Changes In Movement Strategies Research Articles

Age-Related Differences in Kinematics, Kinetics, and Muscle Synergy Patterns Following a Sudden Gait Perturbation: Changes in Movement Strategies and Implications for Fall Prevention Rehabilitation

Falls in older adults are leading causes of fatal and non-fatal injuries, negatively impacting quality of life among those in this demographic. Most elderly falls occur due to unrecoverable limb collapse during balance control in the single-limb support (SLS) phase. To understand why older adults are more susceptible to falls than younger adults, we investigated age-related differences in lower limb kinematics, kinetics, and muscle synergy patterns during SLS, as well as their relationship to postural control strategies. Thirteen older and thirteen younger healthy adults were compared during the SLS phase of balance recovery following an unexpected surface drop perturbation. Compared to younger adults, older adults demonstrated (1) greater trunk flexion, (2) increased hip extension torque and reduced hip abduction torque of the perturbed leg, and (3) higher postural sway. Trunk flexion was correlated with a delayed latency to the start of lateral-to-medial displacement of center of mass from the perturbation onset. The group-specific muscle synergy revealed that older adults exhibited prominent activation of the hip extensors, while younger adults showed prominent activation of the hip abductors. These findings provide insights into targeted balance rehabilitation and indicate ways to improve postural stability and reduce falls in older adults.

Fatigue, induced via repetitive upper-limb motor tasks, influences trunk and shoulder kinematics during an upper limb reaching task in a virtual reality environment.

BackgroundEfficient shoulder movement depends on the ability of central nervous system to integrate sensory information and to create an appropriate motor command. Various daily encountered factors can potentially compromise the execution of the command, such as fatigue. This study explored how fatigue influences shoulder movements during upper limb reaching.MethodsForty healthy participants were randomly assigned to one of two groups: Control or Fatigue Group. All participants completed an upper limb reaching task at baseline and post-experimental, during which they reached four targets located at 90° of shoulder abduction, 90° external rotation at 90° abduction, 120° scaption, and 120° flexion in a virtual reality environment. Following the baseline phase, the Fatigue Group completed a shoulder fatigue protocol, while Controls took a 10-minute break. Thereafter, the reaching task was repeated. Upper limb kinematic (joint angles and excursions) and spatiotemporal (speed and accuracy) data were collected during the reaching task. Electromyographic activity of the anterior and middle deltoids were also collected to characterize fatigue. Two-way repeated-measures ANOVA were performed to determine the effects of Time, Group and of the interaction between these factors.ResultsThe Fatigue group showed decreased mean median power frequency and increased electromyographic amplitudes of the anterior deltoid (p < 0.05) following the fatigue protocol. Less glenohumeral elevation, increased trunk flexion and rotation and sternoclavicular elevation were also observed in the Fatigue group (Group x Time interaction, p < 0.05). The Control group improved their movement speed and accuracy in post-experimental phase, while the Fatigue group showed a decrease of movement speed and no accuracy improvement (Group x Time interaction, p < 0.05).ConclusionIn a fatigued state, changes in movement strategy were observed during the reaching task, including increased trunk and sternoclavicular movements and less glenohumeral movement. Performance was altered as shown by the lack of accuracy improvement over time and a decrease in movement speed in the Fatigue group.

The Relationship Between Perception Of Ankle Instability And Dynamic Balance In Individuals With A History Of Ankle Sprains

PURPOSE: Ankle sprains are common injuries which can progress to chronic ankle instability (CAI) and balance impairments. While objective data guide treatment for individuals with CAI, the patient’s subjective experience is often overlooked and not counted in the adoption of plan of care. Individual perception of ankle instability is an important factor and has the potential to influence presentation of sensorimotor impairments either through neuromotor or fear-avoidance mechanisms. The purpose of this study was to explore the contribution of perception of unilateral and bilateral CAI on a dynamic balance test. METHODS: Subjects were males and females 18-35 years old (n=25, age= 23.8 ± 1.8 yr.). All subjects completed the Cumberland Ankle Instability Tool (CAIT) to measure perceived ankle instability (lower CAIT scores are associated with greater perceived instability). Dynamic balance was assessed using 3 repetitions in each direction (anterior, postero-medial, and postero-lateral) of the Y-Balance Test (YBT). Asymmetries in CAIT scores and reach distances were calculated by subtracting right leg values from left leg values. Further comparisons were analyzed between groups of bilaterally highest (>80%) and lowest (<20%) combined CAIT scores. RESULTS: There was a significant positive moderate correlation between CAIT asymmetries and asymmetries in the anterior reach (r=0.526, p=0.007) and the posteromedial reach scores (r= 0.554, p=0.004). Significant differences were found between participants with the highest (n=5) and lowest (n=5) bilateral CAIT scores in right posteromedial reach (101.60 ± 9.91 vs 86.80 ± 5.89, p=0.02), right posterolateral reach (96.40 ± 7.70 vs 76.80 ± 4.87, p=0.001), and right composite score (89.96 ± 5.93 vs 78.44 ± 3.85, p=0.007). CONCLUSION: Subjects reporting increased perceived ankle instability demonstrated decreased YBT performance on the side of perceived instability. Decreased reach distances may be attributable to neuromuscular consequences of ankle injury, changes in movement strategy associated with apprehension, or both. In fact, the larger the perceived asymmetries the greater the performance deficits. These findings may help clinicians contextualize sensorimotor assessment results in patients with a history of ankle sprain.

