Coordination of posture and movement

Are Rotations and Translations of Head Posture Related to Gait and Jump Parameters?

This study assessed the relationship between head posture displacements and biomechanical parameters during gait and jumping. One hundred male and female students (20 ± 3 yrs) were assessed via the PostureScreen Mobile® app to quantify postural displacements of head rotations and translations including: (1) the cranio-vertebral angle (CVA) (°), (2) anterior head translation (AHT) (cm), (3) lateral head translation in the coronal plane (cm), and (4) lateral head side bending (°). Biomechanical parameters during gait and jumping were measured using the G-Walk sensor. The assessed gait spatiotemporal parameters were cadence (steps/min), speed (m/s), symmetry index, % left and right stride length (% height), and right and left propulsion index. The pelvic movement parameters were (1) tilt symmetry index, (2) tilt left and right range, (3) obliquity symmetry index, (4) obliquity left and right range, (5) rotation symmetry index, and (6) rotation left and right range. The jump parameters measured were (1) flight height (cm), (2) take off force (kN), (3) impact Force (kN), (4) take off speed (m/s), (5) peak speed (m/s), (6) average speed concentric phase (m/s), (7) maximum concentric power (kW), (8) average concentric power (kW) during the counter movement jump (CMJ), and (9) CMJ with arms thrust (CMJAT). At a significance level of p ≤ 0.001, moderate-to-high correlations (0.4 < r < 0.8) were found between CVA, AHT, lateral translation head, and all the gait and jump parameters. Weak correlations (0.2 < r < 0.4) were ascertained for lateral head bending and all the gait and jump parameters except for gait symmetry index and pelvic symmetry index, where moderate correlations were identified (0.4 < r < 0.6). The findings indicate moderate-to-high correlations between specific head posture displacements, such as CVA, lateral head translation and AHT with the various gait and jump parameters. These findings highlight the importance of considering head posture in the assessment and optimization of movement patterns during gait and jumping. Our findings contribute to the existing body of knowledge and may have implications for clinical practice and sports performance training. Further research is warranted to elucidate the underlying mechanisms and establish causality in these relationships, which could potentially lead to the development of targeted interventions for improving movement patterns and preventing injuries.

Anticipatory postural adjustments mediate the changes in fear-related behaviors in individuals with chronic low back pain

OBJECTIVES

The role(s) of anticipatory postural adjustments (APAs) in changes in subsequent motor and postural controls in response to movement perturbations are unclear in individuals with chronic low back pain (CLBP). This study aimed to clarify the relationships among kinesiophobia, APAs, lumbar kinematic output, and postural control associated with lumbar movement in individuals with CLBP.

METHODS

CLBP participants (n=48) and healthy controls (HCs) without CLBP (n=22) performed a bend-forward task using their lumbar region on a force platform and returned upright. Each participant's lumbar movements were recorded using an electrogoniometer. We calculated the APA duration, the duration of lumbar direction changes from forward to backward, and the center of pressure (COP) position after lumbar movement tasks completion.

RESULTS

Compared with the HCs, the duration of direction changes in lumbar movement and the APA duration in CLBP participants were prolonged, and the COP position was shifted forward. The mediation analysis revealed that the duration of lumbar direction changes in the CLBP group was subjected to a significant indirect effect of APAs and a direct effect of kinesiophobia, and the COP position was subjected to a significant indirect effect of kinesiophobia through APAs.

CONCLUSIONS

APAs partially mediate the relationship between kinesiophobia and changes in lumbar motor control and mediate the relationship between kinesiophobia and postural control in response to movement perturbations. These findings expand our understanding of APAs in altered subsequent movement and postural controls due to kinesiophobia in individuals with CLBP.

Site-Specific Muscle Loss in the Abdomen and Anterior Thigh in Elderly Males with Locomotive Syndrome

Although locomotive syndrome (LS) is a condition of reduced mobility, little information is available regarding the loss of site-specific skeletal muscle mass. The aim of the present study is to examine site-specific muscle loss in elderly males with LS. A total of 100 men ranging in age from 65 to 74 years were divided into two groups (LS and non-LS) using LS risk tests including the stand-up test, two-step test, and the 25-question geriatric locomotive function scale Muscle thickness (MTH) at eight sites-anterior and posterior thigh (AT and PT, respectively), anterior and posterior lower leg (AL and PL, respectively), rectus abdominis (RA), anterior and posterior upper arm (AU and PU, respectively), and anterior forearm (AF)-was evaluated using B-mode ultrasound. Furthermore, the 30-s chair stand test (CS-30), 10-m walking time, zig-zag walking time, and sit-up test were assessed as physical functions. There were no significant differences in age and body mass index between the LS and non-LS groups. The percentage of skeletal muscle was lower in the LS group than in the non-LS group. Although there were no differences in the MTH of AU, PU, AF, PT, Al and PL, site-specific muscle loss was observed at RA and AT in the LS group. CS-30, 10-m walking time, zig-zag walking time, and sit-up test in the LS group were all worse than those in the non-LS group. The MTHs of RA and AT were both correlated to those physical functions. In conclusion, the LS group had site-specific muscle loss and worse physical functions. This study suggests that site-specific changes may be associated with age-related physical functions. These results may suggest what the essential characteristics of LS are.

Toward a motor signature in autism: Studies from human-machine interaction

BACKGROUND

Autism spectrum disorder (ASD) is a heterogeneous group of neurodevelopmental disorders which core symptoms are impairments in socio-communication and repetitive symptoms and stereotypies. Although not cardinal symptoms per se, motor impairments are fundamental aspects of ASD. These impairments are associated with postural and motor control disabilities that we investigated using computational modeling and developmental robotics through human-machine interaction paradigms.

METHOD

First, in a set of studies involving a human-robot posture imitation, we explored the impact of 3 different groups of partners (including a group of children with ASD) on robot learning by imitation. Second, using an ecological task, i.e. a real-time motor imitation with a tightrope walker (TW) avatar, we investigated interpersonal synchronization, motor coordination and motor control during the task in children with ASD (n=29), TD children (n=39) and children with developmental coordination disorder (n=17, DCD).

