Mechanical work, energetic cost, and gait efficiency in children with cerebral palsy

Comparing the effectiveness of robotic plantarflexion resistance and biofeedback between overground and treadmill walking

Individuals with diminished walking performance caused by neuromuscular impairments often lack plantar flexion muscle activity. Robotic devices have been developed to address these issues and increase walking performance. While these devices have shown promise in their ability to increase musculature engagement of the lower limbs when used on a treadmill, most have not been developed or validated for overground walking and community use. Overground walking may limit the effectiveness of robotic devices due to differences in gait characteristics between walking terrains and reduced user engagement. The purpose of this study was to validate our multimodal robotic gait training system for overground walking in individuals with neuromuscular gait impairments. This untethered wearable robotic device can provide an ankle resistive torque proportional to the users' biological ankle torque. The device can also provide audio biofeedback based on users' plantar pressure intending to increase ankle power and muscle activity of the plantar flexors. Seven individuals with cerebral palsy participated. Participants walked overground and on a treadmill with our robotic gait training system in a single testing session. Results showed all seven participants to increase peak plantar flexor muscle activity, 10.3% on average, when walking with the gait trainer overground compared to treadmill. When compared to typical baseline overground walking, overground gait trainer use caused individuals to have slightly less knee joint excursion (3°) and moderately more ankle joint excursion (7°). This work supports our vision of using the wearable robotic device as a gait aid and rehabilitation tool in the home and community settings.

Fatigue-related gait adaptations in children with cerebral palsy

AIM

To obtain insights into the effects of fatigue on the kinematics, kinetics, and energy cost of walking (ECoW) in children with cerebral palsy (CP).

METHOD

In this prospective observational study, 12 children with CP (mean age 12 years 9 months, SD 2 years 7 months; four females, eight males) and 15 typically developing children (mean age 10 years 8 months, SD 2 years 4 months; seven females, eight males) followed a prolonged intensity-based walking protocol on an instrumented treadmill, combined with gas analysis measurements. The protocol consisted of consecutive stages, including a 6-minute walking exercise (6MW) at comfortable speed, 2 minutes of moderate-intensity walking (MIW) (with a heart rate > 70% of its predicted maximal), and 4 minutes walking after MIW. If necessary, the speed and slope were incremented to reach MIW. Outcomes were evaluated at the beginning and end of the 6MW and after MIW.

RESULTS

With prolonged walking, Gait Profile Scores deteriorated slightly for both groups (p < 0.01). Knee flexion increased during early stance (p = 0.004) and ankle dorsiflexion increased during late stance (p = 0.034) in children with CP only. Negligible effects were found for kinetics. No demonstrable change in ECoW was found in either group (p = 0.195).

INTERPRETATION

Kinematic deviations in children with CP are progressive with prolonged walking. The large variation in adaptations indicates that an individual approach is recommended to investigate the effects of physical fatigue on gait in clinical practice.

Atypical triceps surae force and work patterns underlying gait in children with cerebral palsy

The purpose of this study was to quantitatively assess Achilles tendon mechanical behavior during gait in children with cerebral palsy (CP). We used a newly designed noninvasive sensor to measure Achilles tendon force in 11 children with CP (4F, 8-16 years old) and 15 typically developing children (controls) (9F, 8-17 years old) during overground walking. Mechanical work loop plots (force-displacement plots) were generated by combining muscle-tendon kinetics, kinematics, and EMG activity to evaluate the Achilles tendon work generated about the ankle. Work loop patterns in children with CP were substantially different than those seen in controls. Notably, children with CP showed significantly diminished work production at their preferred speed compared to controls at their preferred speed and slower speeds. Despite testing a heterogeneous population of children with CP, we observed a homogenous spring-like muscle-tendon behavior in these participants. This is in contrast with control participants who used their plantar flexors like a motor during gait. Statement of Clinical Significance: These data demonstrate the potential for using skin-mounted sensors to objectively evaluate muscle contributions to work production in pathological gait.

Glycine receptor subunit-ß -deficiency in a mouse model of spasticity results in attenuated physical performance, growth and muscle strength