Lower limb muscle fatigability is not associated with changes in movement strategies for balance control in the upright stance.

Fatigue is a distressing symptom inversely related to postural stability in adults with neuromuscular and systemic diseases. However, there is no information about the effects of lower limb muscles fatigability on the movement strategies for balance control in the upright standing. This study enrolled 41 healthy subjects (female/male: 22/19; age 23±3years; body mass index 25.4±3.7kg/m2). Participants underwent posturography and surface electromyography of the gastrocnemius medialis muscle during a sustained, fatiguing voluntary contraction of the gastrocnemius preceded and followed by quiet standing (120s). Amplitude of electromyograms and fatigability were evaluated using the root mean square (RMS) value and both the RMS and spectral median frequency (fmed) slopes. Balance control was evaluated using the center-of-pressure elliptic area (Area) and average velocity (Vavg). Movement strategies for balance control were evaluated using the number of high-density regions (nHDR) and spatial patterns of the three-dimensional statokinesigram. Mean time to muscle fatigability was 258±190s. Area and Vavg but not nHDR increased after the fatiguing task. Single-centered spatial patterns were predominant in both tasks (pre-fatigue: n=22/41; post-fatigue: n=19/41), with no evidence of an association between the spatial patterns and tasks (γ=0.237, 95%CI=[-0.338; 0.542]). Lower limb muscle fatigability increases postural instability, but it is not associated with changes in movement strategies for balance control in the upright stance.

Post-stroke motor recovery and cortical organization following Constraint-Induced Movement Therapies: a literature review.

[Purpose] This review synthesizes findings from studies on two forms of Constraint-Induced Movement Therapies: the original Constraint-Induced Movement Therapy and the modified Constraint-Induced Movement Therapy, in adult stroke patients including the evidence, current limitations and future directions. [Methods] We critically reviewed studies evaluating the effectiveness of Constraint-Induced Movement Therapies in chronic stoke focusing on the functional (i.e. motor recovery) and the neural (i.e. cortical organization) levels. [Results] Constraint-Induced Movement Therapies seemed to improve the upper limb functional usage in chronic stoke with no reliable neurophysiological underlying mechanisms. The Motor Activity Log was the common outcome measuring motor recovery. The work that has been done on modified Constraint-Induced Movement Therapy was far less than the work done on the original Constraint-Induced Movement Therapy. [Conclusion] Evident lack of understanding of the association between changes in motor recovery and the underlying neural mechanisms in-terms of measures of assessing and defining functional recovery (i.e Motor Activity Log) that lacks sufficient sensitivity to characterize changes in movement strategies and thereby lack of distinction between recovery and behavioral compensation. Future studies should employ using kinematic metrics to quantify and explain the training-related changes in behavior following Constraint-Induced Movement Therapies in chronic stroke.

Optical Hand Tracking: A Novel Technique for the Assessment of Bradykinesia in Parkinson's Disease.

Evaluation of therapies for Parkinson's disease (PD) may benefit from objective quantification of the separate movement components of bradykinesia (i.e., velocity, amplitude, and rhythm). This study evaluated the sensitivity and reliability of parameters derived from recently available optical hand tracking techniques for patient-friendly, automated quantification of bradykinesia of the upper extremity in PD. Fifty-seven patients with PD and 57 healthy individuals (controls) performed repetitive finger tapping (RFT), alternating hand movements (AHM), and alternating forearm movements (AFM). Movement components of bradykinesia (i.e., velocity, frequency, amplitude, hesitations, and halts) were quantified using optical hand tracking. Reliability was quantified using intraclass correlation coefficients in a subgroup of 12 patients with PD and 12 controls (test-retest) and in all 57 controls (intra-trial). RFT and AHM were successfully recorded in 94% of all participants. Movement components differed between patients with PD and controls and were correlated with clinical ratings. Velocity and halt duration appeared to be most useful (i.e., the largest difference between the PD and control groups, good reliability) for the quantification of RFT, whereas frequency appeared to be most useful for the quantification of AHM. Other variables, such as frequency and amplitude of RFT, showed poor test-retest reliability, because they were susceptible to changes in movement strategy. AFM was excluded from the analysis because of problems with hand recognition. Novel optical hand tracking techniques yield promising results for patient-friendly quantification of bradykinesia of the upper extremity in PD. Future work should aim to optimize optical hand tracking and reduce susceptibility to changes in strategy.

