Human Movement Science最新文献

Objective

Methods

Results

Conclusions

Sprinting at maximum velocity requires fast angular motion of the thigh and effective hamstring function for optimum performance and injury prevention. In this cross-sectional investigation of 21 male sprinters, we acquired thigh angular kinematics while sprinting at top speed (range: 8.96–10.17 m/s), and then measured eccentric hamstring strength capacities using an isokinetic dynamometer during the same test session. In agreement with the hypotheses, thigh angular motion rates and the associated eccentric hamstring strength capacities were both significantly correlated with top speed (r-values: ∼0.5; p < 0.05). Additionally, when the participants were sorted by top speed, there were significant differences between the faster group and the slower group. Notably, on average the faster group showed faster thigh motion (angular acceleration: 10.3 kdeg/s², 11 % greater than slower group) and higher eccentric hamstring strength capacities (peak moment: 2.26 Nm/kg, 14 % greater than slower group). This investigation indicates that fast thigh angular motion and eccentric hamstring strength are both important for sprint performance.

Cycling requires the integration of gaze behaviors, body movements, and bicycle movements. However, whether these movements contribute to skilled cycling performance, such as cycling on straight and narrow paths are uncertain. The present study aimed to differentiate optokinetic nystagmus (OKN) from vestibulo-ocular reflex (VOR) that characterize the relationship between eye and head movements during cycling on straight and narrow path, and to identify gaze behaviors, body movements, and bicycle movements that contribute to cycling performance. Nineteen participants with no prior competitive experience cycled three times on a 12-cm wide path. The participants were asked to avoid deviating from the path as much as possible. The measured variables were gaze behavior in a sagittal plane, body movement, and bicycle movement. As a result, OKN was observed among 16 of the 19 participants. The cross-correlation between the eye and head did not show negative value, indicating the absence of VOR. These results suggest that the participants moved their eyes while keeping their heads stable during cycling on a straight and narrow path. In the results of the multiple regression analysis, the variables with small standard deviations (SD) of the steering angle and upward eye position were related to a lower deviation from the path. These results suggest that a small SD of the steering angle and directed gaze in the forward direction may contribute to skilled cycling.

Background

Joint position sense (JPS) is crucial for maintaining posture, protecting joints, and carrying out daily activities such as walking. Studies show that exercises to strengthen muscles and improve proprioception can positively impact JPS during passive and less complex activities. Evidence suggests that motor training can effectively enhance sensory function, including JPS, due to the extensive connections between the motor cortex and somatosensory areas. Gait retraining using real-time feedback has improved outcomes among patients with musculoskeletal disorders. The effect of gait retraining on JPS has not been investigated. This study assessed the effects of gait retraining to reduce knee extension in joint position sense in individuals with knee hyperextension walking patterns.

Methods

Ten women with asymptomatic knee hyperextension (KH) >5° during overground walking participated in this study. Sagittal-plane kinematics were assessed using a three-dimensional (3D) motion analysis system. The JPS was assessed using the Knee Position Active Reproduction Test. The knee with the highest hyperextension was the focus of the gait retraining intervention, which consisted of six 1-h sessions using verbal instructions and visual kinematic feedback. Comparisons of peak knee extension during walking and knee JPS overall error (RMSE) were made using a paired t-test.

Results

Gait retraining intervention significantly reduced knee extension angle during walking (83.8 % change; p < 0.001; Cohen's d = −1.6) and improved knee JPS (62 % change; p = 0.023; Cohen's d = 0.8) post-training. In addition, the improvements in joint kinematics (36.7 % change; p = 0.005; Cohen's d = −1.2) and JPS (52.6 % change; p = 0.015; Cohen's d = 0.9) were observed in the untrained knee.

Significance

Gait retraining can improve joint position sense. This study addresses a gap in our understanding of how gait retraining can influence JPS. Our results corroborate that gait retraining is an evolving and promising strategy for improving gait outcomes, particularly in individuals with KH walking patterns.

The Fitts' task is a simple and effective method for evaluating motor capacity that can be used to reveal detailed aspects of visuomotor control when hand and eye kinematics are recorded simultaneously. With advances in technology, the classical Fitts' reciprocal tapping task was modified for use with digitizer tablets and computer screens that require sliding rather than tapping hand movements, which may rely on different visuomotor control strategies. Given the ubiquity of digital devices and touchscreens that often require execution of sliding movements, it is important to compare the underlying visuomotor control and eye-hand coordination involved in reciprocal sliding and tapping movements, which was the aim of the current study. Twelve young adults performed both tasks while their hand and eye movements were recorded. Results revealed motor capacity was significantly higher (p < 0.0001, d = 2.67) in the tapping task (19.62 ± 5.89 bits/s) compared to the sliding task (7.87 ± 2.02 bits/s). Examining hand kinematics showed the deceleration interval was significantly longer in the sliding compared to the tapping task at the lowest task difficulty (ID 2.28: 0.160 s ± 0.026 vs 0.129 s ± 0.017; p < 0.01), which was exacerbated as task difficulty increased (ID 6.97: 0.355 s ± 0.059 vs 0.226 s ± 0.020, p < 0.0001), indicating greater reliance on visual feedback during the sliding task. Examining temporal eye-hand coordination pattern showed that hand movement initiation tended to precede eye movement in both tasks. Overall, the results of this study provide a comprehensive examination of eye and hand kinematics demonstrating salient differences in visuomotor control between tapping and sliding movements. The findings also reveal a novel insight into the temporal pattern of eye-hand coordination for reciprocal tapping and sliding movements, which is in contrast to previous studies that examined discrete (rather than reciprocal) target-directed pointing movements where the eyes typically precede the hand by approximately 100 ms. In conclusion, the current study revealed substantial differences between the two tasks, one major finding being the sliding movements were performed slower compared to parabolic tapping hand movements, which may have implications for designing interactive digital devices and assessment of eye-hand coordination.

