• Journal of the Ergonomics Society of Korea
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• v.36 no.5
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• pp.395-409
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• 2017

Objective: The purpose of this study was to optimize the number and positions of foot pressure sensors using the reliability analysis of the center of pressure (COP) in smart shoes. Background: Foot pressure can be different according to foot region, and it is important which region of the foot pressure needs to be measured. Method: Thirty adults (age: $20.5{\pm}1.8years$, body weight: $71.4{\pm}6.5kg$, height: $1.76{\pm}0.04m$) participated in this study. The foot pressure data were collected using the insole of Pedar-X system (Novel GmbH, USA) with a sampling frequency of 100Hz during 1.3m/s speed walking on the treadmill (Instrumented treadmill, Bertec, USA). The intraclass correlation coefficients (ICC) were calculated between the COP positions using 4, 5, 6, 7, 8, and 99 sensors, while one-way repeated measure ANOVA was performed between the standard deviation (SD) of the COP positions. Results: The medio-lateral (M/L) COP position using 99 sensors was positively correlated with the M/L COP positions using 6, 7, and 8 sensors; however, it was not correlated with the M/L COP positions using 4 and 5 sensors during landing phase (1~4%) (p<.05). The antero-posterior (A/P) COP position using 99 sensors was positively correlated with the A/P COP positions using 4, 5, 6, 7, and 8 sensors (p<.05). The SD of the COP position using 99 sensors was smaller than the SD of the M/L COP positions using 4, 5, 6, 7, and 8 sensors (p<.05). Conclusion: Based on our findings, it is desirable to arrange at least 6 sensors in smart shoes. Application: The study of optimizing the number and positions of foot pressure sensors would contribute to developing more effective smart shoes using foot pressure technology.

• Physical Therapy Korea
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• v.8 no.2
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• pp.73-85
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• 2001

The purpose of this study was to investigate whether the standing balance could be influenced by the different foot positions. Seventeen patients with hemiplegia were tested for the static and dynamic balance under the different foot positions. In the balance test, subject stood by bearing weight on one foot, and the other foot was positioned in three different positions (symmetric, $45^{\circ}$ anterolateral, and anterior position). This study used the Kinesthetic ability trainer (KAT2000) to measure the standing balance. The results were as follows: 1) There were significant differences in the static standing balance in different foot positions with both weight-bearing on the paretic limb and on the nonparetic limb (p<.05). 2) There were also significant differences in the dynamic standing balance in different foot positions with both weight-bearing on the paretic limb and on the nonparetic limb (p<.05). 3) There was a significant difference when the paretic weight-bearing and the nonparetic weight-bearing were compared (p<.01). 4) when the paretic weight-bearing and the nonparetic weight-bearing were compared, anterior foot position showed a significant difference in the dynamic standing balance (p<.05), but $45^{\circ}$ anterolateral foot position did not show a significant difference (p>.05). In this study, the standing balance showed a significant difference according to different foot positions in hemiparetic patients, and standing balance was better when they stood by bearing weight on the nonparetic limb. These results indicate that it is a necessary to consider both weight-bearing limb and foot position not only in the rehabilitation program but also in achieving the stability in the independent life.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.84-94
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• 2018

The purpose of this study was to compare the balance ability at different foot positions using K A T 2000 (Berg, Inc, vista, CA.1994). Thirty (male 15, female 15) normal subjects participated in this study. All subjects were tested at a one leg position or a two leg position that were toe-in $25^{\circ}$, toe-out $25^{\circ}$, and $45^{\circ}$. The starting position was where the subject crossed their arms across the chest and flexed knees slightily. The results of each test were displayed on a screen in a score format, which indicated balance index. These collected data were analyzed by using one way ANOVA, and t-test. The results of this study were as follows: When changing the angle of the foot in the one-foot and two-foot standing positions, there was no statistically significant difference, but the balance performance with the foot rotated by $25^{\circ}$ was better than that with the foot rotated by $45^{\circ}$. When changing the direction of the foot in the one-foot and two-foot standing positions, there was no statistically significant difference, but the balance performance with the foot rotated laterally was better - except for the case when the foot was medially rotated by $25^{\circ}$ in the right-foot static standing position. When the feet were medially rotated by $25^{\circ}$ in the two-foot static standing position, and were medially rotated by $25^{\circ}$ and $45^{\circ}$ in the one-foot static standing position, the balance performance of females was better than that of males. In this study, it was found that the balance performance of the subjects changed when the position of the foot was shifted on an unstable base of support. However, there was little correlation between balance performance and the height, weight and foot length of the subjects. It is necessary to conduct a follow-up study targeting various age groups and those with various diseases using an unstable platform or applying different physical or visual conditions, such as the length of the legs. Physical therapists need to consider the position of the foot in clinical settings for a better balance training or assessment.

