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Lumbar stabilization exercises (LSE) lead to high levels of erector spinae muscle (ESM) activation, which has a positive effect on improving physical function. The purpose of this study is to identify factors explaining changes in muscle strength after 7 weeks of LSE and to evaluate changes in stiffness and contraction of the ESM. All participants (male: n = 42, age = 28.26 ± 10.97) were assessed for 60°/s isokinetic extensor muscle strength and tension using a tensiomyography (TMG) and isokinetic device before and after LSE. Maximum displacement (Dm) and average velocity up to 90% Dm (Vc 90) were significantly different before and after LSE. Additionally, participants' 60°/s isokinetic extensor strength was significantly higher after exercise. A regression analysis was conducted to test the explanatory power of the variables, and positive results were obtained in the increase in extensor strength before and after Vc 90 and LSE. Furthermore, statistical significance was set at p < 0.05. After LSE, the increase in 60°/s isokinetic extensor strength and ESM's Dm and Vc 90 can be interpreted as positive changes post-exercise in endurance muscles with a higher percentage of type I fibers. Our results can contribute to predicting the long-term exercise effect in sedentary workers and developing an individualized strategic exercise program.

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Background: This study investigated the effects of lower limb movements on dynamic postural stability (DPS) during drop landing in adult women with patellofemoral pain syndrome (PFPS). Methods: Thirty-eight adult women were recruited and divided into two groups, the PFPS group and the control group. The study participants performed a single-leg drop landing from a 30 cm box, and their lower limb movements and DPS were measured. Differences between groups were examined using independent sample t-tests. In addition, stepwise multiple linear regression was used to examine the kinematic parameters that contribute to the DPS. Results: The PFPS group had significantly lower hip flexion, internal rotation, knee flexion, ankle external rotation, pelvic oblique, tilt, rotation, and higher hip abduction, knee valgus, and ankle plantarflexion. In terms of DPS, the PFPS group had a significantly higher anteroposterior and a lower mediolateral than that of the control group. In the control group, regression analysis revealed a controlled anteroposterior using knee flexion, while the PFPS group controlled mediolateral through ankle plantarflexion. Conclusions: Patients with PFPS experienced more shock on their knee joint during landing than patients in the control group with greater anteroposterior instability and lower mediolateral instability.

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Purpose: Individuals with mechanical ankle instability (MAI) and functional ankle instability (FAI) present with residual movement dysfunctions after an initial lateral ankle sprain. This study investigated leg stiffness control to determine how behavioural characteristics between MAI and FAI differ during single-leg drop landing movement. Methods: Thirty individuals (10 with MAI, 10 with FAI, and 10 healthy controls) participated in this study. During single-leg drop landing movement, we estimated dimensionless leg stiffness, peak vertical force (PVF), change in the displacement of leg movement, loading rate, angular joint movement, and internal joint moment for impaired and unimpaired legs, respectively. Univariate one-way analysis of variance was used for each dependent variable across leg conditions. Results: The MAI group had lower dimensionless leg stiffness with greater change in the displacement of leg movement for the impaired leg than the FAI and control groups. Moreover, reduced leg stiffness was associated with greater hip joint flexion movement in the MAI group, whereas ankle dorsiflexion movement increased to decrease the leg stiffness in the FAI and control groups. Conclusion: These findings indicate that lower leg stiffness in the MAI group than in the FAI group may be attributed to compensatory actions to minimise reliance on their ankle movement after landing.

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This study investigated continuous visuomotor tracking capabilities between athletes and non-athlete controls using isometric force control paradigm. Nine female athletes and nine female age-matched controls performed unilateral hand-grip force control tasks with their dominant and non-dominant hands at 10% and 40% of maximal voluntary contraction (MVC), respectively. Three conventional outcome measures on force control capabilities included mean force, force accuracy, and force variability, and we additionally calculated two nonlinear dynamics variables including force regularity using sample entropy and force stability using maximal Lyapunov exponent. Finally, we performed correlation analyses to determine the relationship between nonlinear dynamics variables and conventional measures for each group. The findings indicated that force control capabilities as indicated by three conventional measures were not significantly different between athlete and non-athlete control groups. However, the athletes revealed less force regularity and greater force stability across hand conditions and targeted force levels than those in non-athlete controls. The correlation analyses found that increased force regularity (i.e., less sample entropy values) at 10% of MVC and decreased force regularity (i.e., greater sample entropy values) at 40% of MVC were significantly related to improved force accuracy and variability for the athlete group, and these patterns were not observed in the non-athlete control group. These findings suggested that the athletes may use different adaptive force control strategies as indicated by nonlinear dynamics tools.

