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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.

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.

There is limited information regarding the cause for the different etiologies in individuals with initial lateral ankle sprains (LAS) who have chronic ankle instability (CAI) and no recurrence or instability for 12 months (copers) following initial LAS. Assessing the movement patterns of copers and individuals with CAI and LAS recurrence is essential for identifying the mechanical factors that affect patient outcomes.Does coordination and coordination variability of rearfoot, midfoot, and forefoot present a potentially causative pattern for CAI or coper?This cross-sectional study included 35 males who were divided into the CAI (n = 13), coper (n = 12), and control group (n = 10). Participants performed rearfoot strike running on the treadmill at a fixed speed of 3.5 m/s. The coupling angle between the rearfoot, midfoot, and forefoot, representing intersegmental coordination, was calculated using the modified vector coding technique and categorized into four coordination patterns. The coupling angle standard deviation served represented coordination variability during the stance phase.One control participant and one CAI participant were excluded, and final analyses were performed on the CAI (n = 12), coper (n = 12), and control (n = 9) groups. During late stance, the coper group showed a significantly greater proportion of in-phase with distal dominancy (p = 0.02, effect size=0.17) and a significantly lower proportion of in-phase with proximal dominancy (p = 0.05, effect size=0.17), than the CAI group. During the early stance, the coper group showed a significantly lower proportion of anti-phase with distal dominancy than the CAI group (p = 0.03, effect size=0.18). There were no differences in intra-foot variability among the groups.The intra-foot coordination observed in the coper group suggests that this movement pattern may reduce the risk of ankle sprains.

Purpose Sprinting is the most common activity associated with hamstring strain injuries in soccer. However, the potential mechanisms for hamstring strain injuries during the initial acceleration phase of sprinting are unclear. Therefore, this study aimed to characterize the kinematics and activation of the hamstring muscles in soccer players to define the potential mechanism of hamstring strain injury.Methods Ten male soccer players with no lower-limb injuries in the past year were recruited for this study. Each participant was instructed to perform a minimum of three successful 15 m sprints. Hamstring kinematics and activations were estimated by employing musculoskeletal modeling and wireless electromyography to define potential injury mechanisms.Results During the initial acceleration phase, the hamstring muscles undergo great strain and high activation levels during the late swing and early stance phases. The hamstring muscles experienced great strain and overload during the late swing and foot strike of the running gait cycle. Additionally, the biceps femoris long head was significantly more stretched than the semimembranosus and semitendinosus (p p Conclusion Based on these results, hamstring injuries are likely to occur during the late-swing and early stance of the running gait cycle, with the biceps femoris long head being more susceptible to injuries than other hamstring muscles.

Center of pressure (COP) tracking during posture transition is an ideal scale for determining the recurrence of an ankle injury, thereby preventing chronic ankle instability (CAI). However, the same is difficult to determine because the reduced ability of certain patients (who experienced sprain) to control posture at the ankle joint is masked by the chain of hip and ankle joint motion. Thus, we observed the effects of knee joint immobilization/non-immobilization on postural control strategies during the posture transition task and attempted to evaluate the detailed pathophysiology of CAI. Ten athletes with unilateral CAI were selected. To examine differences in COP trajectories in the CAI side and non-CAI legs, patients stood on both legs for 10 s and one leg for 20 s with/without knee braces. COP acceleration during the transition was significantly higher in the CAI group with a knee brace. The COP transition from the double- to single-leg stance phase was significantly longer in the CAI foot. In the CAI group, the fixation of the knee joint increased COP acceleration during postural deviation. This suggests that there is likely an ankle joint dysfunction in the CAI group that is masked by the hip strategy.

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.

