An electromyographic analysis of obligatory (hemiplegic cerebral palsy) and voluntary (normal) unilateral toe-walking

Toe-walking and its impact on first and second rocker in gait patterns with different degrees of artificially emulated soleus and gastrocnemius contracture

BACKGROUND

Toe-walking is one of the most common gait deviations (due to soleus and/or gastrocnemius muscle contractures), compromising the first (heel rocker) and second (ankle rocker) of the foot during walking. The aim of this study is to evaluate the effect of emulated artificially gastrocnemius and soleus contractures on the first and second rocker during walking.

METHOD

An exoskeleton was built to emulate contractures of the bilateral gastrocnemius and soleus muscles. Ten healthy participants were recruited to walk under the following conditions: without emulated contractures or with bilateral emulated contractures at 0°,10°, 20° and 30° of plantarflexion of the soleus or gastrocnemius in order to create an artificial restriction of dorsiflexion ankle movement. A linear regression from the ankle plantar-dorsiflexion angle pattern was performed on 0-5 % of the gait cycle (first rocker) and on 12-31 % of the gait cycle (second rocker) to compute the slope of the curve. The proportion of participants with the presence of the first and second rocker was then computed. A Statistical Parametric Mapping (SPM) analysis assessed the kinematic variations among different degrees of emulated contractures.

FINDINGS

The first and second rockers are completely absent from 10° of plantarflexion emulated contracture. The data indicate there was a non-linear shift of the gait pattern of the ankle kinematics and an important shift toward plantarflexion values with the loss of the rockers.

INTERPRETATION

This study suggests that toe-walking in the experimental simulation situation is not necessarily due to a high emulated contracture level and can occur with a small emulated contracture by an adaptation choice. This study may improve interpretation of clinical gait analysis and shows that the link between the level of gastrocnemius/soleus emulated contracture and progression of toe-walking (increased plantarflexion during gait) is not linear.

Influence of sagittal pelvic attitude on gait pattern in normally developed people and interactions with neurological pathologies: A pilot study

Background

Gait Analysis of healthy people, imitating pathological conditions while walking, has increased our understanding of biomechanical factors. The influence of the pelvis as a biomechanical constraint during gait is not specifically studied. How could mimicking a pelvic attitude influence the dynamic mechanical interaction of the body segments? We proposed an investigation of the pelvic attitude role on the gait pattern of typically developed people when they mimicked pelvic anteversion and posteroversion.

Materials and methods

Seventeen healthy volunteers were enrolled in this study (mean age 24.4 ± 5.5). They simulated a pelvic anteversion and posteroversion during walking, exaggerating these postures as much as possible. 3D gait analysis was conducted using an optoelectronic system with eight cameras (Vicon MX, Oxford, United Kingdom) and two force plates (AMTI, Or-6, Watertown, MA, United States). The kinematic, kinetic, and spatio-temporal parameters were compared between the three walking conditions (anteversion, posteroversion, and normal gait).

Results

In Pelvic Anteversion gait (PA) we found: increased hip flexion (p < 0.0001), increased knee flexion during stance (p = 0.02), and reduction of ankle flexion-extension Range of Motion (RoM) compared with Pelvic Normal gait (PN). In Pelvic Posteroversion gait (PP) compared with PN, we found: decreased hip flexion-extension RoM (p < 0.01) with a tendency to hip extension, decreased knee maximum extension in stance (p = 0.033), and increased ankle maximum dorsiflexion in stance (p = 0.002).

Conclusion

The configuration of PA contains gait similarities and differences when compared with pathologic gait where there is an anteversion as seen in children with Cerebral Palsy (CP) or Duchenne Muscular Dystrophy (DMD). Similarly, attitudes of PP have been described in patients with Charcot-Marie-Tooth Syndrome (CMT) or patients who have undergone Pelvic Osteotomy (PO). Understanding the dynamic biomechanical constraints is essential to the assessment of pathological behavior. The central nervous system adapts motor behavior in interaction with body constraints and available resources.

Respective Contributions of Instrumented 3D Gait Analysis Data and Tibial Motor Nerve Block on Presurgical Spastic Equinus Foot Assessment: A Retrospective Study of 40 Adults

Spastic equinus foot is a common deformity in neurologic patients who compromise walking ability. It is related to the imbalance between weak dorsiflexion and overactive plantar flexor muscles. To achieve the best functional results after surgical management, the challenge is to identify the relevant components involved in the deformity using several methods, namely, examination in the supine position, motor nerve blocks allowing transient anesthesia of suspected overactive muscles, and kinematic and electromyographic data collected during an instrumented 3D gait analysis. The procedure is not standardized; its use varies from one team to another. Access to gait analysis laboratories is limited, and some teams do not perform motor nerve blocks. When both examinations are available, instrumental data from the instrumented 3D gait analysis can be used to specify muscle targets for motor blocks, but data collected from both examinations are sometimes considered redundant. This retrospective cohort analysis compared examination in the supine position, temporary motor nerve blocks, and instrumented 3D gait analysis data in 40 adults after brain or spinal cord injuries. Clinical data collected before motor nerve block was not associated with instrumental data to assess calf muscle's overactivity and tibialis anterior function. Improvement of ankle dorsiflexion in the swing phase after tibial motor nerve block was associated with soleus spastic co-contraction during this phase corroborating its involvement in ankle dorsiflexion defects. This study showed the relevance of tibial motor nerve block to remove spastic calf dystonia and facilitate the assessment of calf contracture. It also underlined the need for complementary and specific analyses of the tibialis anterior abnormal activation pattern after motor nerve block to confirm or deny their pathological nature.

Altered Muscle Contributions are Required to Support the Stance Limb During Voluntary Toe-Walking

Toe-walking characterizes several neuromuscular conditions and is associated with a reduction in gait stability and efficiency, as well as in life quality. The optimal choice of treatment depends on a correct understanding of the underlying pathology and on the individual biomechanics of walking. The objective of this study was to describe gait deviations occurring in a cohort of healthy adult subjects when mimicking a unilateral toe-walking pattern compared to their normal heel-to-toe gait pattern. The focus was to characterize the functional adaptations of the major lower-limb muscles which are required in order to toe walk. Musculoskeletal modeling was used to estimate the required muscle contributions to the joint sagittal moments. The support moment, defined as the sum of the sagittal extensive moments at the ankle, knee, and hip joints, was used to evaluate the overall muscular effort necessary to maintain stance limb stability and prevent the collapse of the knee. Compared to a normal heel-to-toe gait pattern, toe-walking was characterized by significantly different lower-limb kinematics and kinetics. The altered kinetic demands at each joint translated into different necessary moment contributions from most muscles. In particular, an earlier and prolonged ankle plantarflexion contribution was required from the soleus and gastrocnemius during most of the stance phase. The hip extensors had to provide a higher extensive moment during loading response, while a significantly higher knee extension contribution from the vasti was necessary during mid-stance. Compensatory muscular activations are therefore functionally required at every joint level in order to toe walk. A higher support moment during toe-walking indicates an overall higher muscular effort necessary to maintain stance limb stability and prevent the collapse of the knee. Higher muscular demands during gait may lead to fatigue, pain, and reduced quality of life. Toe-walking is indeed associated with significantly larger muscle forces exerted by the quadriceps to the patella and prolonged force transmission through the Achilles tendon during stance phase. Optimal treatment options should therefore account for muscular demands and potential overloads associated with specific compensatory mechanisms.