Effects of neuromuscular reeducation on hip mechanics and functional performance in patients after total hip arthroplasty: A case series

BackgroundFollowing total hip arthroplasty, patients demonstrate compensatory movement strategies during activities of daily living such as walking and stair climbing. Movement compensations are important markers of functional decline in older adults and are related to poor functional capacity. Despite increased utilization of hip arthroplasty, persistent movement compensation, and functional performance deficits, no consensus on postoperative rehabilitation exists. Neuromuscular reeducation techniques offer a strategy to improve movement quality by emphasizing hip abductor performance and pelvic stability. This case series illustrates changes in movement strategy around the hip in response to targeted neuromuscular reeducation techniques after hip arthroplasty. MethodsFive participants received an 8-week exercise program following total hip arthroplasty, emphasizing targeted neuromuscular reeducation techniques hallmarked by specific, weight-bearing exercise to improve hip abductor performance and pelvic stability. Five additional participants were supervised and followed for comparison. FindingsParticipants in the neuromuscular reeducation program improved their internal hip abductor moments and vertical ground reaction forces during walking and stair climbing. They also improved their functional performance and hip abductor strength outcomes. InterpretationTargeted neuromuscular reeducation techniques after total hip arthroplasty provided a positive effect on biomechanical outcomes, functional performance, and muscle strength. Through focused use of the hip abductor muscles, increased internal hip abductor moments were observed. This intervention potentially promotes pelvic stability, and may contribute to improved performance on tasks such as stair climbing, fast walking, and balance. The results suggest that neuromuscular reeducation offers a unique effect on movement strategy and function for patients following total hip arthroplasty.

How the mode of action affects evidence of planning and movement kinematics in aging: End‐state comfort in older adults

Motor deficits are commonly observed with age; however, it has been argued that older adults are more adept when acting in natural tasks and do not differ from young adults in these contexts. This study assessed end-state comfort and movement kinematics in a familiar task to examine this further. Left- and right-handed older adults picked up a glass (upright or overturned) as if to pour water in four modes of action (pantomime, pantomime with image/cup as a guide, actual grasping). With increasing age, a longer deceleration phase (in pantomime without a stimulus) and less end-state comfort (in pantomime without a stimulus and image as a guide) was displayed as the amount of contextual information available to guide movement decreased. Changes in movement strategies likely reflect an increased reliance on feedback control and demonstration of a more cautious movement. A secondary aim of this study was to assess hand preference and performance, considering conflicting reports of manual asymmetries with age. Performance differences in the Grooved Pegboard place task indicate left handers may display a shift towards right handedness in some, but not all cases. Summarizing, this study supports age-related differences in planning and control processes in a familiar task, and changes in manual asymmetries with age in left handers.

Within-Match PlayerLoad™ Patterns During a Simulated Soccer Match: Potential Implications for Unit Positioning and Fatigue Management.

To assess the acute alterations in triaxial accelerometry (PlayerLoad [PL(VM)]) and its individual axial planes (anteroposterior PlayerLoad [PL(AP)], mediolateral PlayerLoad [PL(ML)], and vertical PlayerLoad [PL(V)]) during a standardized 90-min soccer match-play simulation (SAFT90). Secondary aims of the study were to assess the test-retest reliability and anatomical location of the devices. Semiprofessional (n = 5) and university (n = 15) soccer players completed 3 trials (1 familiarization, 2 experimental) of SAFT90. PlayerLoad and its individual planes were measured continuously using micromechanical-electrical systems (MEMS) positioned at the scapulae (SCAP) and near the center of mass (COM). There were no between-halves differences in PL(VM); however, within-half increases were recorded at the COM, but only during the 1st half at the SCAP. Greater contributions to PL(VM) were provided by PL(V) and PL(ML) when derived from the SCAP and COM, respectively. PL(VM) (COM 1451 ± 168, SCAP 1029 ± 113), PL(AP) (COM 503 ± 99, SCAP 345 ± 61), PL(ML) (COM 712 ± 124, SCAP 348 ± 61), and PL(V) (COM 797 ± 184, SCAP 688 ± 124) were significantly greater at the COM than at the SCAP. Moderate and high test-retest reliability was observed for PlayerLoad and its individual planes at both locations (ICC .80-.99). PlayerLoad and its individual planes are reliable measures during SAFT90 and detected within-match changes in movement strategy when the unit was placed at the COM, which may have implications for fatigue management. Inferring alterations in lower-limb movement strategies from MEMS units positioned at the SCAP should be undertaken with caution.

