Anticipatory and pre-planned actions: A comparison between young soccer players and swimmers

The present study investigated whether a difference exists in reactive and proactive control for sport considered open or closed skills dominated. Sixteen young (11-12 years) athletes (eight soccer players and eight swimmers) were asked to be engaged into two games competitions that required either a reactive and a proactive type of control. By means of kinematic (i.e. movement time and duration) and dynamic analysis through the force platform (i.e. Anticipatory Postural Adjustments, APAs), we evaluated the level of ability and stability in reacting and anticipating actions. Results indicated that soccer players outperformed swimmers by showing higher stability and a smaller number of falls during the competition where proactive control was mainly required. Soccer players were able to reach that result by anticipating actions through well-modulated APAs. On the contrary, during the competition where reactive control was mainly required, performances were comparable between groups. Therefore, the development of specific action control is already established at 11-12 years of age and is enhanced by the training specificity

Muscle belly gearing positively affects the force-velocity and power-velocity relationships during explosive dynamic contractions

Changes in muscle shape could play an important role during contraction allowing to circumvent some limits imposed by the fascicle force-velocity (F-V) and power-velocity (P-V) relationships. Indeed, during low-force high-velocity contractions, muscle belly shortening velocity could exceed muscle fascicles shortening velocity, allowing the muscles to operate at higher F-V and P-V potentials (i.e., at a higher fraction of maximal force/power in accordance to the F-V and P-V relationships). By using an ultrafast ultrasound, we investigated the role of muscle shape changes (vastus lateralis) in determining belly gearing (muscle belly velocity/fascicle velocity) and the explosive torque during explosive dynamic contractions (EDC) at angular accelerations ranging from 1000 to 4000°.s-2. By means of ultrasound and dynamometric data, the F-V and P-V relationships both for fascicles and for the muscle belly were assessed. During EDC, fascicle velocity, belly velocity, belly gearing, and knee extensors torque data were analysed from 0 to 150 ms after torque onset; the fascicles and belly F-V and P-V potentials were thus calculated for each EDC. Absolute torque decreased as a function of angular acceleration (from 80 to 71 Nm, for EDC at 1000 and 4000°.s-1, respectively), whereas fascicle velocity and belly velocity increased with angular acceleration (P < 0.001). Belly gearing increased from 1.11 to 1.23 (or EDC at 1000 and 4000°.s-1, respectively) and was positively corelated with the changes in muscle thickness and pennation angle (the changes in latter two equally contributing to belly gearing changes). For the same amount of muscle's mechanical output (force or power), the fascicles operated at higher F-V and P-V potential than the muscle belly (e.g., P-V potential from 0.70 to 0.56 for fascicles and from 0.65 to 0.41 for the muscle belly, respectively). The present results experimentally demonstrate that belly gearing could play an important role during explosive contractions, accommodating the largest part of changes in contraction velocity and allowing the fascicle to operate at higher F-V and P-V potentials

Postural adjustments to self-triggered perturbations under conditions of changes in body orientation

We studied anticipatory and compensatory postural adjustments (APAs and CPAs) associated with self-triggered postural perturbations in conditions with changes in the initial body orientation. In particular, we were testing hypotheses on adjustments in the reciprocal and coactivation commands, role of proximal vs. distal muscles, and correlations between changes in indices of APAs and CPAs. Healthy young participants stood on a board with full support or reduced support area and held a standard load in the extended arms. They released the load in a self-paced manned with a standard small-amplitude arm movement. Electromyograms of 12 muscles were recorded and used to compute reciprocal and coactivation indices between three muscle pairs on both sides of the body. The subject's body was oriented toward one of three targets: straight ahead, 60° to the left, and 60° to the right. Body orientation has stronger effects on proximal muscle pairs compared to distal muscles. It led to more consistent changes in the reciprocal command compared to the coactivation command. Indices of APAs and CPAs showed positive correlations across conditions. We conclude that the earlier suggested hierarchical relations between the reciprocal and coactivation command could be task-specific. Predominance of negative or positive correlations between APA and CPA indices could also be task-specific

Energetics of walking in individuals with cerebral palsy and typical development, across severity and age: A systematic review and meta-analysis