Comparison of the Gait Biomechanical Constraints in Three Different Type of Neuromotor Damages

Background and Objective

Absolute angle represents the inclination of a body segment relative to a fixed reference in space. This work compares the absolute and relative angles for exploring biomechanical gait constraints.

Methods

Gait patterns of different neuromotor conditions were analyzed using 3D gait analysis: normal gait (healthy, H), Cerebral Palsy (CP), Charcot Marie Tooth (CMT) and Duchenne Muscular Dystrophy (DMD), representing central and peripheral nervous system and muscular disorders, respectively. Forty-two children underwent gait analysis: 10 children affected by CP, 10 children by CMT, 10 children by DMD and 12 healthy children. The kinematic and kinetic parameters were collected to describe the biomechanical pattern of participants’ lower limbs. The absolute angles of thigh, leg and foot were calculated using the trigonometric relationship of the tangent. For each absolute series, the mean, range, maximum, minimum and initial contact were calculated. Kinematic and kinetic gait data were studied, and the results were compared with the literature.

Results

Statistical analysis of the absolute angles showed how, at the local level, the single segments (thigh, leg and foot) behave differently depending on the pathology. However, if the lower limb is studied globally (sum of the kinematics of the three segments: thigh, leg and foot), a biomechanical constraint emerges.

Conclusion

Each segment compensates separately for the disease deficit so as to maintain a global biomechanical invariance. Using a model of inter-joint co-variation could improve the interpretation of the clinical gait pattern.

Synergies are minimally affected during emulation of cerebral palsy gait patterns

Muscle synergy analysis is commonly used to characterize motor control during dynamic tasks like walking. For clinical populations, such as children with cerebral palsy (CP), synergies are altered compared to nondisabled (ND) peers and have been associated with both function and treatment outcomes. However, the factors that contribute to altered synergies remain unclear. In particular, the extent to which synergies reflect altered biomechanics (e.g., changes in gait) or underlying neurologic injury is debated. To evaluate the effect that altered biomechanics have on synergies, we compared synergy complexity and structure while ND individuals (n = 14) emulated four common CP gait patterns (equinus, equinus-crouch, mild-crouch, and moderate crouch). Secondarily, we compared the similarity of ND synergies during emulation to synergies from a retrospective cohort of individuals with CP walking in similar gait patterns (n = 28 per pattern). During emulation, ND individuals recruited similar synergies as baseline walking. However, pattern-specific deviations in synergy activations and complexity emerged. In particular, equinus gait altered plantarflexor activation timing and reduced synergy complexity. Importantly, ND synergies during emulation were distinct from those observed in CP for all gait patterns. These results suggest that altered gait patterns are not primarily driving the changes in synergies observed in CP, highlighting the value of using synergies as a tool to capture patient-specific differences in motor control. However, they also highlight the sensitivity of both synergy activations and complexity to altered biomechanics, which should be considered when using these measures in clinical care.

Analysis of foot kinematics during toe walking in able-bodied individuals using the Oxford Foot Model

Various neurological and musculoskeletal disorders can induce pathologic toe walking and lead to changes in foot kinematics. In this study, we analyzed the differences in foot kinematics between toe walking and heel-toe walking (HW) in able-bodied individuals. Twenty young healthy adults performed three gaits: HW, comfortable-height toe walking (CTW), and maximum-height toe walking (MTW). Oxford Foot Model was used for gait analysis. Toe walking showed increase of forefoot plantarflexion and hindfoot internal rotation compared to HW. Thus, our results may help distinguish the pathologic mechanism of the equinus gait in various disorders from the kinematic change of toe walking itself.

The effect of musculoskeletal model scaling methods on ankle joint kinematics and muscle force prediction during gait for children with cerebral palsy and equinus gait

Clinical gait analysis incorporated with neuromusculoskeletal modelling could provide valuable information about joint movements and muscle functions during ambulation for children with cerebral palsy (CP). This study investigated how imposing pre-calculated joint angles during musculoskeletal model scaling influence the ankle joint angle and muscle force computation. Ten children with CP and equinus gait underwent clinical gait analysis. For each participant, a "default" (scaled without pre-calculated joint angles) and a "PJA" (scaled with pre-calculated ankle joint angles) model were generated to simulate their gait. Ankle joint angles were calculated with an inverse kinematic (IK) and direct kinematic (DK) approach. Triceps surae and tibialis anterior muscle forces were predicted by static optimisation and EMG-assisted modelling. We found that PJA-derived ankle angles showed a better agreement with what derived from the DK approach. The tibialis anterior muscle prediction was more likely to be affected by the scaling methods for the static optimisation approach and the gastrocnemius muscle force prediction was more likely to be influenced for the EMG-assisted modelling. This study recommends using the PJA model since the good consistency between IK and DK-derived joint angles facilitates communication among different research disciplines.

Greater Reliance on Cerebral Palsy-Specific Muscle Synergies During Gait Relates to Poorer Temporal-Spatial Performance Measures

Children with cerebral palsy typically exhibit reduced complexity of muscle coordination patterns during walking; however, the specific patterns that characterize their gait abnormalities are still not well documented. This study aimed to identify the specific repertoire of muscle coordination patterns in children with CP during walking compared to same-aged peers without CP and their relationships to gait performance. To identify muscle coordination patterns, we extracted muscle synergies from 10 children with CP and 10 age-matched typically developing children (TD). K-mean clustering and discriminant analyses of all extracted synergies were used to group similar synergies. Then, weight-averaged z-scores were quantified for each cluster to determine their group-specific level. In this cohort, 10 of the 17 distinct clusters were largely CP-specific while six clusters were seen mainly in TD, and one was non-specific. CP-specific clusters generally showed merging of two TD synergies, excessive antagonist co-activation, decreased muscle activation compared to TD, and complex or atypical pattern. Significant correlations were found between weight-averaged z-scores and step length asymmetry, cadence asymmetry, self-selected treadmill speed and AP-COM displacement of the pelvis such that greater CP-specificity of muscle synergies was related to poorer performance, thus indicating that CP-specific synergies can influence motor dysfunction.