Several prior studies involving "expected" single-leg landings have not succeeded in establishing a difference between copers and a control group.Does expected and unanticipated single-leg landing affect dynamic postural stability in lateral ankle sprain individuals with chronic ankle instability (CAI), copers, and controls?In this prospective cross-sectional study, physically active adults with CAI (n = 12), copers (n = 12), and controls (n = 12) were included. Participants performed expected single-leg landing by stepping off a 30-cm box. They also performed unanticipated landings including side-step cutting, side-step cutting at 60°, single-leg landing, and forward stepping. The expected and unanticipated conditions of each groups were compared in terms of time to stabilization (TTS) and center of pressure (COP) for the anterior-posterior (AP) and medial-lateral (ML) conditions. To analyze the data, a mixed-model one-way analysis of variance and a Tukey-Kramer post hoc test were performed.A significant condition × group interaction was observed in only TTS ML, with the CAI group demonstrating a significantly longer TTS ML than the coper (p 0.001) and control (p 0.001) groups during unanticipated trials. In addition, group interaction effects were observed for COP AP and TTS AP. The coper group demonstrated significantly longer COP AP and TTS AP than the control group (p 0.001).The CAI group demonstrated a significantly longer TTS ML than the coper and control groups during the unanticipated condition, and the coper group demonstrated significantly longer TTS AP and COP AP than the control group. Thus, longer COP AP and TTS AP sway time in the coper group may be a protection mechanism, allowing greater freedom in the AP plane while quickly controlling ML sway and preventing lateral ankle sprains. These findings can help in the prevention of lateral ankle sprains and assessment of dynamic postural control.

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.

Objective Children with spastic cerebral palsy (CP) have gait impairments resulting from decreased selective motor control, an inability to move the leg joints independently of one another, relying on excessive flexion or extension coupling across the 3 joints. Infants with white matter injury are at high risk of CP and have decreased selective motor control as early as 1 month corrected age. An in-home kicking-activated mobile task was developed to motivate more selective hip-knee control of infants at high risk of CP. The purposes of this study were to determine the feasibility of the in-home mobile task and to determine whether infants at high risk of CP and infants with typical development (TD) learn the association between their leg movements and mobile activation. Methods Ten infants at high risk of CP based on neuroimaging and 11 infants with TD participated in this cohort study at 3.5 to 4.5 months corrected age. Each infant participated in the in-home kicking-activated mobile task for 8 to 10 min/d, 5 d/wk, for 6 weeks. Learning was assessed weekly based on an increase in the time that the infant demonstrated the reinforced leg actions when interacting with the kicking-activated mobile compared with spontaneous kicking. Results With regard to feasibility, participation averaged 92% for infants at high risk of CP and 99% for infants with TD. With regard to learning, the group at high risk of CP demonstrated learning of the task for 2 of 6 weeks, whereas the group with TD demonstrated learning for all 6 weeks. Conclusions Infants at high risk of CP demonstrated learning of the kicking-activated mobile task but at a reduced amount compared with infants with TD. Further research is necessary to determine whether the kicking-activated mobile task has potential as an intervention to motivate more selective hip-knee control and improve walking outcomes of infants at high risk of CP. Impact This study investigated the feasibility of an in-home kicking-activated mobile task, a discovery learning task designed to motivate infants at high risk of CP to engage in the intensive task practice necessary to promote their learning abilities and selective motor control. Lay Summary CP is a lifelong disorder of movement caused by abnormal development or early damage to the brain. If an in-home infant kicking-activated mobile task could be used to motivate certain types of age-appropriate leg movements of infants who are at high risk of CP, the task could help improve walking outcomes, which eventually could contribute to improving children’s ability to participate in daily life. This study showed that infants at high risk of CP did learn the infant kicking-activated mobile task but at a much reduced amount compared with infants who are developing typically; so, this is a first step in determining whether the task has potential to motivate more age-appropriate leg movements in infants at high risk of cerebral palsy.

Flatfoot presents decreased medial longitudinal arch (MLA), and such foot deformity involves intrinsic foot muscles dysfunction. Flatfoot can be classified into flexible and stiff types according to arch height flexibility (AHF). Short foot exercise (SFE) is an intrinsic foot muscle strengthening exercise, which is reportedly effective against flatfoot. However, its effectiveness against flexible or stiff types in flatfoot is unclear. We examined the effect of AHF in individuals with flatfoot during abductor hallucis muscle (AbH) activity and medial longitudinal arch during SFE. Foot alignment was assessed using the arch height index during standing, and individuals with flatfoot (N = 16) were recruited. The AbH activity and MLA angle during SFE while maintaining single-leg standing were assessed. The relationship between AHF and AbH activity and between AHF and MLA angle ratio was analyzed using correlation coefficients. Additional correlations between AHF and AbH activity were observed with the outliers removed. There were no correlations between AHF and AbH muscle activity and between AHF and MLA angle ratio. However, with the 2 outliers removed, moderate correlations between AHF and AbH activity were significant (r = 0.64, p = .01). AbH activity during SFE increased in individuals with flatfoot for high AHF (flexible type). Thus, SFE may be more effective for individuals with flatfoot having a high AHF. These findings may be helpful when making decisions for surgery and rehabilitation.

