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This study aimed to evaluate the effect of age and intellectual disability (ID) on postural balance parameters, dual-task cost (DTC), and choice reaction time (CRT). Fifty-eight individuals with ID and 55 peers without ID performed a postural stance balance task under two conditions: a single task with eyes open and dual task involving an additional cognitive task (light sequence). Four postural balance parameters (total displacement, total sway area, mediolateral, and anteroposterior dispersion), cost of the dual task ([DTC%] = [(single-task performance − dual-task performance)/single-task performance] × 100), and CRT were recorded, calculated, and analyzed. All postural control parameters reflected poorerperformance during the dual-task condition, nevertheless, DTC was significantly higher only in individuals with ID and only for the total sway area, F(1, 111) = 5.039, p = .027, and mediolateral dispersion, F(1, 111) = 6.576, p = .012. CRT was longer in individuals with ID compared with the individuals without ID, F(1, 111) = 94.979, p ≤ .001, while age did not have a significant effect on the DTC nor on the CRT, F(1, 111) = 0.074, p = .786. In conclusion, an additional cognitive task during the postural balance task had a detrimental effect on various postural balance parameters, leading to increased DTC in terms of total sway area, mediolateral dispersion, and prolonged CRT in individuals with ID.

Over the past two decades, motor imagery (MI) has been used as a supplementary treatment approach to regain physical function in patients with stroke. However, the baseline treatment and the quality of study methodology for new treatment approaches have improved. This systematic review examined the evidence published in the past few decades on the effectiveness of MI on upper- and lower-extremity function and functional performance in patients with stroke. A total of 29 randomized controlled and crossover trials that compared MI with other interventions were analyzed. In addition, the outcomes were grouped into upper-, lower-extremity function, and functional performance for data analysis. More than half of the upper-extremity function studies reported improved performance in Fugl-Meyer assessment, Wolf motor function test, and box and block test in both acute and chronic stages. Lower-extremity function and functional performance were primarily investigated using Fugl-Meyer assessment, gait speed and parameters, activities of daily living, and balance ability. When considering only high-quality studies, six of 15 on upper extremity reported significant effects, whereas five of 15 reported nonsignificant effects. In addition, six of 14 studies on gait and balance reported significant effects. This systematic review suggests that both MI training and conventional rehabilitation programs effectively enhance upper limb functional abilities, including improvements in gait speed and balance, in individuals with acute and chronic stroke. Although the studies published during the past few decades showed heterogeneity in onset after stroke, research protocol, training intensity, and research methodology quality, none of them reported the long-term effects.

Objectives: The static and dynamic correlations of postural stability to its three potential contributors, namely, proprioception, tactile sensation, and strength remain unclear among people with chronic ankle instability (CAI). This study aimed to compare static and dynamic postural stability, along with proprioception, tactile sensation, and strength between people with and without CAI and explore their correlations. Methods: Sixty-seven participants with CAI and 67 participants without CAI were enrolled in this study. Ankle proprioception, plantar tactile sensation, and lower limb strength were measured by a proprioception test device, a set of monofilaments, and a strength testing system, respectively. Static and dynamic postural stability were measured during standing and jump landing on a force plate and indicated by the root mean square of center of pressure and time to stability. Results: Compared to people without CAI, people with CAI had poorer postural stability, proprioception, tactile sensation, and strength. Both groups demonstrated correlation between proprioception and static postural stability, but only people without CAI showed correlation between proprioception and dynamic postural stability. Both groups demonstrated a correlation between tactile sensation and static postural stability, but not with dynamic stability. Both groups demonstrated a correlation between strength and both static and dynamic postural stability. Conclusions: People with CAI had deficits in static and dynamic postural stability, proprioception, tactile sensation, and strength. Among people with CAI, proprioception, tactile sensation, and strength can help maintain static postural stability; strength can help maintain dynamic postural stability, whereas proprioception may not provide sufficient information for dynamic postural stability.

