Motor Control最新文献

Purpose: The purpose of this study was to examine the balance recovery strategy in children with hearing (HI) and visual impairments (VI) compared with those without these disorders.

Materials and methods: This study featured a cross-sectional design with subjects (N = 45) placed within one of three equally stratified purposive groups (HI, VI, and comparison) within the age range of 9-13 years (mean = 11.43, SD = 1.5). Balance recovery strategy was measured in static and after-perturbation conditions by a four-camera Vicon system used to record three-dimensional lower body kinematic data. A repeated-measures analysis of variance (3 × 2, Group × Condition) was utilized to analyze data. Significance was set at p ≤ .05.

Results: In the static condition, the results of the study showed that there was no significant difference between the groups in the ankle joint sway (p > .05). In hip joint sway, VI children had greater sway compared with comparison (p = .001) and HI children (p = .02). Also, HI children had greater sways than comparison (p = .02). In the after-perturbation condition, the results showed that VI children had greater sway in the hip and ankle joints than HI children (p = .001) and comparison (p = .001) to restore and maintain balance.

Conclusion: It seems that comparison as well as higher proportion VI children use a hip strategy to maintain and restore balance. Also, it seems that HI children use a different strategy (ankle strategy) to maintain and restore balance compared with comparison and VI children.

The present study examined how humans use the target information provided immediately before the onset of motor output to prepare the initial motor command in the target force production task. Twenty healthy individuals participated in this study. A target cursor indicating the target force, and a force cursor indicating the force produced with index finger flexion were presented, and participants produced force in response to the appearance of the force cursor so that it moved toward the target cursor as fast as possible. The rate of force development in a time window of 0-100 ms after the onset of force development, representing the intensity of the initial motor command without online feedback adjustment, was measured. The present findings support the hypotheses that humans use the target information provided immediately before the onset of motor output to prepare the initial motor command, and they simultaneously prepare the initial motor command for the intermediate of multiple potential targets using the information of targets provided in previous trials. Another hypothesis, that humans use the information of the target or motor process of the trial immediately before the current trial to prepare the initial motor command, was not supported.

This study aimed to investigate the kinematic changes in obstacle avoidance and prehension tasks performed simultaneously by older adults with a history of falls at different levels of task difficulty. Twenty-six older adults were divided into faller and nonfaller groups. The experimental protocol was divided into two different tasks: walking with obstacle avoidance and walking with obstacle avoidance combined with a reach-to-grasp task. Two types of sensors (Kinect v2 and Leap Motion Controller, respectively) were used to analyze gait and grasp. Fallers presented kinematic changes associated with the grasping task during obstacle avoidance, such as a decrease in the velocity of the center of mass and the step length, an increase in the step width, a decrease in toe-obstacle horizontal distance, and an increase in vertical foot clearance distance, and an increase in movement time in the grasping task compared with nonfallers. To cope with the obstacle avoidance demands of both walking and grasping, fallers turned to a specific sequencing strategy. While slowing down, they attended first to the grasping task and then to crossing the obstacle on the floor.

Several devices (e.g., linear transducers) have been used for predicting resistance training intensity. However, subjective scales, such as rating of perceived exertion (RPE), are proposed as reliable and easier-to-use tools for monitoring intensity during resistance training. Accordingly, different perceptive scales have been presented in previous research for monitoring intensity during resistance training with elastic bands. The aim was to assess the accuracy and reliability of RPE for quantifying the potential maximal repetitions that could be performed at a given RPE (from 2 to 8 of 10) obtained in the first repetition. For this purpose, 13 recreationally active participants (age: 26.33 [6.52] years, body mass index: 24.97 [5.08] kg/m2) were involved in two familiarization and two experimental sessions. In each session, participants randomly performed one set at each intensity of the first repetition from 2/10 to 8/10 until volitional failure in three different exercises (fly, military press, and push-press). An individual grip width of the elastic band was chosen in each set. The number of repetitions and heart rate were assessed. Significance level was set at p < .05. Repetitions decreased when intensity increased (p < .01) and heart rate was higher in the global exercise (i.e., push-press; p < .05), but nonsignificant differences between intensities were reported. The level of experience influenced the number of repetitions performed (p < .05). Intersession reliability was set from good to excellent (range: 0.64-0.91). Therefore, the RPE of the first repetition is a relevant and reliable parameter related to the total number of repetitions performed for each RPE value in trained participants enrolled in elastic bands resistance training.

Proprioception is essential for precise movement as it helps the body transmit important data about its surroundings to the central nervous system for maintaining body posture and position. This study aimed to investigate the effect of direction and joint angle on upper limb proprioception. Thirty individuals (all males) completed a position reproduction activity in 13 directions and three joint angles. It was discovered that upper limb proprioception is dependent on joint angle, direction, and range of motion. The position reproduction error was found to be dependent on the direction, which had a significantly lower accuracy in the direction with a larger range of motion. In addition, upper limb repositioning errors increased at greater limb elevation angles. Our findings also showed that the joint angle did not significantly affect the absolute error of elbow flexion. With an increase in the elbow flexion, the increase of the gravitational moment of the upper arm and hand coupled with the increase of the muscle arm of the biceps brachii possibly causes slight changes in muscle length perceived by spindles or muscular force perceived by Golgi tendon organs.