Calf raise test (CRT) is used in rehabilitation and sports medicine to evaluate calf muscle function. The Calf Raise application (CRTo validate the CRObservational cross-sectional validation study.CRT outcomes (i.e., repetitions, positive work, total height, peak height, fatigue index, and peak power) were assessed in thirteen individuals (6 males, 7 females) on three occasions on both legs using the CRValidity of CRCR

Objective Decreased selective motor control limits gait function of children with spastic cerebral palsy (CP). Infants at high risk of CP demonstrate decreased selective motor control by 1 month of age. To motivate more selective hip-knee control, infants at high risk of CP participated in an in-home kicking-activated mobile task. The purpose of this study was to determine whether infants at high risk of CP and infants with typical development (TD) demonstrated increased selective hip-knee control during 2-minute intervals of the mobile task when they demonstrated learning of the association between their leg movement and mobile activation vs during 2-minute intervals when they did not demonstrate learning. Methods Participants in this cohort study included 10 infants at high risk of CP based on neuroimaging and 11 infants with TD at 3.5 to 4.5 months of age. Each infant participated in the in-home kicking-activated mobile task for 8 to 10 min/d, 5 d/wk, for 6 weeks. Over 80,000 kicks were extracted and classified for each infant as occurring during 2-minute intervals of the task when the infant demonstrated learning vs not learning based on mobile activation time above baseline. Results Infants demonstrated kicks with more selective hip-knee control during 2-minute intervals of the mobile task when they demonstrated learning compared with when they did not demonstrate learning for 4 of 6 weeks in the cohort at high risk of CP and for 2 of 6 weeks in the cohort with TD. Conclusion Participation in the in-home kicking-activated mobile task may motivate more selective hip-knee control of infants at high risk of CP. Impact This study is a first step toward developing an intervention to promote selective hip-knee control of infants at high risk of CP, with the ultimate goal of optimizing future walking function. Lay Summary This study showed that playing with an in-home infant kicking-activated mobile may motivate infants at high risk of CP to produce more age-appropriate leg movements.

Background An excessive daily cumulative hip moment in the frontal plane (determined as the product of hip moment impulse in the frontal plane during the stance phase and mean number of steps per day) is a risk factor for the progression of hip osteoarthritis. Moreover, walking speed and step length decrease, whereas cadence increases in patients with hip osteoarthritis. However, the effects of step length and cadence on hip moment impulse in the frontal plane during the stance phase are not known. Therefore, this study aimed to examine the effects of step length and cadence on hip moment impulse in the frontal plane during the stance phase. Methods We used a public dataset (kinetic and kinematic data) of over-ground walking and selected 31 participants randomly from the full dataset of 57 participants. The selected participants walked at a self-selected speed and repeated the exercise 15 times. We analyzed the data for all 15 trials for each participant. Multiple regression analysis was performed with the hip moment impulse in the frontal plane during the stance phase as the dependent variable and step length and cadence as independent variables. Results The adjusted R2 in this model was 0.71 (p < 0.001). The standardized partial regression coefficients of step length and cadence were 0.63 (t = 5.24; p < 0.001) and −0.60 (t = − 4.58; p < 0.001), respectively. Conclusions Our results suggest that low cadence, not short step length, increases the hip moment impulse in the frontal plane. Our findings help understand the gait pattern with low hip moment impulse in the frontal plane.

