Corrigendum: In-contest body acceleration profiles for the judo male and female weight divisions.

[This corrects the article DOI: 10.3389/fspor.2024.1372314.].

Is screening for motor skill deficits in Tyrolean preschool children warranted and feasible? A protocol for a two-stage cross-sectional study.

INTRODUCTION: Children with developmental coordination disorder (DCD) show deviations in motor development and motor skills in early childhood where the learning and execution of coordinated motor skills are below the level expected for their age. Early detection of DCD is critical to provide an opportunity for intervention and support, yet many cases remain undetected until school age. The study described aims to determine the warranty, feasibility and validity of a mobility screening in Tyrolean kindergartens and evaluate its potential benefit to enhance the motor development prospects of affected children. METHODS AND ANALYSIS: This research employs a two-stage cross-sectional approach with 6 months of follow-up assessments. The initial stage involves a playful mobility screening for all participating kindergarten children, followed by individual assessments for those displaying conspicuous motor skills. Motor skills will be evaluated using MobiScreen 4-6 and the Movement Assessment Battery for Children-2. Prior to the screening, informed consent is obtained from kindergarten bodies and authorities, parents and the children themselves. Parents are provided with information sheets and questionnaires to assess their attitudes and their child's eligibility. The study described aims to form a representative sample of kindergarten children, aged 4-6, in Tyrol. To target approximately 20-40 children with DCD for follow-up, the goal is to include 650 children, assuming an incidence of 3%-6%. For the follow-up, matching control groups will be formed and information about how identified motor deficits were addressed, including therapies or sports, will be gathered. Quantitative data will mainly be analysed descriptively, while feedback from kindergarten teachers regarding the practical implementation will be analysed using qualitative content analyses, according to Mayring. ETHICS AND DISSEMINATION: The study has been approved by the Research Committee for Scientific Ethical Questions (RCSEQ 3369/24). Findings will be disseminated through contributions, peer-reviewed journals, and conferences.

Efficacy of hinged and carbon fiber ankle-foot orthoses in children with unilateral spastic cerebral palsy and drop-foot gait pattern.

BACKGROUND: In children with unilateral spastic cerebral palsy (USCP), ankle-foot orthoses (AFOs) are widely used to correct common gait deviations such as a drop-foot pattern. Most studies on this topic have investigated specific time points while omitting other parts of the gait cycle. OBJECTIVES: This study investigated the separate effects of prefabricated carbon fiber AFOs and custom-made hinged AFOs compared with barefoot walking in children with USCP with a drop-foot gait pattern using statistical parametric mapping. STUDY DESIGN: Retrospective, cross-sectional, repeated measures study. METHODS: Twenty ambulatory children (9.9 ± 2.5 years) with USCP and a drop-foot gait pattern were included. Kinematics, kinetics, and spatiotemporal parameters assessed during 3-dimensional gait analysis were compared between barefoot and AFO walking. Statistical parametric mapping was used to compare joint angles and moment waveforms. Kinematics, kinetics and spatiotemporal parameters assessed during 3-dimensional gait analysis were compared between barefoot and AFO walking for each AFO type but not between the 2 AFO types. RESULTS: Compared with barefoot walking, there was a steeper sole angle at initial contact, corresponding to a heel strike pattern, and an increased ankle dorsiflexion in swing with the use of both AFOs. The ankle plantar flexion moment during loading response increased. Ankle power generation during pre-swing decreased in the carbon fiber AFO group when walking with AFOs. CONCLUSIONS: Both AFOs were beneficial for improving a drop-foot gait pattern in these small patient groups and can, therefore, be recommended to treat this gait deviation in patients with unilateral cerebral palsy. However, the reduction in ankle power generation during push-off and additional goals targeted by AFOs, such as correction of structural or flexible foot deformities, should be considered for prescription.

In-contest body acceleration profiles for the judo male and female weight divisions.