RESULTS

From the human-robot experiments, we evidenced that motor signature at both groups' and individuals' levels had a key influence on imitation learning, posture recognition and identity recognition. From the more dynamic motor imitation paradigm with a TW avatar, we found that interpersonal synchronization, motor coordination and motor control were more impaired in children with ASD compared to both TD children and children with DCD. Taken together these results confirm the motor peculiarities of children with ASD despite imitation tasks were adequately performed.

DISCUSSION

Studies from human-machine interaction support the idea of a behavioral signature in children with ASD. However, several issues need to be addressed. Is this behavioral signature motoric in essence? Is it possible to ascertain that these peculiarities occur during all motor tasks (e.g. posture, voluntary movement)? Could this motor signature be considered as specific to autism, notably in comparison to DCD that also display poor motor coordination skills? We suggest that more work comparing the two conditions should be implemented, including analysis of kinematics and movement smoothness with sufficient measurement quality to allow spectral analysis.

Influence of dual-task constraints on the interaction between posture and movement during a lower limb pointing task

One of the challenges regarding human motor control is making the movement fluid and at a limited cognitive cost. The coordination between posture and movement is a necessary requirement to perform daily life tasks. The present experiment investigated this interaction in 20 adult men, aged 18-30 years. The cognitive costs associated to postural and movement control when kicking towards a target was estimated using a dual-task paradigm (secondary auditory task). Results showed that addition of the attentional demanding cognitive task yielded a decreased kicking accuracy and an increased timing to perform the movement, mainly during the backswing motion. In addition, significant differences between conditions were found for COP and COM displacement (increased amplitude, mean speed) on the anteroposterior axis. However, no significant differences between conditions were found on the mediolateral axis. Finally, EMG analysis showed that dual-task condition modified the way anticipatory postural adjustments (APAs) were generated. More specifically, we observed an increase of the peroneus longus activity, whereas the temporal EMG showed a decrease of its latency with respect to movement onset. These results suggested a functional adaptation resulting in an invariance of overall APAs, emphasizing that cognitive, postural, and motor processes worked dependently.

Task-space separation principle: a force-field approach to motion planning for redundant manipulators

In this work, we address human-like motor planning in redundant manipulators. Specifically, we want to capture postural synergies such as Donders' law, experimentally observed in humans during kinematically redundant tasks, and infer a minimal set of parameters to implement similar postural synergies in a kinematic model. For the model itself, although the focus of this paper is to solve redundancy by implementing postural strategies derived from experimental data, we also want to ensure that such postural control strategies do not interfere with other possible forms of motion control (in the task-space), i.e. solving the posture/movement problem. The redundancy problem is framed as a constrained optimization problem, traditionally solved via the method of Lagrange multipliers. The posture/movement problem can be tackled via the separation principle which, derived from experimental evidence, posits that the brain processes static torques (i.e. posture-dependent, such as gravitational torques) separately from dynamic torques (i.e. velocity-dependent). The separation principle has traditionally been applied at a joint torque level. Our main contribution is to apply the separation principle to Lagrange multipliers, which act as task-space force fields, leading to a task-space separation principle. In this way, we can separate postural control (implementing Donders' law) from various types of tasks-space movement planners. As an example, the proposed framework is applied to the (redundant) task of pointing with the human wrist. Nonlinear inverse optimization (NIO) is used to fit the model parameters and to capture motor strategies displayed by six human subjects during pointing tasks. The novelty of our NIO approach is that (i) the fitted motor strategy, rather than raw data, is used to filter and down-sample human behaviours; (ii) our framework is used to efficiently simulate model behaviour iteratively, until it converges towards the experimental human strategies.

Segmental specificity in belly dance mimics primal trunk locomotor patterns

Belly dance was used to investigate control of rhythmic undulating trunk movements in humans. Activation patterns in lumbar erector spinae muscles were recorded using surface electromyography at four segmental levels spanning T10 to L4. Muscle activation patterns for movement tempos of 2 Hz, 3 Hz, and as fast as possible (up to 6 Hz) were compared to test the hypothesis that frequency modulates muscle timing, causing pattern changes analogous to gait transitions. Groups of trained and untrained female subjects were compared to test the hypothesis that experience modifies muscle coordination patterns and the capacity for selective motion of spinal segments. Three distinct coordination patterns were observed. An ipsilateral simultaneous pattern (S) and a diagonal synergy (D) dominated at lower frequencies. The S pattern was selected most often by novices and resembled the standing wave of activation underlying the alternating lateral trunk bending in salamander trotting. At 2 Hz, most trained subjects selected the D pattern, suggesting a greater capacity for segmental specificity compared with untrained subjects. At 3-4 Hz, there emerged an asynchronous pattern (A) analogous to the rostral-caudal traveling wave in salamander and lamprey swimming. The neural networks and mechanisms identified in primitive vertebrates, such as chains of coupled oscillators and segmental crossed inhibitory connections, could explain the patterns observed in this study in humans. Training allows modification of these patterns, possibly through improved capacity for selectively exciting or inhibiting segmental pattern generators.NEW & NOTEWORTHY Belly dance provides a novel approach for studying spinal cord neural circuits. New evidence suggests that primitive locomotor circuits may be conserved in humans. Erector spinae activation patterns during the hip shimmy at different tempos are similar to those observed in salamander walking and swimming. As movement frequency increases, a sequential pattern similar to lamprey swimming emerges, suggesting that primal involuntary control mechanisms dominate in fast lateral rhythmic spine undulations even in humans.

Human motor adaptation in whole body motion

The main role of the sensorimotor system of an organism is to increase the survival of the species. Therefore, to understand the adaptation and optimality mechanisms of motor control, it is necessary to study the sensorimotor system in terms of ecological fitness. We designed an experimental paradigm that exposed sensorimotor system to risk of injury. We studied human subjects performing uncon- strained squat-to-stand movements that were systematically subjected to non-trivial perturbation. We found that subjects adapted by actively compensating the perturbations, converging to movements that were different from their normal unperturbed squat-to-stand movements. Furthermore, the adapted movements had clear intrinsic inter-subject differences which could be explained by different adapta- tion strategies employed by the subjects. These results suggest that classical optimality measures of physical energy and task satisfaction should be seen as part of a hierarchical organization of optimality with safety being at the highest level. Therefore, in addition to physical energy and task fulfillment, the risk of injury and other possible costs such as neural computational overhead have to be considered when analyzing human movement.

