Key performance indicators and leg positioning for the kick-start in competitive swimmers

The aim of the study was to (1) assess the test-retest reliability of a novel performance analysis system for swimming (KiSwim) including an instrumented starting block and optical motion capture system, (2) identify key performance indicators (KPI) for the kick-start, (3) determine the most beneficial position of the strong leg and (4) investigate the effect of acute reversal of leg positioning. During three sessions, kick-starts of 15 competitive swimmers were investigated. Eighteen kinematic and kinetic parameters showed high reliability (ICC>0.75) from which principal component analysis identified seven KPI (i.e., time to 15 m, time on-block, depth at 7.5 m, horizontal take-off velocity, horizontal impulse back plate, horizontal peak force back plate and vertical peak force front plate). For the preferred start position, the back plate showed a higher horizontal peak force (0.71 vs. 0.96 x body mass; p < 0.001) and impulse (0.191 vs. 0.28Ns/BW; p < 0.001) compared to front plate. Acute reversal of the leg position reduced performance (i.e., increased time to 15 m and reduced horizontal take-off velocity). However, plate-specific kinetic analysis revealed a larger horizontal peak force (p < 0.001) and impulse (p < 0.001) for the back compared to the front plate in any start position investigated. Therefore, swimmers are encouraged to position the strong leg in the back

Can developmental trajectories in gait variability provide prognostic clues in motor adaptation among children with mild cerebral palsy? A retrospective observational cohort study

AimTo investigate whether multiple domains of gait variability change during motor maturation and if this change over time could differentiate children with a typical development (TDC) from those with cerebral palsy (CwCP).MethodsThis cross-sectional retrospective study included 42 TDC and 129 CwCP, of which 99 and 30 exhibited GMFCS level I and II, respectively. Participants underwent barefoot 3D gait analysis. Age and parameters of gait variability (coefficient of variation of stride-time, stride length, single limb support time, walking speed, and cadence; as well as meanSD for hip flexion, knee flexion, and ankle dorsiflexion) were used to fit linear models, where the slope of the models could differ between groups to test the hypotheses.ResultsMotor-developmental trajectories of gait variability were able to distinguish between TDC and CwCP for all parameters, except the variability of joint angles. CwCP with GMFCS II also showed significantly higher levels of gait variability compared to those with GMFCS I, these levels were maintained across different ages.InterpretationThis study showed the potential of gait variability to identify and detect the motor characteristics of high functioning CwCP. In future, such trajectories could provide functional biomarkers for identifying children with mild movement related disorders and support the management of expectations

Does Subthalamic Deep Brain Stimulation Impact Asymmetry and Dyscoordination of Gait in Parkinson’s Disease?

Background. Subthalamic deep brain stimulation (STN-DBS) is an effective treatment for selected Parkinson’s disease (PD) patients. Gait characteristics are often altered after surgery, but quantitative therapeutic effects are poorly described. Objective. The goal of this study was to systematically investigate modifications in asymmetry and dyscoordination of gait 6 months postoperatively in patients with PD and compare the outcomes with preoperative baseline and to asymptomatic controls without PD. Methods. A convenience sample of thirty-two patients with PD (19 with postural instability and gait disorder (PIGD) type and 13 with tremor dominant disease) and 51 asymptomatic controls participated. Parkinson patients were tested prior to the surgery in both OFF and ON medication states, and 6-months postoperatively in the ON stimulation condition. Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) I to IV and medication were compared to preoperative conditions. Asymmetry ratios, phase coordination index, and walking speed were assessed. Results. MDS-UPDRS I to IV at 6 months improved significantly, and levodopa equivalent daily dosages significantly decreased. STN-DBS increased step time asymmetry (hedges’ g effect sizes [95% confidence interval] between pre- and post-surgery: .27 [-.13, .73]) and phase coordination index (.29 [-.08, .67]). These effects were higher in the PIGD subgroup than the tremor dominant (step time asymmetry: .38 [-.06, .90] vs .09 [-.83, 1.0] and phase coordination index: .39 [-.04, .84] vs .13 [-.76, .96]). Conclusions. This study provides objective evidence of how STN-DBS increases asymmetry and dyscoordination of gait in patients with PD and suggests motor subtypes‐associated differences in the treatment response

Revealing the Optimal Thresholds for Movement Performance: A Systematic Review and Meta-Analysis to Benchmark Pathological Walking Behaviour