Introduction: This study aimed to determine the body accelerations (BA) profile of the judo contest of the male and female weight divisions and to ascertain the involvement of the vertical, mediolateral and anteroposterior axes in it. Methods: Forty-eight male and forty-eight female national and international level athletes (some of them medalists in World, European and national championships) participated in a 5-min simulated contest (official fight time plus breaks) against an opponent of the same sex and weight division, wearing an accelerometer. Heart rate, blood lactate and ratings of perceived exertion were recorded to certify that the athletes performed the fullest. Results: The t2way test expressed differences in the athletes' BA (p = 0.001) and three profiles were identified: the light/middle weight male divisions, the light/middle weight female divisions and the heavy male and female ones. Athletes of all weight divisions performed their BA during the contest in all three directions (the one-sample Person's chi-square did not detect any significantly predominant one: p = 0.400, p = 0.631, p = 0.844, p = 0.749, p = 0.644 and p = 0.895, for male light, moderate and heavy, female light, moderate and heavyweight athletes, respectively). Monte Carlo method simulations suggested as the most likely scenarios those with BA involving all axes, with a slight preference of the anteroposterior and mediolateral ones. Discussion: These results suggest that the demands on judo athletes in a contest differ between weight classes and sexes.

Do Bernstein's Stages of Learning Apply after Stroke? A Scoping Review on the Development of Whole-Body Coordination after Cerebrovascular Accidents.

Stroke is one of the leading causes of disability around the world, presenting unique challenges in motor development during the rehabilitation process. Based on studies in movement and sports science, thorough knowledge has accumulated on the development of movement skills. Through the works of Nikolai Bernstein, it has been established that when learning new skills, people tend to first simplify coordination by 'freezing' their degrees of freedom, after which they start building efficiency by 'releasing' specific degrees of freedom. If a similar pattern of development can be established post-stroke, it would imply that lessons learned in sports skill acquisition can also be implemented to optimize stroke rehabilitation. The current scoping review aims to assess whether the Bernsteinian freezing-to-releasing stages of learning also apply to developing whole-body movement skills after stroke. To this end, we systematically screened the existing literature for studies involving a longitudinal measure of whole-body coordination after a stroke. Only five articles met the criteria for inclusion, indicating a gap in research on this topic. Based on the observations within these articles, we could neither confirm nor reject whether the freezing-to-releasing process can apply after a stroke. We could, however, hypothesize a detailed description of the freezing-to-releasing process, which can be assessed in future works.

Bilateral Deficits in Dynamic Postural Stability in Females Persist Years after Unilateral ACL Injury and Are Modulated by the Match between Injury Side and Leg Dominance.

Previous research has documented brain plasticity after an anterior cruciate ligament (ACL) tear and suggests that these neural adaptations contribute to poorer motor control. Since both brain hemispheres show adaptations, we hypothesized that reduced dynamic stability occurs not only in the injured, but also the contralateral, uninjured leg. Further, given brain hemispheric specialization's impact on motor coordination, we hypothesized the need to consider the injury side. A total of 41 female athletes and 18 controls performed single-leg jump-landings. Dynamic postural stability was measured as time-to-stabilization (TTS). We found reduced medio-lateral dynamic stability for the ACL injured leg (p = 0.006) with a similar trend for the contralateral leg (p = 0.050) compared to the control group. However, when distinguishing between injuries to the dominant and non-dominant legs, we found increased medio-lateral TTS only if the injury had occurred on the dominant side where landings on injured (p = 0.006) and contralateral (p = 0.036) legs required increased TTS. Assessments of dynamic stability, e.g., in the context of return-to-sport, should consider the injury side and compare results not only between the injured and the contralateral leg, but also to uninjured controls. Future research should not pool data from the dominant-leg ACL with non-dominant-leg ACL injuries when assessing post-injury motor performance.

Ergonomic saddle design features influence lumbar spine motion and can reduce low back pain in mountain biking.

Low back pain is common in mountain biking due to the sustained flexion of the lumbar spine, particularly during fatiguing hill climbs. In this study, we investigated whether an ergonomic mountain bike saddle including a raised rear, a longitudinal dip, and a subtle lateral instability (the 'Active'-technology) can reduce acute low back pain at the end of a hill climb (>1 h) in a group of mountain bikers with a history of cycling-related low back pain (n = 28). In addition, we conducted a laboratory experiment to investigate the isolated effects of the 'Active'-technology on the cyclists' pelvis and spine motion as well as on the activity of surrounding muscles. The field test demonstrated a significant reduction in numerical low back pain ratings with the experimental saddle compared to the riders' own standard saddle (p = 0.001, strong effect). The laboratory-based data suggested that the 'Active'-technology does lead to potentially beneficial effects on pelvis-spine kinematics and muscle activity, which in combination with an optimised saddle geometry may explain the observed reduction in low back pain following mountain bike hill climbing.