Background: Individuals with cerebral palsy (CP) report physical fatigue as a main cause of limitation, deterioration and eventually cessation of their walking ability. A consequence of higher level of fatigue in individuals with CP leads to a less efficient and long-distance walking ability. Research question: This systematic review investigates the difference in 1) walking energy expenditure between individuals with CP and age-matched typically developing (TD) individuals; and 2) energetics of walking across Gross Motor Function Classification System (GMFCS) levels and age. Methods: Five electronic databases (PubMed, Web of Science, CINAHL, ScienceDirect and Scopus) were searched using search terms related to CP and energetics of walking. Results: Forty-one studies met inclusion criteria. Thirty-one studies compared energy expenditure between CP and age-matched controls. Twelve studies correlated energy expenditure and oxygen cost across GMFCS levels. Three studies investigated the walking efficiency across different ages or over a time period. A significant increase of energy expenditure and oxygen cost was found in individuals with CP compared to TD age-matched individuals, with a strong relationship across GMFCS levels. Significance: Despite significant differences between individuals with CP compared to TD peers, variability in methods and testing protocols may play a confounding role. Analysis suggests oxygen cost being the preferred/unbiased physiological parameter to assess walking efficacy in CP. To date, there is a knowledge gap on age-related changes of walking efficiency across GMFCS levels and wider span of age ranges. Further systematic research looking at longitudinal age-related changes of energetics of walking in this population is warranted

Can spatial filtering separate voluntary and involuntary components in children with dyskinetic cerebral palsy?

The design of myocontrolled devices faces particular challenges in children with dyskinetic cerebral palsy because the electromyographic signal for control contains both voluntary and involuntary components. We hypothesized that voluntary and involuntary components of movements would be uncorrelated and thus detectable as different synergistic patterns of muscle activity, and that removal of the involuntary components would improve online EMG-based control. Therefore, we performed a synergy-based decomposition of EMG-guided movements, and evaluated which components were most controllable using a Fitts' Law task. Similarly, we also tested which muscles were most controllable. We then tested whether removing the uncontrollable components or muscles improved overall function in terms of movement time, success rate, and throughput. We found that removal of less controllable components or muscles did not improve EMG control performance, and in many cases worsened performance. These results suggest that abnormal movement in dyskinetic CP is consistent with a pervasive distortion of voluntary movement rather than a superposition of separable voluntary and involuntary components of movement

Increased task-uncorrelated muscle activity in childhood dystonia

Even if movement abnormalities in dystonia are obvious on observation-based examinations, objective measures to characterize dystonia and to gain insights into its pathophysiology are still strongly needed. We hypothesize that motor abnormalities in childhood dystonia are partially due to the inability to suppress involuntary variable muscle activity irrelevant to the achievement of the desired motor task, resulting in the superposition of unwanted motion components on the desired movement. However, it is difficult to separate and quantify appropriate and inappropriate motor signals combined in the same muscle, especially during movement

ANTHROPOMETRY AND MOTOR FITNESS IN CHILDREN AGED 6-12 YEARS

This study aimed at evaluating motor abilities and anthropometric parameters in children aged 6-12 years and their interrelationships. One hundred fifty-two children underwent standard anthropometry (BMI, waist circumference, waist-to-hip ratio, sum of five skinfolds) and motor fitness tests (standing long jump and 30m dash). Data were stratified by age (6-7, 8-9, 10-12 years) and sex (M/F), and the Spearman correlation coefficient was used to evaluate the correlation between BMI and the other anthropometric measurements in each class as well as the correlation between anthropometric parameters and fitness tests. The effect of age, sex, and individual anthropometric measurement on velocity or jump length was evaluated by ANOVA. BMI positively correlated with waist circumference and subcutaneous fat, and negatively correlated with body density. Motor fitness was not significantly affected by BMI, while sum of five skinfolds negatively associated with velocity in males aged 6-7 years and with jump length in females aged 8-12 years. Motor fitness significantly correlated with age, and performance was higher in males. Moreover, motor fitness tests positively correlated with each other, especially in females. In the 6-12 years period motor performance improves with age and improvement is partially sex-related; this correlation is higher in boys, possibly because of their lesser amount of fat. Subcutaneous fat is a better predictor of physical fitness than BMI or waist circumference. Results also suggest that explosive strength and velocity are related the 6-12 years age span, possibly because both are power events, which involve horizontal movement of the centre of mass