In order to address whether increased levels of movement output variability indicate pathological performance, we systematically reviewed and synthesized meta-analysis data on healthy and pathological motor behavior. After screening up to 24’000 reports from four databases, 85 studies were included containing 2409 patients and 2523 healthy asymptomatic controls. The optimal thresholds of variability with uncertainty boundaries (in % Coefficient of Variation ± Standard Error) were estimated in 7 parameters: stride time (2.34 ± 0.21), stride length (2.99 ± 0.37), step length (3.34 ± 0.84), swing time (2.94 ± 0.60), step time (3.35 ± 0.23), step width (15.87 ± 1.86), and dual-limb support time (6.08 ± 2.83). All spatio-temporal parameters exhibited a positive effect size (pathology led to increased variability) except step width variability (Effect Size = −0.21). By objectively benchmarking thresholds for pathological motor variability also presented through a case-study, this review provides access to movement signatures to understand neurological changes in an individual that are apparent in movement variability. The comprehensive evidence presented now qualifies stride time variability as a movement biomarker, endorsing its applicability as a viable outcome measure in clinical trials

Functional competency of lower limb musculature in the elderly

Körperlich aktiv zu sein ist Grundlage unseres täglichen Lebens. Für alle diese Aktivitäten ist das kontinuierliche Zusammenspiel des senso-motorischen System (SMS) erforderlich. Die Kontrolle der verschiedenen afferenten und efferenten Subsysteme innerhalb des SMS basiert auf Feedback-Mechanismen, die die Aufrechterhaltung des Gleichgewichts und der Stabilität während den verschiedensten statischen als auch dynamischen Aktivitäten ermöglichen. Trotz dieser Kontroll- und Stabilisierungssystems ist das kinematische und kinetische Resultat nicht konstant; stattdessen ist bei globalen „Ganzkörper-Bewegungen“, und lokaler Muskelanspannung ständig eine gewisse Variabilität vorhanden. Die Interpretation dieser Variabilität bei Bewegungshandlungen ist kontrovers. Wobei große Variabilität ist nicht zwangsläufig ein Indikator für Defizite des SMS darstellt. Das Ziel dieser Dissertation war, die Variabilität bei lokalen und globalen Bewegungshandlungen in statischen und dynamischen Ausgangstellungen zu quantifizieren. Darüberhinaus, wurde der Zusammenhang zwischen lokaler Variabilität der Muskelkraftproduktion und der Variabilität bei globalen Bewegungshandlungen. Die Ergebnisse zeigen, dass lokale und globale Variabilität von Bewegungshandlungen in Menge und Muster verändert sind, nach Störung des SMS durch: Ermüdung, Veränderungen der Umfeldbedingungen, Alterung und bei Personen mit Sturzerfahrung. Außerdem wurde gezeigt, dass sowohl zu große als auch zu kleine Variabilität, ein entscheidendes funktionelles Defizit bei älteren Personen darstellt. Dieser Dissertation hebt die Bedeutung der Variabilität während wiederholter Bewegungshandlungen hervor, welche einen funktionellen Biomarker für die Beurteilung von Bewegungsstörungen darstellt. In der klinische Praxis könnte dieser helfen bei der frühen Identifikation von Personen mit Bewegungsstörungen, zur Entwicklung von individual-spezifischen Rehabilitationsmaßnahmen, sowie der Beurteilung verschiedener Therapieansätze.Undertaking activities is fundamental throughout daily living. In order to successfully perform these activities, continuous involvement of the human sensori-motor system (HSMS) is required. The HSMS involves feedback mechanisms to control numerous afferent and the efferent subsystems to ensure maintenance of balance and stability during both static and dynamic activities. Despite such control and stabilizing mechanisms, the kinematic and kinetic output of a task is not constant; instead variability occurs during continuous performance of both global tasks such as standing and walking, as well as local force production. The interpretation of variability during output task performance remains controversial, with larger levels of variability not always indicating deficits in human-motor performance. The aim of this dissertation was to assess variability during local as well as global task performance in static and dynamic settings. Furthermore, the association between the level of variability during local force production and variability during global tasks such as standing and walking was also investigated. The results within this dissertation showed that variability during task performance is modified in magnitude as well as in structure after perturbation due to fatigue, changes in environmental conditions, and aging, as well as in fall-prone elderly individuals. Furthermore, both high as well as low levels of variation constitute a key functional deficit among elderly individuals. This dissertation highlights the importance of considering trial-to-trial variations during continuous task performance as a key functional biomarker for motor-related pathologies. Effective assessment of such measures of variability in clinical settings could effectively complement current clinical practice for both early and effective identification of individuals with motor-related pathology, designing subject-specific rehabilitation programs, and evaluating therapy efficacy

