Human Movement Science最新文献

Purpose

To determine whether the application of continuous lateral trunk support forces during walking would improve trunk postural control and improve gait performance in children with CP.

Materials and methods

Nineteen children with spastic CP participated in this study (8 boys; mean age 10.6 ± 3.4 years old). Fourteen of them were tested in the following sessions: 1) walking on a treadmill without force for 1-min (baseline), 2) with lateral trunk support force for 7-min (adaptation), and 3) without force for 1-min (post-adaptation). Overground walking pre/post treadmill walking. Five of them were tested using a similar protocol but without trunk support force (i.e., control).

Results

Participants from the experimental group showed enhancement in gait phase dependent muscle activation of rectus abdominis in late adaptation period compared to baseline (P = 0.005), which was retained during the post-adaptation period (P = 0.036), reduced variability of the peak trunk oblique angle during the late post-adaptation period (P = 0.023), and increased overground walking speed after treadmill walking (P = 0.032). Participants from the control group showed modest changes in kinematics and EMG during treadmill and overground walking performance. These results suggest that applying continuous lateral trunk support during walking is likely to induce learning of improved trunk postural control in children with CP, which may partially transfer to overground walking, although we do not have a firm conclusion due to the small sample size in the control group.

Humans frequently prepare for agile movements by decreasing stability. This facilitates transitions between movements but increases vulnerability to external disruptions. Therefore, humans might weigh the risk of disruption against the gain in agility and scale their stability to the likelihood of having to perform an agility-demanding action. We used the theory of motor synergies to investigate how humans manage this stability-agility tradeoff under uncertainty. This theory has long quantified stability using the synergy index, and reduction in stability before movement transitions using anticipatory synergy adjustment (ASA). However, the impact of uncertainty - whether a quick action should be executed or inhibited - on ASA is unknown. Furthermore, the impact of ASA on execution and inhibition of the action is unclear.

We combined multi-finger, isometric force production with the go/no-go paradigm. Thirty participants performed constant force (no-go task), rapid force pulse (go task), and randomized go and no-go trials (go/no-go task) in response to visual cues. We measured the pre-cue finger forces and computed ASA using the uncontrolled manifold method and quantified the spatio-temporal features of the force after the visual cue. We expected ASA in both go/no-go and go tasks, but larger ASA for the latter.

Surprisingly, we observed ASA only for the go task. For the go/no-go task, 53% of participants increased stability before the cue. The high stability hindered performance, leading to increased errors in no-go trials and lower peak forces in go trials. These results align with the stability-agility tradeoff. It is puzzling why some participants increased stability even though 80% of the trials demanded agility. This study indicates that individual differences in the effect of task uncertainty and motor inhibition on ASA is unexplored in motor synergy theory and presents a method for further development.

In this study, we investigated how the temporal properties of the preparation phase for upper limb movements are affected by the reaching direction and distance. Twelve right-handed participants performed three motor tasks: two types of reaching movements and one finger-lifting movement. The reaching movements were performed from the home position to 15 target locations (five directions and three distances) as quickly and precisely as possible under two conditions: pre-cueing the target to allocate the sufficient time for the motor-planning process before movement initiation, and no-cuing. The finger lifting movement was performed by lifting the index finger (from the home position) upward in the air as quickly as possible. The reaction time (RT), movement time (MT), and kinematics of the index finger were obtained for each condition. In addition, differential RTs (DRT) were calculated by subtracting the RT for no-cue lifting from that for no-cue reaching, thereby implicitly representing the time required for the motor-planning process for reaching movements. The results indicated the anisotropy of the DRTs being larger in the forward and left-forward directions than that in the right-forward direction, and larger in the forward direction than that in the right direction for the middle distance. It is suggested that the temporal costs of the motor-planning process depend on the movement direction and distance. In the kinematic analysis, the MTs showed the anisotropy being the largest in the left-forward among all directions. Meanwhile, the time from peak velocity to terminate the movement (TFPV) was significantly longer in the left-forward direction when no-cueing the target than when pre-cueing. These results suggest that reaching movement is refined during the online-control process to accomplish the intended performance if a reaching movement under the no-cue condition is initiated before building sufficient motor planning, especially in the direction requiring large temporal costs. It is likely that humans achieve their intended movements by allocating the temporal costs required before and after movement initiation according to the difficulty of motor control which varies with the direction and distance.

The phase of signals representing cyclic behavioural patterns provides valuable information for understanding the mechanisms driving the observed behaviours. Methods usually adopted to estimate the phase, which are based on projecting the signal onto the complex plane, have strict requirements on its frequency content, which limits their application. To overcome these limitations, input signals can be processed using band-pass filters or decomposition techniques. In this paper, we briefly review these approaches and propose a new one. Our approach is based on the principles of Empirical Mode Decomposition (EMD), but unlike EMD, it does not aim to decompose the input signal. This avoids the many problems that can occur when extracting a signal's components one by one. The proposed approach estimates the phase of experimental signals that have one main oscillatory component modulated by slower activity and perturbed by weak, sparse, or random activity at faster time scales. We illustrate how our approach works by estimating the phase dynamics of synthetic signals and real-world signals representing knee angles during flexion/extension activity, heel height during gait, and the activity of different organs involved in speech production.