• 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.

• Physical Therapy Korea
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• v.8 no.2
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• pp.1-16
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• 2001

This study was designed to identify the effects of foot position on electromyographic (EMG) activity of the quadriceps femoris during maximum voluntary contraction (MVC) in standing. Twenty young adults who had not experienced any knee injuries were recruited. Their Q-angles were within a normal range. They were asked to stand in five different foot positions ($40^{\circ}$ externally rotated, $30^{\circ}$ internally rotated, neutral, $20^{\circ}$ plantarflexed, and $10^{\circ}$ dorsiflexed foot position). The EMG activities of the vastus lateralis (VL), rectus femoris (RF), and vastus medialis oblique (VMO) were recorded in standing by surface electrodes and normalized by MVC EMG values derived from manual muscle test. The normalized EMG activity levels (%MVC EMG) of muscles in the five foot positions were compared using repeated measures ANOVA. The EMG activity levels of the VL, RF, and VMO were the highest when foot was externally rotated. The EMG activity levels of the VL and RF were significantly different among the foot positions (p<.05). However, EMG activity levels of the VL, RF, VMO, and VMO/VL ratio did not show significant differences in each foot position (p> .05). The results suggest that the quadriceps femoris may be effectively activated by performing MVC at an externally rotated foot position. Therefore, the externally rotated foot position can be considered as an effective foot position for quadriceps femoris strengthening exercise. Further studies are needed to identify whether there are differences in the effects of foot position on muscle strength after MVC exercise of quadriceps femoris in standing.

• The Journal of Korean Physical Therapy
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• v.31 no.2
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• pp.76-81
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• 2019

Purpose: This study examined the effects of squatting with different foot positions on the muscle activation of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles in subjects with genu varum. Methods: Thirty four subjects participated in this study. Surface electromyography was used to measure the muscle activation of the VMO and VL muscles at the knee angles ($15^{\circ}$, $60^{\circ}$) at three foot positions (internal rotation, neutral position, external rotation) during squatting. Results: Muscle activation differences at different knee angles and foot positions differed significantly between the VMO and VL muscles in both the varus and normal groups. In addition, there was a significant difference according to the knee angles with the foot in external rotation in the VMO and VL ratio. In the varus group, however, the VMO and VL ratio were significantly different only with the feet in internal rotation. In the muscle activation changes of the knee angle differences in the foot position, there was no significant difference in the varus group, but both the VMO and VL muscles were significant different in the normal group. Conclusion: In both groups, regardless of the foot position, muscle activation of the VMO and VL muscles increased with increasing knee flexion angle. In the normal group, when squatting with the feet in external rotation, the VMO and VL muscles activations increased with increasing knee angle. In the varus group, however, the foot position did not affect the VMO or VL muscle activation. This study shows that subjects with genu varum and normal subjects have different VMO and VL muscle activation patterns during squat exercises.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.11
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• pp.1053-1059
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• 2013

Heading bias effects in PNS using IMUs attached to shoes are analyzed in this paper. The navigation algorithms of a single foot PNS where one IMU is attached to a foot and dual foot PNSs where two IMUs are attached to each foot are derived. Two navigation algorithms are proposed for the dual foot PNS: 1) the positions from the independent right and left foot PNSs are averaged to provide the final position, 2) the right and left foot PNSs are correlated and it provides positions of each foot. Furthermore, it is proven that two methods are equal. Using the derived navigation algorithms the effect of heading bias caused by a misalignment of the moving direction and IMU is analyzed. The analysis explains the position error of a single foot PNS is diverged while the heading bias is effectively compensated in dual foot PNSs because of the symmetry of heading biases. The experimental results confirm the analysis.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.4
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• pp.55-65
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• 2021