Clinical Relevance of State-of-the-Art Analysis of Surface Electromyography in Cerebral Palsy

Surface electromyography (sEMG) can be used to assess the integrity of the neuromuscular system and its impairment in neurological disorders. Here we will consider several issues related to the current clinical applications, difficulties and limited usage of sEMG for the assessment and rehabilitation of children with cerebral palsy. The uniqueness of this methodology is that it can determine hyperactivity or inactivity of selected muscles, which cannot be assessed by other methods. In addition, it can assist for intervention or muscle/tendon surgery acts, and it can evaluate integrated functioning of the nervous system based on multi-muscle sEMG recordings and assess motor pool activation. The latter aspect is especially important for understanding impairments of the mechanisms of neural controllers rather than malfunction of individual muscles. Although sEMG study is an important tool in both clinical research and neurorehabilitation, the results of a survey on the clinical relevance of sEMG in a typical department of pediatric rehabilitation highlighted its limited clinical usage. We believe that this is due to limited knowledge of the sEMG and its neuromuscular underpinnings by many physiotherapists, as a result of lack of emphasis on this important methodology in the courses taught in physical therapy schools. The lack of reference databases or benchmarking software for sEMG analysis may also contribute to the limited clinical usage. Despite the existence of educational and technical barriers to a widespread use of, sEMG does provide important tools for planning and assessment of rehabilitation treatments for children with cerebral palsy.

Toe walking in children with cerebral palsy: a possible functional role for the plantar flexors

Equinus and toe walking are common locomotor disorders in children with cerebral palsy (CP) walking barefoot or with normal shoes. We hypothesized that, regardless of the type of footwear, the plantar flexors do not cause early equinus upon initial foot contact but decelerate ankle dorsiflexion during weight acceptance (WA). This latter action promoted by early flat-foot contact is hypothesized to be functional. Hence, we performed an instrumented gait analysis of 12 children with CP (Gross Motor Function Classification System class: I or II; mean age: 7.2 yr) and 11 age-matched typically developing children. The participants walked either barefoot, with unmodified footwear (4° positive-heel shoes), or with 10° negative-heel shoes (NHSs). In both groups, wearing NHSs was associated with greater ankle dorsiflexion upon initial foot contact, and greater tibialis anterior activity (but no difference in soleus activity) during the swing phase. However, the footwear condition did not influence the direction and amplitude of the first ankle movement during WA and the associated peak negative ankle power. Regardless of the footwear condition, the CP group displayed 1) early flattening of the foot and ample dorsiflexion (decelerated by the plantar flexors) during WA and 2) low tibialis anterior and soleus activities during the second half of the swing phase (contributing to passive equinus upon foot strike). In children with CP, the early action of plantar flexors (which typically decelerate the forward progression of the center of mass) may be a compensatory mechanism that contributes to the WA's role in controlling balance during gait.NEW & NOTEWORTHY Adaptation to walking in negative-heel shoes was similar in typically developing children and children with cerebral palsy: it featured ankle dorsiflexion upon initial contact, even though (in the latter group) the soleus was always spastic in a clinical examination. Hence, in children with cerebral palsy, the early deceleration of ankle dorsiflexion by the plantar flexors (promoted by early flattening of the foot, and regardless of the type of footwear) may have a functional role.

Muscle activity in children with spastic unilateral cerebral palsy when walking with ankle-foot orthoses: an explorative study

BACKGROUND

A hinged ankle-foot orthosis is prescribed for children with spastic unilateral cerebral palsy to improve gait function by correcting spastic equinus. However, little is known about how orthotic management relates to muscle activity during walking in this population.

RESEARCH QUESTION

Does muscle activity in medial gastrocnemius and tibialis anterior change in children with spastic unilateral cerebral palsy when walking with hinged ankle-foot orthoses featuring two different footplate designs?

METHODS

In this prospective, repeated-measures trial, electromyographic activity in medial gastrocnemius and tibialis anterior was recorded from 17 children (mean age: 8.4 years ± 1.3 years) with spastic unilateral cerebral palsy walking barefoot and with two designs of hinged ankle-foot orthosis. The orthotic devices consisted of custom-made hinged ankle-foot orthoses with unmodified, flatter footplates and rectified, contoured footplates. Primary outcome measures were total muscle activity, quantified as the area under a linear envelope, and relative change in profiles of muscle activity, depicted by curves of mean difference with 95% confidence bands.

RESULTS

No statistical difference was found in total activity of either muscle for the ankle-foot orthosis with an unmodified footplate but a significant reduction in muscle activity of tibialis anterior was seen for the ankle-foot orthosis with a contoured footplate relative to barefoot walking. Profiles of change in muscle activity were significantly altered for both shank muscles between all walking conditions. The most pronounced differences were decreased activity in medial gastrocnemius during early stance phase and lower activity in tibialis anterior during swing phase with orthotic devices.

SIGNIFICANCE

Orthotic management with hinged ankle-foot orthoses may mitigate spastic activation of medial gastrocnemius in children with spastic unilateral cerebral palsy but also appears to functionally inactivate tibialis anterior during gait. The hinged ankle-foot orthosis with an unmodified footplate corresponded with better performance by facilitating more functional muscle activity while impeding spastic response.

Maturation of feedforward toe walking motor program is impaired in children with cerebral palsy