Prior work has demonstrated the presence of hysteresis effects in the control of affordance-guided behavior, in that behavioral transitions around a critical action boundary vary with directions of change in said action boundary. To date, research on this topic has overlooked the influence of the global context on these phenomena. We employ an affordance-based reaching task, whereby participants were asked to move a target to a goal by passing through one of two apertures (size variable or size constant). It was found that the direction of change in the size of the variable aperture influenced the point of behavioral transitions, and this effect interacted with the location of a given goal. In addition, we considered fluctuations in the entropy of participants’ reach trajectories as a window into the nature of the behavioral phase transitions. Differences in the structure of entropy were found depending on the direction of change in the size variable aperture. These results are discussed in light of a dynamical systems approach, and recommendations for future work are made.

Previous work suggests that synergistic activity among motor elements implicated in force production tasks underlies enhanced performance stability associated with visual feedback. A hallmark of synergistic activity is reciprocal compensation, that is, covariation in the states of motor elements that stabilizes critical performance variables. The present study examined if characteristics of reciprocal compensation are indicators of individuals’ capacity to respond adaptively to variations in the resolution of visual feedback about criterion performance. Twenty healthy adults (19.25 ± 1.25 years; 15 females and five males) pressed two sensors with their index fingers to produce a total target force equivalent to 20% of their maximal voluntary contraction under nine conditions that differed in the spatial resolution of real-time feedback about their performance. By combining within-trial uncontrolled manifold and sample entropy analyses, we quantified the amount and degree of irregularity (i.e., non-repetitiveness) of reciprocal compensations over time. We found a U-shaped relationship between performance stability and gain. Importantly, this relationship was moderated by the degree of irregularity of reciprocal compensation. Lower irregularity in reciprocal compensation patterns was related to individuals’ capacity to maintain (or minimize losses in) performance under changes in feedback resolution. Results invite future investigation into how interindividual variations in reciprocal compensation patterns relate to differences in control strategies supporting adaptive responses in complex, visually guided motor tasks.

Functional independence of the transversus abdominis (TrA) from other trunk muscles for postural control is still unclear. This study aimed to clarify the specific function of the TrA to control standing posture by vibratory stimulation of the triceps surae. Fifteen men participated in this study. Muscle activity of the TrA, internal oblique, lumbar multifidus, gluteus maximus, rectus femoris, biceps femoris, gastrocnemius, and tibialis anterior was measured using fine-wire and surface electrodes. Participants were asked to maintain a quiet standing posture with and without vibration of the triceps surae, which induced a kinesthetic illusion and the concomitant backward sway of the body. The muscle activity of each muscle for 10 s was extracted with and without vibration. The muscle activity levels were compared between the conditions by a paired t-test or Wilcoxon signed-rank test. The activity of the TrA and rectus femoris was increased, whereas the internal oblique showed no change as a result of the induced kinesthetic illusion. In addition, the activity of the multifidus and biceps femoris was decreased. The TrA and rectus femoris could contribute to control the backward sway of the body. Furthermore, the TrA may have functional independence from the internal oblique during standing postural control. These results warrant further study in patients with low back pain.

Motor imagery (MI) is frequently used in tennis players. This pilot study aimed to assess whether the MI modality and preference of skilled tennis players could influence their service performance when using MI before serving first balls. Twenty expert players (M _age = 18.6 years) completed the movement imagery questionnaire (third version) to assess their MI modality scores (internal visual, external visual, and kinesthetic) and their MI preference. Participants completed 4 experimental counterbalanced sessions spread over 4 weeks, each including the completion of 20 first-serve balls in match condition. The sessions included a control condition (i.e., only physical practice trials) and three MI conditions during which the players had to mentally imagine themselves performing a serve according to one of the imagery modalities, either internal visual, external visual, or kinesthetic, before serving. The percentage of success, the speed of the service balls (measured by a tablet with SWING VISION and a radar gun), and an efficiency score were recorded and then evaluated by experts and served as performance indicators and dependent variables. The results of this study showed that players benefited from MI before serving and that almost a third of the participants achieved a higher percentage of success and efficiency scores when using their preferred MI modality. These results lead us, in an applied way, to suggest to skilled tennis players to determine their MI preference and to have recourse to the mental simulation of a successful serve before serving the first balls in match condition.