Motor Control最新文献

This study examined whether table tennis as a method of sensorimotor training improves haptic and motor function and to what extent haptic function gain correlates with changes in motor ability in children with probable developmental coordination disorder (pDCD). Children with pDCD were randomly assigned to the table tennis and nontraining control groups. The children in the table tennis group received 36 sessions of table tennis training, including ball balancing, hitting the ball against the wall, strokes, and serving. Haptic sensitivity, acuity, and motor function domains were measured. The results showed a 41.5% improvement in haptic sensitivity in children exposed to table tennis training compared with 2.8% in those without training. This improved haptic sensitivity significantly correlated with motor function gain, suggesting that somatosensory gains occur simultaneously with changes in motor function in children with pDCD. This novel upper limb motor training approach may be an interesting method of sensorimotor training in neurological rehabilitation in children with pDCD.

The upstart is commonly used on bars in artistic gymnastics following a release and regrasp skill, where the gymnast will perform a flighted element before catching the bar. The variability of the flighted element leads to varying initial conditions prior to the upstart. The aim of the study was to understand how technique can be manipulated in order to ensure success at the task despite this variability. More specifically, the study aimed to quantify the ranges of initial angular velocity a gymnast could cope with in an upstart using (a) a fixed timing technique, (b) with one additional parameter to modify timings as a function of initial angular velocity, and (c) a further additional parameter to extend the range. Relationships were established, using computer simulation modeling, between the movement pattern parameters, which defined the technique, and the initial angular velocity of the upstart. A two-parameter relationship outperformed both the one-parameter relationship and the fixed timing solution in terms of the range of initial angular velocities the model could cope with. One of the two parameters governed the time by which the initiation of the shoulder extension should be reduced as a function of increased initial angular velocity, and the other parameter performed the same function for the remaining timing parameters at the hip and shoulder. The present study suggests that gymnasts, and, therefore, humans, may be able to modify movement patterns to cope with uncertain initial conditions using a relatively small number of parameters.

The purpose of this study was to assess the efficacy of a combined training program (CTP) in reducing the effects of dual tasking on the temporal parameters and kinematics of gait, as compared with single-task gait. A controlled, randomized, intervention study was performed in an intervention group and a control group. The intervention group attended three weekly CTP sessions for 24 weeks. Gait pattern was evaluated prior to the baseline intervention, at 12 weeks, and at 24 weeks (Repost). The sample was composed of 22 subjects diagnosed with multiple sclerosis with an Expanded Disability Status Scale score of 0-5.5. A total of 12 patients were allocated to the intervention group and another 10 to the control group. A three-dimensional photogrammetry scanner was connected to a selective attention system designed to present a dual-task gait condition. Dual tasking had an impact on all spatiotemporal parameters of gait, and the most remarkable effect of dual tasking was on double-support time, which increased by 9% with respect to normal walking. In contrast, dual tasking had a trivial effect on single-support time. The CTP was effective in reducing the effects of dual tasking on stride length and velocity of the center of mass after Repost of training (p < .05). The CTP reduced time in double-support phase, whereas single-support time increased after Repost of intervention. The application of the CTP had no effect on the cost of the double task after 12 weeks of intervention. It is suggested to increase the application time over Repost.

The study assessed the manifestation of a regulated locomotion pattern while clearing the first two hurdles during running. In addition, the effect of a hurdles' learning design, using specific activities and manipulated task constraints, on regulation strategies and kinematic reorganization was examined. Pre- and posttests were conducted. Twenty-four young athletes were randomly assigned into an experimental and a control group, and performed 18 training sessions, consisting of a hurdle-based intervention for experimental participants and a more generalized athletics training for control participants. Different footfall variability curves were recorded, suggesting that young athletes regulated locomotion pattern to clear the hurdles according to their needs. Task-specific training contributed to lower values of variability for the entire approach run and to functional movement reorganization, affording learners to take-off further from the hurdle with a higher horizontal velocity, leading to a more flat hurdle clearance stride and to a significant hurdle running performance improvement.