Voluntary toe walking in adults is characterized by feedforward control of ankle muscles in order to ensure optimal stability of the ankle joint at ground impact. Toe walking is frequently observed in children with cerebral palsy, but the mechanisms involved have not been clarified. Here, we investigated maturation of voluntary toe walking in typically-developing children and typically-developed adults and compared it to involuntary toe walking in children with cerebral palsy. Twenty-eight children with cerebral palsy (age 3-14 years), 24 typically-developing children (age 2-14 years) and 15 adults (mean age 30.7 years) participated in the study. EMG activity was measured from the tibialis anterior and soleus muscles together with knee and ankle joint position during treadmill walking. In typically-developed adults, low step-to-step variability of the drop of the heel after ground impact was correlated with low tibialis anterior and high soleus EMG with no significant coupling between the antagonist muscle EMGs. Typically-developing children showed a significant age-related decline in EMG amplitude reaching an adult level at 10-12 years of age. The youngest typically-developing children showed a broad peak EMG-EMG synchronization (>100 ms) associated with large 5-15 Hz coherence between antagonist muscle activities. EMG coherence declined with age and at the age of 10-12 years no correlation was observed similar to adults. This reduction in coherence was closely related to improved step-to-step stability of the ankle joint position. Children with cerebral palsy generally showed lower EMG levels than typically-developing children and larger step-to-step variability in ankle joint position. In contrast to typically-developing children, children with cerebral palsy showed no age-related decline in tibialis anterior EMG amplitude. Motor unit synchronization and 5-15 Hz coherence between antagonist EMGs was observed more frequently in children with cerebral palsy when compared to typically-developing children and in contrast to typically-developing participants there was no age-related decline. We conclude that typically-developing children develop mature feedforward control of ankle muscle activity as they age, such that at age 10-12 years there is little agonist-antagonist muscle co-contraction around the time of foot-ground contact during toe walking. Children with cerebral palsy, in contrast, continue to co-contract agonist and antagonist ankle muscles when toe walking. We speculate that children with cerebral palsy maintain a co-contraction activation pattern when toe walking due to weak muscles and insufficient motor and sensory signalling necessary for optimization of feedforward motor programs. These findings are important for understanding of the pathophysiology and treatment of toe walking.

EMG-Based Characterization of Walking Asymmetry in Children with Mild Hemiplegic Cerebral Palsy

Hemiplegia is a neurological disorder that is often detected in children with cerebral palsy. Although many studies have investigated muscular activity in hemiplegic legs, few EMG-based findings focused on unaffected limb. This study aimed to quantify the asymmetric behavior of lower-limb-muscle recruitment during walking in mild-hemiplegic children from surface-EMG and foot-floor contact features. sEMG signals from tibialis anterior (TA) and gastrocnemius lateralis and foot-floor contact data during walking were analyzed in 16 hemiplegic children classified as W1 according to Winter’ scale, and in 100 control children. Statistical gait analysis, a methodology achieving a statistical characterization of gait by averaging surface-EMG-based features, was performed. Results, achieved in hundreds of strides for each child, indicated that in the hemiplegic side with respect to the non-hemiplegic side, W1 children showed a statistically significant: decreased number of strides with normal foot-floor contact; decreased stance-phase length and initial-contact sub-phase; curtailed, less frequent TA activity in terminal swing and a lack of TA activity at heel-strike. The acknowledged impairment of anti-phase eccentric control of dorsiflexors was confirmed in the hemiplegic side, but not in the contralateral side. However, a modified foot-floor contact pattern is evinced also in the contralateral side, probably to make up for balance requirements.

Kinematics can help to discriminate the implication of iliopsoas, hamstring and gastrocnemius contractures to a knee flexion gait pattern

BACKGROUND

Excessive Knee Flexion Gait Pattern (KFGP) is a common gait deviation in many pathological conditions. The contractures of the muscles that have been identified as being responsible of KFGP are: iliopsoas, hamstring and gastrocnemius.

RESEARCH QUESTION

How do isolated contractures of the iliopsoas, hamstrings and gastrocnemius impact knee flexion during gait?

METHODS

Three levels of contracture (mild, moderate and severe) were simulated bilaterally using an exoskeleton on 10 healthy participants for iliopsoas, hamstring and gastrocnemius muscles. A gait analysis session was performed to evaluate the joint kinematics according to the different simulated contractures. Thirty one parameters were chosen to analyze the kinematics of the thorax, pelvis, hip, knee and ankle. A principal component analysis (PCA) was used to determine the kinematic parameters influenced by contractures.

RESULTS

In addition to a permanent knee flexion observed for the three muscles with contracture: the contracture of the iliopsoas induces a large hip flexion with pronounced anterior pelvis tilt; the contracture of the hamstrings induces an ankle dorsiflexion during the support phase with a posterior pelvis tilt; the contracture of the gastrocnemius induces an absence of first and second rocker of the ankle with a slight flexion of hip and a slight anterior pelvis tilt.

SIGNIFICANCE

These results support the identification of the muscles responsible for a KFGP. A better knowledge of the interactions between contractures and associated joint kinematics of the same and adjacent joints will support the interpretation of gait analyses by more precisely and faster targeting the concerned muscle.

Feedforward neural control of toe walking in humans

KEY POINTS

Activation of ankle muscles at ground contact during toe walking is unaltered when sensory feedback is blocked or the ground is suddenly dropped. Responses in the soleus muscle to transcranial magnetic stimulation, but not peripheral nerve stimulation, are facilitated at ground contact during toe walking. We argue that toe walking is supported by feedforward control at ground contact.

ABSTRACT

Toe walking requires careful control of the ankle muscles in order to absorb the impact of ground contact and maintain a stable position of the joint. The present study aimed to clarify the peripheral and central neural mechanisms involved. Fifteen healthy adults walked on a treadmill (3.0 km h^-1 ). Tibialis anterior (TA) and soleus (Sol) EMG, knee and ankle joint angles, and gastrocnemius-soleus muscle fascicle lengths were recorded. Peripheral and central contributions to the EMG activity were assessed by afferent blockade, H-reflex testing, transcranial magnetic brain stimulation (TMS) and sudden unloading of the planter flexor muscle-tendon complex. Sol EMG activity started prior to ground contact and remained high throughout stance. TA EMG activity, which is normally seen around ground contact during heel strike walking, was absent. Although stretch of the Achilles tendon-muscle complex was observed after ground contact, this was not associated with lengthening of the ankle plantar flexor muscle fascicles. Sol EMG around ground contact was not affected by ischaemic blockade of large-diameter sensory afferents, or the sudden removal of ground support shortly after toe contact. Soleus motor-evoked potentials elicited by TMS were facilitated immediately after ground contact, whereas Sol H-reflexes were not. These findings indicate that at the crucial time of ankle stabilization following ground contact, toe walking is governed by centrally mediated motor drive rather than sensory driven reflex mechanisms. These findings have implications for our understanding of the control of human gait during voluntary toe walking.

