Investigating the impact of developmental coordination difficulties across home, school, and community settings: Findings from the Australian Impact for DCD survey.

AIM: To evaluate the participation difficulties experienced by children with developmental coordination disorder (DCD) in home, school, and community environments. METHODS: The Impact for DCD survey was completed by primary caregivers of 4-18-year-old children with DCD (or synonymous diagnosis) (n = 429). OUTCOMES AND RESULTS: The greatest participation difficulties experienced at home included dressing, eating with utensils, self-care tasks and drawing/writing reported by over 70% of families. At school, fine motor difficulties were also frequently reported, with additional difficulties keeping up or completing tasks, and not feeling supported at school. Socialisation challenges and bullying were also commonly reported (34.9%). As a result of participation difficulties at school, 5.4% were home schooled. Many children engaged in community activity, with 72.0% currently engaged in at least one organised sports-based activity. CONCLUSIONS AND IMPLICATIONS: Increased recognition of the widespread impact of DCD in a child's life is crucial at an individual and societal level. Parents reported their children experiencing significant participation restrictions and difficulties. The findings of this large-scale study have revealed that most children with DCD are not receiving the support they need to thrive, especially at school. This largely reflects a lack of understanding and recognition of the condition and its associated challenges.

Psychosocial wellbeing, parental concerns, and familial impact of children with developmental coordination disorder.

BACKGROUND: Developmental Coordination Disorder (DCD) is a neurodevelopmental condition impacting motor skill acquisition and competence. While previous studies have identified adverse psychosocial outcomes in DCD, they are limited by small or population-screened, community-based samples. AIMS: To understand the psychosocial difficulties, parental concerns, and familial impacts of childhood DCD in a large population-based sample. METHODS AND PROCEDURES: Parents of 310 children aged 4 - 18 years with a diagnosis of DCD (or synonymous term) completed the Impact for DCD survey. Parent-rated measures of emotional problems, peer problems, and prosocial behaviour were compared to normative data. Parental concerns for the impact of DCD on participation, interaction, emotional well-being, and the family system were examined. OUTCOMES AND RESULTS: Compared to typically developing children, children with DCD were rated significantly higher for emotional and peer problems, and significantly lower for prosocial behaviours. Parents most commonly reported concerns for their child's future and withdrawal from physical activity. The presence of one or more co-occurring disorders did not significantly influence outcomes. CONCLUSION AND IMPLICATIONS: Findings highlight the poor psychosocial outcomes for children with DCD. Crucially, poor psychosocial outcomes were just as likely in those with a single diagnosis of DCD as those with DCD and multiple co-occurring diagnoses. Parents reported concerns for their child (i.e., non-participation and social withdrawal) that are not targeted in existing DCD intervention modalities and emphasised the impact of DCD on the whole family unit. WHAT THIS PAPER ADDS: This paper presents data from the largest parent-reported survey of children with a known diagnosis of DCD (or synonymous labels). It highlights the significant impact of DCD on psychosocial outcomes in children across age groups. The children in this study were rated by their parents to have significantly higher levels of emotional and peer problems, and lower prosocial behaviours, than similarly aged Australian children without DCD. It also challenges the misconception that poor psychosocial outcomes in DCD are the result of co-occurring disorders, with outcomes observed to be as poor in children with a sole diagnosis of DCD in this sample. Furthermore, findings highlighted the significant worry and concern that parents with DCD face, particularly around their child's participation and their emotional health. Finally, parents reported on the considerable impact that DCD had on their family unit, regularly causing worry and concern, influencing their choice of activities, and causing financial strain. These concerns and impacts are not addressed in current intervention models for DCD and highlight the need for support mechanisms moving forward.

A statistical shape model of soleus muscle morphology in spastic cerebral palsy.