Humboldt-Universität zu Berlin

Functional competency of lower limb musculature in the elderly zur Erlangung des akademischen Grads Dr. phil. eingereicht an der Philosophischen Fakultät IV für Institut für Sportwissenschaft vo

Extreme levels of noise constitute a key neuromuscular deficit in the elderly

Fluctuations during isometric force production tasks occur due to the inability of musculature to generate purely constant submaximal forces and are considered to be an estimation of neuromuscular noise. The human sensori-motor system regulates complex interactions between multiple afferent and efferent systems, which results in variability during functional task performance. Since muscles are the only active component of the motor system, it therefore seems reasonable that neuromuscular noise plays a key role in governing variability during both standing and walking. Seventy elderly women (including 34 fallers) performed multiple repetitions of isometric force production, quiet standing and walking tasks. No relationship between neuromuscular noise and functional task performance was observed in either the faller or the non-faller cohorts. When classified into groups with either nominal (group NOM, 25th –75th percentile) or extreme (either too high or too low, group EXT) levels of neuromuscular noise, group NOM demonstrated a clear association (r2&gt;0.23, p&lt;0.05) between neuromuscular noise and variability during task performance. On the other hand, group EXT demonstrated no such relationship, but also tended to walk slower, and had lower stride lengths, as well as lower isometric strength. These results suggest that neuromuscular noise is related to the quality of both static and dynamic functional task performance, but also that extreme levels of neuromuscular noise constitute a key neuromuscular deficit in the elderl

Cortical Contribution to Linear, Non-linear and Frequency Components of Motor Variability Control during Standing

Motor variability is an inherent feature of all human movements and reflects the quality of functional task performance. Depending on the requirements of the motor task, the human sensory-motor system is thought to be able to flexibly govern the appropriate level of variability. However, it remains unclear which neurophysiological structures are responsible for the control of motor variability. In this study, we tested the contribution of cortical cognitive resources on the control of motor variability (in this case postural sway) using a dual-task paradigm and furthermore observed potential changes in control strategy by evaluating Ia-afferent integration (H-reflex). Twenty healthy subjects were instructed to stand relaxed on a force plate with eyes open and closed, as well as while trying to minimize sway magnitude and performing a “subtracting-sevens” cognitive task. In total 25 linear and non-linear parameters were used to evaluate postural sway, which were combined using a Principal Components procedure. Neurophysiological response of Ia-afferent reflex loop was quantified using the Hoffman reflex. In order to assess the contribution of the H-reflex on the sway outcome in the different standing conditions multiple mixed-model ANCOVAs were performed. The results suggest that subjects were unable to further minimize their sway, despite actively focusing to do so. The dual-task had a destabilizing effect on PS, which could partly (by 4%) be counter-balanced by increasing reliance on Ia-afferent information. The effect of the dual-task was larger than the protective mechanism of increasing Ia-afferent information. We, therefore, conclude that cortical structures, as compared to peripheral reflex loops, play a dominant role in the control of motor variability

Editorial: Nonlinear dynamics and complex patterns in the human musculoskeletal system and movement

ISSN:2296-418

Adapting Footfall Rhythmicity to Auditory Perturbations Affects Resilience of Locomotor Behavior: A Proof-of-Concept Study

For humans, the ability to effectively adapt footfall rhythm to perturbations is critical for stable locomotion. However, only limited information exists regarding how dynamic stability changes when individuals modify their footfall rhythm. In this study, we recorded 3D kinematic activity from 20 participants (13 males, 18–30 years old) during walking on a treadmill while synchronizing with an auditory metronome sequence individualized to their baseline walking characteristics. The sequence then included unexpected temporal perturbations in the beat intervals with the subjects required to adapt their footfall rhythm accordingly. Building on a novel approach to quantify resilience of locomotor behavior, this study found that, in response to auditory perturbation, the mean center of mass (COM) recovery time across all participants who showed deviation from steady state (N = 15) was 7.4 (8.9) s. Importantly, recovery of footfall synchronization with the metronome beats after perturbation was achieved prior (+3.4 [95.0% CI +0.1, +9.5] s) to the recovery of COM kinematics. These results highlight the scale of temporal adaptation to perturbations and provide implications for understanding regulation of rhythm and balance. Thus, our study extends the sensorimotor synchronization paradigm to include analysis of COM recovery time toward improving our understanding of an individual’s resilience to perturbations and potentially also their fall risk.ISSN:1662-453XISSN:1662-454