Simulating the effect of muscle weakness and contracture on neuromuscular control of normal gait in children

Altered neural control of movement and musculoskeletal deficiencies are common in children with spastic cerebral palsy (SCP), with muscle weakness and contracture commonly experienced. Both neural and musculoskeletal deficiencies are likely to contribute to abnormal gait, such as equinus gait (toe-walking), in children with SCP. However, it is not known whether the musculoskeletal deficiencies prevent normal gait or if neural control could be altered to achieve normal gait. This study examined the effect of simulated muscle weakness and contracture of the major plantarflexor/dorsiflexor muscles on the neuromuscular requirements for achieving normal walking gait in children. Initial muscle-driven simulations of walking with normal musculoskeletal properties by typically developing children were undertaken. Additional simulations with altered musculoskeletal properties were then undertaken; with muscle weakness and contracture simulated by reducing the maximum isometric force and tendon slack length, respectively, of selected muscles. Muscle activations and forces required across all simulations were then compared via waveform analysis. Maintenance of normal gait appeared robust to muscle weakness in isolation, with increased activation of weakened muscles the major compensatory strategy. With muscle contracture, reduced activation of the plantarflexors was required across the mid-portion of stance suggesting a greater contribution from passive forces. Increased activation and force during swing was also required from the tibialis anterior to counteract the increased passive forces from the simulated dorsiflexor muscle contracture. Improvements in plantarflexor and dorsiflexor motor function and muscle strength, concomitant with reductions in plantarflexor muscle stiffness may target the deficits associated with SCP that limit normal gait.

Factors affecting premature plantarflexor muscle activity during hemiparetic gait

In hemiparetic stroke survivors, premature plantarflexor muscle activity (PPF) often appears as a gait abnormality from terminal swing to the loading response on the paretic side. This study aimed to discern factors giving rise to PPF. Lower extremity function, spasticity magnitude, and gait electromyograms were assessed in 31 hemiparetic stroke survivors. Mean amplitudes during gait phases were determined for the paretic soleus, tibialis anterior, rectus femoris, and biceps femoris. The subjects were classified into PPF and non-PPF groups based on their relative soleus amplitude at different phases of gait, and group differences in each measurement were calculated and subjected to logistic regression. The PPF group showed less activity of the tibialis anterior during the swing phase but greater activity of the rectus femoris during the swing phase and of the biceps femoris, both prematurely and during the loading response. Logistic regression revealed premature activity of the biceps femoris to be a significant variable related to presence of PPF (odds ratio = 1.054). PPF in hemiparetic gait may work with the biceps femoris to supplement compromised lower extremity extension strength. PPF might be reduced by attaining enhanced strength of the hip and knee extensors at the time of initial contact during gait.

Influence of different degrees of bilateral emulated contractures at the triceps surae on gait kinematics: The difference between gastrocnemius and soleus

INTRODUCTION

Ankle plantarflexion contracture results from a permanent shortening of the muscle-tendon complex. It often leads to gait alterations. The objective of this study was to compare the kinematic adaptations of different degrees of contractures and between isolated bilateral gastrocnemius and soleus emulated contractures using an exoskeleton.

METHODS

Eight combinations of contractures were emulated bilaterally on 10 asymptomatic participants using an exoskeleton that was able to emulate different degrees of contracture of gastrocnemius (biarticular muscle) and soleus (monoarticular muscle), corresponding at 0°, 10°, 20°, and 30° ankle plantarflexion contracture (knee-flexed and knee-extended). Range of motion was limited by ropes attached for soleus on heel and below the knee and for gastrocnemius on heel and above the knee. A gait analysis session was performed to evaluate the effect of these different emulated contractures on the Gait Profile Score, walking speed and gait kinematics.

RESULTS

Gastrocnemius and soleus contractures influence gait kinematics, with an increase of the Gait Profile Score. Significant differences were found in the kinematics of the ankles, knees and hips. Contractures of soleus cause a more important decrease in the range of motion at the ankle than the same degree of gastrocnemius contractures. Gastrocnemius contractures cause greater knee flexion (during the stance phase) and hip flexion (during all the gait cycle) than the same level of soleus contractures.

CONCLUSION

These results can support the interpretation of the Clinical Gait Analysis data by providing a better understanding of the effect of isolate contracture of soleus and gastrocnemius on gait kinematics.

Feasibility and reliability of using an exoskeleton to emulate muscle contractures during walking

Contracture is a permanent shortening of the muscle-tendon-ligament complex that limits joint mobility. Contracture is involved in many diseases (cerebral palsy, stroke, etc.) and can impair walking and other activities of daily living. The purpose of this study was to quantify the reliability of an exoskeleton designed to emulate lower limb muscle contractures unilaterally and bilaterally during walking. An exoskeleton was built according to the following design criteria: adjustable to different morphologies; respect of the principal lines of muscular actions; placement of reflective markers on anatomical landmarks; and the ability to replicate the contractures of eight muscles of the lower limb unilaterally and bilaterally (psoas, rectus femoris, hamstring, hip adductors, gastrocnemius, soleus, tibialis posterior, and peroneus). Sixteen combinations of contractures were emulated on the unilateral and bilateral muscles of nine healthy participants. Two sessions of gait analysis were performed at weekly intervals to assess the reliability of the emulated contractures. Discrete variables were extracted from the kinematics to analyse the reliability. The exoskeleton did not affect normal walking when contractures were not emulated. Kinematic reliability varied from poor to excellent depending on the targeted muscle. Reliability was good for the bilateral and unilateral gastrocnemius, soleus, and tibialis posterior as well as the bilateral hamstring and unilateral hip adductors. The exoskeleton can be used to replicate contracture on healthy participants. The exoskeleton will allow us to differentiate primary and compensatory effects of muscle contractures on gait kinematics.

Orthotic correction of lower limb function during gait does not immediately influence spinal kinematics in spastic hemiplegic cerebral palsy

BACKGROUND AND PURPOSE

Foot equinus and leg length discrepancy (LLD) are common problems in hemiplegic cerebral palsy (hCP), both causing secondary deviations of pelvic motion during gait. It can therefore be assumed that the spinal deviations observed in hCP patients are secondary as a compensation for the position of the pelvis arising from the disturbed leg function. This study investigated the effects of correcting lower extremity function by orthotics on spinal gait kinematics in hCP patients.

METHODS

Ten adolescent hCP patients and 15 healthy controls were included. Using a validated and previously used enhanced marker set, sagittal and frontal plane spinal curvature angles as well as general trunk and lower extremity kinematics were measured while walking barefoot as well as with an orthotic correction (only hCP patients) using a 12-camera motion capture system.

RESULTS

The hCP patients in both the barefoot and orthotic conditions indicated clinically relevant greater lumbar lordosis angles (d≥0.96, p≤0.071), smaller thoracic kyphosis angles (d≥0.84, p≤0.142) and differences in frontal plane lumbar curvature angles (d≥1.00, p≤0.105) compared to controls. However, these angles were not influenced by the successful restoration of a normal heel-to-toe gait pattern and the correction of any LLD using lower extremity orthotics.

CONCLUSIONS

Spinal gait deviations in adolescents with mild hCP seemed not to result secondarily from foot equinus or LLD, but probably from structural deformities such as hip flexor contractures. Future research should address long-term effects of an AFO treatment as well as the relationship between spinal kinematics and severity of disease.