This study investigated morphological characteristics of the soleus muscle in cerebral palsy (CP) and typically developing (TD) cohorts using a statistical shape model and differentiated dominant features between the two cohorts. We generated shape models of CP and TD cohorts to characterize dominant features within each. We then generated a combined shape model of both CP and TD to assess deviations of the cohorts' soleuses from a common mean shape, and statistically analysed differences between the cohorts. The shape models revealed similar principal components (PCs) with different variance between groups. The CP shape model yielded a distinct feature (superior-inferior shift of the broad central region) accounting for 8.1% of the model's cumulative variance. The combined shape model presented two PCs where differences arose between CP and TD cohorts: size and aspect ratio of length-width-thickness. The distinct appearance characteristic in the CP model-described above-may implicate impaired muscle function in children with CP. Overall, children with CP had smaller muscles that also tended to be long, thin, and narrow. Shape modelling captures dominant morphological features of structures, which was used here to quantitatively describe CP muscles and further probe our understanding of the disease's impact on the muscular system.

The unmet clinical needs of children with developmental coordination disorder.

BACKGROUND: The aim of this study was to understand the challenges experienced by families obtaining a diagnosis and therapy for developmental coordination disorder (DCD). METHODS: Parents of 435 children aged 4-18 years with persistent motor difficulties consistent with a diagnosis of DCD completed an online survey. Diagnostic timeline and diagnostic label/s received were examined, along with therapies accessed. RESULTS: There was inconsistent diagnostic terminology (nine separate terms) with more children diagnosed with dyspraxia (64.7%) than DCD (48.8%). Even though most parents (87.0%) reported that receiving a diagnosis was helpful, children did not receive a diagnosis until years after seeking help (mean 2.8 ± 2.3 years). Many children were diagnosed with at least one co-occurring neurodevelopmental, language or learning disorder (70.0%). Almost all families had accessed therapy for their child's movement difficulties (93.9%), but more than half did not have access to funding to support therapy costs (57.8%) and reported that the costs caused financial strain (52.6%). Two out of every three families reported that they did not feel the current level of therapy was sufficient. CONCLUSIONS: This critical advocacy research highlights inconsistent and incorrect terminology and the challenges families experience in obtaining a diagnosis and adequate access to therapy for their child's movement difficulties. IMPACT: This is the first comprehensive study to examine the challenges families experience gaining a diagnosis and therapy for their child with DCD. Families regularly experienced prolonged diagnosis; 45% waited between 2 and 4 years. There is no clear diagnostic pathway, with children more likely to be diagnosed with dyspraxia than the correct clinical diagnosis of DCD. More extensive implementation of the diagnostic guidelines into clinical practice is needed.

Measuring skeletal muscle morphology and architecture with imaging modalities in children with cerebral palsy: a scoping review.

AIM: To investigate the use of ultrasound and magnetic resonance imaging (MRI) methodologies to assess muscle morphology and architecture in children with cerebral palsy (CP). METHOD: A scoping review was conducted with systematic searches of Medline, Embase, Scopus, Web of Science, PubMed, and PsycInfo for all original articles published up to January 2019 utilizing ultrasound and/or MRI to determine morphological and architectural properties of lower limb skeletal muscle in children with CP. RESULTS: Eighty papers used ultrasound (n=44), three-dimensional ultrasound (n=16), or MRI (n=20) to measure at least one muscle parameter in children and adolescents with CP. Most research investigated single muscles, predominantly the medial gastrocnemius muscle, included children classified in Gross Motor Function Classification System levels I (n=62) and II (n=65), and assessed fascicle length (n=35) and/or muscle volume (n=35). Only 21 papers reported reliability of imaging techniques. Forty-six papers assessed measures of Impairment (n=39), Activity (n=24), and Participation (n=3). INTERPRETATION: Current research study design, variation in methodology, and preferences towards investigation of isolated muscles may oversimplify the complexities of CP muscle but provide a foundation for the understanding of the changes in muscle parameters in children with CP. WHAT THIS PAPER ADDS: Current evidence is biased towards the medial gastrocnemius muscle and more functionally able children with cerebral palsy (CP). Variations in imaging techniques and joint positioning limit comparisons between studies. Clinimetric testing of parameters of CP muscle is not always considered. Assessment of parameter(s) of muscle with measures of participation is sparse.