Understanding the effects of spaceflight on head–trunk coordination during walking and obstacle avoidance

Prolonged exposure to spaceflight conditions results in a battery of physiological changes, some of which contribute to sensorimotor and neurovestibular deficits. Upon return to Earth, functional performance changes are tested using the Functional Task Test (FTT), which includes an obstacle course to observe post-flight balance and postural stability, specifically during turning. The goal of this study was to quantify changes in movement strategies during turning events by observing the latency between head-and-trunk coordinated movements. It was hypothesized that subjects experiencing neurovestibular adaptations would exhibit head-to-trunk locking (‘en bloc’ movement) during turning, exhibited by a decrease in latency between head and trunk movement. FTT data samples were collected from 13 ISS astronauts and 26 male 70-day head down tilt bed rest subjects, including bed rest controls (10 BRC) and bed rest exercisers (16 BRE). Samples were analyzed three times pre-exposure, immediately post-exposure (0 or 1-day post) and 2–3 times during recovery from the unloading environment. Two 3D inertial measurements units (XSens MTx) were attached to subjects, one on the head and one on the upper back. This study focused primarily on the yaw movements about the subject׳s center of rotation. Time differences (latency) between head and trunk movement were averaged across a slalom obstacle portion, consisting of three turns (approximately three 60° turns). All participants were grouped as ‘decreaser’ or ‘increaser’, relating to their change in head-to-trunk movement latency between pre- and post-environmental adaptation measures. Spaceflight unloading (ISS) showed a bimodal response between the ‘increaser’ and ‘decreaser’ group, while both bed rest control (BRC) and bed rest exercise (BRE) populations showed increased preference towards a ‘decreaser’ categorization, displaying greater head–trunk locking. It is clear that changes in movement strategies are adopted during exposure to an unloading environment. These results further the understanding of vestibular–somatosensory convergence and support the use of bed rest as an exclusionary model to better understand sensorimotor changes in spaceflight.

Effects of work experience on fatigue-induced biomechanical changes during repetitive asymmetric lifts/lowers

Repetitive lifting/lowering is associated with an increased risk of work-related low back disorders (WRLBDs), and fatigue may exacerbate such risk. Work methods used by experienced workers are potential models for developing worker training to reduce WRLBDs, though whether experience modifies the effects of fatigue on WRLBD risk is largely unknown. Here, six novices and six experienced workers completed 185 cycles of repetitive, asymmetric lifts/lowers. Physical demands, whole-body balance and torso movement stability were assessed using torso kinematics/kinetics, linear/angular momenta and Lyapunov exponents, respectively. Several fatigue-induced changes in movement strategies were evident. Novices decreased and experienced workers increased peak lumbar moments post-fatigue, suggesting lower WRLBD risks among the former in terms of torso kinetics. Other than lumbar moments, though, fatigue substantially reduced group-level differences in torso twisting velocities and accelerations. Post-fatigue movement strategies of experienced workers thus did not appear to be advantageous in terms of WRLBD risk.Practitioner Summary: Fatigue induced changes in movement strategies during a repetitive, asymmetric lifting/lowering task. Novices and experienced workers adapted to fatigue differently, with diminished post-fatigue differences in lifting strategies. Regarding work-related low back disorder risks, the post-fatigue movement strategies of experienced workers did not appear superior to those of novices.

Null referential subjects in the history of Swedish

This article is concerned with null referential subjects in Old Swedish (ca. 1225–1526), and addresses the problem of why the scope for such subjects has been reduced during the history of Swedish. Within diachronic syntax it has been a common assumption that syntactic change is caused by changes in morphology. However, this study shows that deflexion only to a limited extent can explain the loss of null referential subjects in Old Swedish, since the most striking change in their use seems to take place during Early Old Swedish (ca. 1225–1375) before the loss of person agreement: whereas referential subjects could be omitted from verb-second main clauses and subordinate clauses in Early Old Swedish, in Late Old Swedish corresponding subjectless clauses are uncommon. Within the framework of generative grammar it is argued that this is an effect of changes in movement strategies to the subject position, [Spec, IP]: whereas movement to the subject position is syntactically determined in Modern Swedish, in Early Old Swedish the corresponding move is pragmatically determined. The study is based on a corpus of approximately 193,400 words, collected from 12 Old Swedish texts.

