The Validity of Hawkin Dynamics Wireless Dual Force Plates for Measuring Countermovement Jump and Drop Jump Variables.

Force plate testing is becoming more commonplace in sport due to the advent of commercially available, portable, and affordable force plate systems (i.e., hardware and software). Following the validation of the Hawkin Dynamics Inc. (HD) proprietary software in recent literature, the aim of this study was to determine the concurrent validity of the HD wireless dual force plate hardware for assessing vertical jumps. During a single testing session, the HD force plates were placed directly atop two adjacent Advanced Mechanical Technology Inc. in-ground force plates (the "gold standard") to simultaneously collect vertical ground reaction forces produced by 20 participants (27 ± 6 years, 85 ± 14 kg, 176.5 ± 9.23 cm) during the countermovement jump (CMJ) and drop jump (DJ) tests (1000 Hz). Agreement between force plate systems was determined via ordinary least products regression using bootstrapped 95% confidence intervals. No bias was present between the two force plate systems for any of the CMJ and DJ variables, except DJ peak braking force (proportional bias) and DJ peak braking power (fixed and proportional bias). The HD system may be considered a valid alternative to the industry gold standard for assessing vertical jumps because fixed or proportional bias was identified for none of the CMJ variables (n = 17) and only 2 out of 18 DJ variables.

Behavioral gender differences in school-age children with autism.

This study examined differences in internalizing and externalizing behaviors between school-aged boys and girls diagnosed with autism spectrum disorder (ASD). Eighty-nine children between the ages of 8 and 16 years participated in this study: 17 girls (M = 11.5 years, SD = 2.3) and 72 boys (M = 11.3 years, SD = 2.2). Participants were matched on the Autism Diagnostic Observation Schedule, Second Edition and Full-Scale IQ (FSIQ > 64). The results indicated that, girls had higher reported instances of Bullying, less Anger Control, and poorer Emotional Self-Control than boys on the Behavior Assessment System for Children, Second Edition. Groups did not differ on subscales of the Social Communication Scale. While evidence of increased externalizing behaviors is less common in girls, there is evidence supporting these differing behaviors that warrant further research.

Optimal Loading for Force Production in the Straight Bar Deadlift: Force-Time Characteristics in Strength-Trained Adults.

ABSTRACT: Lawson, C, Mundy, P, Lyons, M, and Duncan, MJ. Optimal loading for force production in the straight bar deadlift: Force-time characteristics in strength-trained adults. J Strength Cond Res 35(6): 1636-1641, 2021-This study sought to identify whether there is an optimum load in relation to peak force development and rate of force development (RFD) in the straight bar deadlift and to examine whether baseline strength levels influence this optimum load. Twelve strength-trained men (mean age ± SD; 25.1 ± 5.4 years) performed 3 deadlift repetitions at loads of 10% intervals of 20-90% of their predetermined individual 1 repetition maximum (1RM). Peak vertical force (PFz) and RFD were determined from each repetition. The repetition at each percentage of 1RM that produced the greatest PFz was used for analysis. All data were collected on an AMTI force platform. Repeated-measures analysis of variance indicated significant differences in PFz across loads of 20-90% 1RM (p = 0.001) with a linear increase in PFz with increasing % of 1RM. The highest PFz occurred at 90% of 1RM. For RFD, there was a significant main effect for load (p = 0.018) where instantaneous RFD was significantly higher at 80 and 90% 1RM compared with 20% 1RM. When analyses were re-run using baseline strength as a covariate, the results did not change, indicating that baseline strength did not influence the PFz or RFD output. These results suggest that there is no significant difference in RFD between adjacent loads, but that peak force production was greatest at 90% 1RM in the straight bar deadlift.

Effect of Barbell Load on Vertical Jump Landing Force-Time Characteristics.