Mountain Hiking: Prolonged Eccentric Muscle Contraction during Simulated Downhill Walking Perturbs Sensorimotor Control Loops Needed for Safe Dynamic Foot-Ground Interactions.

Safe mountain hiking requires precise control of dynamic foot-ground interactions. In addition to vision and vestibular afferents, limb proprioception, sensorimotor control loops, and reflex responses are used to adapt to the specific nature of the ground contact. Diminished leg dexterity and balance during downhill walking is usually attributed to fatigue. We investigated the supplementary hypothesis that the eccentric contractions inherent to downhill walking can also disrupt muscle proprioception, as well as the sensorimotor control loops and reflex responses that depend on it. In this study, we measured leg dexterity (LD), anterior-posterior (AP) and medio-lateral (ML) bipedal balance, and maximal voluntary leg extension strength in young and healthy participants before and after 30 min of simulated downhill walking at a natural pace on a treadmill at a 20° decline. Post-pre comparisons of LD (p < 0.001) and AP balance (p = 0.001) revealed significant reductions in dynamic foot-ground interactions after eccentric exercise without an accompanying reduction in leg extension strength. We conclude that eccentric contractions during downhill walking can disrupt the control of dynamic foot-ground interactions independently of fatigue. We speculate that mountaineering safety could be improved by increasing conscious attention to compensate for unadjusted proprioception weighting, especially in the descent.

Walking Stability and Risk of Falls.

Walking stability is considered a necessary physical performance for preserving independence and preventing falls. The current study investigated the correlation between walking stability and two clinical markers for falling risk. Principal component analysis (PCA) was applied to extract the three-dimensional (3D) lower-limb kinematic data of 43 healthy older adults (69.8 ± 8.5 years, 36 females) into a set of principal movements (PMs), showing different movement components/synergies working together to accomplish the walking task goal. Then, the largest Lyapunov exponent (LyE) was applied to the first five PMs as a measure of stability, with the interpretation that the higher the LyE, the lower the stability of individual movement components. Next, the fall risk was determined using two functional motor tests-a Short Physical Performance Battery (SPPB) and a Gait Subscale of Performance-Oriented Mobility Assessment (POMA-G)-of which the higher the test score, the better the performance. The main results show that SPPB and POMA-G scores negatively correlate with the LyE seen in specific PMs (p ≤ 0.009), indicating that increasing walking instability increases the fall risk. The current findings suggest that inherent walking instability should be considered when assessing and training the lower limbs to reduce the risk of falling.

Distinct coordination patterns integrate exploratory head movements with whole-body movement patterns during walking.

Visual guidance of gait is an important skill for everyday mobility. While this has often been studied using eye-tracking techniques, recent studies have shown that visual exploration involves more than just the eye; head movement and potentially the whole body is involved for successful visual exploration. This study aimed to assess coordinative patterns associated with head movement and it was hypothesized that these patterns would span across the body, rather than being localized. Twenty-one (after exclusions) healthy young adult volunteers followed a treadmill walking protocol designed to elicit different types of head movements (no stimuli compared to stimuli requiring horizontal, vertical, and mixed gaze shifts). Principal Component Analysis was used to establish whole-body correlated patterns of marker movement (Principal Movements; PMs) related to the activity of the head. In total 37 higher order PMs were found to be associated with head movement, two of these showed significant differences between trials associated with strong head rotations in the horizontal and sagittal plane. Both of these were associated with a whole-body pattern of activity. An analysis of the higher order components revealed that exploratory head movements are associated with distinct movement patterns, which span across the body. This shows that visual exploration can produce whole-body movement patterns that have a potentially destabilizing influence. These findings shed new light on established results in visual search research and hold relevance for fall and injury prevention.

Focus of Attention in Coach Instructions for Technique Training in Sports: A Scrutinized Review of Review Studies.

