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Purpose: We previously reported that a Hammerobics exercise using weights can enhance trunk and lower extremity muscles, some studies suggested that training effects could also be expected without heavy weights. If the muscle activity induced by Hammerobics swinging with a 'light plastic ball' equals or surpasses that of the isometric static squat and synchronized squat with a heavy ball, this training approach could alleviate joint strain, fostering an exercise regimen universally accessible across generations, benefit for workouts sports and rehabilitation. Methods: Fifteen healthy men participated in this study. By using surface electromyography, muscle activities for the abductor hallucis, tibialis anterior, tibialis posterior, peroneus longus, rectus femoris, biceps femoris long head, semitendinosus, gluteus maximus, multifidus, and internal oblique muscles were measured during a light Hammerobics synchronized squat (HSS-light), Hammerobics synchronized squat, and conventional isometric squat, and statistically compared. Results: The front-to-back tibialis anterior activity of HSS-light was significantly higher than that of conventional isometric squat. The activities of all other muscles, except for the multifidus, were not significantly different between these exercises in the front-to-back and back-to-front phases. Compared to the Hammerobics synchronized squat, the light Hammerobics synchronized squat showed no differences in front-to-back tibialis anterior, rectus femoris, biceps femoris long head, and internal oblique activities and back-to-front abductor hallucis, tibialis anterior, rectus femoris, and internal oblique activities. Conclusion: The HSS-light could stimulate muscles to the same level as the conventional isometric squat without weight bearing. While the HSS-light was less effective than the Hammerobics synchronized squat, there was no significant difference in internal oblique, rectus femoris, and tibialis anterior activities between these exercises. Hence, the HSS-light is an exercise method that can be viable approach to promoting accessible workouts sports and rehabilitation. [ABSTRACT FROM AUTHOR]

This study aimed to determine differences in the hip abductor muscle activity during clam exercise at different hip flexion and femoral anteversion angles. Thirty healthy females were divided into two groups based on the femoral anteversion angle: the excessive femoral anteversion group and the normal group. Clam exercise was performed at three different hip flexion angles (60°, 45°, and 30°). Tensor fascia latae, gluteus medius, and superior portion of gluteus maximus activities were measured during the exercise, and the results were normalized to the activity during maximum voluntary isometric contraction to calculate the gluteal-to-tensor fascia latae muscle activation index. The superior portion of gluteus maximus activities at a hip flexion of 60° and 45° were greater than that at 30°. The excessive femoral anteversion group had a lower gluteal-to-tensor fascia latae muscle activation index than the normal group; the gluteal-to-tensor fascia latae muscle activation index for hip flexion at 60° was higher than that at 45°, and the gluteal-to-tensor fascia latae muscle activation index for hip flexion at 60° and 45° were higher than that at 30°. Therefore, the femoral anteversion angle and hip joint position were related to the activity of the hip abductor muscles during clam exercise. These findings may provide a rationale for instructing exercises to maximize the activity of the hip abductor muscles in individuals with an excessive femoral anteversion angle. [ABSTRACT FROM AUTHOR]

Context: Deficits in knee extension strength after anterior cruciate ligament reconstruction have been a major problem. The inadequate recovery of the knee extension strength of surgical limb reportedly delays return to sports and increases reinjury risk. Accordingly, the early detection of knee extension strength deficits after reconstruction may help plan early interventions to manage impairment. This study aimed to clarify the association between knee extension strength at 3 and 6 months after anterior cruciate ligament reconstruction. Design: Retrospective study. Methods: Fifty patients who underwent primary anterior cruciate ligament reconstruction using hamstring grafts were included. At 3 months postoperatively, the limb symmetry index (LSI) of isokinetic knee extension strength (IKE) at 60°/s, degree of swelling, passive range of motion of knee flexion and extension, and anterior leg reach distance were measured. At 6 months postoperatively, the LSI of IKE was measured at 60°/s, which was used as the main outcome. A correlation analysis was performed with the LSI of IKE at 6 months postoperatively as the dependent variable and the LSI of IKE at 3 months postoperatively as the independent variable. Subsequently, a multiple regression analysis was performed, with LSI of IKE at 6 months postoperatively as the dependent variable; LSI of IKE at 3 months postoperatively as the independent variable; and other variables, demographic information, and surgical data as covariates. Results: The correlation analysis revealed that the LSIs of IKE at 3 and 6 months postoperatively were correlated (r =.535, P <.001). In the multiple regression analysis, the LSI of IKE at 3 months postoperatively was significantly associated with that at 6 months postoperatively, even when other variables were included as covariates (R2 =.349, P =.004). Conclusion: Asymmetry of knee extension strength at 3 months postoperatively could be more useful than other variables related to knee strength in predicting the asymmetry of knee extension strength at 6 months postoperatively. [ABSTRACT FROM AUTHOR]

