a biped robot is falling down ...

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.149-163
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• 2006

The purpose of this study was to compare the lower extremity's joint and segment coupling patterns between forward and backward running in subjects who were twelve healthy males. Three-dimensional kinematic data were collected with Qualisys system while subjects ran to forward and backward. The thigh internal/external rotation and tibia internal/external rotation, thigh flexion/extension and tibia flexion/extension, tibia internal/external rotation and foot inversion/eversion, knee internal/external rotation and ankle inversion/eversion, knee flexion/extension and ankle inversion/eversion, knee flexion/extension and ankle flexion/extension, and knee flexion/extension and tibia internal/external rotation coupling patterns were determined using a vector coding technique. The comparison for each coupling between forward and backward running were conducted using a dependent, two-tailed t-test at a significant level of .05 for the mean of each of five stride regions, midstance(1l-30%), toe-off(31-50%), swing acceleration(51-70%), swing deceleration(71-90), and heel-strike(91-10%), respectively. 1. The knee flexion/extension and ankle flexion/extension coupling pattern of both foreward and backward running over the stride was converged on a complete coordination. However, the ankle flexion/extension to knee flexion/extension was relatively greater at heel-strike in backward running compared with forward running. At the swing deceleration, backward running was dominantly led by the ankle flexion/extension, but forward running done by the knee flexion/extension. 2. The knee flexion/extension and ankle inversion/eversion coupling pattern for both running was also converged on a complete coordination. At the mid-stance. the ankle movement in the frontal plane was large during forward running, but the knee movement in the sagital plane was large during backward running and vice versa at the swing deceleration. 3. The knee flexion/extension and tibia internal/external rotation coupling while forward and backward run was also centered on the angle of 45 degrees, which indicate a complete coordination. However, tibia internal/external rotation dominated the knee flexion/extension at heel strike phase in forward running and vice versa in backward running. It was diametrically opposed to the swing deceleration for each running. 4. Both running was governed by the ankle movement in the frontal plane across the stride cycle within the knee internal/external rotation and tibia internal/external rotation. The knee internal/external rotation of backward running was greater than that of forward running at the swing deceleration. 5. The tibia internal/external rotation in coupling between the tibia internal/external rotation and foot inversion/eversion was relatively great compared with the foot inversion/eversion over a stride for both running. At heel strike, the tibia internal/external rotation of backward running was shown greater than that of forward(p<.05). 6. The thigh internal/external rotation took the lead for both running in the thigh internal/external rotation and tibia internal/external rotation coupling. In comparison of phase, the thigh internal/external rotation movement at the swing acceleration phase in backward running worked greater in comparison with forward running(p<.05). However, it was greater at the swing deceleration in forward running(p<.05). 7. With the exception of the swing deceleration phase in forward running, the tibia flexion/extension surpassed the thigh flexion/extension across the stride cycle in both running. Analysis of the specific stride phases revealed the forward running had greater tibia flexion/extension movement at the heel strike than backward running(p<.05). In addition, the thigh flexion/extension and tibia flexion/extension coupling displayed almost coordination at the heel strike phase in backward running. On the other hand the thigh flexion/extension of forward running at the swing deceleration phase was greater than the tibia flexion/extension, but it was opposite from backward running. In summary, coupling which were the knee flexion/extension and ankle flexion/extension, the knee flexion/extension and ankle inversion/eversion, the knee internal/external rotation and ankle inversion/eversion, the tibia internal/external rotation and foot inversion/eversion, the thigh internal/external rotation and tibia internal/external rotation, and the thigh flexion/extension and tibia flexion/extension patterns were most similar across the strike cycle in both running, but it showed that coupling patterns in the specific stride phases were different from average point of view between two running types.

• Physical Therapy Korea
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• v.25 no.4
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• pp.19-26
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• 2018

Background: Alignment of the lower limb is an important factor, influencing balance and gait in kinematics and kinetics, in patients with and without a flat arched foot. Flat arched foot are associated with the range of motion (ROM) of the hip and alignments of the knee joints, is strongly influenced. Objects: The purpose of this research was to investigate the relationship between hip joint ROM and quadriceps angle (Q-angle), by dividing them into two groups according to the presence or absence of flat feet, using a navicular drop test (NDT) and resting calcaneal stance position (RCSP). Methods: Forty elderly patients were allocated to the experimental group (flat foot group, n1=20) or the control group (non-flat group, n2=20). Universal and digital goniometer, tractograph and tape measure were used to determine the related changes in the hip ROM, Q-angle, NDT and RCSP. Results: Data were analyzed using the Pearson correlation coefficients. Active internal ROM of the hip joint (right, r=.803, p<.001), (left, r=.951, p<.001) were highly correlated with NDT, and also, was moderately correlated with Q-angle (right, r=.562, p=.019), (left, r=.757, p<.001). Passive internal ROM of the hip joint (right, r=.742, p=.001), (left, r=.922, p<.001) were highly correlated with NDT, and also, was moderately correlated with RCSP (right, r=-.530, p=.029) and with Q-angle (right, r=.710, p=.001), (left, r=.698, p=.002) in the flat foot group. However, no strong correlation among the hip ROM, NDT, RCSP and Q-angle were found in the non-flat foot group. Conclusion: This research may provide evidence of the correlations between hip internal ROM and flat foot.