Bilateral coordination is commonly impaired in neurodevelopmental conditions including cerebral palsy, developmental coordination disorder, and autism spectrum disorder. However, we lack objective clinical assessments that can quantify bilateral coordination in a clinically feasible manner and determine age-based norms to identify impairments. The objective of this study was to use augmented reality and computer vision to characterize bilateral reaching abilities in typically developing children. Typically developing children (n = 133) ages 6–17 years completed symmetric and asymmetric bilateral reaching tasks in an augmented reality game environment. We analyzed the number of target pairs they could reach in 50 s as well as the time lag between their hands reaching the targets. We found that performance on both tasks developed in parallel, with development slowing but not plateauing after age 12. Children performed better on the symmetric task than asymmetric, both in targets reached and with shorter hand lags. Variability between children in hand lag decreased with age. We also found gender differences with females outperforming males, which were most pronounced in the 10–11 year olds. Overall, this study demonstrates parallel development through childhood and adolescence of symmetric and asymmetric reaching abilities. Furthermore, it demonstrates the ability to quantify bilateral coordination using computer vision and augmented reality, which can be applied to assess clinical populations.

This study explored the impact of choice and preference for what is chosen or assigned on performance on a motor task. Using an experimental design with a dart-throwing task, 90 novice participants were randomized into four groups: Choice-Like condition, Choice-Dislike condition, Assigned-Like condition, and Assigned-Dislike condition, resulting of the manipulation of choice (vs. assignation) of a task-irrelevant element and preference (irrelevant element: darts color and design). The study found that participants who were given the opportunity to choose their own dart for a throwing task performed better than those who were not given the choice. Participants who threw a dart they preferred also had better scores than those who threw a dart they did not like. However, the interactive effects of choice and preference on performance were inconclusive, and whereas being assigned with a disliked element was the worst condition for performance, and being allowed to choose preferred elements the most facilitatory one, nothing else can be concluded on the impact of both conditions alone or in combination. These results suggest that both choice and preference can positively impact performance in closed motor learning tasks and have practical applications for training and execution in athletic performance. Further investigations are warranted to delve into the interplay of choice and preference in diverse contexts and populations.

Individuals with bilateral spastic cerebral palsy (BSCP) reportedly has problems with anticipatory postural adjustments (APAs) while standing. However, the use of coactivation strategy in APAs in individuals with BSCP has conflicting evidence. Hence, this study aimed to investigate postural muscle activities in BSCP during unilateral arm flexion task in which postural perturbations occur in the sagittal, frontal, and horizontal planes. We included 10 individuals with BSCP with level II on the Gross Motor Function Classification System (BSCP group) and 10 individuals without disability (control group). The participants stood on a force platform and rapidly flexed a shoulder from 0° to 90° at their own timing. Surface electromyograms were recorded from the rectus femoris, medial hamstring, tibialis anterior, and medial gastrocnemius. The control group showed a mixture of anticipatory activation and inhibition of postural muscles, whereas the BSCP group predominantly exhibited anticipatory activation with slight anticipatory inhibition. Compared with the control group, the BSCP group tended to activate the ipsilateral and contralateral postural muscles and the agonist–antagonist muscle pairs. The BSCP group had a larger disturbance in postural equilibrium, quantified by the peak displacement of center of pressure during the unilateral arm flexion, than those without disability. Individuals with BSCP may use coactivation strategy, mainly the anticipatory activation of postural muscle activity, during a task that requires a selective postural muscle activity to maintain stable posture.

Coordinative patterns require experience and learning to be acquired, producing movements that offer efficient solutions to various situations and involving certain degree of variability. This coordination variability implies functionality in movement, but it can be impacted by the type of sport practice from early years. The purpose of this work is to analyze the coordination variability and coordination patterns in a specific action such as single-leg landing in children practicing gymnastics, volleyball and non-sporting children.

Thirty children (15 girls) performed 10 successful trials of single-leg landing from a height of 25 cm. A motion capture system (9 cameras) was used to capture 3D thigh and shank kinematics. To identify the significant effect of children's groups on coordination and coordination variability during single-leg landing, one-dimensional Statistical Parametric Mapping (SPM) was used.

Regarding the coordination patterns, in the frontal plane, during the attenuation phase of single-leg landing, the control group exhibited a higher frequency of Anti-Phase with proximal dominancy compared to the sport groups (i.e., gymnastics, and volleyball). In addition, in the sagittal plane during the second peak phase, volleyball players exhibited a higher coordination variability than the gymnastics.

The children in the control group showed a greater frequency of antiphasic movements, which indicates the influence of training at an early age, being a determining factor in the increase or not of variability.