This cross-sectional study examined the immediate effects of four types of real-time feedback during overground gait performed using inertial measurement units on gait kinematics in healthy young participants. Twelve healthy young participants (mean age: 27.1 years) performed 60-s gait trials with each of the following real-time feedback: walking spontaneously (no feedback trial); increasing the ankle plantar-flexion angle during the late stance (ankle trial); increasing the leg extension angle, defined the location of the ankle joint relative to the hip joint in the sagittal plane, during late stance (leg trial); and increasing the knee flexion angle during the swing phase (knee trial). Tilt angles and accelerations of the pelvis and lower limb segments were measured using seven inertial measurement units pre- and postfeedback trials. The differences in gait parameters pre- and postfeedback according to the types of feedback were compared using one-factor repeated-measures analysis of variance, Friedman test, and post hoc test. Real-time feedback in the ankle trial increased gait speed, step length, and ankle plantar-flexion angle compared to the no feedback trial (p ≤ .001). Meanwhile, real-time feedback in the leg trial increased step length and hip extension angle compared to the no feedback trial (p ≤ .001) and showed a tendency to increase gait speed and leg extension angle. Real-time feedback using inertial measurement units increased gait speed immediately with specific changes in gait kinematics in healthy participants. This study might imply the possibility of clinical application for overground gait training, and further studies are needed to clarify the effectiveness for older people.

Humans experience unanticipated external postural perturbations and recover their posture faster via involuntary responses than voluntary responses. Previous cross-sectional comparisons between athletes and untrained populations have suggested that daily motor experiences can lead to adaptations in the reflex system, but the temporal aspect of this adaptation has been unclear. Here we show that judokas have an earlier muscle activation response to even non-judo-specific external perturbations compared with an untrained population. The response latency to a backward push-and-release type postural perturbation was compared between male judokas (n = 7, career >13 years, ranging from world champions to prefectural competitors) and untrained nonjudokas (n = 7). Latency was defined as the instant of tibialis anterior muscle activity onset. Judokas exhibited shorter latency (20.6 ± 7.1 ms) than nonjudokas (28.3 ± 8.9 ms). The rank order of latency in judokas did not correlate with their competition performance. We suggest that daily training in responding to perturbations might improve some parts of the sensorimotor pathway relating to postural response latency, and that this excellence in involuntary response is independent of athletic performance. The findings provide a novel perspective for understanding postural control ability in humans.

Background: Individuals with visual impairment have balance deficits; therefore, this systematic review aimed to provide comprehensive insights into the balance control of individuals with visual impairments when compared with individuals with full vision.

Methods: Primary sources were obtained from eight databases including PubMed, LILACS, Science Direct, SCOPUS, CINAHL, PEDro, CENTRAL, and Web of Science. The search period covered years from inception to January 10, 2022.

Results: A total of 20 studies with 29 trials with 1,280 participants were included in the systematic review. The results showed that individuals with sight had better static and dynamic balance than individuals with visual impairment (p = .001). However, individuals with visual impairment had significantly better static balance with visual perturbation and stronger static balance with visual and proprioception perturbation (p = .001). Furthermore, individuals with sight had better balance control than individuals with visual impairment who participated in sports (p = .001). Finally, individuals with visual impairment who participated in sports had better balance control than sedentary people with visual impairment (p = .001).

Conclusion: Individuals with visual impairment have defects in both dynamic and static balance when compared to individuals with sight. In addition, balance improved with increasing age in individuals with visual impairment while balance control was dependent on the proprioception and vestibular systems. Also, individuals with sight had better balance than individuals with visual impairment who participated in sports and individuals with visual impairment who participated in sports compared with sedentary people with visual impairment.

Several computational models make predictions about the activation states of individual elements of an action sequence during planning and execution; however, the neural mechanisms of action planning are still poorly understood. Simple chaining models predict that only the first response in an action sequence should be active during planning. Conversely, some parallel activation models suggest that during planning, a serial inhibition process places the individual elements of the action into a serial order across a winner-takes-all competitive choice gradient in which earlier responses are more active, and hence likely to be selected for execution compared with later responses. We triggered transcranial magnetic stimulation pulses at 200 or 400 ms after the onset of a five-letter word, in which all but one response was planned and typed with the left hand, except for a single letter which required a right index finger response exclusively at one of five serial positions. We measured the resulting motor-evoked potentials at the right index finger as a marker for the activation state of that planned response. We observed no difference in motor-evoked potential amplitude across any serial position when a right index finger response was planned at 200 ms after the onset of the word; however, we observed a graded pattern of activation at 400 ms, with earlier positions that required a right index finger response showing greater motor-evoked potentials amplitude compared with later positions. These findings provide empirical support for competitive queuing computational models of action planning.

Previous studies have demonstrated that both visual and proprioceptive feedback play vital roles in mental practice of movements. Tactile sensation has been shown to improve with peripheral sensory stimulation via imperceptible vibratory noise by stimulating the sensorimotor cortex. With both proprioception and tactile sensation sharing the same population of posterior parietal neurons encoding within high-level spatial representations, the effect of imperceptible vibratory noise on motor imagery-based brain-computer interface is unknown. The objective of this study was to investigate the effects of this sensory stimulation via imperceptible vibratory noise applied to the index fingertip in improving motor imagery-based brain-computer interface performance. Fifteen healthy adults (nine males and six females) were studied. Each subject performed three motor imagery tasks, namely drinking, grabbing, and flexion-extension of the wrist, with and without sensory stimulation while being presented a rich immersive visual scenario through a virtual reality headset. Results showed that vibratory noise increased event-related desynchronization during motor imagery compared with no vibration. Furthermore, the task classification percentage was higher with vibration when the tasks were discriminated using a machine learning algorithm. In conclusion, subthreshold random frequency vibration affected motor imagery-related event-related desynchronization and improved task classification performance.