Background

This study examined (i) adaptations in muscle activity following perturbation-based balance training (PBT) using treadmill belt-accelerations or PBT using walkway trips and (ii) whether adaptations during treadmill PBT transfer to a walkway trip.

Methods

Thirty-eight older people (65+ years) undertook two PBT sessions, including 11 treadmill belt-accelerations and 11 walkway trips. Surface electromyography (EMG) was measured bilaterally on the rectus femoris (RF), tibialis anterior (TA), semitendinosus (ST) and gastrocnemius medial head (GM) during the first (T1) and eleventh (T11) perturbations. Adaptations (within-subjects - 1st vs 11th perturbations for treadmill and walkway PBT) and their transfer (between-subjects – 1st walkway trip after treadmill PBT vs 1st walkway trip with no prior training) effects were examined for the EMG parameters.

Results

Treadmill PBT reduced post-perturbation peak muscle activation magnitude (left RF, TA, ST, right RF, ST, GM), onset latency (right TA), time to peak (right RF) and co-contraction index (knee muscles) (P < 0.05). Walkway PBT reduced post-trip onset latencies (right TA, ST), peak magnitude (left ST, right GM), time to peak (right RF, ST) and pre-perturbation muscle activity (right TA) (P < 0.05). Those who undertook treadmill PBT were not different to those without prior training during the first walkway trip (P > 0.05).

Conclusions

Both treadmill and walkway PBT induced earlier initiation and peak activation of right limb muscles responsible for the first recovery step. Treadmill PBT also reduced co-contraction of the knee muscles. Adaptations in muscle activity following treadmill PBT did not transfer to a walkway trip.

Texting while walking (TWW) is a dual-task activity that young adults perform in their everyday lives. TWW has been reported to affect gait characteristics such as gait speed, stride length, and cadence. However, the influence of TWW on lower extremity gait function has not been investigated. Therefore, the purpose of this study was to quantify gait function by examining gait symmetry and using a time series analysis. Twenty-eight young adults (14 males, 14 females) walked at their preferred speed for 10 m as a baseline condition and a 10 m TWW task. Three-dimensional segment tracking was achieved utilizing a lower extremity and trunk marker set and the Model Statistic was used to test for statistical differences between the hip, knee, and ankle angular joint positions. The hip yielded the most asymmetries (25 out of 101 points) throughout the gait cycle, while asymmetries for the knee and ankle joints yielded 16 out of 101 points and 11 out of 101 points, respectively. The outcomes of this study suggest there are differences between baseline and TWW gait symmetry, however, the percentage of the gait cycle affected was less than 25 % - indicating gait function is not strongly influenced by texting while walking in young adults.

Emerging research suggests that muscular and kinematic responses to overhead work display a high degree of variability in fatigue-related muscular and kinematics changes, both between and within individuals when evaluated across separate days. This study examined whether electromyographic (EMG), kinematic, and kinetic responses to an overhead drilling task performed until volitional fatigue were comparable to those of a repeated identical exposure of the task completed 1 week later. Surface EMG and intramuscular EMG, sampled from 7 shoulder muscles, and right upper limb kinematics and kinetics were analyzed from 15 male and 14 female participants. No significant day-to-day changes in EMG mean power frequency (MPF) were observed, though serratus anterior displayed significantly less fatigue-related increase in EMG root-mean-squared (RMS) signal amplitude on day 2. Unfatigued upper kinematics on day 2 featured an increase in thoracohumeral elevation, elbow flexion, and decrease in wrist ulnar deviation compared to unfatigued state on day 1. Fatigue-related changes in shoulder joint flexion moment that were present on day 1 were reduced on day 2, suggesting that a more efficient overhead work strategy was learned and preserved across successive days. Day-to-day changes in upper limb joint angle variability, quantified by median absolute deviation (MdAD), were joint dependent. Despite yielding a variable fatigue-related kinetic strategy on both days, kinematic and kinetic fatigue-related changes on a second day of completing an overhead drilling task suggested a potential kinematic learning effect.

When individuals stand, they sway and so have to maintain their balance. It is generally expected that task performance is worse when standing and swaying than when sitting and therefore not swaying. In contrast, we hypothesized that greater sway is associated with better task performance in the absence of external perturbations of posture. Twenty-four healthy, young adults performed two goal-directed, modified Stroop tasks (incongruent and reversed incongruent) in four body position conditions (standing against a vertical surface, and standing freely with a wide, standard or narrow stance). Centre of pressure (COP) sway, head sway, eye movements, visual attention, and task performance were recorded. Partial correlation analyses showed significant positive associations between task performance and some COP and head sway variables, after controlling for the level of visual attention. Analyses of variance with three factors (body position, task difficulty, target distance) also showed significant interaction effects between body position (and therefore postural sway) and the number of accurate target findings. The presence of these interactions showed that narrow stance was both the best body position for performing the incongruent task and the worst body position for performing the reversed incongruent task. Overall, COP sway and head sway can increase task performance. Hence, healthy, young adults in quiet stance appear to use sway to explore their environment more effectively. However, it should be borne in mind that our hypothesis was formulated solely with regard to healthy, young adults standing in quiet stance.