ABSTRACT: Lake, JP, Mundy, PD, Comfort, P, McMahon, JJ, Suchomel, TJ, and Carden, P. Effect of barbell load on vertical jump landing force-time characteristics. J Strength Cond Res 35(1): 25-32, 2021-The aim of this study was to quantify the effect that barbell load has on the jump height and force-time characteristics of the countermovement jump (CMJ). Fifteen strength-trained men (mean ± SD: age 23 ± 2 years, mass 84.9 ± 8.1 kg, and height 1.80 ± 0.05 m) performed 3 CMJs with no additional load, and with barbell loads of 25, 50, 75, and 100% of body mass on 2 force plates recording at 1,000 Hz. Propulsion and landing force-time characteristics were obtained from force-time data and compared using analysis of variance and effect sizes. Jump height decreased significantly as load increased (26-71%, d = 1.80-6.87). During propulsion, impulse increased with load up to 75% of body mass (6-9%, d = 0.71-1.08), mean net force decreased (10-43%, d = 0.50-2.45), and time increased (13-50%, d = 0.70-2.57). During landing, impulse increased as load increased up to 75% of body mass (5 to 12%, d = 0.54-1.01), mean net force decreased (13-38%, d = 0.41-1.24), and time increased (20-47%, d = 0.65-1.47). Adding barbell load to CMJ significantly decreases CMJ height. Furthermore, CMJ with additional barbell load increases landing phase impulse. However, while mean net force decreases as barbell load increases, landing time increases so that jumpers are exposed to mechanical load for longer. Practitioners should exercise caution when implementing loaded CMJ to assess their athletes.

Self-Esteem, Internalizing Symptoms, and Theory of Mind in Youth With Autism Spectrum Disorder.

Self-esteem is a potent indicator of mental health in typically developing (TYP) individuals. It is surprising that there have been few comprehensive investigations of self-esteem in children and adolescents with autism spectrum disorder (ASD), given that they are at high risk for comorbid mental health problems, such as depression and anxiety. The objectives of the current study were to assess how youth with ASD rate their self-esteem compared to age-matched TYP youth and to examine how self-esteem relates to internalizing psychopathology and theory of mind in the two groups. Seventy-three children and adolescents, ages 9 to 17, were administered a battery of questionnaires assessing self-esteem and internalizing symptoms, as well as tasks designed to measure theory of mind. Results indicated that youth with ASD rated their self-esteem significantly lower than did TYP youth. Self-esteem was strongly related to depression in both groups but was negatively related to theory of mind only for youth with ASD. These results may provide important insights into how individuals with ASD form evaluations of their own self-worth and illustrate how increasing self-awareness in individuals with ASD is not without risks.

The reliability and validity of the bar-mounted PUSH BandTM 2.0 during bench press with moderate and heavy loads.

The aim of this study was to assess the reliability and validity of the bar-mounted PUSH BandTM 2.0 to determine peak and mean velocity during the bench press exercise with a moderate (60% one repetition maximum [1RM]) and heavy (90% 1RM) load. We did this by simultaneously recording peak and mean velocity using the PUSH BandTM 2.0 and three-dimensional motion capture from participants bench pressing with 60% and 90% 1RM. We used ordinary least products regression to assess within-session reliability and whether the PUSH BandTM 2.0 could accurately predict motion capture velocity. Results showed that PUSH BandTM 2.0 and motion capture peak and mean velocity reliability was acceptable with both loads. While there was a tendency for the PUSH BandTM 2.0 to slightly overestimate peak and mean velocity, there was no fixed bias. However, mean velocity with 60 and 90% 1RM demonstrated proportional bias (differences between predicted and motion capture values increase with magnitude). Therefore, PUSH BandTM 2.0 peak velocity with 60 and 90% 1RM is valid, but mean velocity is not.

A review of joint attention and social-cognitive brain systems in typical development and autism spectrum disorder.

