Motor Control最新文献

The purpose of the present systematic review and meta-analysis was to explore the effects of mental fatigue on upper and lower body strength endurance. Searches for studies were performed in the PubMed/MEDLINE and Web of Science databases. We included studies that compared the effects of a demanding cognitive task (set to induce mental fatigue) with a control condition on strength endurance in dynamic resistance exercise (i.e., expressed as the number of performed repetitions at a given load). The data reported in the included studies were pooled in a random-effects meta-analysis of standardized mean differences. Seven studies were included in the review. We found that mental fatigue significantly reduced the number of performed repetitions for upper body exercises (standardized mean difference: -0.41; 95% confidence interval [-0.70, -0.12]; p = .006; I2 = 0%). Mental fatigue also significantly reduced the number of performed repetitions in the analysis for lower body exercises (standardized mean difference: -0.39; 95% confidence interval [-0.75, -0.04]; p = .03; I2 = 0%). Our results showed that performing a demanding cognitive task-which induces mental fatigue-impairs strength endurance performance. Collectively, our findings suggest that exposure to cognitive tasks that may induce mental fatigue should be minimized before strength endurance-based resistance exercise sessions.

Cutaneous feedback from feet is involved in regulation of muscle activity during locomotion, and the lack of this feedback results in motor deficits. We tested the hypothesis that locomotor changes caused by local unilateral anesthesia of paw pads in the cat could be reduced/reversed by electrical stimulation of cutaneous and proprioceptive afferents in the distal tibial nerve during stance. Several split-belt conditions were investigated in four adult female cats. In addition, we investigated the effects of similar distal tibial nerve stimulation on overground walking of one male cat that had a transtibial, bone-anchored prosthesis for 29 months and, thus, had no cutaneous/proprioceptive feedback from the foot. In all treadmill conditions, cats walked with intact cutaneous feedback (control), with right fore- and hindpaw pads anesthetized by lidocaine injections, and with a combination of anesthesia and electrical stimulation of the ipsilateral distal tibial nerve during the stance phase at 1.2× threshold of afferent activation. Electrical stimulation of the distal tibial nerve during the stance phase of walking with anesthetized ipsilateral paw pads reversed or significantly reduced the effects of paw pad anesthesia on several kinematic variables, including lateral center of mass shift, cycle and swing durations, and duty factor. We also found that stimulation of the residual distal tibial nerve in the prosthetic hindlimb often had different effects on kinematics compared with stimulation of the intact hindlimb with paw anesthetized. We suggest that stimulation of cutaneous and proprioceptive afferents in the distal tibial nerve provides functionally meaningful motion-dependent sensory feedback, and stimulation responses depend on limb conditions.

Instep kick is one of the most effective kicking techniques in soccer. Lower extremity muscles and joints play a crucial role during instep kick. However, external (EF) and internal focus and their effect on the muscles are still ambiguous. In this study, 13 male adolescent soccer players were included and aimed to hit the targets in internal and EF conditions. Lower extremity muscle activations were measured with surface electromyography, and kinematics were measured with a high-speed video camera. Muscle activations and movement latencies were analyzed in four different phases (backswing, leg cocking, acceleration, and follow-through) of kicking. While 10 out of 13 participants kicked accurately in internal focus, only five out of 13 in EF kicked accurately. Gastrocnemius muscle activations increased significantly in EF in all phases except acceleration. Movement latencies were found 0.07 ± 0.002 s for accurate and 0.05 ± 0.004 s for inaccurate kicks in EF. A correlation has been found between accuracy and movement latency in EF (R = .67). Our results suggest that novices cannot yet coordinate their muscles in EF, cocontraction ratio increases. Therefore, training strategies that aim to reduce the cocontraction ratio can help the athlete increase performance through better motor coordination. Moreover, better motor coordination may be beneficial in preventing injuries (joint stiffness, etc.) caused by increased cocontraction ratio.

Fatigue at individual joints is known to affect interjoint coordination during repetitive multijoint tasks. However, how these coordination adjustments affect overall task stability is unknown. Twelve participants completed a repetitive pointing task at rest and after fatigue of the shoulder, elbow, and trunk. Upper-limb and trunk kinematics were collected. Uncontrolled manifold framework was applied to a kinematic model to link elemental variables to endpoint fingertip position. Mixed and one-way analysis of variances determined effects (phase and fatigue location) on variance components and synergy index, respectively. The shoulder fatigue condition had the greatest impact in causing increases in variance components and a decreased synergy index in the late phase of movement, suggesting more destabilization of the interjoint task caused by shoulder fatigue.