Background: Plantar sensation and ankle proprioception occur in a stage-like variance across the life span. However, changes in adolescents, young adults, middle-aged adults, and older adults remain unclear. The aim of this study was to investigate the differences of plantar sensation and ankle proprioception in adolescents to older adults.

Methods: A total of 212 participants were recruited in the study and were divided into four groups, including adolescents (n = 46), young adults (n = 55), middle-aged adults (n = 47), and older adults (n = 54). Plantar tactile sensitivity/tactile acuity/vibration threshold and ankle movement threshold/joint position sense/force sense were assessed in all groups. The Kruskal-Wallis H test was used to analyze the differences in Semmes-Weinstein monofilaments between different age groups in different plantar positions. One-way analysis of variance was used to determine differences in foot vibration threshold, two-point discrimination, and ankle proprioception between different age groups.

Results: Significant differences were found in the Semmes-Weinstein monofilament test (p < .001), the two-point discrimination test (p < .05), and the vibration threshold test (p < .05) in the six tested plantar positions among adolescents, young adults, middle-aged adults, and older adults. For ankle proprioception, significant differences were found in movement thresholds in ankle plantar flexion (p = .01), ankle dorsiflexion (p < .001), ankle inversion (p < .001), and ankle eversion (p < .001), as well as relative absolute errors in the ankle force senses of ankle plantar flexion (p = .02) and ankle dorsiflexion (p = .02) across the four age groups.

Conclusion: Plantar sensation and ankle proprioception were sensitive in adolescents and young adults than in middle-aged adults and older adults.

It is well-known that multitasking impairs the performance of one or both of the concomitant ongoing tasks. Previous studies have mainly focused on how a secondary task can compromise visual or auditory information processing. However, despite dual tasking being critical to motor performance, the effects of dual-task performance on proprioceptive information processing have not been studied yet. The purpose of the present study was, therefore, to investigate whether sensorimotor task performance would be affected by the dual task and if so, in which phase of the sensorimotor task performance would this negative effect occur. The kinematic variables of passive and active knee movements elicited by the leg drop test were analyzed. Thirteen young adults participated in the study. The dual task consisted of performing serial subtractions. The results showed that the dual task increased both the reaction time to counteract passive knee-joint movements in the leg drop test and the threshold to detect those movements. The dual task did not affect the speed and time during the active knee movement and the absolute angle error between the final and the target knee angles. Furthermore, the results showed that the time to complete the sensorimotor task was prolonged in dual tasking. Our findings suggest that dual tasking reduces motor performance due to slowing down proprioceptive information processing without affecting movement execution.

The aim of this study was to explore the effects of mental fatigue from smartphone use and Stroop task on bench press force-velocity (F-V) profile, one-repetition maximum (1RM), and countermovement jump (CMJ) performance. Twenty-five trained subjects (age = 25.8 ± 5.7 years) completed three sessions separated by 1 week following a randomized double-blinded crossover design. Each session consisted of F-V relationship, 1RM, and CMJ measurements after performing 30 min of control, social media, or Stroop task. Perceived mental fatigue and motivation were recorded. Mental fatigue, motivation, CMJ height, bench press 1RM, and F-V profile variables (maximal force, maximal velocity, and maximal power) were compared between interventions. Significant differences were found for mental fatigue between interventions (p ≤ .001). Both ST (p ≤ .001) and SM (p = .007) induced higher mental fatigue than control. However, no significant differences between interventions were observed for any other variable (p = .056-.723). The magnitude of the differences between interventions ranged from negligible to small (effect sizes ≤ 0.24). These results suggest that although both ST and SM were effective to induce mental fatigue, neither ST nor SM affected CMJ performance, bench press 1RM, or any variable of the F-V profile compared with the control task.