Prevalence of Motor Difficulties in Autism Spectrum Disorder: Analysis of a Population-Based Cohort.

Motor impairment is not currently included in the diagnostic criteria or evaluation of autism. This reflects the lack of large-scale studies demonstrating its prominence to advocate for change. We examined the prevalence of motor difficulties at the time of diagnosis in a large sample of children with autism utilizing standardized assessment, and the relationship between motor difficulties, core autism symptomology, and other prominent clinical features. Vineland Adaptive Behavior Scales were administered to children from the Western Australian Register for Autism Spectrum Disorders aged ≤6 years (N = 2,084; 81.2% males, 18.8% females). Prevalence of motor difficulties was quantified based on scores from the motor domain of the Vineland and then compared to other domains of functioning within the Vineland (communication, daily living, and socialization), the DSM criteria, intellectual level, age, and gender. Scores on the Vineland indicated that 35.4% of the sample met criteria for motor difficulties (standard score <70), a rate almost as common as intellectual impairment (37.7%). Motor difficulties were reported by diagnosing clinicians in only 1.34% of cases. Motor difficulties were common in those cases meeting diagnostic criteria for impairments in nonverbal behavior and the presence of restricted and repetitive behaviors. The prevalence of motor difficulties also increased with increasing age of diagnosis (P < 0.001). Findings from the present study highlight the need for further consideration of motor difficulties as a distinct specifier within the diagnostic criteria for ASD. Autism Res 2020, 13: 298-306. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: In this population-based cohort that included 2,084 children with autism aged ≤6 years, over one-third met the criteria for motor difficulties, a rate almost as common as intellectual disability. This study demonstrates that motor difficulties are a prominent feature of the autism phenotype requiring further consideration in both the diagnostic criteria and evaluation of autism.

Physiological characteristics, self-perceptions, and parental support of physical activity in children with, or at risk of, developmental coordination disorder.

Children with low movement proficiency have been identified as having poorer physiological and psychosocial outcomes; however, the varied measurement approaches used to assess these outcomes have varied resulting in conflicting evidence regarding the presence and magnitude of differences compared to Typically Developing (TD) children. Additionally, there has been limited research into the role of parental support for physical activity (PA) in this group. We compared children with varying levels of movement proficiency on physiological characteristics and self-perceptions regarding PA. In addition, these children's parents were compared on physiological characteristics and support of their children's PA. Children (N = 117) aged 6 to 12 years, along with their parent/guardian, participated in this study. Children were classified according to the Movement Assessment Battery for Children-2 test (Typically Developing (TD) = 60; At Risk = 19; Developmental Coordination Disorder (DCD) = 38). Children's PA, muscle strength, cardio-respiratory fitness (CRF), body composition, and self-perceptions regarding PA were assessed, with parents assessed on CRF, body composition, and PA support. Compared to TD children, children with DCD had lower PA (p = 0.036), predilection (p ≤0.001) and adequacy (p ≤0.001) regarding PA, higher body fat percentage (p = 0.019), and received less logistic support (i.e., transportation) from their parents (p = 0.012). TD children had increased muscle strength compared to the DCD (p ≤ 0.001) and At Risk (p ≤ 0.001) groups. Results indicated that, relative to TD children, children with DCD have multiple physiological deficits, receive less parental logistic support for PA involvement, and report lower scores on psychological constructs that are predictive of PA involvement.

Visual tracking behaviour of two-handed catching in boys with developmental coordination disorder.