This article provides a review of the increasingly detailed imaging literature on the neurodevelopment of joint attention. Many findings from this literature support and inform the hypothesis that the neurodevelopment of joint attention contributes to the functional development of neural systems for human social cognition. Joint attention begins to develop by 5 months of age and is tantamount to the ability to adopt a common perspective with another person. It involves a whole-brain system with nodes in the: (a) dorsal and medial frontal cortex, (b) orbital frontal/insula cortex, (c) anterior/posterior cingulate cortex, (d) superior temporal cortex, (e) precuneus/parietal cortex, and (f) amygdala and striatum. This system integrates triadic information processing about (a) self-attention/action, (b) information about others' attention/action during social interactions that involve, (c) coordinated attention as well as processing a common referent in space. The results of this new imaging literature have the potential to advance current models of social cognition and the social brain, which rarely consider the contribution of the cognitive neurodevelopment of joint attention. The new neuroscience of joint attention is also extremely valuable for clinical research on social-cognitive neurodevelopmental disorders. This is most clearly the case for autism spectrum disorder (ASD) because it is consistent with the hypothesis of substantial functional neurodevelopmental continuity between the preschool impairments of joint attention, and childhood theory of mind ability that characterizes the development of ASD.

Concurrent Validity of a Portable Force Plate Using Vertical Jump Force-Time Characteristics.

This study examined concurrent validity of countermovement vertical jump reactive strength index modified and force-time characteristics recorded using a 1-dimensional portable and laboratory force plate system. Twenty-eight men performed bilateral countermovement vertical jumps on 2 portable force plates placed on top of 2 in-ground force plates, both recording vertical ground reaction force at 1000 Hz. Time to takeoff; jump height; reactive strength index modified; and braking and propulsion impulse, mean net force, and duration were calculated from the vertical force from both force plate systems. Results from both systems were highly correlated (r ≥ .99). There were small (d < 0.12) but significant differences between their respective braking impulse, braking mean net force, propulsion impulse, and propulsion mean net force (P < .001). However, limits of agreement yielded a mean value of 1.7% relative to the laboratory force plate system (95% confidence limits, 0.9%-2.5%), indicating very good agreement across all of the dependent variables. The largest limits of agreement were for jump height (2.1%), time to takeoff (3.4%), and reactive strength index modified (3.8%). The portable force plate system provides a valid method of obtaining reactive strength measures, and several underpinning force-time variables, from unloaded countermovement vertical jump. Thus, practitioners can use both force plates interchangeably.

Support leg action can contribute to maximal instep soccer kick performance: an intervention study.

This investigation assessed whether a Technique Refinement Intervention designed to produce pronounced vertical hip displacement during the kicking stride could improve maximal instep kick performance. Nine skilled players (age 23.7 ± 3.8 years, height 1.82 ± 0.06 m, body mass 78.5 ± 6.1 kg, experience 14.7 ± 3.8 years; mean ± SD) performed 10 kicking trials prior to (NORM) and following the intervention (INT). Ground reaction force (1000 Hz) and three-dimensional motion analysis (250 Hz) data were used to calculate lower limb kinetic and kinematic variables. Paired t-tests and statistical parametric mapping examined differences between the two kicking techniques across the entire kicking motion. Peak ball velocities (26.3 ± 2.1 m · s-1 vs 25.1 ± 1.5 m · s-1) and vertical displacements of the kicking leg hip joint centre (0.041 ± 0.012 m vs 0.028 ± 0.011 m) were significantly larger (P < 0.025) when performed following INT. Further, various significant changes in support and kicking leg dynamics contributed to a significantly faster kicking knee extension angular velocity through ball contact following INT (70-100% of total kicking motion, P < 0.003). Maximal instep kick performance was enhanced following INT, and the mechanisms presented are indicative of greater passive power flow to the kicking limb during the kicking stride.

The effects of barbell load on countermovement vertical jump power and net impulse.

The aim of this study was to examine the effects of barbell load on countermovement vertical jump (CMJ) power and net impulse within a theoretically valid framework, cognisant of the underpinning force, temporal, and spatial components. A total of 24 resistance-trained rugby union athletes (average ± SD: age: 23.1 ± 3.4 years; height: 1.83 ± 0.05 m; body mass (BM): 91.3 ± 10.5 kg) performed maximal CMJ under 5 experimental conditions in a randomised, counterbalanced order: unloaded, and with additional loads of 25%, 50%, 75%, and 100% of BM. Peak power and average power were maximised during the unloaded condition, both decreasing significantly (P < 0.05) as load increased. Net impulse was maximised with 75% of BM, which was significantly greater (P < 0.05) than the unloaded and 100% of BM conditions. Net mean force and mean velocity were maximised during the unloaded condition and decreased significantly (P < 0.05) as load increased, whereas phase duration increased significantly (P < 0.05) as load increased. As such, the interaction between barbell load and the underpinning force, time, and displacement components should be considered by strength and conditioning coaches when prescribing barbell loads.