Trunk Postural Muscle Timing Is Not Compromised In Low Back Pain Patients Clinically Diagnosed With Movement Coordination Impairments

Trunk muscle timing impairment has been associated with nonspecific low back pain (NSLBP), but this finding has not been consistent. This study investigated trunk muscle timing in a subgroup of patients with NSLBP attributed to movement coordination impairment (MCI) and matched asymptomatic controls in response to a rapid arm-raising task. Twenty-one NSLBP subjects and 21 matched controls had arm motion and surface EMG data collected from seven bilateral trunk muscles. Muscle onset and offset relative to deltoid muscle activation and arm motion, duration of muscle burst and abdominal-extensor co-contraction time were derived. Trunk muscle onset and offset latencies, and burst and co-contraction durations were not different (p > .05) between groups. Patterns of trunk muscle activation and deactivation relative to arm motion were not different. Task performance was similar between groups. Trunk muscle timing does not appear to be an underlying impairment in the subgroup of NSLBP with MCI.

Direct effects of Facio-Oral Tract Therapy(®) on swallowing frequency of non-tracheotomised patients with acute neurogenic dysphagia

OBJECTIVES

The aim of this study was to investigate the direct effect of Facio-Oral Tract Therapy(®) on swallowing frequency of non-tracheotomised patients with acute neurogenic dysphagia.

METHODS

Within a pre-, post-/during and follow-up study design, 19 non-tracheotomised dysphagic patients were included consecutively and treated according to three specific preselected Facio-Oral Tract Therapy stimulation techniques.

RESULTS

The primary outcome was the direct effect of the three different Facio-Oral Tract Therapy stimulation techniques on the number of swallows. We found a significant effect of Facio-Oral Tract Therapy on swallowing frequency as compared to baseline with an increase by 65.63% and medium effect size of D = 0.62. No significant difference could be demonstrated when comparing baseline to follow-up.

CONCLUSION

For the first time, this positive therapy effect could be demonstrated on a population of non-tracheotomised patients. Facio-Oral Tract Therapy seems to be an appropriate means for improving effectiveness and safety of swallowing. Since improvement was not long lasting, it appears to be reasonable to apply therapy frequently during the day with the plausible result of minimising the amount of aspirated saliva and thereby reducing the risk of aspiration pneumonia. Further studies may consider choosing a randomised controlled trial design to demonstrate that change in swallow frequency is related to the target intervention only.

Reaching forward: effects of a preceding task and aging

Forward reaching is an integral part of many essential daily activities. It is often performed while standing quietly or after standing up from a seated position. This study sought to determine how a preceding balance task and aging would affect the task performance and movement strategy. Twenty-two healthy young and 20 older adults participated in this study and performed forward reaching under two task conditions. In forward reach (FR), reaching was performed during quiet standing. In up-and-reach (UR), subjects stood up from a seated position and then reached forward. A motion analysis system was used to calculate the location of the center of mass (COM) and joint angles at the initial and final positions, and the finger, COM, and joint angular displacements during the reaching task. For both groups, UR was initiated in a more flexed posture and had a significantly shorter reach distance and greater ankle dorsiflexion angle, compared to FR. The location of the COM, however, did not differ between the two task conditions. Older adults were found to significantly slow down their downward and forward COM motions in UR but not young adults. These findings showed that a preceding balance task increased the task demand and required modifications in the movement strategy. For older adults, the impact of increased task demand was greater, and adopting a cautious strategy could help to complete the task safely.

Walking on ballast impacts balance

Railroad workers often perform daily work activities on irregular surfaces, specifically on ballast rock. Previous research and injury epidemiology have suggested a relationship between working on irregular surfaces and postural instability. The purpose of this study was to examine the impact of walking on ballast for an extended duration on standing balance. A total of 16 healthy adult males walked on a 7.62 m × 4.57 m (25 ft × 15 ft) walking surface of no ballast (NB) or covered with ballast (B) of an average rock size of about 1 inch for 4 h. Balance was evaluated using dynamic posturography with the NeuroCom(®) Equitest System(™) prior to experiencing the NB or B surface and again every 30 min during the 4 h of ballast exposure. Dependent variables were the sway velocity and root-mean-square (RMS) sway components in the medial-lateral and anterior-posterior directions. Repeated measures ANOVA revealed statistically significant differences in RMS and sway velocity between ballast surface conditions and across exposure times. Overall, the ballast surface condition induced greater sway in all of the dynamic posturography conditions. Walking on irregular surfaces for extended durations has a deleterious effect on balance compared to walking on a surface without ballast. These findings of changes in balance during ballast exposure suggest that working on an irregular surface may impact postural control.

Interpreting the need for initial support to perform tandem stance tests of balance

BACKGROUND

Geriatric rehabilitation reimbursement increasingly requires documented deficits on standardized measures. Tandem stance performance can characterize balance, but protocols are not standardized. Objective The purpose of this study was to explore the impact of: (1) initial support to stabilize in position and (2) maximum hold time on tandem stance tests of balance in older adults. Design A cross-sectional secondary analysis of observational cohort data was conducted.

METHODS

One hundred seventeen community-dwelling older adults (71% female, 12% black) were assigned to 1 of 3 groups based on the need for initial support to perform tandem stance: (1) unable even with support, (2) able only with support, and (3) able without support. The able without support group was further stratified on hold time in seconds: (1) <10 (low), (2) 10 to 29, (medium), and (3) 30 (high). Groups were compared on primary outcomes (gait speed, Timed "Up & Go" Test performance, and balance confidence) using analysis of variance.

RESULTS

Twelve participants were unable to perform tandem stance, 14 performed tandem stance only with support, and 91 performed tandem stance without support. Compared with the able without support group, the able with support group had statistically or clinically worse performance and balance confidence. No significant differences were found between the able with support group and the unable even with support group on these same measures. Extending the hold time to 30 seconds in a protocol without initial support eliminated ceiling effects for 16% of the study sample. Limitations Small comparison groups, use of a secondary analysis, and lack of generalizability of results were limitations of the study.