BACKGROUND: Developmental coordination disorder (DCD) is a motor learning disability that affects coordination resulting in an inability to perform movement skills at an age appropriate level. One area suspected to contribute to the movement difficulties experienced are deficits in visuomotor control. AIMS: This study investigated visual tracking behaviour during catching in children with DCD. METHODS AND PROCEDURES: Twenty-four boys completed the study: 11 with DCD (9.43 years ±0.73) and 13 controls (9.16 years ± 0.68). Participants performed 10 central catching trials, with the best five used to evaluate tracking behaviour and motor responses. OUTCOMES AND RESULTS: Prior to ball release, the DCD group exhibited more fixations (p = 0.043) of lesser duration (p = 0.045). During flight, the DCD group took longer to initiate smooth pursuit (p = 0.003) however, once initiated, both groups were effectively able to maintain smooth pursuit. Despite initial delays, these had no impact on movement initiation time (p = 0.173), however, movement time was significantly slower in the DCD group (p = 0.031). CONCLUSIONS AND IMPLICATIONS: The results of this study demonstrate that catching performance in children with DCD likely reflect a combination of errors in attending to visual information and movement organisation.

Muscle morphology of the lower leg in ambulant children with spastic cerebral palsy.

INTRODUCTION: In this study we aimed to determine the lower limb morphological characteristics of skeletal muscle of ambulant children with spastic cerebral palsy (CP) and typically developing (TD) children. METHODS: Seventeen children with spastic diplegic CP (10 boys and 7 girls, 5-12 years of age, Gross Motor Function Classification System [GMFCS] level I or II) and 19 TD children (8 boys and 11 girls, 5-11 years of age) underwent lower limb T1-weighted MRI. Morphological characteristics of the triceps surae, including muscle volume, anatomical cross-sectional area, muscle length, and subcutaneous adipose tissue, were digitally quantified, and the proportional distribution calculated. RESULTS: Children with GMFCS II had significantly reduced muscle volume, cross-sectional area, and muscle length, and increased subcutaneous fat compared with TD children. Children classified as GMFCS II consistently exhibited the greatest deficits in all morphology variables. DISCUSSION: Morphological variables were significantly different between the groups. These alterations have the potential to influence the functional capabilities of the triceps surae muscle group. Muscle Nerve 58:818-823, 2018.

Reliability and validity of the adapted Resistance Training Skills Battery for Children.

OBJECTIVES: Resistance training (RT) is emerging as a training modality to improve motor function and facilitate physical activity participation in children across the motor proficiency spectrum. Although RT competency assessments have been established and validated among adolescent cohorts, the extent to which these methods are suitable for assessing children's RT skills is unknown. This project aimed to assess the psychometric properties of the adapted Resistance Training Skills Battery for Children (RTSBc), in children with varying motor proficiency. DESIGN: Repeated measures design with 40 participants (M age=8.2±1.7years) displaying varying levels of motor proficiency. METHODS: Participants performed the adapted RTSBc on two occasions, receiving a score for their execution of each component, in addition to an overall RT skill quotient child (RTSQc). Cronbach's alpha, intra-class correlation (ICC), Bland-Altman analysis, and typical error were used to assess test-retest reliability. To examine construct validity, exploratory factor analysis was performed alongside computing correlations between participants' muscle strength, motor proficiency, age, lean muscle mass, and RTSQc. RESULTS: The RTSBc displayed an acceptable level of internal consistency (alpha=0.86) and test-retest reliability (ICC range=0.86-0.99). Exploratory factor analysis supported internal test structure, with all six RT skills loading strongly on a single factor (range 0.56-0.89). Analyses of structural validity revealed positive correlations for RTSQc in relation to motor proficiency (r=0.52, p<0.001) and strength scores (r=0.61, p<0.001). CONCLUSIONS: Analyses revealed support for the construct validity and test-retest reliability of the RTSBc, providing preliminary evidence that the RTSBc is appropriate for use in the assessment of children's RT competency.

Reduced relative volume in motor and attention regions in developmental coordination disorder: A voxel-based morphometry study.