Power and impulse applied during push press exercise.

The aim of this study was to quantify the load, which maximized peak and mean power, and impulse applied to these loads, during the push press and to compare them to equivalent jump squat data. Resistance-trained men performed 2 push press (n = 17; age: 25.4 ± 7.4 years; height: 183.4 ± 5 cm; body mass: 87 ± 15.6 kg) and jump squat (n = 8 of original 17; age: 28.7 ± 8.1 years; height: 184.3 ± 5.5 cm; mass: 98 ± 5.3 kg) singles with 10-90% of their push press and back squat 1 repetition maximum (1RM), respectively, in 10% 1RM increments while standing on a force platform. Push press peak and mean power was maximized with 75.3 ± 16.4 and 64.7 ± 20% 1RM, respectively, and impulses applied to these loads were 243 ± 29 N·s and 231 ± 36 N·s. Increasing and decreasing load, from the load that maximized peak and mean power, by 10 and 20% 1RM reduced peak and mean power by 6-15% (p ≤ 0.05). Push press and jump squat maximum peak power (7%, p = 0.08) and the impulse that was applied to the load that maximized peak (8%, p = 0.17) and mean (13%, p = 0.91) power were not significantly different, but push press maximum mean power was significantly greater than the jump squat equivalent (∼9.5%, p = 0.03). The mechanical demand of the push press is comparable with the jump squat and could provide a time-efficient combination of lower-body power and upper-body and trunk strength training.

Methodological considerations in assessing countermovement jumps with handheld accentuated eccentric loading.

This study aimed to compare the agreement between three-dimensional motion capture and vertical ground reaction force (vGRF) in identifying the point of dumbbell (DB) release during a countermovement jump with accentuated eccentric loading (CMJAEL), and to examine the influence of the vGRF analysis method on the reliability and magnitude of CMJAEL variables. Twenty participants (10 male, 10 female) completed five maximal effort CMJAEL at 20% and 30% of body mass (CMJAEL20 and CMJAEL30, respectively) using DBs. There was large variability between methods in both loading conditions, as indicated by the wide limits of agreement (CMJAEL20 = -0.22 to 0.07 s; CMJAEL30 = -0.29 to 0.14 s). Variables were calculated from the vGRF data, and compared between four methods (forward integration (FI), backward integration (BI), FI adjusted at bottom position (BP), FI adjusted at DB release point (DR)). Greater absolute reliability was observed for variables from DR (CV% ≤ 7.28) compared to BP (CV% ≤ 13.74), although relative reliability was superior following the BP method (ICC ≥ 0.781 vs ≥ 0.606, respectively). The vGRF method shows promise in pinpointing the DB release point when only force platforms are accessible, and a combination of FI and BI analyses is advised to understand CMJAEL dynamics.

Research on social attention in autism and the challenges of the research domain criteria (RDoC) framework.

The fuzzy nature of categories of psychopathology, such as autism, leads to significant research challenges. Alternatively, focusing research on the study of a common set of important and well-defined psychological constructs across psychiatric conditions may make the fundamental etiological processes of psychopathology easier to discern and treat (Cuthbert, 2022). The development of the research domain criteria (RDoC) framework is designed to guide this new research approach (Insel et al., 2010). However, progress in research may be expected to continually refine and reorganize the understanding of the specifics of these mental processes (Cuthbert & Insel, 2013). Moreover, knowledge gleaned from the study of both normative and atypical development can be mutually informative in the evolution of our understanding of these fundamental processes. A case in point is the study of social attention. This Autism 101 commentary provides an educational summary of research over the last few decades indicates that social attention is major construct in the study of human social-cognitive development, autism and other forms of psychopathology. The commentary also describes how this research can inform the Social Process dimension of the RDoC framework.