Perceptual-motor planning and performance in dynamical postural control

Lo scopo principale di questa dissertazione \ue8 di comprendere in maniera pi\uf9 approfondita il controllo dinamico della postura nel movimento umano. In particolare, qui ci approcciamo al problema prendendo in considerazione differenti compiti motori e analizzando differenti popolazioni in tre studi diversi. Nel primo viene presa in considerazione l\u2019azione motoria della salita delle scale. In questo esperimento le popolazioni testate erano giovani ed anziani e lo scopo principale era di comprendere se ci sono differenti strategie posturali e percettive sia durante la pianificazione che durante l\u2019esecuzione del movimento a causa della diminuzione del livello di capacit\ue0 motorie. Gli altri due studi invece focalizzano pi\uf9 l\u2019attenzione sullo sviluppo degli aggiustamenti posturali, prima e durante l\u2019azione motoria, quando le capacit\ue0 motorie raggiungono livelli ottimali di prestazione. In questi ultimi due casi le popolazioni prese in considerazione erano atleti di alto livello in cui essi primeggiano nell\u2019azione da loro eseguita nell\u2019esperimento, per cui di conseguenza lo scopo di questi studi era di spiegare come l\u2019alta prestazione emerge in specifiche sinergie muscolari causate dall\u2019esperienze motoria degli atleti. Anche se i tre esperimenti hanno in comune il controllo dinamico della postura, differenti modelli teorici del controllo motorio ispirano ciascuno di essi. Da una parte ci riferiamo al concetto di \u201cequifinalit\ue0\u201d formulata da Nicolay Bernstein (1967) e al concetto di \u201caffordance\u201d formulata da J.J. Gibson (1979). Queste due idee prese insieme ispirano il primo studio presentato. Dall\u2019altra parte, la legge formulata da Paul Fitts (1954) ispira gli ultimi due esperimenti. Nel\u2019introduzione presenteremo in sequenza queste idee e i loro relativi modelli: per prima l\u2019equifinalit\ue0, seguendo l\u2019affordance e poi la legge di Fitts. Per cui questi tre concetti teorici verranno applicati al controllo dinamico della postura, e un capitolo finale affronter\ue0 i modo dettagliato l\u2019argomento riguardante il controllo posturale. Successivamente verranno presentati i tre esperimenti.The main aim of this dissertation is to obtain a deeper understanding about the dynamics of postural control in human movement. In particular here we approach the problem by including several motor tasks and by testing different populations in three separate studies. The first one deals with the action of climbing stairs. In this experiment the populations tested were old and young adults and the main aim was to reveal whether there are different perceptive/motor postural strategies either for planning as well as for executing the action due to the decrease of the level of motor skill. The other two studies instead focalize more the attention on the development of postural adjustments, before and during the action performance, when the level of motor skill reaches its optimality. In these latter two cases the populations tested were elite athletes performing actions in which they excel, and as a consequence the aim of these studies was to reveal how excellence merges from the developments of specific muscular synergies due to practice. Even though the three experiments share issues related to the dynamics of postural control, different models and theoretical frameworks inspire each one. On the one hand, we refer to the concept of movement \u201cequifinality\u201d formulated by Nicolay Bernstein (1967) and to the concept of \u201caffordance\u201d formulated by J.J. Gibson (1979). These two ideas taken together inspired the first study presented. On the other hand, the law formulated by Paul Fitts (1954) inspired the latter two experiments. In the introduction we will present in sequence these ideas and their relative models: first equifinality, followed by affordance, and then Fitts\u2019 law. Since these three theoretical concepts are applied to the dynamics of postural control, a final chapter will discuss more in depth issues related to the control of posture. Then the three experiments will be presented

The fitts\u2019 law and the anticipatory postural adjustment

The fitts\u2019 law and the anticipatory postural adjustmen

The speed-accuracy trade-off effects on the gait initiation planning

The speed-accuracy trade-off effects on the gait initiation plannin