The impact of characteristic physical functions on location of arm pain in youth baseball players is unclear. This study aimed to identify the differences in characteristic physical functions between youth baseball players with and without throwing-related arm pain and to clarify these differences according to location of shoulder and elbow pain during pitching. One-hundred nine junior high school baseball players (aged 12-15 years) who participated in a medical checkup underwent clinical assessment, ultrasonography, and physical function measurements. Bilateral passive range of motion (ROM) of the shoulder and elbow were measured. Shoulder muscle tests measured the strength of the throwing arm. Before the examinations, participants completed a questionnaire about their age, gender, years of play, and position in baseball. Participants were divided into 4 groups according to arm pain: non-injured group (no pain), shoulder pain group, medial elbow pain group, and osteochondritis dissecans (OCD) of the humeral capitellum group. Group differences in physical function and baseball exposure variables were analyzed through parametric and nonparametric tests. Twenty-six players sustained throwing-related pain in the shoulder or elbow. Elbow extension and flexion deficits were significantly greater with elbow injury. Our study suggests that dominant elbow extension and flexion ROM may increase the risk of throwing-related elbow pain in junior high school baseball players. We could not clarify the characteristics of shoulder pain in this study; thus, further research is required to improve understanding of these characteristics and their implications.

Background Recent reports have shown that the daily cumulative moment in the frontal plane (i.e., product of hip moment impulse in the frontal plane during the stance phase and mean steps per day) is a risk factor for hip osteoarthritis. This study aimed to clarify the effect of contralateral cane use on hip moment impulse in the frontal plane of the stance limb. Methods This study included 15 healthy subjects who walked under four experimental conditions: (1) without a cane and (2–4) contralateral cane use with 10%, 15%, and 20% body weight support (BWS), respectively. To maintain the same walking speed in all conditions, the cadence was set to 80 steps/min, and the step length was fixed. The hip moment impulses in the frontal plane (i.e., area under the hip ab-adduction moment waveform) and peak hip adduction moments in all conditions were calculated. Results Contralateral cane use significantly decreased the hip moment impulse in the frontal plane and peak hip adduction moment compared to non-cane use. Moreover, the hip moment impulse in the frontal plane and peak hip adduction moment decreased significantly with increased cane BWS. There were no significant differences in walking speed, cadence, and step length between the four conditions. Conclusion Contralateral cane use decreases the hip moment impulse in the frontal plane and peak hip adduction moment in the stance limb. These findings may help clarify how to delay the progression of hip osteoarthritis.

Purpose: It is unclear whether biarticular hamstring muscles (HAM) can act as knee extensors or not. The purpose of this study is to identify the conditions that HAM can act as a knee extensor by using a computational simulation approach.Methods: The modified Gait2392 musculoskeletal model was used in this study. The posture was determined with a hip flexion angle that ranged from -30° to 90° and a knee flexion angle that ranged from -10 ° to 90 °. The simulations were executed under two conditions: all segments are free to move, non-contact with the ground (nCG), and the foot is constrained on the ground, contact with the ground (CG). Induced acceleration analysis was applied to determine the contribution of the HAM to the knee angular acceleration.Results: Three key findings were discovered. 1) HAM can act as knee extensors that have CG condition as well as nCG condition. 2) The HAM function changes depending on the posture. 3) The range of the hip joint that HAM was able to act as a knee extensor was expanded for the CG condition from the nCG condition.Conclusions: We identified the situations in which HAM can act as knee extensors and demonstrated that the HAM function on the knee joint changes depending on the posture and the foot contact condition. Our findings suggest that HAM can be used as compensatory movement strategy for patients with a reduced capacity to generate knee extension if the patients have enough HAM strength.

Background: Excessive mechanical loading, in the form of the joint contact force, has been reported to promote osteoarthritis in vitro and vivo in mice. However, it has also been reported that an excessive hip adduction moment impulse during the stance phase likely contributes to the progression of hip osteoarthritis. The relationship between the hip adduction moment impulse and hip joint contact force (impulse, and first and second peaks) during the stance phase is unclear. The objective of the present study was to clarify this relationship. Methods: A public dataset pertaining to the overground walking of 84 healthy adults, in which the participants walked at a self-selected speed, was considered. The data of three trials for each participant were analyzed. The relationship between the hip adduction moment and hip joint contact force, in terms of the impulse and first and second peaks, during the stance phase was evaluated using correlation coefficients.Results: The hip adduction moment impulse during the stance phase was positively correlated with the hip joint contact force impulse and not correlated with the first and second peak hip joint contact forces. Furthermore, the first and second peak hip adduction moments during the stance phase were positively correlated with the first and second peak hip joint contact forces, respectively. Conclusions: These findings indicate that the hip joint contact force impulse during the stance phase can be used as an index to determine the risk factors for the progression of hip osteoarthritis.