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BACKGROUND: The prevalence of idiopathic scoliosis is rapidly increasing in Korean children, but research on the disorder is limited compared to that in other countries. Accordingly, in the present study, we aimed to investigate the relationship between idiopathic scoliosis and body mass index (BMI) levels in Korean children. METHODS: This cross-sectional study enrolled elementary school students and middle school first graders in the Capital Area in Korea. The participants underwent body composition measurements and screening for idiopathic scoliosis. Idiopathic scoliosis was defined as a Cobb angle of ≥10°. The students were classified into three groups-the severely underweight (SUW: BMI < 16 kg/m2) group, the underweight group (UW: 16 ≤ BMI < 18.5 kg/m2), and the normal weight group (NW: 18.5 ≤ BMI < 25 kg/m2) to compare the risk of idiopathic scoliosis across BMI levels. RESULTS: The final cohort comprised 1375 participants. The odds ratio (OR) of idiopathic scoliosis was 0.69 (95% confidence interval (CI): 0.50-0.94) and 0.66 (95% CI: 0.49-0.89) for the UW and the NW groups, respectively, with the SUW group as the reference. This shows that the risk decreased significantly by 31% and 34% in the UW and the NW groups, respectively. After controlling for age and sex, the corresponding ORs were 0.72 (95% CI: 0.52-0.98) and 0.70 (95% CI: 0.51-0.96), and the risk significantly decreased by 28% and 30% in the UW and the NW groups, respectively. CONCLUSIONS: Low body weight is closely associated with spinal deformity and idiopathic scoliosis.

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Hallux valgus (HV), which is mainly caused by the wearing of narrow-width and high-heeled shoes, disrupts gait behavior because it deforms lower limb joints. There is limited information regarding the relationship between the foot disease HV and lower limb joints. Previous studies evaluating abnormal gait patterns caused by deformity used spatiotemporal parameters; however, they failed to characterize the overall gait dynamics. To address this issue, this study is aimed at characterizing the gait stability of patients with HV and examining the joints that are critically affected by HV. To assess complex gait dynamics, we quantified the potential changes in gait stability by using the maximum Lyapunov exponent (MLE). Angular displacements of the ankle, knee, and hip in the sagittal plane during walking were investigated to calculate the MLE for gait stability based on foot conditions (i.e., barefoot, flat shoes, and high heels). During walking, a large MLE (P < 0.05) was noted for the knee joints of subjects with HV, relative to the other lower limb joints. HV appears to have the most critical effect on the knee joints during walking. Ankle movement exhibited higher dynamic stability than the other joint movements of the lower limb (P < 0.05). The type of shoe used in the experiment showed no significant dependence with gait stability and joint movement (P > 0.05). Quantitative assessments of dynamic stability using the MLE may help clinicians assess the overall gait dynamics of HV patients and other people suffering from gait disturbances.

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Background: The prevalence of scoliosis in Korean elementary school students is increasing, leading to various physical and psychological problems. This study aimed to investigate the association between low body weight and scoliosis among Korean elementary school students. Methods: This was a cross-sectional analysis. Participants were 1062 elementary school students in the metropolitan areas of Korea. Participants were evaluated for scoliosis based on body composition, including weight and height, and with spine structure analysis equipment. Scoliosis diagnosis was defined as having a Cobb's angle greater than 10°. Results: Participants were divided into Normal Weight (NW), Underweight (UW), and Severely Underweight (SUW) groups. Results show that the UW and SUW groups had significantly higher risks of developing scoliosis (odds ratio (OR): 1.43, 95% CI (confidence interval): 1.07⁻1.90; OR: 1.45, 95% CI: 1.02⁻2.05) compared to the NW group; after controlling for age and gender, the OR were 1.44 (95% CI: 1.08⁻1.92) and 1.46 (95% CI: 1.01⁻2.09), respectively. Conclusions: Low weight and the risk of developing scoliosis are very closely associated. Maintenance of appropriate and normal weight in Korean elementary school students appears to be a very effective method for preventing and reducing the risk of scoliosis.

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OBJECTIVE: Postmenopausal women have increased arterial stiffness compared with premenopausal women. Regular physical activity including aerobic and resistance exercises are recommended to lower cardiovascular disease risk and to enhance musculoskeletal health in these women. This study examined the effect of combined circuit exercise on arterial stiffness in hypertensive postmenopausal women. Furthermore, it ascertained whether performing this exercise program is feasible in local public health centers with better accessibility than research and commercial facilities. METHODS: Among 24 hypertensive postmenopausal women, 16 finished this study in either the control (n = 8) or exercise (n = 8) group. Except for one participant who withdrew from the study due to the difficulty of the exercise program, seven participants withdrew due to reasons unrelated to the study. Circuit-type exercise (aerobic- and resistance-combined) program was applied to the exercise group, 60 min/d and 3 d/wk for 12 weeks under supervision. Brachial-ankle pulse wave velocity was measured to assess arterial stiffness. RESULTS: In response to the combined exercise, brachial-ankle pulse wave velocity was significantly reduced in the hypertensive women (-0.7 m/s; P < 0.05). Weight, body mass index, and total cholesterol level were also significantly decreased after the exercise program (-2.1 kg, -0.8 kg/m, and -16 mg/dL, respectively; P < 0.05). In addition, changes in arterial stiffness were related to body adiposity, blood pressure, and blood lipid alterations (r = 0.61-0.70; P < 0.01). CONCLUSIONS: Circuit combined exercise is an effective intervention to improve arterial stiffness in hypertensive postmenopausal women, and is feasible in local public health centers.

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