CONCLUSIONS

Requiring initial support to stabilize in tandem stance appears to reflect meaningful deficits in balance-related mobility measures, so failing to consider support may inflate balance estimates and confound hold time comparisons. Additionally, 10-second maximum hold times limit discrimination of balance in adults with a higher level of function. For community-dwelling older adults, we recommend timing for at least 30 seconds and documenting initial support for consideration when interpreting performance.

The effect of increasing external degrees of freedom on force production and neuromuscular stabilisation

Evidence suggests that during interaction with different environmental dynamics the necessity to stabilise the involved joints leads to altered efficiency in force transmission to the surroundings and a specific orchestration of motor control strategies. However, little is known about the modalities of the changes associated with altered environmental dynamics. In 29 healthy participants, electromyographic (EMG) signals from four muscles of the right leg (M. peroneus longus, M. tibialis anterior, M. vastus medialis, M. gastrocnemius medialis) and three dimensions of force (Fx, Fy, Fz) were recorded. The participants were to exert force against an external object by performing a unilateral leg extension task with the task being influenced by either 0, 1 or 3 mechanical degrees of freedom. We hypothesised that the ankle stabilising muscles would increase their activities with increasing degrees of freedom (DoF), and that increasing external degrees of freedom results in decreased muscle force exerted during the movement task. The progressive change in the type of mechanical interaction from stable to unstable caused a loss of the ability to apply force in movement direction (Fz) which was accompanied by a reduction of Fy and Fx force dimensions. These reductions corresponded to maximum losses of 23% for Fz, 33% for Fx and 41% for Fy in the three degrees of freedom condition (all P < 0.001). Next, the individual muscles showed specific tuning effects, depending on the type of mechanical interaction. Our results suggest that the loss of the ability to exert force effectively against the external object is due to the neuromuscular stabilisation process of the involved joints. The change of the degrees of freedom conditions allowed for assessment of movement- or stabilisation-related adjustments of the motor system.

Adaptability of anticipatory postural adjustments associated with voluntary movement

The control of balance is crucial for efficiently performing most of our daily motor tasks, such as those involving goal-directed arm movements or whole body displacement. The purpose of this article is twofold. Firstly, it is to recall how balance can be maintained despite the different sources of postural perturbation arising during voluntary movement. The importance of the so-called “anticipatory postural adjustments” (APA), taken as a “line of defence” against the destabilizing effect induced by a predicted perturbation, is emphasized. Secondly, it is to report the results of recent studies that questioned the adaptability of APA to various constraints imposed on the postural system. The postural constraints envisaged here are classified into biomechanical (postural stability, superimposition of motor tasks), (neuro) physiological (fatigue), temporal (time pressure) and psychological (fear of falling, emotion). Overall, the results of these studies point out the capacity of the central nervous system (CNS) to adapt the spatio-temporal features of APA to each of these constraints. However, it seems that, depending on the constraint, the “priority” of the CNS was focused on postural stability maintenance, on body protection and/or on maintenance of focal movement performance.

Influence of temporal pressure on anticipatory postural control of medio-lateral stability during rapid leg flexion

During leg flexion from erect posture, postural stability along the medio-lateral direction is organized in advance during "anticipatory postural adjustments" (APAs). This study aimed to investigate the influence of temporal pressure on this anticipatory postural control of medio-lateral stability. Eight young healthy participants performed series of leg flexions (1) as soon as possible in response to an acoustic signal (reaction-time condition; condition with temporal pressure) and (2) in a self-initiated condition (no temporal pressure). Results showed that APAs duration was shorter in the reaction-time condition as compared to the self-initiated condition; this shortening was compensated by an increase in the medio-lateral center-of-pressure displacement so that the dynamic stability reached at foot-off, as measured by the "extrapolated center-of-mass", remained unchanged. It is concluded that when a complex task is performed under temporal pressure, the central nervous system is able to modulate the spatio-temporal features of APAs in a way to both hasten the initiation of the voluntary movement and maintain optimal conditions of dynamic stability. In other words, it seems that the central nervous system does not "trade off optimal stability for speed of movement initiation under reaction-time condition", as it had been proposed in the literature.

Motor activity in children with autism: a review of current literature

Physical therapists have expanded their role and visibility in the treatment of children with autism spectrum disorders (ASD). Limitations in motor activity have not been considered in the assessments of core deficits of this population; however, physical therapists should be prepared to discuss and address these limitations in children with ASD.

PURPOSE

The primary purposes of this review were to summarize current evidence for motor activity limitations in children with ASD and suggest further areas of research in physical therapy and autism while considering how physical therapy may benefit children with autism.

METHOD

A literature search was carried out in 2009 and 2010 by using multiple search engines.

RESULTS

Forty-nine articles met inclusion criteria and were included in the review.

CONCLUSION

Findings indicate that limitations in motor activity may be present in individuals with ASD, and further research is needed to identify specific functional limitations.

Attentional demands associated with obstacle crossing while carrying a load

The extent to which different locomotor tasks require cognitive control is not well characterized. In this article, the authors consider the potential increase in attentional demands associated with carrying an anterior load while clearing an obstacle. Nine healthy male volunteers participated in 80 walking trials, 20 in each of 4 conditions: 1 no load condition (NL) and 3 carrying conditions (2KG, 5KG, and 10KG). Of the 20 trials in each condition, 12 included a probe reaction time (PRT) test during lead limb obstacle crossing, which was used to measure cognitive load. A load-dependent increase in PRT was observed, with PRT in the 2KG condition being significantly greater than in the NL condition, and PRT in the 5KG and 10KG conditions being significantly greater than in the 2KG condition. These results suggested that cognitive load was increased when: (a) the obstacle was occluded from vision by the load, and (b) the magnitude of load was increased.

A decision-algorithm defining the rehabilitation approach: 'Facial oral tract therapy'

AIM

The aim of this study was to describe and define the rehabilitation approach: 'Facial Oral Tract Therapy' (F.O.T.T.).

METHOD

We defined the content and process of the rehabilitation approach (F.O.T.T.) in a decision-algorithm supported by a manual with supplementary material. The algorithm was developed by a research occupational therapist and an F.O.T.T. senior instructor. We used an inductive approach combining existing knowledge from: F.O.T.T. instructors, therapists trained in using the F.O.T.T. approach, and existing literature. A group of F.O.T.T. instructors and the originator of the treatment approach Mrs. Kay Coombes has given comments to and approved the algorithm.