Writing Self-Concept, Text Engagement, and Writing Practices Across Contexts: Comparisons Between School-Age Children on the Autism Spectrum and Their Non-Autistic Peers.

PURPOSE: Autistic children demonstrate highly variable written language skills. Existing research has focused on examining autistic children's performance on direct assessments of written language. In contrast, few studies have sought to understand how autistic children conceptualize their writing abilities or engage with writing across different contexts compared to non-autistic peers. METHODS: This study used a researcher-designed questionnaire to examine writing self-concept, text engagement with different writing activities, and writing practices and beliefs across school and non-school contexts in school-age (10-18 years old) autistic children compared to their non-autistic peers. Data analysis approaches included "multiple indicators, multiple causes" (MIMIC) modeling; correlational and multiple regression analysis; non-parametric Mann-Whitney U tests; and principal components analysis. RESULTS: Groups did not differ in their writing self-concept ratings. Furthermore, both groups engaged with a variety of different writing activities to a similar extent except for text messages being lower for the autistic group. Five components were extracted via principal components analysis on items related to writing practices and beliefs across contexts; groups did not differ across the components. Overall, the non-autistic group showed more consistent relationships between writing self-concept as well as writing practices and beliefs with performance on a narrative writing task when compared to the autistic group. CONCLUSION: Results offer a preliminary understanding into how autistic children engage with writing across contexts for a variety of purposes when compared to their non-autistic peers and offer implications for continued research and educational practice.

Building for the Future: A Systematic Review of the Effects of Eccentric Resistance Training on Measures of Physical Performance in Youth Athletes.

BACKGROUND: Eccentric resistance training is recognised as an effective stimulus for enhancing measures of muscular strength and power in adult populations; however, its value in youth athletes is currently not well understood. OBJECTIVE: The aim of this systematic review was to critically appraise the effects of eccentric resistance training on measures of physical performance (i.e. muscular strength, jump, sprint and change of direction) in youth athletes 18 years of age and under. METHODS: Original journal articles published between 1950 and June 2022 were retrieved from electronic search engines of PubMed, SPORTDiscus and Google Scholar's advanced search option. Full journal articles investigating the acute and chronic effects of eccentric resistance training on measures of physical performance in youth athletes (i.e. a person 18 years of age or under who competes in sport) were included. The methodological quality and bias of each study were assessed prior to data extraction using a modified Downs and Black checklist. RESULTS: The search yielded 749 studies, of which 436 were duplicates. Three-hundred studies were excluded based upon title and abstract review and a further 5 studies were removed following the modified Downs and Black checklist. An additional 14 studies were identified during backward screening. Accordingly, 22 studies were included in our systematic review. The Nordic hamstring exercise and flywheel inertial training were the most frequently used eccentric resistance training methods in youth athletes. Improvements in physical performance following the Nordic hamstring exercise are dependent upon an increase in the breakpoint angle, rather than training volume (sets and repetitions), and are further elevated with the addition of hip extension exercises or high-speed running. A minimum of 3 familiarisation trials is necessary to elicit meaningful adaptations following flywheel inertial training. Furthermore, an emphasis should be placed upon decelerating the rotating flywheel during the final one to two thirds of the eccentric phase, rather than gradually throughout the entire eccentric phase. CONCLUSIONS: The findings of this systematic review support the inclusion of eccentric resistance training in youth athletes to improve measures of muscular strength, jump, sprint and change of direction performance. The current eccentric resistance training methods are predominantly limited to the Nordic hamstring exercise and flywheel inertial training; however, the efficacy of accentuated eccentric loading to improve jump performance warrants attention in future investigations.

Observations of Player (de)Selection Within a Professional UK Soccer Academy.