This study aimed to explore the effects of mental fatigue (MF) induced by an incongruent Stroop task (ST) and by using social media (SM) compared to watching a documentary (control) on dynamic resistance training. Twenty-one resistance-trained males attended three identical experimental sessions with the only difference of the randomized cognitive task (ST, SM, or control). Each session consisted of (a) baseline MF and motivation visual analogue scale responses, (b) cognitive task, (c) postvisual analogue scale responses, (d) warm-up, and (e) resistance training based on three sets of bench press at 65% of one-repetition maximum till concentric failure. Number of repetitions, ratings of perceived exertion, mean velocity of repetitions, and three repetitions in reserve estimated by subjects were recorded for each set. Both ST (p < .001) and SM (p = .010) effectively induced MF, but only ST impaired the number of repetitions performed in Set 2 (p = .036) and generated higher-than-normal levels of ratings of perceived exertion even reaching significant differences compared to SM in Set 1 (p = .005). However, SM also affected neuromuscular performance by impairing movement velocity in Set 1 (p = .003). The ability of estimating three repetitions in reserve or motivation was not affected by any condition (p range = .362-.979). MF induced by ST impaired the number of repetitions performed, what seems to be mediated by higher-than-normal levels of ratings of perceived exertion. Besides, SM also impaired the ability to apply force against 65% of one-repetition maximum measured by movement velocity.

Deficits in movement patterns during cutting while running might place soccer players at risk of injury. The objective was to compare joint angles and intersegment coordination between sexes and ages during an unanticipated side-step cutting task in soccer players. This cross-sectional study recruited 11 male (four adolescents and seven adults) and 10 female (six adolescents and four adults) soccer players. Three-dimensional motion capture was used to measure lower-extremity joint and segment angles as participants performed an unanticipated cutting task. Hierarchical linear models examined relationships between joint angle characteristics with age and sex. Continuous relative phase was used to quantify intersegment coordination amplitude and variability. These values were compared between age and sex groups using analysis of covariance. Adult males had greater hip flexion angle excursions than adolescent males, while adult females had smaller excursions than adolescent females (p = .011). Females had smaller changes in hip flexion angles (p = .045), greater hip adduction angles (p = .043), and greater ankle eversion angles (p = .009) than males. Adolescents had greater hip internal rotation (p = .044) and knee flexion (p = .033) angles than adults, but smaller changes in knee flexion angles at precontact compared with stance/foot off (p < .001). For intersegment coordination, females were more out-of-phase than males in the foot/shank segment in the sagittal plane. There were no differences in intersegment coordination variability between groups. Differences in joint motion during an unanticipated cutting task were present between age groups and sexes. Injury prevention programs or training programs may be able target specific deficits to lower injury risk and improve performance.

The referent control theory (RCT) for action and perception is an advanced formulation of the equilibrium-point hypothesis. The RCT suggests that rather than directly specifying the desired motor outcome, the nervous system controls action and perception indirectly by setting the values of parameters of physical and physiological laws. This is done independently of values of kinematic and kinetic variables including electromyographic patterns describing the motor outcome. One such parameter-the threshold muscle length, λ, at which motoneurons of a given muscle begin to be recruited, has been identified experimentally. In RCT, a similar parameter, the referent arm position, R, has been defined for multiple arm muscles as the threshold arm position at which arm muscles can be quiescent but activated depending on the deflection of the actual arm position, Q, from R. Changes in R result in reciprocal changes in the activity of opposing muscle groups. We advanced the explanatory power of RCT by combining the usual biomechanical descriptions of motor actions with the identification of the timing of R underlying arm movements made with reversals in three directions and to three different extents. We found that in all movements, periods of minimization of the activity of multiple muscles could be identified at ∼61%-86% of the reaching extent in each direction. These electromyographic minimization periods reflect the spatial coordinates at which the R and Q overlap during the production of movements with reversals. The findings support the concept of the production of arm movement by shifting R.