Valgus Bracing Affords Short-Term Treatment Solution Across Walking and Sit-To-Stand Activities

Since activities of daily living do not exist in isolation this prospective study examined biomechanical function during level walking and sit-to-stand activities over two months of brace use by subjects with varying grades of knee osteoarthritis. Kinematic and kinetic data were collected using infrared cameras and force platforms; clinical scores compared perceived and measured functional effects. There was no significant change in pain for any grades of OA but activity levels were significantly higher at one month in the moderate OA grades and at two months for the low OA grades. Mechanical constraints and changes in movement strategies were consistent across tasks and OA grade. This study provides valuable data for further studies aimed at refining the use and optimization of valgus bracing efficacy.

Temporal strategy and performance during a fatiguing short-cycle repetitive task

This study investigated temporal changes in movement strategy and performance during fatiguing short-cycle work. Eighteen participants performed six 7-min work blocks with repetitive reaching movements at 0.5 Hz, each followed by a 5.5-min rest break for a total duration of 1 h. Electromyography (EMG) was collected continuously from the upper trapezius muscle, the temporal movement strategy and timing errors were obtained on a cycle-to-cycle basis, and perceived fatigue was rated before and after each work block. Clear signs of fatigue according to subjective ratings and EMG manifestations developed within each work block, as well as during the entire hour. For most participants, timing errors gradually increased, as did the waiting time at the near target. Changes in temporal movement strategy were negatively correlated with changes in the level and variability of EMG, suggesting that an adaptive temporal strategy offset the development of unstable motor solutions in this fatiguing, short-cycle work. Practitioner Summary: Sustained performance of operators is essential to maintain competitiveness. In this study of repetitive work, participants gradually changed their temporal movement strategy, for possibly alleviating the effects of fatigue. This suggests that in order to effectively counteract fatigue and sustain performance, industrial production should allow extensive spatial and temporal flexibility.

Effect of Acute Fatigue of the Hip Abductors on Control of Balance in Young and Older Women

Bellew JW, Panwitz BL, Peterson L, Brock MC, Olson KE, Staples WH. Effect of acute fatigue of the hip abductors on control of balance in young and older women. Objective To examine the effects of acute fatigue of the hip abductors on the control of balance in young and older women. Design Pretest-posttest. Setting University research laboratory. Participants Healthy young women (n=20; age, 23.0±1.5y; height, 166.52±4.5cm; mass, 65.33±10.5kg) and community-dwelling older women (n=20; age, 71.65±7.2y; height, 162.31±3.8cm; mass, 71.16±11.6kg) without a fall history. Intervention Measurements of control of single-limb balance before and after fatiguing the hip abductors of the dominant leg. Main Outcome Measure Performance on 3 clinical assessments of control of balance: the modified Functional Reach Test in the forward, left, and right directions; the Lower-Extremity Reach Test in forward and lateral directions; and the Single-Limb Stance Time Test (SLSTT). Results Although the younger subjects showed a significantly greater control of balance than the older women in most tests, control of balance after acute fatigue failed to show a significant decline in either age group. The only exception to this was the SLSTT in the younger women in whom a significant 26% decline was noted ( P<.05). Conclusions Acute fatigue of the hip abductors did not result in a decreased control of balance in healthy young or older women without fall history. Despite considerable changes in movement strategies used to complete the postfatigue tests of balance, quantitative measures of balance did not decrease.

Changes in sensory organization test scores with age.

The goals of this study were to collect normative data on asymptomatic, ambulatory, community-dwelling adults on a standard diagnostic test of vestibular function in balance and to determine if their responses differ significantly from younger adults. Subjects were divided into four age groups, 18-44 years (young), 45-69 years (middle-aged), 70-79 (old), and 80-89 (elderly). Subjects were seen in the neurotologic diagnostic laboratory at a tertiary care facility. Their dynamic balance was tested under a variety of sensory conditions using the EquiTest (NeuroCom), a standard diagnostic test. The data from one subtest, the Sensory Organization Test (SOT) were evaluated. These data showed significant age-associated declines in overall score and changes in movement strategy. These results suggest that those parts of the vestibular system involved with balance have age-related declines through the end of the life span, even in asymptomatic people, and that these changes do not level off but continue into the ninth decade. Therefore, when elderly people are evaluated for balance disorders age-appropriate norms should be used. These results also suggest that declines in motor performance on laboratory tests are not directly related to reduced independence in essential activities of daily living in elderly people.