Gastrocnemius muscle-tendon interaction during walking in typically-developing adults and children, and in children with spastic cerebral palsy

BACKGROUND

Our understanding of the interaction of muscle bellies and their tendons in individuals with muscle pathology is limited. Knowledge of these interactions may inform us of the effects of musculoskeletal pathologies on muscle-tendon dynamics and the subsequent neurological control strategies used in gait. Here, we investigate gastrocnemius muscle-tendon interaction in typically-developing (TD) adults and children, and in children with spastic cerebral palsy (SCP).

METHODS

We recruited six TD adults (4 female; mean age: 34 yrs. (24-54)), eight TD children (5 female; mean age: 10 yrs. (6-12)) and eight independently ambulant children with SCP (5 female; mean age 9 yrs. (6-12); 3 unilaterally-affected). A combination of 3D motion capture and 2D real-time ultrasound imaging were used to compute the gastrocnemius musculo-tendinous unit (MTU) length and estimate muscle belly and tendon lengths during walking. For the TD subjects, the measurements were made for heel-toe walking and voluntary toe-walking.

RESULTS

The gastrocnemius muscle bellies of children with SCP lengthened during single support (p = 0.003). In contrast, the muscle bellies of TD subjects did not demonstrate an increase in length over the period of single support under heel-toe or toe-walking conditions.

CONCLUSION

We observed lengthening of the gastrocnemius muscle bellies in children with SCP during single support, a phase of the gait cycle in which the muscle is reported consistently to be active. Repeated lengthening of muscle bellies while they are active may lead to muscle damage and have implications for the natural history of gait in this group.

Effects of contracture on gait kinematics: A systematic review

BACKGROUND

Contractures of a major joint in the lower limbs may impair human walking in addition to other daily living activities. A contracture is defined as the inability of a joint to perform the full range of motion and excessive resistance during passive mobilization of the joint. Few studies have reported methods describing how to evaluate contractures. Understanding the association among all of these studies seems essential to improve patient management. Therefore, we conducted a systematic review on this topic to elucidate the influence of contractures on gait kinematics.

METHODS

An electronic search in the literature will be conducted. Studies were screened by title and abstract and full texts were evaluated secondarily for definitive inclusion. The quality of the included studies was assessed independently by the two review authors with the Modified Quality Assessment Checklist. The included studies were separated into three categories: pathological contracture versus healthy controls (descriptive), simulated contracture versus healthy controls (experimental), and pre- and post-kinematics after surgical muscle lengthening (surgery).

FINDINGS

From a total of 4402 references, 112 original articles were selected, and 28 studies were identified in this systematic review. No significant difference between raters was observed on the total score of the Modified Quality Assessment Checklist.

INTERPRETATION

Contractures influence walking depending on the location (muscle) and the contracture level (muscle-tendon length). After giving a definition of contracture, this review identified some contracture alterations, such as plantarflexion, knee flexion and hip flexion contractures, with a kinematic description and presented possible different compensations.

Multiple gait patterns within the same Winters class in children with hemiplegic cerebral palsy

BACKGROUND

Previous literature hypothesized that Winters type I are mainly characterized by a hypo-activation of dorsiflexors and type II by hyperactivation of plantarflexors around initial contact. However, it is currently not known if hemiplegic children belonging to the same Winters class really share the same muscle activation patterns, although this information might have relevant clinical implications in the patient management.

METHODS

Gait data of 38 hemiplegic cerebral palsy children (16 Winters type I, 22 Winters type II) were analyzed, focusing on the foot and shank. A 2.5-minute walk test was considered, corresponding to more than 100 gait cycles for each child, analyzing the muscle activation patterns of tibialis anterior and gastrocnemius lateralis. The large stride-to-stride variability of gait data was handled in an innovative way, processing separately: 1) distinct foot-floor contact patterns, and for each specific foot-floor contact pattern 2) distinct muscle "activation modalities", averaging only across gait cycles with the same number of activations, and obtaining, in both cases, the pattern frequency-of-occurrence.

FINDINGS

At least 2 representative foot-floor contact patterns within each Winters group, and up to 4-5 distinct muscle activation patterns were documented.

INTERPRETATION

It cannot be defined a predominant muscle activation pattern specific for a Winters group. For a correct clinical assessment of a hemiplegic child, it is advisable to record and properly analyze gait signals during a longer period of time (2-3 min), rather than (subjectively) selecting a few "clean" gait cycles, since these cycles may not be representative of the patient's gait.

Changes in muscle activity in typically developing children walking with unilaterally induced equinus

BACKGROUND

Distinguishing changes in lower limb muscle activation during gait caused by abnormal motor control or adaptations to the presence of a fixed equinus remains a challenge. The objective of this study was to determine a threshold degree of equinus at which changes in muscle activity occur and to characterize adaptive patterns of muscle activity in typically developing children walking with unilateral induced equinus.

METHODS

Ten typically developing children were included. A customized orthosis was fitted to the right ankle. Five conditions of dorsiflexion limitation were evaluated: 10° dorsiflexion, 0°, 10°, 20° of plantar flexion and maximum plantar flexion. Muscle activity of the rectus femoris, vastus lateralis, hamstring, tibialis anterior and soleus muscles of both limbs was recorded.

FINDINGS

Significant changes in muscle activation and co-activation occurred from 10° of plantar flexion in the orthosis limb and from maximum plantar flexion in the contralateral limb. Soleus activation occurred prematurely in terminal swing and increased with the degree of equinus. Tibialis anterior activation was increased during initial and midswing and was decreased during terminal swing. From the -20° condition, hamstring activation was increased during the loading response. Vastus lateralis and rectus femoris activation was increased during stance phase. Similar changes in tibialis anterior and soleus activation occurred on the contralateral side. Changes in co-activation occurred in the soleus/tibialis anterior muscle pair in both limbs.

INTERPRETATION

This study provides indications regarding changes in muscle activity during simulation of equinus gait which should be helpful for therapeutic decision making.