RESULT

The algorithm consist of five flowcharts: 'one assessment' chart guiding the therapist in the examination of the patient and four 'treatment charts', one for each of the four areas of F.O.T.T.: swallowing and eating; oral hygiene; breathing, voice, and speech articulation; facial expression, giving guidance on interventions. The algorithm outlines all important components in the treatment that the therapist should decide to use or not to use in the intervention. The algorithm is supported by a manual with criteria of when to use which components.

CONCLUSION

This algorithm is designed to be a practical guideline to therapists using F.O.T.T. in clinical practice and in educational settings. The use of this algorithm may support standardization of F.O.T.T. and thereby promote and maintain the quality in the treatment. This in turn will facilitate research that addresses F.O.T.T. and outcomes.

Prevention of physical training-related injuries recommendations for the military and other active populations based on expedited systematic reviews

BACKGROUND

The Military Training Task Force of the Defense Safety Oversight Council chartered a Joint Services Physical Training Injury Prevention Working Group to: (1) establish the evidence base for making recommendations to prevent injuries; (2) prioritize the recommendations for prevention programs and policies; and (3) substantiate the need for further research and evaluation on interventions and programs likely to reduce physical training-related injuries.

EVIDENCE ACQUISITION

A work group was formed to identify, evaluate, and assess the level of scientific evidence for various physical training-related injury prevention strategies through an expedited systematic review process. Of 40 physical training-related injury prevention strategies identified, education, leader support, and surveillance were determined to be essential elements of a successful injury prevention program and not independent interventions. As a result of the expedited systematic reviews, one more essential element (research) was added for a total of four. Six strategies were not reviewed. The remaining 31 interventions were categorized into three levels representing the strength of recommendation: (1) recommended; (2) not recommended; and (3) insufficient evidence to recommend or not recommend.

EVIDENCE SYNTHESIS

Education, leadership support, injury surveillance, and research were determined to be critical components of any successful injury prevention program. Six interventions (i.e., prevent overtraining, agility-like training, mouthguards, semirigid ankle braces, nutrient replacement, and synthetic socks) had strong enough evidence to become working group recommendations for implementation in the military services. Two interventions (i.e., back braces and pre-exercise administration of anti-inflammatory medication) were not recommended due to evidence of ineffectiveness or harm, 23 lacked sufficient scientific evidence to support recommendations for all military services at this time, and six were not evaluated.

CONCLUSIONS

Six interventions should be implemented in all four military services immediately to reduce physical training-related injuries. Two strategies should be discouraged by all leaders at all levels. Of particular note, 23 popular physical training-related injury prevention strategies need further scientific investigation, review, and group consensus before they can be recommended to the military services or similar civilian populations. The expedited systematic process of evaluating interventions enabled the working group to build consensus around those injury prevention strategies that had enough scientific evidence to support a recommendation.

Anticipatory postural control strategies related to predictive perturbations

Balance reactions can be seen as responses to sensory information on a feedback basis, but when a balance threatening situation can be predicted, an anticipatory postural control strategy can be used. This study describes characteristics of proactive postural adjustments related to repetitive rhythmic perturbations. Furthermore, the study aimed to investigate age dependency of these anticipatory strategies. Fourteen young (age 27+/-2 years) and 10 community-dwelling elderly adults (76+/-5 years) participated in this study. Centre of pressure displacement was evaluated while the participants were standing on a moveable force plate. Perturbations consisted of alternating left/right frontal plane tilts of the platform or alternating forward/backward slides in the sagittal plane. Automation of postural control was evaluated by a dual task approach after familiarization to the perturbations. Centre of pressure displacement 200 ms before a tilt perturbation was significantly related to the direction of the perturbation. This early postural adjustment was significantly increased during the dual task condition. The dual task effect was more pronounced in the elderly, but this age-effect was not significant due to large inter-individual variation. The frequency of stepping reactions as response to slide perturbations decreased with conditioning, but increased again in the elderly during dual task condition.

CONCLUSION

This study showed that both young and elderly use anticipatory postural control strategies to minimize the impact of predictable perturbations. The proactive postural adjustments are further enhanced when a concurrent cognitive task is introduced. Postural control seems less automated in elderly and becomes insufficient during very challenging perturbations.

Methodological and interpretive issues in posture-cognition dual-tasking in upright stance

The traditionally separate researches on cognitive functions and basic coordinations such as stance and locomotion are coming together in the study of posture-cognition dual-tasking. The importance of this growing research area lies not only in the ubiquitous coexistence of postural and cognitive tasks but also in the observation that posture control very often has the dual role of securing the body's safety and balance while also providing a versatile, stable physical substrate well-suited to perception-action tasks. Although dual-task investigations strongly suggest that posture control and higher level cognition have common resource requirements, inconsistencies in the data and differences in experimental design make it difficult to distill a fuller understanding of the specific mechanisms behind posture-cognition dual-tasking. In this paper, we review the literature on upright standing with concurrent cognitive tasks, and highlight paradigmatic variations that possibly contribute to dual-task data differences. Implications arising from theoretical assumptions made about the role of postural control in the concurrent performance of cognitive tasks are also discussed.

Anticipatory postural adjustments in children with cerebral palsy and children with typical development

PURPOSE

We sought to examine whether children with cerebral palsy (CP) demonstrate anticipatory postural adjustments (APAs) similar to those observed in children with typical development (TD).

METHODS

A sample of convenience of 14 children, seven with CP and seven with TD, participated in this study. The center of pressure (COP) was calculated from ground reaction force data collected from the AMTI (OR-6) force platform as the child reached forward while standing.

RESULTS

Posterior COP shift frequently was observed in both groups of children before arm movement. However, the children with CP showed greater variability and significantly shorter amplitude of the APA COP excursion as compared with those with TD.

CONCLUSIONS

The control of APAs is problematic for some children with CP and, therefore, intervention designed to facilitate APAs may be beneficial for those children.