The present study engaged in an ethnographical observation of the processes used to determine player (de)selections within a professional academy. English category-2 youth academy players (n = 96) from U10-U16 age groups undertook anthropometric profiling (height, mass and somatic maturation) and fitness assessments (10 m, 20 m & 30 m linear sprints, 505-agility test, countermovement and squat jumps). Each players lead coach (n = 4) subjectively graded players utilising a red, amber and green (RAG) rating system on a weekly (current performance) and quarterly (perceived potential) basis, across 25 weeks. A MANCOVA, controlling for maturation, was applied to determine differences in (de)selection by physical performance. Mann Whitney-U tests were used to distinguish difference in (de)selection by subjective grading (weekly and quarterly). The key finding was that quarterly subjective gradings established a higher cumulative score of green ratings in selected players and a low cumulative score of red ratings, and vice versa for deselected players (P ≤ 0.001 to 0.03). However, whilst these findings suggest that quarterly subjective grades of potential were able to provide the best predictors for player (de)selection, the findings should be viewed with caution due to high potential for confirmatory bias.

The Construct Validity of the Childhood Joint Attention Rating Scale (C-JARS) in School-Aged Autistic Children.

Preliminary evidence from the Childhood Joint Attention Rating Scale (C-JARS; Mundy et al., 2017) suggests symptoms related to diminished joint attention and the spontaneous sharing of experience with others can be assessed with a parent-report measure in children and adolescents with autism. This study was designed to expand on the previous study by examining the validity of both a Social Symptom (SS) and a Prosocial (PS) scale of the C-JARS in a study of school-aged autistic children (n  = 89) with and without co-occurring intellectual disability (ID), as well as an age matched neurotypical sample (n  = 62). Results indicated that both C-JARS scales were sensitive and specific with respect to identifying the diagnostic status of the children. In addition, the PS scale was sensitive to differences in cognitive abilities (IQ) and sex differences in the autism group. These results are consistent with the hypothesis that joint attention and spontaneous sharing of experience symptoms are not only characteristic of preschool children with autism but may also constitute a developmentally continuous dimension of the social phenotype of autism that can be measured in school-aged children.

Conversation During a Virtual Reality Task Reveals New Structural Language Profiles of Children with ASD, ADHD, and Comorbid Symptoms of Both.

Many studies have utilized standardized measures and storybook narratives to characterize language profiles of children with Autism Spectrum Disorder (ASD) and Attention Deficit/Hyperactivity Disorder (ADHD). They report that structural language of these children is on par with mental-age-matched typically developing (TD) peers. Few studies have looked at structural language profiles in conversational contexts. This study examines conversational speech produced in a virtual reality (VR) paradigm to investigate the strengths and weaknesses of structural language abilities of these children. The VR paradigm introduced varying social and cognitive demands across phases. Our results indicate that children from these diagnostic groups produced less complex structural language than TD children. Moreover, language complexity decreased in all groups across phases, suggesting a cross-etiology sensitivity to conversational contexts.

The Need for Eccentric Speed: A Narrative Review of the Effects of Accelerated Eccentric Actions During Resistance-Based Training.

Eccentric training as a method to enhance athletic performance is a topic of increasing interest to both practitioners and researchers. However, data regarding the effects of performing the eccentric actions of an exercise at increased velocities are limited. This narrative review aimed to provide greater clarity for eccentric methods and classification with regard to temporal phases of exercises. Between March and April 2021, we used key terms to search the PubMed, SPORTDiscus, and Google Scholar databases within the years 1950-2021. Search terms included 'fast eccentric', 'fast velocity eccentric', 'dynamic eccentric', 'accentuated eccentric loading', and 'isokinetic eccentric', analysing both the acute and the chronic effects of accelerated eccentric training in human participants. Review of the 26 studies that met the inclusion criteria identified that completing eccentric tempos of < 2 s increased subsequent concentric one repetition maximum performance, velocity, and power compared with > 4 s tempos. Tempos of > 4 s duration increased time under tension (TUT), whereas reduced tempos allowed for greater volume to be completed. Greater TUT led to larger accumulation of blood lactate, growth hormone, and testosterone when volume was matched to that of the reduced tempos. Overall, evidence supports eccentric actions of < 2 s duration to improve subsequent concentric performance. There is no clear difference between using eccentric tempos of 2-6 s if the aim is to increase hypertrophic response and strength. Future research should analyse the performance of eccentric actions at greater velocities or reduced time durations to determine more factors such as strength response. Tempo studies should aim to complete the same TUT for protocols to determine measures for hypertrophic response.