Spinal motor outputs during step-to-step transitions of diverse human gaits

Aspects of human motor control can be inferred from the coordination of muscles during movement. For instance, by combining multimuscle electromyographic (EMG) recordings with human neuroanatomy, it is possible to estimate alpha-motoneuron (MN) pool activations along the spinal cord. It has previously been shown that the spinal motor output fluctuates with the body's center-of-mass motion, with bursts of activity around foot-strike and foot lift-off during walking. However, it is not known whether these MN bursts are generalizable to other ambulation tasks, nor is it clear if the spatial locus of the activity (along the rostrocaudal axis of the spinal cord) is fixed or variable. Here we sought to address these questions by investigating the spatiotemporal characteristics of the spinal motor output during various tasks: walking forward, backward, tiptoe and uphill. We reconstructed spinal maps from 26 leg muscle EMGs, including some intrinsic foot muscles. We discovered that the various walking tasks shared qualitative similarities in their temporal spinal activation profiles, exhibiting peaks around foot-strike and foot-lift. However, we also observed differences in the segmental level and intensity of spinal activations, particularly following foot-strike. For example, forward level-ground walking exhibited a mean motor output roughly 2 times lower than the other gaits. Finally, we found that the reconstruction of the spinal motor output from multimuscle EMG recordings was relatively insensitive to the subset of muscles analyzed. In summary, our results suggested temporal similarities, but spatial differences in the segmental spinal motor outputs during the step-to-step transitions of disparate walking behaviors.

Effects of supramalleolar osteotomies for ankle osteoarthritis on foot kinematics and lower leg muscle activation during walking

BACKGROUND

Early stages of asymmetric ankle osteoarthritis can be treated by joint preserving supramalleolar osteotomies that surgically realign the ankle and unload degenerated cartilage. While studies have already shown pain relief and functional improvements, the effects on gait biomechanics are largely unknown. This study investigated patients' gait pattern after supramalleolar osteotomies by focusing on foot kinematics and lower leg muscle activation.

METHODS

An instrumented three-dimensional gait analysis with simultaneous electromyography of gastrocnemius medialis and lateralis, soleus, peroneus longus, and tibialis anterior muscles was performed on 12 patients with ankle osteoarthritis, seven of which were followed up 12-18months postoperatively. Additionally, seven different long-term follow-up patients (8-9years postoperatively) and 15 healthy control subjects were measured. The waveforms of the foot kinematics and muscle activation were analyzed using principal component analysis.

FINDINGS

Compared to healthy controls, principal component scores that affected the sagittal range of motion of the hindfoot and hallux were lower in all patient groups, while scores that affected the timing of the peaks in the sagittal forefoot motion were mainly altered in short-term follow-up patients. Lower principal component scores in patients with ankle osteoarthritis and short-term follow-up patients resulted in a less pronounced peak activation of gastrocnemius medialis and soleus.

INTERPRETATION

Both postoperative patient groups showed similar adaptations in their gait pattern as those observed in patients with ankle osteoarthritis. These changes are probably related to the lower ankle mobility. However, the reduced mobility seems to affect the patients' well-being less than a painful joint.

The association between premature plantarflexor muscle activity, muscle strength, and equinus gait in patients with various pathologies

This study provides an overview on the association between premature plantarflexor muscle activity (PPF), muscle strength, and equinus gait in patients with various pathologies. The purpose was to evaluate whether muscular weakness and biomechanical alterations are aetiological factors for PPF during walking, independent of the underlying pathology. In a retrospective design, 716 patients from our clinical database with 46 different pathologies (orthopaedic and neurologic) were evaluated. Gait analysis data of the patients included kinematics, kinetics, electromyographic activity (EMG) data, and manual muscle strength testing. All patients were clustered three times. First, patients were grouped according to their primary pathology. Second, all patients were again clustered, this time according to their impaired joints. Third, groups of patients with normal EMG or PPF, and equinus or normal foot contact were formed to evaluate the association between PPF and equinus gait. The patient groups derived by the first two cluster methods were further subdivided into patients with normal or reduced muscle strength. Additionally, the phi correlation coefficient was calculated between PPF and equinus gait. Independent of the clustering, PPF was present in all patient groups. Weak patients revealed PPF more frequently. The correlations of PPF and equinus gait were lower than expected, due to patients with normal EMG during loading response and equinus. These patients, however, showed higher gastrocnemius activity prior to foot strike together with lower peak tibialis anterior muscle activity in loading response. Patients with PPF and a normal foot contact possibly apply the plantarflexion-knee extension couple during loading response. While increased gastrocnemius activity around foot strike seems essential for equinus gait, premature gastrocnemius activity does not necessarily produce an equinus gait. We conclude that premature gastrocnemius activity is strongly associated with muscle weakness. It helps to control the knee joint under load independent from the underlying disease, and it is therefore a secondary deviation. If treated as primary target, caution should be exercised.

On the imitation of CP gait patterns by healthy subjects

The comparison of gait imitated by healthy subjects with real pathological CP gaits is expected to contribute to a better distinction between primary deviations directly induced by neurological troubles and secondary compensatory deviations in relation with the biomechanics of the pathological gait. However, the ability of healthy subjects for imitating typical CP gaits such as "jump" or "crouch" gaits still remains to be determined. The present study proposes to investigate healthy subjects imitating these typical CP gait patterns. 10 healthy adult subjects performed three types of gait: one "normal" and two imitated "jump" and "crouch" gaits. Kinematics and kinetics of the hip, knee and ankle were computed in the sagittal plane. Rectified normalized EMG was also analysed. Our data were compared with reference data. For the statistical analysis, the coefficient of multicorrelation has been used. It has been demonstrated that healthy subjects were able to voluntarily modify their gait pattern with a high level of intra-session and inter-subject reproducibility as quantified by a CMC values higher than 0.76 for all parameters. The comparison with literature reference data showed that healthy subjects not could perfectly reproduce a CP gait, however could only simulate the main characteristics of "crouch" and "jump" gaits pattern. As a perspective, pathological gaits imitated by healthy subjects could be used as valuable additional material to analyse the relationship between a voluntarily modified posture and the altered muscle activation to explore a new paradigm on pathological gait pattern analysis and musculoskeletal modelling.

Muscle contributions to center of mass acceleration adapt to asymmetric walking in healthy subjects

Symmetrical limb movement requires complex muscle coordination patterns. Consequently, coordination impairments lead to asymmetric gait patterns, as often seen in stroke subjects. Split-belt walking has previously been used to induce limping-like walking in able-bodied adults. The goal of this study is to analyze how muscle coordination patterns that control the centre of mass are modulated during an asymmetric gait pattern imposed on healthy subjects. These modulations can be uniquely related to the biomechanics of limping as no pathology is present. Forward simulations of limping-like walking (split-belt) and corresponding symmetric conditions (tied-belt) were generated for twelve healthy subjects. Our results show that the differences between 'fast' and 'slow' leg contributions during split-belt walking are not attributable to simple differences in speed between the belts, because most split-belt muscle contributions differ from tied-belt walking. Different types of modulations, inducing increased, decreased or even reversed asymmetry (e.g. plantarflexors, biceps femoris short head, and quadriceps respectively), underlie limping-like walking in healthy subjects. In general, these patterns present large similarities with adaptations previously described in hemiplegic subjects. However, differences were found with gluteus medius and biceps femoris short head contributions in hemiplegic subjects, suggesting that the latter are not just related to limping, but to concomitant deficits.

