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Jones fracture is a common injury in soccer players, caused by overload on the fifth metatarsal (M5) that can occur during crossover cutting. This study aimed to investigate the effects of the hip internal rotation (HIR) range in passive and dynamic conditions and foot progression angle (FPA) on the forces applied to the M5 during crossover cutting. The study included 20 men with experience playing soccer. The passive HIR was measured in the prone position. A 3-dimensional motion analysis system, force plates, and Footscan were used to measure the angle of the lower limb, including dynamic HIR, FPA, and plantar pressure to the M5, during crossover cutting in the 45° direction. Pearson correlation coefficient was measured to examine the relationship between variables. Passive and dynamic HIR were not related to the plantar pressure on the M5 (P >.05). However, increased FPA in movement direction correlated with a reduction in plantar pressure on the M5 (r = −.56, P <.01). Minimizing the FPA with respect to the new direction during crossover cutting reduced plantar pressure on the M5 and thus could prevent Jones fracture. [ABSTRACT FROM AUTHOR]

This study quantified the spatial exploration of 13 infants born very and extremely preterm (PT) at 4 months corrected age as they learned that moving their feet vertically to cross a virtual threshold activated an infant kick-activated mobile and compared results to 15 infants born full-term (FT) from a previously published study. Spatial exploration was quantified using two general spatial exploration variables (exploration volume and exploration path), two task-specific spatial variables (duration of time in the task-specific region of interest and vertical variance of kicks), and one non-task-specific spatial variable (horizontal variance of kicks). The infants born PT, similar to FT, increased their general spatial exploration and duration in the region of interest and did not change the vertical and horizontal variances of kicks. However, the infants born PT, compared to FT, spent less time in the task-specific region of interest and had a greater non-task-specific horizontal variance throughout the task. This may indicate that infants born PT and FT exhibit similar general spatial exploration, but infants born PT exhibit less task-specific spatial exploration. Future research is necessary to determine the contribution of learning and motor abilities to the differences in task-specific exploration between infants born PT and FT.

Exploration is considered essential to infant learning, but few studies have quantified infants' task exploration. The purpose of this study was to quantify how infants explored task space with their feet while learning to activate a kick-activated mobile. Data were analyzed from fifteen 4-month-old infants who participated in a 10-min mobile task on 2-3 consecutive days. Infants learned that their vertical leg movements above a systematically increased threshold height activated the mobile. Five kinematic variables were analyzed: (a) exploration space volume, (b) exploration path length, (c) duration of time in the region of interest around the threshold that activated the mobile, (d) task-specific vertical variance of kicks, and (e) non-task-specific horizontal variance of kicks. The infants increased their general spatial exploration, volume, and path, and the infants adapted their exploration by maintaining their feet within the region of interest, although the task-specific region increased in height as the threshold increased. The infants used task-specific strategies quantified by the increased variance of kicks in the vertical direction and no change in the horizontal variance of kicks. Quantifying infants' task exploration may provide critical insights into how learning emerges in infancy and enable researchers to more systematically describe, interpret, and support learning.

Flatfoot is a well‐known foot deformity, with a prevalence of 11.2%–29.0% among adults. Running injuries can occur in individuals with flatfoot; however, the underlying mechanism remains unknown. We investigated the coordination pattern and variability among foot joints while running by comparing participants with neutral foot and with flatfoot. Participants with neutral foot (n = 15) and flatfoot (n = 15) were asked to run at their preferred speed. Using the modified vector coding technique, the coupling angle between the foot joints, representing interjoint coordination, was calculated and categorized into four coordination patterns. The standard deviation of the coupling angle was computed to measure the coordination variability during the stance phase. There were no differences in the spatiotemporal parameters (speed, step length, and cadence) between the groups. In the sagittal rearfoot and sagittal midfoot coordination patterns, the flatfoot group showed a significantly greater proportion of anti‐phase with proximal dominancy and a lower proportion of in‐phase with proximal dominancy than the neutral foot group during early stance. Coordination variabilities between the sagittal rearfoot and sagittal midfoot (midstance), between the sagittal midfoot and sagittal forefoot (early stance), and between the frontal rearfoot and sagittal midfoot (midstance) were greater in the flatfoot group than in the neutral foot group. This may explain why those with flatfoot are likely to experience running injuries. [ABSTRACT FROM AUTHOR]

To reduce the iron loss, motor cores are designed with many layers of silicon steel sheets, and these sheets are elastically joined using the embossed regions. In this study, we investigate how the embossing position affects the joining strength using 0.5-mm-thick silicon steel sheets. Specifically, we embossed and stacked pairs of rectangular specimens and then conducted separation tests. The separation force increased as the embossing position moved further from the specimen's edge. In addition, finite element analysis predicted the radial compressive stress of the interlocked projections, and it exhibits similar variation to the experimentally measured separation force with the changing embossing position. [ABSTRACT FROM AUTHOR]