This study aimed to investigate the relationship of sit-to-stand and walking performance with leg muscle strength and core muscle endurance in people with multiple sclerosis (PwMS) with mild disabilities. In this study, 49 PwMS (Expanded Disability Status Scale score = 1.59 ± 0.79) and 26 healthy controls were enrolled. The functional performances, including sit-to-stand and walking performances, were evaluated with the five-repetition sit-to-stand test, timed up and go test, and 6-min walking test. The PwMS finished significantly slower five-repetition sit-to-stand, timed up and go, and 6-min walking test than the healthy controls. In addition, the significant contributors were the weakest trunk lateral flexor endurance for five-repetition sit-to-stand; the Expanded Disability Status Scale score, and the weakest hip adductor muscle for timed up and go; the weakest hip extensor muscles strength for 6-min walking test. The functional performances in PwMS, even with mild disabilities, were lower compared with healthy controls. Decreases in both leg muscle strength and core muscle endurance are associated with lower functional performance in PwMS.

This article discusses material from the doctoral thesis of Wilhlem Camerer, which was devoted to the topic of the timing of voluntary movements, and appeared in 1866, thus being one of the earliest studies of any aspect of time perception. It was conducted under the supervision of Karl von Vierordt, at the University of Tübingen in Germany. The data reported come from Camerer's attempts to make a movement over a distance of about 65 mm, either by flexion or extension of his arm, with the behavior recorded via a kymograph, and measured from its trace. Most of his data come from his attempts to make movements at a constant speed, with the speed varying from one trial to another from 5 to 60 mm/s, but he also conducted a study where the movement was intended to be accelerated or decelerated during the trial. In general, when extension movements were intended to be performed with constant speed, a gradual increase in movement speed usually occurred throughout the movement duration. For flexions the opposite occurred, albeit less clearly. Camerer linked the apparent distortions of speed to Vierordt's experiments on the perception of time and his thesis contains what is probably the first mention of Vierordt's Law, the proposition that short times are judged as longer, and long times as shorter, than they really are.

The aim of this study was to analyze the acute effects of an incremental resistance test on psychomotor vigilance in 16 soccer players under-19 years old (age 16.42 ± 0.85 years). Borg 15-point subjective perception of effort scale, the psychomotor vigilance task test, and the Yo-Yo intermittent recovery test were used. Four evaluation sessions were conducted with different intensities of efforts (30%-40%, 60%-75%, 80%-90%, and 100%) on different days (counterbalanced order). A repeated-measures analysis of variance was performed in the reaction time of the psychomotor vigilance task. The results showed that participants responded faster during efforts between 80% and 90% of maximal oxygen uptake (501.20 ± 70.77 ms). From that threshold, the players decreased their performance through a longer reaction time (601.23 ± 85.05 ms; p value < .001). The main findings were that the reaction time performance was worse at the lowest and highest effort conditions (5 and 17 km/hr, respectively). This fact helps to focus on the importance of designing and proposing training tasks with medium-high efforts to provoke optimal reaction times in young soccer players.

Difficulty with implicit learning plays an important role in the symptomology of autism spectrum disorder (ASD). However, findings in motor learning are inconsistent. This study evaluated implicit sequence learning and its relationship with motor ability in children with and without ASD. We adopted a classic serial reaction time task with a retention task and three awareness tests. The Movement Assessment Battery for Children was administered to assess children's motor ability. Significant learning differences between children with and without ASD were only found in retention but not immediately after the serial reaction time task. These findings suggest that the impaired implicit learning in ASD is characterized as impaired consolidation where the relatively permanent changes are missing. Exploratory moderation analyses revealed a significant relationship between implicit learning and motor ability for individuals with faster response time. We argue the importance of response speed for optimal learning and should be weighted more for future intervention in children with ASD.

The present study expands on current understanding of dual-task cognitive-motor interference, by including cortical activation measures to both traditional and ecologically valid dual-task paradigms. Fifteen individuals with multiple sclerosis and 14 control participants underwent mobility testing while wearing functional near-infrared spectroscopy. In the absence of increased prefrontal cortical activation, subjects with multiple sclerosis performed significantly worse on measures of cognition under both single- and dual-task conditions. These findings suggest that persons with multiple sclerosis may be unable to allocate additional cortical resources to cognition under dual-task conditions, leading to significant cognitive-motor interference and decrements in performance. This study is the first to investigate cortical activation across several commonly used and ecologically valid dual-task assessments.