The effect of task uncertainty on muscle activation patterns in 8–10-year-old children

BACKGROUND AND PURPOSE

Postural muscle activity accompanying voluntary arm movements has been researched extensively in adults; however, few studies of this kind have been conducted with children. It is not clear whether children respond like adults to internal perturbations, and if so, whether this response is similar across a variety of task conditions. The aims of the present study were to determine the postural muscle activity demonstrated by 8-10-year-old children when performing a rapid shoulder flexion movement and to compare the pattern produced under simple reaction-time versus complex reaction-time conditions.

METHOD

Fifteen children with typical motor development participated in this comparative design study. The activity of anterior deltoid and contralateral rectus abdominis, internal oblique, erector spinae, rectus femoris, biceps femoris, tibialis anterior and gastrocnemius muscles was recorded via surface electromyography (EMG). Two tasks were performed: a simple task involving a right shoulder flexion movement; and a complex task involving a right or left shoulder flexion movement. Reaction time (RT) and movement time (MT) of the arm action were also recorded.

RESULTS

Muscle latencies in the complex task were longer than those for the simple task, although only the gastrocnemius muscle showed a significant difference (p = 0.013). Reaction time was also significantly later in the complex task (p = 0.003). Movement time was not significantly different between conditions.

CONCLUSIONS

A decrease in task certainty delayed postural muscle activation and reaction time in children aged 8-10 years. The study also demonstrated that children in this age group utilized a mixed postural strategy rather than a proximal-to-distal or distal-to-proximal pattern, reported in adult studies. Movement time remained unchanged.

Anticipatory postural adjustment in selected trunk muscles in poststroke hemiparetic patients

OBJECTIVES

To study electromyographic characteristics of anticipatory postural adjustment in axial and lateral, posterior and anterior trunk muscles during the performance of upper-and lower-limb flexion tasks, in subjects with hemiparesis after stroke and to determine the relationship between anticipatory activity and subjects' motor and functional status.

DESIGN

A nonrandomized control study.

SETTING

Geriatric rehabilitation center in Israel.

PARTICIPANTS

Fifty poststroke hemiparetic patients and 30 healthy control subjects.

INTERVENTION

Electromyographic activity of the lumbar erector spinae and of the latissimus dorsi muscles was recorded bilaterally during flexion of either arm and from the 2 rectus abdominis and obliquus externus muscles during flexion of either hip.

MAIN OUTCOME MEASURES

Muscles' onset latency, cross-correlation values between the temporal activation profile of corresponding pairs and between ipsilateral muscular pairs, symmetry in activation magnitude of corresponding muscles, and relation between electromyographic activity and motor and functional performance

RESULTS

Onset latencies of trunk muscles were partially delayed in the patients with longest hindrance displayed by the erector spinae ipsilateral to the flexing arm (P<.04). Temporal synchronization between pertinent muscular pairs was lower in the patients than in the healthy subjects, with significant group differences (P<.05 or lower) in the correlations between ipsilateral pairs of trunk muscles. Activation of the corresponding lateral trunk muscles in the patients was significantly less symmetrical than in the controls (P<.03 or lower) because of reduced activity on the paretic body side, especially on flexing of the paretic limbs. Conversely, in the controls as well as on the nonparetic side of the patients, limb flexion was associated with increased activity in the ipsilateral lateral trunk muscle. The erector spinae muscle in both groups and on both sides was more active on the contralateral side than on the ipsilateral side to the flexing arm. The reduced activity level in trunk muscles on the paretic body side was associated with deficiencies in motor and functional abilities.

CONCLUSIONS

Major impairments in the activity of trunk muscles in hemiparetic subjects were manifested in the reduced activity level of the lateral trunk muscles, in delayed onset, and in reduced synchronization between activation of pertinent muscular pairs. These problems were associated with motor and functional deficits and warrant specific consideration during physical rehabilitation of post stroke hemiparetic patients.

Postural control in children: implications for pediatric practice

Based on a systems theory of motor control, reactive postural control (RPA) and anticipatory postural control (APA) in children are reviewed from several perspectives in order to develop an evidence-based intervention strategy for improving postural control in children with limitations in motor function. Research on development of postural control, postural control in children with specific motor disabilities, and interventions to improve postural control is analyzed. A strategy for intervention to improve postural control systems at the impairment and functional activity levels based on a systems theoretical perspective is presented. Suggestions for research to improve evidence for best practice are provided.

Postural control and cognitive task performance in healthy participants while balancing on different support-surface configurations

Postural control during normal upright stance in humans is a well-learned task. Hence, it has often been argued that it requires very little attention. However, many studies have recently shown that postural control is modified when a cognitive task is executed simultaneously especially in the elderly and in the presence of pathology. This study examined postural control modifications when a cognitive task of varying difficulty levels is added. Postural stance difficulty was also varied. Results from this study suggest that a generalized capacity interference may occur due to the larger interference found with the addition of a cognitive task in the more novel and difficult postural task. Because the performance of the cognitive task was tapered by a speed-difficulty trade-off, it was not possible to determine whether a change in the level of difficulty of the cognitive task occurred and if it would produce larger dual-task interference.

Theoretical considerations in balance assessment

Although balance control is an integral component of all daily activities, its complex and flexible nature makes it difficult to assess adequately. This paper discusses balance by examining it in relation to function and the physical environment. Balance is affected by both the task being undertaken and the surroundings in which it is performed. Different tasks and environments alter the biomechanical and information processing needs for balance control. These issues are discussed and a modification of Gentile s Taxonomy of Tasks is suggested for analysis of clinical balance tests, some of which are used as examples.

Horizontal plane head stabilization during locomotor tasks

Frequency characteristics of head stabilization were examined during locomotor tasks in healthy young adults(N = 8) who performed normal walking and 3 walking tasks designed to produce perturbations primarily in the horizontal plane. In the 3 walking tasks, the arms moved in phase with leg movement, with abnormally large amplitude, and at twice the frequency of leg movement. Head-in-space angular velocity was examined at the predominant frequencies of trunk motion. Head movements in space occurred at low frequencies (< 4.0 Hz) in all conditions and at higher frequencies (> 4.0 Hz) when the arms moved at twice the frequency of the legs. Head stabilization strategies were determined from head-on-trunk with respect to trunk frequency profiles derived from angular velocity data. During natural walking at low frequencies (< 3.0 Hz), head-on-trunk movement was less than trunk movement. At frequencies 3.0 Hz or greater, equal and opposite compensatory movement ensured head stability. When arm swing was altered, compensatory movement guaranteed head stability at all frequencies. Head stabilization was successful for frequencies up to 10.0 Hz during locomotor tasks. Maintaining head stability at high frequencies during voluntary tasks suggests that participants used feedforward mechanisms to coordinate head and trunk movements. Maintenance of head stability during dynamic tasks allows optimal conditions for vestibulo-ocular reflex function.