BACKGROUND AND OBJECTIVES: Developmental coordination disorder (DCD) is a prevalent childhood movement disorder, impacting the ability to perform movement skills at an age appropriate level. Although differences in grey matter (GM) volumes have been found in related developmental disorders, no such evidence has been linked with DCD to date. This cross-sectional study assessed structural brain differences in children with and without DCD. METHODS: High-resolution structural images were acquired from 44 children aged 7.8-12 years, including 22 children with DCD (≤16th percentile on MABC-2; no ADHD/ASD), and 22 typically developing controls (≥20th percentile on MABC-2). Structural voxel-based morphology analysis was performed to determine group differences in focal GM volumes. RESULTS: Children with DCD were found to have significant, large, right lateralised reductions in grey matter volume in the medial and middle frontal, and superior frontal gyri compared to controls. The addition of motor proficiency as a covariate explained the between-group GM volume differences, suggesting that GM volumes in motor regions are reflective of the level of motor proficiency. A positive correlation between motor proficiency and relative GM volume was also identified in the left posterior cingulate and precuneus. CONCLUSIONS: GM volume reductions in premotor frontal regions may underlie the motor difficulties characteristic of DCD. It is possible that intervention approaches targeting motor planning, attention, and executive functioning processes associated with the regions of reduced GM volume may result in functional improvements in children with DCD.

Adaptation of the Resistance Training Skills Battery for Use in Children Across the Motor Proficiency Spectrum.

PURPOSE: The study aim was to adapt the Resistance Training Skills Battery for use in children and assess its interrater and intrarater reliability. The RTSBc provides an assessment of resistance training (RT) skill competency and an indication of readiness to perform RT. The RTSBc includes 6 basic RT skills. Scoring for individual RT skills is based on the number of performance criteria correctly demonstrated and a gross resistance training skills quotient for children (RTSQc) is calculated by summing the individual skill scores. METHODS: Twenty participants (mean age = 8.2 ± 1.8 years) were assessed while performing the RTSBc on 2 occasions. The 3 raters completing the assessments had varying levels of movement analysis and RT experience and received training in how to appraise RT skill competency using the RTSBc. RESULTS: Interrater reliability for the 3 raters was very good for the RTSQc (ICC = 0.92) and individual RT skills (ICC range = 0.82-0.94). Intrarater reliability of the live rater was also very good for the RTSQc (ICC = 0.97) and individual RT skills (ICC range = 0.87-0.95). CONCLUSION: This study has demonstrated the interrater and intrarater reliability of the RTSBc for children with varying levels of motor proficiency. The RTSBc can be used reliably within and between-raters to assess the RT skill competency of children.

Cortical functioning in children with developmental coordination disorder: a motor overflow study.

This study examined brain activation in children with developmental coordination disorder (DCD) to reveal areas that may contribute to poor movement execution and/or abundant motor overflow. Using functional magnetic resonance imaging, 13 boys with DCD (mean age = 9.6 years ±0.8) and 13 typically developing controls (mean age = 9.3 years ±0.6) were scanned performing two tasks (finger sequencing and hand clenching) with their dominant hand, while a four-finger motion sensor recorded contralateral motor overflow on their non-dominant hand. Despite displaying increased motor overflow on both functional tasks during scanning, there were no obvious activation deficits in the DCD group to explain the abundant motor overflow seen. However, children with DCD were found to display decreased activation in the left superior frontal gyrus on the finger-sequencing task, an area which plays an integral role in executive and spatially oriented processing. Decreased activation was also seen in the left inferior frontal gyrus, an area typically active during the observation and imitation of hand movements. Finally, increased activation in the right postcentral gyrus was seen in children with DCD, which may reflect increased reliance on somatosensory information during the execution of complex fine motor tasks.

Ultrasound characterization of medial gastrocnemius tissue composition in children with spastic cerebral palsy.