Objectives This study compares the ankle kinematics and muscle activities of the individuals with chronic ankle instability (CAI), coper, and control groups in normal and inversion single-leg landings. Design cross-sectional study; Setting Biomechanics laboratory. Participants Physically active adults with CAI (N = 12); and coper (N = 12) and control (N = 12) groups. Main outcome measures The participants performed normal and inversion single-leg landing. The muscle activity 200 ms before and after landing of the tibialis anterior, the medial gastrocnemius, and the fibularis longus (FL) were recorded. The FL latency, sagittal and frontal co-contraction indexes (CCI), ankle inversion angle at the initial contact, and the maximum inversion angle were recorded. Results Significantly longer FL latency, decreased FL muscle activity, frontal CCI, and an increased maximum inversion angle at post-landing were discovered during inversion single-leg landing in the CAI group compared to the coper and control groups. However, no significant difference was observed among the CAI and coper groups during normal single-leg landing. Conclusion These results suggest prolonged FL latency and altered ankle kinematics suggest an increased risk of recurrent lateral ankle sprains in CAI with inversion single-leg landing.

Flatfoot is a common foot deformity, which could contribute to running injuries such as medial tibial stress syndrome. Intrafoot kinematics of flatfoot during walking have often been documented using multisegment foot models. However, the intrafoot kinematics of flatfoot during running remains unclear, despite the possible relationship between flatfoot and running injuries. We aimed to clarify rearfoot, midfoot, and forefoot kinematics when running in participants with normal foot and flatfoot. Participants with the normal foot (n = 14) and flatfoot (n = 14) were asked to runover-ground at their preferred speed. Three-dimensional kinematics of the rearfoot, midfoot, and forefoot during running were calculated based on the Rizzoli foot model. A two-sample t-test of statistical parametric mapping was performed to determine differences between normal foot and flatfoot in time histories of intrafoot kinematics during running. No differences were found between groups in characteristics and spatiotemporal parameters. In the frontal rearfoot angle, a significantly increased eversion from 24% to 100% (p < .001) was observed in the flatfoot compared to the normal foot. At the midfoot angle, a significantly increased eversion from 0% to 4% (p < .049) and 21% to 100% (p < .001) was observed in the flatfoot compared to the normal foot. At the forefoot angle, a significantly increased inversion from 6% to 17% (p < .047) was observed in the flatfoot compared to the normal foot. These findings may be useful to explain why flatfoot could contribute to running injuries such as medial tibial stress syndrome.

Prior research supports that infants born very preterm (PT), compared with full term (FT), have early differences in rate of learning and motor control that may hinder their ability to learn challenging motor tasks. Four-month-old infants born FT (n = 18) and PT (n = 18) participated in an infant kick-activated mobile task that was scaffolded to motivate progressively higher kicks. We found the FT group learned the association between their leg movements and mobile activation on the second day, but the PT group learned the association on the third day. Both groups of infants increased the height of their kicks on the day they learned the task, compared with their spontaneous kicking height. These findings suggest that infants born PT have the ability to learn challenging motor tasks, such as kicking high, when participating in a task environment that uses scaffolding.

Low back pain(LBP) is the number one cause of disability worldwide. One factor which might potentially contribute to ongoing pain is impaired spinal movement variability. It is uncertain how movement variability changes during trunk movements in the presence of LBP. In this protocol, we will systematically investigate and compare both the amount and structure of spinal movement variability during repeated trunk motions between people with and without LBP. The results will be reported in line with the PRISMA(Preferred Reporting Items for Systematic Review and Meta-Analysis). Searches will be conducted on CENTRAL, PubMed, MEDLINE, EMBASE, and CINAHL databases, along with a comprehensive review of grey literature and key journals.Three pairs of two independent reviewers will screen potential studies and two independent reviewers assess the risk of bias within studies which meet the inclusion criteria. The Newcastle-Ottawa risk of bias tool will be used to assess the quality of the data.