Human Movement Science最新文献

Purpose

Neural and peripheral effects of induced muscle pain on explosive force production were investigated.

Methods

Nine participants performed two maximal, six explosive, and six electrical stimulations induced (twitches and octets) isometric knee extensions before and after (15 min of rest) receiving an intramuscular injection of hypertonic saline (pain inducer) or isotonic (placebo) infusions in two laboratory visits separated by 7 days.

Results

It was observed a reduction of peak torque production in maximal voluntary contraction in both conditions (9.3 and 3.3% for pain and placebo, respectively) and in the rate of torque development in placebo (7%). There was an increase in the rate of torque development for twitch and octets (10.5 and 15.8%, respectively) in the pain condition and peak torque for twitch (12%) in both conditions (as did the total rate of torque development for octets).

Conclusion

Force production decreases and increases during voluntary and involuntary contractions, respectively, suggesting that acute pain impairs force production via central mechanisms.

We found evidence that Army cadets improved their gaze behavior and performance across time under high and low pressure in a shooting task. The purpose of the study was to determine if male and female cadets developed an optimal quiet eye (QE) onset, a longer QE duration, and decreased pupil diameter variability (PDV) over time under low (LP) and high pressure (HP) conditions. The study was carried out over four sessions, with intervals of 4.5 months. During each session, 16 men and 12 women, first-year cadets of The Brazilian Army Academy, performed ten pistol shots under counterbalanced LP and HP conditions. The cadets shot in the upright position and wore an eye-tracker. Shooting accuracy improved and did not differ for men and women in the LP condition, however during HP the women performed more poorly than the men in session 1 but improved to a level similar to the men in session 4. QE duration Pre (aiming) did not differ during LP, while during HP QE Post (execution) increased across the session for men and women. QE onset 2 (execution) occurred earlier for the men than women during LP, while during HP the women improved to a level similar to the men in sessions 3 and 4. PDV declined across sessions for men and women with the lowest values in sessions 3 and 4. The findings are discussed within social facilitation theory, which states the context of training affects the rate at which improvements in motor skills occur. The results show that women cadets can improve their shooting performance, quiet eye duration, quiet eye onset and pupil diameter variability to a level similar to men if three to four LP and HP training sessions are scheduled across approximately 12–18 months.

Consecutive longitudinal axis rotations are very common in dance, ranging from head spins in break dance to pirouettes in ballet. They pose a rather formidable perceptuomotor challenge – and hence form an interesting window into human motor behaviour – yet they have been scarcely studied. In the present study, we investigated dancers' dizziness and postural stability after consecutive rotations. Rotations were performed actively or undergone passively, either with or without the use of a spotting technique in such an order that all 24 ordering options were offered at least once and not more than twice.

Thirty-four dancers trained in ballet and/or contemporary dance (aged 27.2 ± 5.1 years) with a mean dance experience of 14.2 ± 7.1 years actively performed 14 revolutions in passé or coupé positions with a short gesture leg “foot down” after each revolution. In addition, they were passively turned through 14 revolutions on a motor-driven rotating chair. Participants' centre-of-pressure (COP) displacement was measured on a force-plate before and after the rotations. Moreover, the dancers indicated their subjective feeling of dizziness on a scale from 0 to 20 directly after the rotations. Both the active and passive conditions were completed with and without the dancers spotting.

As expected, dizziness was worse after rotations without the adoption of the spotting technique, both in active and passive rotations. However, the pre-post difference in COP area after active rotations was unaffected by spotting, whereas in the passive condition, spotting diminished this difference. Our results thus suggest that adopting the spotting technique is a useful tool for dizziness reduction in dancers who have to perform multiple rotations. Moreover, spotting appears most beneficial for postural stability when it involves less postural control challenges, such as when seated on a chair and occurs in situations with limited somatosensory feedback (e.g., from the cutaneous receptors in the feet). However, the unexpected finding that spotting did not help postural stability after active rotations needs to be investigated further in future studies, for example with a detailed analysis of whole-body kinematics and eye-tracking.

Background

Motor function and weight status are components of physical fitness that have been implicated in childhood motor and cognitive development. The lateralized readiness potential (LRP), an index of motor planning and action, can provide context surrounding relationships between fitness and brain activity underlying cognitive and motor functions. This study evaluated the relationship between the LRP and motor skills, as well as associations between weight status and neural and behavioral motor functions.

Methods

Children aged 7–13 (n = 35) participated in a cross-sectional study, using the Movement Assessment Battery for Children 2nd edition (MABC-2) to assess balance, manual dexterity, and aiming/catching. The stimulus- (LRP-S) and response-locked (LRP-R) LRPs were elicited from a modified flanker task. Stepwise regressions tested the association between LRPs and MABC-2 components. Linear regressions were conducted to examine BMI and %Fat in relation to LRPs and MABC-2 components.