INTRODUCTION: In this study we aimed to characterize muscle composition of the medial gastrocnemius in children with spastic cerebral palsy (SCP) using quantitative ultrasound. METHODS: Forty children with SCP, aged 4-14 years, participated in this study. Children were grouped according to the gross motor function classification system (GMFCS I-V) and compared with a cohort of age- and gender-matched, typically developing children (TD; n = 12). Ultrasound scans were taken of the medial gastrocnemius. Images were then characterized using grayscale statistics to determine mean echo intensity (EI) and the size and number of spatially connected homogeneous regions (i.e., blobs). RESULTS: Significant differences in skeletal muscle composition were found between children with SCP and their TD peers. Children classified as GMFCS III consistently exhibited the highest EI and blob area. CONCLUSIONS: This study demonstrates altered tissue composition in children with SCP visualized using ultrasound. Further work is required to determine the pathophysiology contributing to these alterations in SCP.

Does muscle size matter? The relationship between muscle size and strength in children with cerebral palsy.

PURPOSE: To investigate the muscle size-strength relationship of the knee flexors and extensors in children with spastic cerebral palsy (CP) in relation to typically developing children (TD). METHODS: Eighteen children with spastic Diplegia, Gross Motor Function Classification System I-III (mean 7 y 5 mo SD 1 y 7 mo) and 19 TD children (mean 7 y 6 mo SD 1 y 9 mo) participated. Muscle volume (MV) and anatomical cross-sectional area (aCSA) were assessed using MRI. Measures of peak torque (PT) and work of the knee flexors and extensors were assessed isometrically and isokinetically using a Biodex dynamometer, and normalised to bodymass (Bm). RESULTS: Children with CP were weaker than their TD peers across all torque variables (p < 0.05). MV and aCSA of the knee flexors (MV: p = 0.002; aCSA: p = 0.000) and extensors (MV: p = 0.003; aCSA: p < 0.0001) were smaller in children with CP. The relationship between muscle size and strength in children with CP was weaker than the TD children. The strongest relationship was between MV and isometric PT/Bm for TD children (r = 0.77-0.84), and between MV and isokinetic work (r = 0.70-0.72) for children with CP. CONCLUSIONS: Children with CP have smaller, weaker muscles than their TD peers. However, muscle size may only partially explain their decreased torque capacity. MV appears to be a better predictor of muscle work in children with CP than aCSA. This is an important area of research particularly in regard to treatment(s) that target muscle and strength in children with CP. Implications for Rehabilitation This research adds to the evidence that children with CP have smaller, weaker knee flexor and extensor muscles than their TD peers. However, unlike their TD peers, muscle size does not necessarily relate to muscle strength. The weak correlation between MRI-derived muscle volume and isometric peak torque suggests children with CP are underpowered relative to their muscle size. For children with CP, muscle volume appears to be the best predictor of isokinetic muscle torque output. Therefore, when assessing the capacity of a muscle, it appears preferable to measure total muscle volume and torque development through a range of motion (isokinetic strength).

Childhood muscle morphology and strength: alterations over six months of growth.

INTRODUCTION: The purpose of this study was to establish the nature and stability of the strength-size relationship for the knee flexors and extensors across a 6-month period of childhood growth. METHODS: Nineteen typically developing children aged 5-11 years underwent lower limb magnetic resonance imaging (MRI) and dynamometry strength assessments on 2 occasions, 6 months apart. Muscle volume (MV) and maximum anatomical cross-sectional area (aCSA) for the knee flexors and extensors were determined using MRI analysis software. Isokinetic dynamometry determined corresponding isometric and isokinetic strength. RESULTS: Strong correlations were found between muscle size and strength for both the knee flexors and extensors (r = 0.84-0.90; P < 0.01). Furthermore, the ratio of strength to muscle size remained consistent across 6 months of prepubescent growth. CONCLUSIONS: Increases in thigh muscle strength were relative to those in muscle size, suggesting that muscle growth may play an important role in the development of strength during childhood.

Catch! Movement kinematics of two-handed catching in boys with Developmental Coordination Disorder.