Literature reports superior performance when focusing one's attention during a movement on environmental effects of that movement (external focus, EF) compared to focusing on the moving body (internal focus, IF). Nevertheless, IF instructions still play an important role in the daily practice of coaches, trainers, and therapists. The current review compiles evidence for focus-of-attention concepts on movement form corrections and technique training. Reviews on the topic and selected additional papers addressing the effect of attentional focus on movement form or on kinetic, kinematic or muscle activity data were included. Both EF and IF instructions affect movement form. The reviews revealed that IF instructions seem to be better applicable to direct movement form changes than EF instructions. In contrast, EF instructions better facilitate optimization within the whole-body coordination, often resulting in better performance outcomes not directly linked to movement pattern changes. Several studies discuss focus-of-attention effects in the context of the optimal feedback control theory expanding on the constrained action hypothesis. In summary, EF and IF instructions both affect form and performance of movements, however, their relative efficacy is situation dependent. The often-purported superiority of EF over IF instructions cannot be generalized to all application contexts.

Perspective on "in the wild" movement analysis using machine learning.

Recent advances in wearable sensing and machine learning have created ample opportunities for "in the wild" movement analysis in sports, since the combination of both enables real-time feedback to be provided to athletes and coaches, as well as long-term monitoring of movements. The potential for real-time feedback is useful for performance enhancement or technique analysis, and can be achieved by training efficient models and implementing them on dedicated hardware. Long-term monitoring of movement can be used for injury prevention, among others. Such applications are often enabled by training a machine learned model from large datasets that have been collected using wearable sensors. Therefore, in this perspective paper, we provide an overview of approaches for studies that aim to analyze sports movement "in the wild" using wearable sensors and machine learning. First, we discuss how a measurement protocol can be set up by answering six questions. Then, we discuss the benefits and pitfalls and provide recommendations for effective training of machine learning models from movement data, focusing on data pre-processing, feature calculation, and model selection and tuning. Finally, we highlight two application domains where "in the wild" data recording was combined with machine learning for injury prevention and technique analysis, respectively.

Whole-body movement analysis using principal component analysis: What is the internal consistency between outcomes originating from the same movement simultaneously recorded with different measurement devices?

A growing number of studies apply Principal Component Analysis (PCA) on whole-body kinematic data to facilitate an analysis of posture changes in human movement. An unanswered question is, how much the PCA outcomes depend on the chosen measurement device. This study aimed to assess the internal consistency of PCA outcomes from treadmill walking motion capture data simultaneously collected through laboratory-grade optical motion capture and field-suitable inertial-based motion tracking. Data was simultaneously collected using VICON (whole-body plug-in gait marker positions) and Xsens (body segment positions) from 20 participants during 2-min treadmill walking. Using PCA, Principal Movements (PMs) were determined using two commonly used practices: on an individual and a grouped basis. For both, correlation matrices were used to determine internal consistency between outcomes from either measurement system for each PM. Both individual and grouped approach showed excellent internal consistency between outcomes from the two systems among the lower order PMs. For the individual analysis, high correlations were only found along the diagonal of the correlation matrix while the grouped analysis also showed high off-diagonal correlations. These results have important implications for future application of PCA in terms of the independence of the resulting PM data, the way group-differences are expressed in higher-order PMs and the interpretation of movement complexity. Concluding, while PCA-outcomes from the two systems start to deviate in the higher order PMs, excellent internal consistency was found in the lower order PMs which already represent about 98% of the variance in the dataset.

Quantitative downhill skiing technique analysis according to ski instruction curricula: A proof-of-concept study applying principal component analysis on wearable sensor data.

Downhill skiing technique represents the complex coordinative movement patterns needed to control skiing motion. While scientific understanding of skiing technique is still incomplete, not least due to challenges in objectively measuring it, practitioners such as ski instructors have developed sophisticated and comprehensive descriptions of skiing technique. The current paper describes a 3-step proof-of-concept study introducing a technology platform for quantifying skiing technique that utilizes the practitioners' expert knowledge. The approach utilizes an inertial measurement unit system (Xsens™) and presents a motion analysis algorithm based on the Principal Movement (PM) concept. In step 1, certified ski instructors skied specified technique elements according to technique variations described in ski instruction curricula. The obtained data was used to establish a PM-coordinate system for skiing movements. In step 2, the techniques parallel and carving turns were compared. Step 3 presents a case study where the technique analysis methodology is applied to advise an individual skier on potential technique improvements. All objectives of the study were met, proving the suitability of the proposed technology for scientific and applied technique evaluations of downhill skiing. The underlying conceptual approach - utilizing expert knowledge and skills to generate tailored variability in motion data (step 1) that then dominate the orientation of the PMs, which, in turn, can serve as measures for technique elements of interest - could be applied in many other sports or for other applications in human movement analyses.