Results

Analyses revealed that LRP-S mean amplitude difference (β = 0.401, P = 0.042) and reaction time interference scores (β = 0.545, P = 0.004) were positively associated with balance, after adjusting for covariates. The LRP-S and interference scores did not predict other MABC-2 outcomes and LRP-R did not predict any MABC-2 components. Further, %Fat (β = −0.439, P = 0.044), not BMI (β = −0.364, P = 0.082), only predicted balance.

Conclusion

We found that changes in the LRP-S amplitude were positively associated with balance, and %Fat was negatively related to balance. This evidence is that fitness components such as weight status and coordination are related to neural markers of motor function which may be useful in intervention designs aimed to improve brain function via improvements in physical fitness and health behaviors.

Stance stability in individuals with bilateral spastic cerebral palsy (BSCP) in various standing postures including the quiet standing (QS) and limits of stability (LoS) has been widely studied. However, the relationships between the QS and LoS remain unclear. This study aimed to determine the relationships between the positions and postural sway in the QS and anteroposterior LoS in individuals with BSCP. It included 27 adolescents and young adults with BSCP (BSCP group) and 27 adolescents and young adults without disability (control group). The position of center of pressure in the anteroposterior direction (CoPy position) and the path length of center of pressure (CoP path length) during the QS and the anterior and posterior LoS (A-LoS and P-LoS, respectively) were measured using a force platform. The CoPy positions in the A-LoS and P-LoS in the BSCP group were limited compared with those in the control group. In the BSCP group, the more anterior the CoPy position in the QS, the more anterior (i.e., limited) it was in the P-LoS. Although the CoP path length in the QS was larger in the BSCP group, those in the A-LoS and P-LoS were larger in the control group. The BSCP group also showed that the more anterior the CoPy position or the longer the CoP path length in the QS, the more decreased the anteroposterior LoS range was. Therefore, assessing various standing postures, including QS and anteroposterior LoS, is important to manage balance impairments in individuals with BSCP.

Background

Early detection of functional decline in the elderly in day care centres facilitates timely implementation of preventive and treatment measures.

Research question

Whether or not a predictive model can be developed by applying image recognition to analyze elderly individuals' posture during the sit-to-stand (STS) manoeuvre.

Methods

We enrolled sixty-six participants (24 males and 42 females) in an observational study design. To estimate posture key point information, we employed a region-based convolutional neural network model and utilized nine key points and their coordinates to calculate seven eigenvalues (X1-X7) that represented the motion curve features during the STS manoeuvre. One-way analysis of variance was performed to evaluate four STS strategies and four types of compensation strategies for three groups with different capacities (college students, community-dwelling elderly, and day care center elderly). Finally, a machine learning predictive model was established.

Results

Significant differences (p < 0.05) were observed in all eigenvalues except X2 (momentum transfer phase, p = 0.168) between participant groups; significant differences (p < 0.05) were observed in all eigenvalues except X2 (p = 0.219) and X3 (hip-rising phase, p = 0.286) between STS patterns; significant differences (p < 0.05) were observed in all eigenvalues except X2 (p = 0.842) and X3 (p = 0.074) between compensation strategies. The motion curve eigenvalues of the seven posture key points were used to build a machine learning model with 85% accuracy in capacity detection, 70% accuracy in pattern detection, and 85% accuracy in compensation strategy detection.

Significance

This study preliminarily demonstrates that eigenvalues can be used to detect STS patterns and compensation strategies adopted by individuals with different capacities. Our machine learning model has excellent predictive accuracy and may be used to develop inexpensive and effective systems to help caregivers to continuously monitor STS patterns and compensation strategies of elderly individuals as warning signs of functional decline.

Objectives

This study tested the effects of combining two bandwidth knowledge of performance (KP) on a complex sports motor skill.

Method

Twenty-two elementary students were divided into combined wide and narrow bandwidth KP (WNG) and control group (CG). The task was the volleyball serve, whose goal was to hit the bull's eye center of a target lying on the floor on the opposite side of the court. The study was composed of a pre-test, acquisition phase and retention test, and had three measures (pre-test, intermediate test, and retention test) with 15 serves recorded each. The acquisition phase consisted of 252 trials. The WNG had a wide bandwidth KP in the first half of the acquisition phase and a narrow one in the second. The CG received KP in all trials. The effects of bandwidth KP were analyzed separately to infer parameters and skill structure learning.

Results

Both groups improved the skill structure from the first to the intermediate test, but only WNG also improved on the retention test. The parameters accuracy improved only on retention compared to the pre-test and intermediate test but had no difference between groups.

Conclusion

Providing information using the bandwidth KP led to an initial engagement and prioritization of skill structure learning.