PURPOSE: To quantify two-handed catching in boys with Developmental Coordination Disorder (DCD) by examining sequencing of the upper limb and trunk segments, and degree of symmetry. METHOD: Thirteen boys with DCD( ̅x=9.36 years ± 0.68) and 13 Controls ( ̅x=9.16 years ± 0.68) participated. Children performed 10 two-handed central catching trials, with the best five trials selected for analysis. RESULTS: The DCD group displayed greater variability in range of motion across all joint rotations in the catch phase. Specifically, increased shoulder flexion, thorax extension and elbow extension. Although the initiation of segmental movement occurred in the same order for the two groups, the DCD group initiated wrist extension considerably earlier. The DCD group also exhibited significant asymmetry in elbow flexion-extension. CONCLUSION: Despite success in performing this simple catching task (88% successful), the DCD group displayed an inefficient, variable and less symmetrical catching technique.

Lycra arm splints in conjunction with goal-directed training can improve movement in children with cerebral palsy.

OBJECTIVES: To investigate the effects of lycra® arm splint wear on goal attainment and three dimensional (3D) kinematics of the upper limb and trunk in children with cerebral palsy (CP). DESIGN: Randomised clinical trial whereby participants were randomised to parallel groups with waiting list control. PARTICIPANTS: Sixteen children with CP (hypertonia) aged 9 to 14 years. INTERVENTION: Three months lycra arm splint wear combined with goal directed training. MAIN OUTCOME MEASURE: Goal attainment scale, and 3D upper limb and trunk kinematics across four upper limb movement tasks. RESULTS: 17/18 children achieved their movement goals following three months of splinting. Selected joint kinematics improved on immediate splint application. Further improvements in joint kinematics were demonstrated following 3 months of splint wear, particularly in elbow extension, shoulder flexion and abduction and in thorax flexion. Only improvements in movement compensations at the thorax remained following removal of the splint. CONCLUSIONS: The lycra® arm splint, made a quantifiable change to the attainment of movement goals of importance to the child. Furthermore, improvements were demonstrated in selected maximum range of movement and joint kinematics during functional tasks at the elbow and shoulder joints and thorax segment in children with CP.

Running biomechanics and lower limb strength associated with prior hamstring injury.

PURPOSE: Hamstrings injury/reinjury is common, but functional reasons for this remain unclear. This study identified bilateral differences in swing phase running biomechanics and isokinetic strength, between the previously hamstring-injured and uninjured limbs of male athletes involved in sprint-based sports. METHODS: Athletes, injury-free during testing, underwent three-dimensional motion analyses to determine bilateral joint kinematics and kinetics during submaximal sprinting. Various hip and knee isokinetic strength tests were performed bilaterally using a Biodex dynamometer. Peak torque (PT) and total work (TW; normalized to body mass) were collected isokinetically from concentric hamstrings (CH), concentric quadriceps (CQ), concentric hip flexors (CHF), and eccentric hamstrings (EH). Three PT and TW ratios were created, namely, CH/CQ, EH/CQ, and EH/CHF, and were compared between the previously injured and uninjured limbs. RESULTS: Lower limb swing phase kinematics and kinetics were similar. Only peak hip flexion angle in late swing was significantly reduced (1.9°) in the previously injured limb. EH PT was decreased (26.2 N·m·kg(-1)) and occurred at shorter hamstring lengths on the previously injured side, whereas CQ TW was increased by 13.6 J·kg(-1). EH/CQ and EH/CHF ratios for PT and TW were reduced on the previously injured limbs. CONCLUSIONS: Although swing phase biomechanics of submaximal sprinting were similar between limbs, the previously injured hamstrings did display significant weakness eccentrically. Residual eccentric weakness may predispose this muscle group to reinjury during late swing, compared with the uninjured limb, because the functional eccentric demand on both limbs was similar. Furthermore, the EH/CHF ratios may better reflect muscle function during sprinting, having the potential to influence rehabilitation to prevent reinjury.