Intervention for Better Knee Alignment during Jump Landing: Is There an Effect of Internally vs. Externally Focused Instructions?

Externally focused attention is known to induce superior results in the movement outcome, whereas focusing attention on the moving body (internal focus) causes conscious control and constrains action. The study investigated effects on knee trajectory and whole-body movement complexity when addressing knee alignment using externally (EF) vs. internally (IF) focused instructions. Young ski racers, n = 24 (12 male), performed landings with subsequent jumps to submaximal height. Movements were tracked and analyzed during the ground contact phase. Sets of jumps were executed without instruction (CON), followed by EF and IF instructions on knee alignment in a random order. Medial-lateral displacement of the knee in landing quantified task achievement, and whole-body principal component analysis was used to compute movement complexity. Knee alignment instructions led to a significantly lower medial knee displacement compared to CON (p = 0.001, ηp2 = 0.35). EF vs. IF did not reach significance. EF, as well as IF instructions increased the prominence of the first movement pattern (p = 0.01, ηp2 = 0.22) with a reduction of higher-order patterns (p = 0.002, W = 0.11), suggesting a strategy of freezing degrees of freedom. Both instructions addressing the movement form positively influenced knee displacement during landing, and both led to a freezing strategy, simplifying whole-body coordination.

Fatigue-related reductions in movement smoothness during a lateral shuffle and side-cutting movement.

Although movement smoothness is considered a hallmark of well-coordinated motor tasks, it is unknown whether markers of movement smoothness can be used to assess the quality of neuromuscular control in athletes. As a first step into this direction, the purpose of this study was to test whether movement smoothness is reduced following a fatiguing lateral shuffle protocol due to fatigue-related adaptations in neuromuscular control. Sixteen healthy adults (7 females) completed a submaximal 3-minute lateral shuffle trial and a maximal fatiguing shuffle trial until task failure. The movement of the pelvis and feet was determined using 3D motion capture at 250 Hz. Movement smoothness was quantified using the log-dimensionless jerk, which represents how often and abruptly the segment acceleration changes over time. Pelvis and foot movement smoothness along with spatiotemporal variables characterizing the shuffling pattern were compared between the beginning and end of the fatiguing shuffle trial using Wilcoxon signed-rank tests (α = 0.05). Pelvis movement smoothness was significantly reduced in all movement directions (p ≤ 0.005, strong effects) while foot movement smoothness was predominantly reduced in the shuffle direction (p ≤ 0.018, moderate to strong effects). Reductions in movement smoothness coincided with a lower peak pelvis speed in shuffle direction (p = 0.007, strong effect) and shorter contact times when changing direction (p = 0.049, moderate effect). These reductions in movement smoothness may be explained by a change in the overall shuffle pattern characterized by "harder" side-cuts as well as by a muscle fatigue-related decline in the ability to precisely plan and execute foot trajectories.

Implications of Optimal Feedback Control Theory for Sport Coaching and Motor Learning: A Systematic Review.

Best practice in skill acquisition has been informed by motor control theories. The main aim of this study is to screen existing literature on a relatively novel theory, Optimal Feedback Control Theory (OFCT), and to assess how OFCT concepts can be applied in sports and motor learning research. Based on 51 included studies with on average a high methodological quality, we found that different types of training seem to appeal to different control processes within OFCT. The minimum intervention principle (founded in OFCT) was used in many of the reviewed studies, and further investigation might lead to further improvements in sport skill acquisition. However, considering the homogenous nature of the tasks included in the reviewed studies, these ideas and their generalizability should be tested in future studies.

A Systematic Review on Detraining Effects after Balance and Fall Prevention Interventions.

Since the COVID-19 pandemic hit, lockdowns have been implemented to fight off infections in countries around the world. Whilst this measure is without a doubt effective against spreading infection, it might also decrease participation in exercise. For older adults, exercise is particularly important in the prevention of falls, and sudden detraining because of a lockdown or due to other causes might have detrimental consequences. This systematic review study aims to assess what is currently known on detraining effects for balance outcomes. Nine studies were included within this review. Results suggest that detraining effects could already be significant as early as 4 weeks after stopping the intervention. Programs that specifically focus on improving balance were more robust against detraining, with most positive effects still being present after 8 weeks. However, even with a specific focus on balance, studies started to show some signs of detraining. The current study is limited by the low number of included studies in the review, indicating a need to further confirm these results.