Contributions of the reticulospinal system to the postural adjustments occurring during voluntary gait modifications

To test the hypothesis that reticulospinal neurons (RSNs) are involved in the formation of the dynamic postural adjustments that accompany visually triggered, voluntary modifications of limb trajectory during locomotion, we recorded the activity of 400 cells (183 RSNs; 217 unidentified reticular cells) in the pontomedullary reticular formation (PMRF) during a locomotor task in which intact cats were required to step over an obstacle attached to a moving treadmill belt. Approximately one half of the RSNs (97/183, 53%) showed significant changes in cell activity as the cat stepped over the obstacle; most of these cells exhibited either single (26/97, 26.8%) or multiple (63/97, 65.0%) increases of activity. There was a range of discharge patterns that varied in the number, timing, and sequencing of the bursts of modified activity, although individual bursts in different cells tended to occur at similar phases of the gait cycle. Most modified cells, regardless of the number of bursts of increased discharge, or of the discharge activity of the cell during unobstructed, control, locomotion, discharged during the passage of the lead forelimb over the obstacle. Thus, 86.9% of the modified cells increased their discharge when the forelimb ipsilateral to the recording site was the first to pass over the obstacle, and 72.2% when the contralateral limb was the first. Approximately one quarter of the RSNs increased their discharge during the passage of each of the four limbs over the obstacle in both the lead (27.1%) and trail (27.9%) conditions. In general, in any one cell, the number and relative sequencing of the subsequent bursts (with respect to the lead forelimb) was maintained during both lead and trail conditions. Patterns of activity observed in unidentified cells were very similar to the RSN activity despite the diverse population of cells this unidentified group may represent. We suggest that the increased discharge that we observed in these reticular neurons reflects the integration of afferent activity from several sources, including the motor cortex, and that this increased discharge signals the timing and the relative magnitude of the postural patterns that accompany the voluntary gait modification. However, based on the characteristics of the patterns of neuronal activity in these cells, we further suggest that while individual RSNs probably contribute to the selection of different patterns of postural activity, the ultimate expression of the postural response may be determined by the excitability of the locomotor circuits within the spinal cord.

Limb apraxias: higher-order disorders of sensorimotor integration

Limb apraxia comprises a wide spectrum of higher-order motor disorders that result from acquired brain disease affecting the performance of skilled, learned movements. At present, limb apraxia is primarily classified by the nature of the errors made by the patient and the pathways through which these errors are elicited, based on a two-system model for the organization of action: a conceptual system and a production system. Dysfunction of the former would cause ideational (or conceptual) apraxia, whereas impairment of the latter would induce ideomotor and limb-kinetic apraxia. Currently, it is possible to approach several types of limb apraxia within the framework of our knowledge of the modular organization of the brain. Multiple parallel parietofrontal circuits, devoted to specific sensorimotor transformations, have been described in monkeys: visual and somatosensory transformations for reaching; transformation of information about the location of body parts necessary for the control of movements; somatosensory transformation for posture; visual transformation for grasping; and internal representation of actions. Evidence from anatomical and functional brain imaging studies suggests that the organization of the cortical motor system in humans is based on the same principles. Imitation of postures and movements also seems to be subserved by dedicated neural systems, according to the content of the gesture (meaningful versus meaningless) to be imitated. Damage to these systems would produce different types of ideomotor and limb-kinetic praxic deficits depending on the context in which the movement is performed and the cognitive demands of the action. On the other hand, ideational (or conceptual) apraxia would reflect an inability to select and use objects due to the disruption of normal integration between systems subserving the functional knowledge of actions and those involved in object knowledge.

Evidence of motor equivalence in a pointing task involving locomotion

A pointing task was performed both while subjects stood beside and while subjects walked past targets that involved differing movement amplitudes and differing sizes. The hand kinematics were considered relative both to a fixed frame of reference in the movement environment (end effector kinematics) and to the subject's body (kinematics of the hand alone). From the former view, there were few differences between standing and walking versions of the task, indicating similarity of the kinematics of the hand. However, when the hand was considered alone, marked differences in the kinematics and spatial trajectories between standing and walking were achieved. Furthermore, kinematic analyses of the trunk showed that subjects used differing amounts of both flexion-extension and rotation movements at the waist depending on whether they were standing or walking as well as on the constraints imposed by target width and movement amplitude. The present results demonstrate the existence of motor equivalence in a combined upper and lower extremity task and that this motor equivalence is a control strategy to cope with increasing task demands. Given the complexity involved in controlling the arm, the torso, and the legs (during locomotion), the movements involved in the present tasks appear to be planned and controlled by considering the whole body as a single unit.

Dyspraxia in a patient with corticobasal degeneration: the role of visual and tactile inputs to action

OBJECTIVES

To investigate the roles of visual and tactile information in a dyspraxic patient with corticobasal degeneration (CBD) who showed dramatic facilitation in miming the use of a tool or object when he was given a tool to manipulate; and to study the nature of the praxic and neuropsychological deficits in CBD.

METHODS

The subject had clinically diagnosed CBD, and exhibited alien limb behaviour and striking ideomotor dyspraxia. General neuropsychological evaluation focused on constructional and visuospatial abilities, calculation, verbal fluency, episodic and semantic memory, plus spelling and writing because impairments in this domain were presenting complaints. Four experiments assessed the roles of visual and tactile information in the facilitation of motor performance by tools. Experiment 1 evaluated the patient's performance of six limb transitive actions under six conditions: (1) after he described the relevant tool from memory, (2) after he was shown a line drawing of the tool, (3) after he was shown a real exemplar of the tool, (4) after he watched the experimenter perform the action, (5) while he was holding the tool, and (6) immediately after he had performed the action with the tool but with the tool removed from his grasp. Experiment 2 evaluated the use of the same six tools when the patient had tactile but no visual information (while he was blindfolded). Experiments 3 and 4 assessed performance of actions appropriate to the same six tools when the patient had either neutral or inappropriate tactile feedback-that is, while he was holding a non-tool object or a different tool.