Threshold of equinus which alters biomechanical gait parameters in children

The main aim of this study was to define the threshold angle of equinus beyond which significant changes in 3D lower limb kinematics and kinetics occur in typically developing children and to describe these changes.A customized orthosis was fitted on the right ankle of 10 typically developing children and was adjusted to +10° ankle dorsiflexion, 0°, -10°, -20° plantarflexion and maximum plantarflexion. Gait was analyzed using an optoelectronic system. A gait velocity of 1m/s was imposed.Most of the kinematic and kinetic changes were significantly altered from the -10° condition. In the sagittal plane, the results showed increased knee flexion at initial contact, increased knee flexion or hyperextension in stance, increased hip flexion at initial contact and increased anterior pelvic tilt. Other changes included increased knee varus, reduced hip adduction and more internal foot progression. The ankle plantarflexion moment was bi-phasic during stance, peak ankle power generation was reduced, peak knee extension moment was decreased and hip extension moments increased. On the contralateral side, there was a significant increase in ankle plantarflexion at initial contact and a significant decrease in knee flexion during swing phaseat maximum plantarflexion.Although slight modifications occurred for smaller degrees of equinus, the results suggest that significant kinematic and kinetic changes occurred during gait in both limbs from 10° of plantarflexion. The results of this study also provide some indications regarding the primary causes of gait deviations and secondary compensatory strategiesin children with a clinical dorsiflexion limitation.

Secondary gait deviations in patients with and without neurological involvement: a systematic review

Pathologies that lead to biomechanical restrictions in human gait interfere with the tightly regulated muscle activation patterns that control the external moments. In order to maintain proper function, secondary mechanisms are required. The aims of this systematic review were (1) to identify secondary mechanisms in pathologic gait that have been described throughout the scientific literature by means of instrumented gait analysis, (2) to distinguish between active compensatory mechanisms and passive physical effects and (3) to identify common compensatory mechanisms that appear to be independent from the underlying disease. A comprehensive literature search revealed 4080 citations for review, whereof 148 studies entered the full-text review. Thirty-six studies were included and the quality of these studies was assessed by two independent reviewers (kappa=0.83). The quality of the included studies showed large variation and several methodological issues were identified. Five studies were further identified describing only passive physical effects, leaving a total of 31 studies reporting on compensations. The qualitative analysis revealed common compensations that appeared to be independent from the underlying pathology. In clinical practice, distinguishing primary from secondary gait deviations can be considered highly important since unnecessary treatment may be avoided. However, given the introduction of general principles of compensatory mechanisms and the fact that certain presumed "compensations" were identified as simple passive physical effects, secondary gait deviations have to be further investigated. Computer simulation studies are valuable, especially in respect of the distinction between compensations and physical effects. Furthermore, the need for a uniform terminology was highlighted.

Simulation of unilateral equinus using an adjustable orthosis in children: design, feasibility and biomechanical effects

BACKGROUND AND AIM

In order to increase understanding of the biomechanical consequences of equinus foot on gait, we developed an orthosis to induce an adjustable degree of unilateral equinus. The aim of this study was to evaluate its feasibility and consequences on 3D ankle kinematics and kinetics.

TECHNIQUE

3D gait analysis was carried out in 10 healthy children without the orthosis, with the non-adjusted orthosis and with the orthosis adjusted to +10°, 0°, -10°, -20° of ankle dorsiflexion and maximum plantarflexion (MP). The amount of dorsiflexion at initial contact was close to the goniometric measurement. Significant kinematic and kinetic changes occurred at -10°, -20° and MP. The mean maximum equinus at initial contact -21.65° ± 4.17 and during stance -11.61° ± 4.82 were larger than those obtained with previous described devices.

DISCUSSION

Our device was easy-to-use and induced an adjustable, well tolerated equinus. It provides a new way to simulate equinus and its biomechanical consequences on gait.

Botulinum toxin A injections do not improve surface EMG patterns during gait in children with cerebral palsy--a randomized controlled study

Children with cerebral palsy who walk with knee flexion during midstance are treated with intramuscular injections of botulinum toxin A (BTX-A) to prevent them from potential deterioration and to improve their mobility. The present study evaluates the effect of this treatment on the muscle activation patterns of the rectus femoris, medial hamstrings and gastrocnemius medialis during gait. Twenty-two children (aged 4-11 years) with cerebral palsy, who walked with knee flexion, were randomly assigned to an intervention group (multilevel BTX-A injections combined with comprehensive rehabilitation) or a control group (usual care). Sagittal and frontal video recordings were made of gait, together with simultaneous surface electromyography recordings of the rectus femoris, medial hamstring and gastrocnemius medialis muscles, before and six weeks after treatment. Abnormal muscle activation patterns were quantified, after gain-normalisation, according to the root mean square difference (RMSD), which is the difference relative to normal patterns. Six weeks after the treatment the RMSD of the gastrocnemius medialis muscles in the intervention group changed significantly, showing a deterioration (p<0.05). This study demonstrated that BTX-A injections do not result in an improvement in lower limb muscle activation patterns during gait. In spite of this lack of direct effect on muscle activation patterns, the combination of BTX-A injections and comprehensive rehabilitation was effective in improving gait kinematics.

A multiple-task gait analysis approach: kinematic, kinetic and EMG reference data for healthy young and adult subjects

Standard clinical gait analysis protocols usually limit to test self-selected speed gait: this approach is generally valid and permits time and cost saving. Yet, the literature evidences suggest that some pathologies (especially at onset or subclinical level) may not primarily affect plain gait, but more demanding locomotor tasks. In the present study we therefore propose a multiple-task gait analysis protocol including: self-selected, increased and decreased speed gait; walking on toes; walking on heels; step ascending and step descending, and apply it to 40 healthy subjects (20 aged 6-17, 20 aged 22-72) thus building extensive reference data set. Published studies already report normative data for some of these tasks, but inhomogeneously (due to different collecting methods and biomechanical models, population characteristics, nature of data). We verify a good correlation between our results and those presented by Schwartz et al. (2008) [12] in their study providing extensive data on the effect of walking speed on the gait of healthy children. In discussing the results, the rationale and effectiveness of each task is confirmed, and we supply an electronic addendum with comprehensive kinematic, kinetic and electromyographic normative data for the considered population, along with a set of reference parameters and related statistical analysis, as a premise for further applications on pathological subjects.