Copers are individuals who have had a lateral ankle sprain but have no history of recurrent lateral ankle sprain, residual symptoms, or functional disability. Copers have shown no significant difference in lower limb kinematics in landing for proactive conditions compared with a control (CTR) group. However, the copers (CPR) group has shown differences compared to CTR and chronic ankle instability (CAI) groups for dynamic balance conditions, suggesting that the trunk may compensate for foot instability during shock absorption. This study aimed to examine the differences in the kinematics and kinetics among CPR, CAI and CTR groups in reactive and proactive single-leg landing tasks. Participants were physically active adults with CAI (n = 14), CPR (n = 14), and CTR (n = 14), who performed proactive and reactive single-leg landings. The lower limb, trunk kinematics, vertical ground reaction force (vGRF) peak value, and the time to minimum peak vGRF were analysed. It might be conceivable that the CPR group could absorb vGRF efficiently by increasing the trunk flexion angle and increasing the time to reach the minimum peak vGRF regardless of landing condition. The results suggest that evaluating the movements of the entire body, including the ankle and trunk, is essential. [ABSTRACT FROM AUTHOR]

Background: Investigating the kinematics of copers, who are individuals with no recurrent ankle sprains, is necessary to prevent the development of chronic ankle instability (CAI). Since the "giving way" of the ankle joint (episodes of excessive inversion of the rearfoot, which do not result in an acute lateral ankle sprain) usually occurs during walking, investigating the intra-foot coordination during walking is necessary. This study aims to identify intra-foot coordination and its variability in copers while walking., Methods: The study included 12 copers, 13 CAIs, and 10 controls. The participants were required to walk on a treadmill at a fixed speed of 1.3 m/s. Using the modified vector coding technique, the coupling angle between the intra-foot joints, representing inter-joint coordination, was calculated and categorized into four coordination patterns. The coupling angle standard deviation represented the coordination variability during the stance phase., Results: The coordination between the rearfoot and midfoot in the frontal plane showed a significantly lower proportion of anti-phase with proximal dominance in the coper group than in the CAI and control groups during mid-stance (p < .05). Regarding coordination between the midfoot and forefoot in the sagittal plane, the coper group also showed a significantly lower proportion of in-phase coordination with distal dominancy than the CAI group during mid-stance (p < .05). For coordination between the midfoot and forefoot in the frontal plane, the coper group also showed a significantly lower proportion of anti-phase with distal dominance than the CAI group during the late stance (p < .05).The coordination variability between the sagittal midfoot and forefoot in the coper group was significantly lower than that in the CAI group and similar to that in the control group during mid-stance (p < .050)., Conclusions: These differences may explain why copers do not experience ankle sprain recurrence.

Background: Low back pain is a common disorder with high severity among dancers. Since Arabesque used in dance is more likely to cause lower back pain, it is important to prevent the onset of lower back pain during arabesque. Previous studies are investigating motion of the lumbar vertebrae during various tasks in targeting dancers. However, since the thoracic and lumbar vertebrae are connected, it is necessary to assess including motion of the thoracic spine. The purpose of this study was to clarify the relationship between the upper, middle, and lower thoracic vertebrae and the upper and lower lumbar vertebrae in dancers during arabesque. Methods: The participants were 13 university students with dance experience, and they performed double-standing and arabesque tasks. During the tasks, the positions of reflective markers attached to the spine (upper, middle, and lower thoracic vertebrae, and upper and lower lumbar vertebrae) were measured using a three-dimensional motion analysis system. The amount of change in the spinal angle of during standing and arabesque were calculated based on positions of spinal markers, and the relationship between the amount of change each spinal region (6 pairs) were analyzed by using Pearson's correlation test. Results: A significant negative correlation was observed between the amount of change in the angle of the middle thoracic vertebrae and the amount of change in the upper lumbar vertebrae ( r  = -.66, P  = .013), which means that as the movement of the middle thoracic vertebrae increases, the movement of the upper lumbar vertebrae decreases. No significant correlation was observed between other spinal angles ( P  > .05). Conclusion: The results of this study suggest that increasing mobility in the middle thoracic vertebrae may be able to prevent hyperextension of the upper lumbar vertebrae, leading to the prevention of upper back pain in dancers., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Jones fracture is a common injury in soccer players, caused by overload on the fifth metatarsal (M5) that can occur during crossover cutting. This study aimed to investigate the effects of the hip internal rotation (HIR) range in passive and dynamic conditions and foot progression angle (FPA) on the forces applied to the M5 during crossover cutting. The study included 20 men with experience playing soccer. The passive HIR was measured in the prone position. A 3-dimensional motion analysis system, force plates, and Footscan were used to measure the angle of the lower limb, including dynamic HIR, FPA, and plantar pressure to the M5, during crossover cutting in the 45° direction. Pearson correlation coefficient was measured to examine the relationship between variables. Passive and dynamic HIR were not related to the plantar pressure on the M5 (P > .05). However, increased FPA in movement direction correlated with a reduction in plantar pressure on the M5 (r = -.56, P < .01). Minimizing the FPA with respect to the new direction during crossover cutting reduced plantar pressure on the M5 and thus could prevent Jones fracture.