RESULTS

Miming of tool use was not facilitated by visual input; moreover, lack of visual information in the blindfolded condition did not reduce performance. The principal positive finding was a dramatic facilitation of the patient's ability to demonstrate object use when he was holding either the appropriate tool or a neutral object. Tools inappropriate to the requested action produced involuntary performance of the stimulus relevant action.

CONCLUSIONS

Tactile stimulation was paramount in the facilitation of motor performance in tool use by this patient with CBD. This outcome suggests that tactile information should be included in models which hypothesise modality specific inputs to the action production system. Significant impairments in spelling and letter production that have not previously been reported in CBD have also been documented.

Postural muscle responses in the spinal cord injured persons during forward reaching

To compensate for postural muscle function loss spinal cord injured (SCI) people have to use parts of the sensorimotor system which are still intact. In this study, postural control was investigated in high and low thoracic SCI people and in able-bodied controls, using a bimanual forward-reaching task. Muscle activity was recorded bilaterally from the erector spinae (ES) at level L3, T9 and T3, latissimus dorsi (LD), ascending part of the trapezius muscle (TPA), serratus anterior (SA), sternocostal head of the pectoralis major (PM) and the oblique abdominal muscles (OA) by means of surface electromyography. Sitting balance was monitored by measuring the changes in the location of the centre of pressure (CP) using a force platform. Muscle activity analyzed in different phases of the movement showed that SCI people adopt different postural adjustments to face the balance changes due to the reaching movement. SCI people make alternative use of non-postural muscles like the LD and TPA to maintain their sitting balance.

Current techniques for assessing physical exposure to work-related musculoskeletal risks, with emphasis on posture-based methods

Physical exposure to risks for potential work-related musculoskeletal injuries has been assessed using a variety of methods, including pen and paper based observation methods, videotaping and computer-aided analysis, direct or instrumental techniques, and various approaches to self-report assessment. These methods are critically reviewed in this paper. The applications of these techniques in ergonomic and epidemiologic studies are considered, and their advantages and shortcomings are highlighted. Finally, a strategy that considers both the ergonomics experts' view and the practitioners' needs for developing a practical exposure assessment tool is then discussed.

Postural sway and stepping response among working population: reproducibility, long-term stability, and associations with symptoms of the low back

OBJECTIVE: To investigate the day-to-day reproducibility and long-term (9 months) stability of variables of postural control, and the associations of these variables with low-back and lower-extremity pain in a working population. DESIGN: Test-retest measurements of 18 healthy subjects. Cross-sectional study of 165 working women and 343 men. BACKGROUND: Sudden loss of postural balance may result in microtraumas of back structures. Therefore workers with decreased postural control may run an increased risk of low-back pain. There are few reports describing the reproducibility of force-plate-based posturography. METHODS: Amplitude and velocity of postural sway were measured with a force-plate in a two-feet stance with eyes open and closed, and in a one-foot stance with eyes open. A stepping response test was developed to measure the dynamic components of balance. RESULTS: The mean differences between the repeated measurements were generally 5-10% and the standard deviations of these differences were up to a quarter or one third of the mean measurement values. Sway velocity showed the best overall reproducibility. Men had a larger sway than women independent of age and anthropometry. The group of non-symptomatic subjects showed wide variation and a slightly lower sway than the groups with low-back or lower-extremity pain. CONCLUSIONS: Postural sway has moderate stability, wide variation, and slight associations with low-back symptoms in a working population.

Postural responses to unilateral arm perturbation in young, elderly, and hemiplegic subjects

OBJECTIVE

To compare postural responses during standing associated with self-paced unilateral arm flexion exhibited by young and elderly healthy subjects and subjects with hemiplegia from stroke.

DESIGN AND SETTING

Descriptive cross-sectional study in a laboratory setting.

PATIENTS

Ten young, 10 elderly healthy subjects, and 12 volunteers with longstanding hemiparesis following stroke were tested. The hemiplegic group had good functional balance scores on the Berg Balance Scale (BBS).

MAIN OUTCOME MEASURES

The peak arm acceleration, center of pressure (CP) excursion speed, and the electromyographic activity in the posterior leg muscles (bilateral hamstrings and triceps surae) were monitored during self-initiated rapid unilateral arm flexion and during quiet stance.

RESULTS

During unilateral arm flexion, the young group showed the highest arm accelerations and lowest CP excursion speeds. The variability of postural responses was largest in the elderly and hemiplegic groups with hemiplegic subjects showing the greatest CP excursion speeds for the lowest arm accelerations. The first burst of activity in ipsilateral hamstrings muscle was the same in all subjects. However, the hemiplegic group had less activation (latency and amplitude) of other posterior leg muscles.

CONCLUSION

The elderly subjects had more variable responses to perturbation than the young subjects despite similar BBS scores. This may indicate that the BBS fails to detect differences in balance at the high end of the scale. Although the hemiplegic subjects demonstrated some anticipatory control of standing balance, they consistently performed poorer than elderly and young controls. The failure to coordinate postural leg muscle activity with focal movement may contribute to the instability of subjects with hemiplegia.

Age Group Differences in Postural Adjustments Associated With a Stepping Task

In this study, differences among age groups in the postural adjustments associated with a stepping task were identified. Twenty subjects from each of 3 age groups, children (8-12 years), young adults (25-35 years), and older adults (65-73 years), performed the task in 2 movement contexts: place and step. In place, the subject simply lifted the foot and placed it on the step. In step, the subject lifted the foot, placed it on the step, and stepped up onto the step. Latencies of postural and focal muscle activation were determined by using surface electromyography and pressure switches. Center of pressure (CP) data were obtained by using a force platform. Subjects in all 3 age groups consistently demonstrated postural adjustments before movement initiation. Children displayed longer postural latencies than young adults as well as disproportionately large values for CP path length. Older adults showed prolonged postural-focal latencies and decreased CP excursions compared with the 2 younger age groups. These results suggest that maturation of coordination between posture and movement may not be fully complete in 8- to 12-year-olds and that increased restraint characterizes the performance of postural adjustments in healthy persons over 65 years of age.