PURPOSE: This study compared the effects of sit-to-stand training with various foot positions combined with visual feedback on the postural alignment and balance. METHODS: Thirty stroke patients were assigned randomly into three groups of standing with a symmetrical foot position (SSF) (n = 10), asymmetrical foot position with the affected foot at the rear (SAF) (n = 10), and visual feedback and asymmetrical foot position (SVAF) (n = 10). Sit-to-stand training with different foot positions was performed for 30 minutes a day, five times a week, for a total of four weeks, and the effects on postural alignment and balance were assessed. RESULTS: The angle between the midline and scapula peak of the affected side was decreased significantly at sitting and thigh-off in the SAF group and at sitting, thigh-off, and standing in the SVAF group (p < .05). The angle between the midline and scapula peak of the non-affected side was increased significantly at sitting and thigh-off in the SAF group and at sitting, thigh-off, and standing in the SVAF group, the difference in the angle between the scapular peaks of the left and right sides was decreased significantly at sitting and thigh-off in SSF group, and at sitting in SAF group (p < .05). In the SVAF group, the angle at sitting, thigh-off, and standing was decreased significantly (p < .05). A comparison of the balance ability showed that BSS in the SVAF group was improved significantly (p < .05). CONCLUSION: Based on these results, the postural alignment and balance ability were improved in stroke patients who participated in sit-to-stand with visual feedback and asymmetrical foot position training.

• PNF and Movement
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• v.20 no.1
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• pp.115-123
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• 2022

Purpose: The aim of this study was to investigate the effects of sit-to-stand training with various foot positions combined with visual feedback on muscle onset time and balance in stroke patients. Methods: Thirty stroke patients were randomly assigned into three standing groups: one with a symmetrical foot position (SSF; n = 10), one with an asymmetrical foot position with the affected foot at the rear (SAF; n = 10), and one with visual feedback and an asymmetrical foot position (SVAF; n = 10). Sit-to-stand training with different foot positions was performed for 30 minutes a day, 5 times a week, for a total of 4 weeks. The effects on muscle onset time and balance were assessed. Results: In a comparison of the onset time of muscle contraction, the onset time of the affected side tibialis anterior and less-affected side gastrocnemius muscle and tibialis anterior was significantly shortened in the SAVF group. And onset time of the less-affected side tibialis anterior was shortened in the SAF group. There was a significant difference in the result of functional reach testing in the SVAF group. Conclusion: VRG was effective in improving muscle activity and balance in elderly women aged 65 and older. In this study, sit-to-stand training with visual feedback and asymmetrical foot position showed significant functional improvement.

• Physical Therapy Korea
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• v.31 no.1
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• pp.63-71
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• 2024

Background: Individuals with pes planus tend to overuse the extrinsic foot muscles, such as the tibialis anterior (TA) and peroneus longus (PL), to compensate for the weakened intrinsic foot muscles, such as the abductor hallucis (AbdH). Furthermore, differences in weight-bearing can affect the activity of muscles in both the intrinsic and extrinsic foot muscles. To date, no study has compared the effects of the short foot exercise (SFE) and toe spread-out exercise (TSO) on intrinsic and extrinsic foot muscle activity and the corresponding ratios in different weight-bearing positions. Objects: To compare the effects of the SFE and TSO on AbdH, TA, and PL activity and the AbdH/TA and AbdH/PL activity ratios in the sitting and standing positions in individuals with pes planus. Methods: Twenty participants with pes planus were recruited. Surface electromyography was used to assess the amplitudes of AbdH, TA, and PL activity. Participants performed both exercises while adopting both the sitting and standing positions. Results: No significant interaction between exercise and position was found regarding the activity of any muscle or ratio of the activity, except for PL activity. We observed a significant increase in AbdH activity during the TSO compared to the SFE, and no significant difference in TA and PL activity between the two exercises. AbdH, TA, and PL activity were significantly higher in the standing position than in the sitting position. Furthermore, the AbdH/PL activity ratio significantly increased in the sitting position, although there was a significant increase in AbdH activity in the standing position. Conclusion: In individuals with pes planus, we recommend performing the TSO in the sitting position, which may increase the activity of the AbdH while concurrently decreasing the activity of the TA and PL, thus strengthening the AbdH.