Past research indicates that anticipatory postural adjustment (APA) errors may be due to the incorrect selection of responses to visual stimuli. In the current study we used the Simon task as a methodological tool to challenge the response selection stage of processing by presenting visual cues with conflicting spatial context; in this case generating a step response to a left pointing arrow which appears to the participant's right side or vice versa. We expected greater mediolateral APA errors, delayed APA and step onset times, and greater lateral CoP displacement prior to stepping for visual cues with incongruent spatial contexts compared to cues with congruent. Thirteen healthy young adults completed step initiation trials (n = 40) from a force platform while whole-body kinematic motion was tracked. Participants were presented with arrows pointing to the left or right, indicating to step with the left or right limb, respectively. These arrows were presented on the same side as the desired step direction (congruent) or the opposite side (incongruent). Results revealed that incongruent trials resulted in significantly more incidences of mediolateral APA errors and greater mediolateral CoP deviations during the APA compared to congruent visual cue context trials. No effects were observed for the temporal outcomes, suggesting that young adults can maintain temporal execution of steps despite these motor control errors. This study demonstrates that the spatial context of visual information significantly impacts the success of response selection processes during step initiation, furthering our knowledge of how humans integrate visual information to initiate whole body movement.

Background

Individuals with Down syndrome (DS) walk with altered gait patterns compared to their typically developing (TD) peers. While walking at faster speeds and with external ankle load, preadolescents with DS demonstrate spatiotemporal and kinetic improvements. However, evidence of joint kinematic adjustments is unknown, which is imperative for targeted rehabilitation design.

Research question

How does increasing walking speed and adding ankle load affect the joint kinematics of children with and without DS during overground walking?

Methods

In this cross-sectional observational study, thirteen children with DS aged 7–11 years and thirteen age- and sex-matched TD children completed overground walking trials. There were two speed conditions: normal speed and fast speed (as fast as possible without running). There were two load conditions: no load and ankle load (2% of body mass added bilaterally above the ankle). A motion capture system was used to register the ankle, knee, and hip joint angles in the sagittal plane. Peak flexion/extension angles, range of motion, and timing of peak angles were identified. In addition, statistical parametric mapping (SPM) was conducted to evaluate the trajectory of the ankle, knee, and hip joint angles across the entire gait cycle.

Results and significance

SPM analysis revealed the DS group walked with greater ankle, knee, and hip flexion compared to the TD group for most of the gait cycle, regardless of condition. Further, increasing walking speed led to improved ankle joint kinematics in both groups by shifting peak plantarflexion closer to toe-off. However, knee extension during stance was challenged in the DS group. Adding ankle load improved hip and knee kinematics in both groups but reduced peak plantarflexion around toe-off. The kinematic adjustments in the DS group suggest specific motor strategies to accommodate their neuromuscular deficits, which can provide a foundation to design targeted gait-based interventions for children with DS.

The ability to coordinate actions between the limbs is important for many operationally relevant tasks associated with space exploration. A future milestone in space exploration is sending humans to Mars. Therefore, an experiment was designed to examine the influence of inherent and incidental constraints on the stability characteristics associated with the bimanual control of force in simulated Martian gravity. A head-up tilt (HUT)/head-down tilt (HDT) paradigm was used to simulate gravity on Mars (22.3° HUT). Right limb dominant participants (N = 11) were required to rhythmically coordinate patterns of isometric forces in 1:1 in-phase and 1:2 multifrequency patterns by exerting force with their right and left limbs. Lissajous displays were provided to guide task performance. Participants performed 14 twenty-second practice trials at 90° HUT (Earth). Following a 30-min rest period, participants performed 2 test trials for each coordination pattern in both Earth and Mars conditions. Performance during the test trials were compared. Results indicated very effective temporal performance of the goal coordination tasks in both gravity conditions. However, results indicated differences associated with the production of force between Earth and Mars. In general, participants produced less force in simulated Martian gravity than in the Earth condition. In addition, force production was more harmonic in Martian gravity than Earth gravity for both limbs, indicating that less force distortions (adjustments, hesitations, and/or perturbations) occurred in the Mars condition than in the Earth condition. The force coherence analysis indicated significantly higher coherence in the 1:1 task than in the 1:2 task for all force frequency bands, with the highest level of coherence in the 1–4 Hz frequency band for both gravity conditions. High coherence in the 1–4 Hz frequency band is associated with a common neural drive that activates the two arms simultaneously and is consistent with the requirements of the two tasks. The results also support the notion that neural crosstalk stabilizes the performance of the 1:1 in-phase task. In addition, significantly higher coherence in the 8–12 Hz frequency bands were observed for the Earth condition than the Mars condition. Force coherence in the 8–12 Hz bands is associated with the processing of sensorimotor information, suggesting that participants were better at integrating visual, proprioceptive, and/or tactile feedback in Earth than for the Mars condition. Overall, the results indicate less neural interference in Martian gravity; however, participants appear to be more effective at using the Lissajous displays to guide performance under Earth's gravity.