Bipolar degradation, which is caused by the expansion of stacking faults (SFs) during operation, has been a serious issue in 4H-SiC power devices. To evaluate the threshold minority carrier density of SF expansion, ρ th , Maeda et al. proposed a theoretical model based on quantum well action and dislocation theory. This model includes SF energy variations, electronic energy lowering due to carrier trapping, and resolved shear stress applied to partial dislocations, τ rss . Though the SF energy and the electric energy lowering were quantitatively established, the effect of τ rss has not been discussed well yet. In this study, we first conducted theoretical predictions of the effect of τ rss on ρ th . Then, based on our previous experiment on the dependence of threshold current density on mechanical external stress, we investigated the dependence of ρ th on τ rss . We conducted submodeling finite element analysis to obtain τ rss induced by both residual stress due to the fabrication process and experimentally applied external stress. Finally, we obtained ρ th at the origin of SF expansion from the experimentally measured threshold current density using device simulation. It was found that the dependence of ρ th on τ rss was almost linear. Its gradient was −0.04 ± 0.01 × 1016 cm−3/MPa, which well agrees with the theoretical prediction of −0.03 ± 0.02 × 1016 cm−3/MPa. Our study makes possible a comprehensive evaluation of the critical condition of bipolar degradation. [ABSTRACT FROM AUTHOR]

Introduction: Kinesiophobia is a fear of physical movement and activity and is known to affect return to sports and second injury after anterior cruciate ligament reconstruction. Objective: To determine the association among landing biomechanics, knee pain, and kinesiophobia in athletes following anterior cruciate ligament reconstruction. Design: A cross‐sectional study. Setting: Clinical center of sports medicine. Participants: This study included 31 athletes who participated in sports after primary, unilateral anterior cruciate ligament reconstruction (age, median [interquartile range]: 20.0 [7.0] years; body mass index: 22.2 [2.6] kg/m2; time from anterior cruciate ligament reconstruction: 24.0 [23.0] months). Interventions: Not applicable. Main Outcome Measures: Kinesiophobia was measured using the Tampa Scale for Kinesiophobia‐11. Knee function included joint laxity, strength, and single‐leg hop distance. Knee pain intensity during sports activities was measured using a numerical rating scale. Vertical ground reaction force was measured, and electromyography data for the vastus medialis and semitendinosus muscles during single‐leg jump landing were collected. Univariate correlation analysis and multiple regression analysis were performed to identify the associations between the Tampa Scale for Kinesiophobia‐11 score and outcome measures. Results: There was no correlation between peak vertical ground reaction force and Tampa Scale for Kinesiophobia‐11 score (Spearman's r = −0.17, p =.355). On multiple regression analyses, lower preparatory vastus medialis activity during landing (beta coefficient = −0.51, p <.001) and knee pain intensity (beta coefficient = 0.57, p <.001) were significantly associated with greater Tampa Scale for Kinesiophobia‐11 scores. Conclusions: In athletes who have participated in sports following anterior cruciate ligament reconstruction, lower preparatory vastus medialis activity during landing and knee pain intensity are associated with greater kinesiophobia. These findings indicate that interventions to address the landing muscle activity pattern and pain control should be performed to decrease kinesiophobia after anterior cruciate ligament reconstruction. [ABSTRACT FROM AUTHOR]