Spasticity is the most common neurological disorder associated with increased muscle contraction causing impaired movement and gait. The aim of this study was to characterize the physical performance, skeletal muscle function, and phenotype of mice with a hereditary spastic mutation (B6.Cg-Glrb^spa/J). Motor function, gait, and physical activity of juvenile and adult spastic mice and the morphological, histological, and mechanical characteristics of their soleus and gastrocnemius medialis muscles were compared with those of their wild-type (WT) littermates. Spastic mice showed attenuated growth, impaired motor function, and low physical activity. Gait of spastic mice was characterized by a typical hopping pattern. Spastic mice showed lower muscle forces, which were related to the smaller physiological cross-sectional area of spastic muscles. The muscle-tendon complex length-force relationship of adult gastrocnemius medialis was shifted toward shorter lengths, which was explained by attenuated longitudinal tibia growth. Spastic gastrocnemius medialis was more fatigue resistant than WT gastrocnemius medialis. This was largely explained by a higher mitochondrial content in muscle fibers and relatively higher percentage of slow-type muscle fibers. Muscles of juvenile spastic mice showed similar differences compared with WT juvenile mice, but these were less pronounced than between adult mice. This study shows that in spastic mice, disturbed motor function and gait is likely to be the result of hyperactivity of skeletal muscle and impaired skeletal muscle growth, which progress with age.

Energetics of walking in individuals with cerebral palsy and typical development, across severity and age: A systematic review and meta-analysis

BACKGROUND

Individuals with cerebral palsy (CP) report physical fatigue as a main cause of limitation, deterioration and eventually cessation of their walking ability. A consequence of higher level of fatigue in individuals with CP leads to a less efficient and long-distance walking ability.

RESEARCH QUESTION

This systematic review investigates the difference in 1) walking energy expenditure between individuals with CP and age-matched typically developing (TD) individuals; and 2) energetics of walking across Gross Motor Function Classification System (GMFCS) levels and age.

METHODS

Five electronic databases (PubMed, Web of Science, CINAHL, ScienceDirect and Scopus) were searched using search terms related to CP and energetics of walking.

RESULTS

Forty-one studies met inclusion criteria. Thirty-one studies compared energy expenditure between CP and age-matched controls. Twelve studies correlated energy expenditure and oxygen cost across GMFCS levels. Three studies investigated the walking efficiency across different ages or over a time period. A significant increase of energy expenditure and oxygen cost was found in individuals with CP compared to TD age-matched individuals, with a strong relationship across GMFCS levels.

SIGNIFICANCE

Despite significant differences between individuals with CP compared to TD peers, variability in methods and testing protocols may play a confounding role. Analysis suggests oxygen cost being the preferred/unbiased physiological parameter to assess walking efficacy in CP. To date, there is a knowledge gap on age-related changes of walking efficiency across GMFCS levels and wider span of age ranges. Further systematic research looking at longitudinal age-related changes of energetics of walking in this population is warranted.

The effects of footplate stiffness on push-off power when walking with posterior leaf spring ankle-foot orthoses

BACKGROUND

Many studies on ankle-foot orthoses investigated the optimal stiffness around the ankle, while the effect of footplate stiffness has been largely ignored. This study investigated the effects of ankle-foot orthosis footplate stiffness on ankle-foot push-off power during walking in able-bodied persons.

METHODS

Twelve healthy participants walked at a fixed speed (1.25 m·s^-1) on an instrumented treadmill in four conditions: shod and with a posterior leaf-spring orthosis with a flexible, stiff or rigid footplate. For each trial, ankle kinematics and kinetics were averaged over one-minute walking. Separate contributions of the ankle joint complex and distal hindfoot to total ankle-foot power and work were calculated using a deformable foot model.

FINDINGS

Peak ankle joint power was significantly higher with the rigid footplate compared to the flexible and stiff footplate and not different from shod walking. The stiff footplate increased peak hindfoot power compared to the flexible and rigid footplate and shod walking. Total ankle-foot power showed a significant increase with increasing footplate stiffness, where walking with the rigid footplate was comparable to shod walking. Similar effects were found for positive mechanical work.

INTERPRETATION

A rigid footplate increases the lever of the foot, resulting in an increased ankle moment and energy storage and release of the orthosis' posterior leaf-spring as reflected in higher ankle joint power. This effect dominates the power generation of the foot, which was highest with the intermediate footplate stiffness. Future studies should focus on how tuning footplate stiffness could contribute to optimizing ankle-foot orthosis efficacy in clinical populations.

Normative Achilles and patellar tendon shear wave speeds and loading patterns during walking in typically developing children

BACKGROUND

Motion analysis is commonly used to evaluate joint kinetics in children with cerebral palsy who exhibit gait disorders. However, one cannot readily infer muscle-tendon forces from joint kinetics. This study investigates the use of shear wave tensiometry to characterize Achilles and patellar tendon forces during gait.

RESEARCH QUESTION

How do Achilles and patellar tendon wave speed and loading modulate with walking speed in typically developing children?

METHODS

Twelve typically developing children (9-16 years old) walked on an instrumented treadmill with shear wave tensiometers over their Achilles (n = 11) and patellar (n = 9) tendons. Wave speeds were recorded at five leg length-normalized walking speeds (very slow to very fast). Achilles and patellar tendon moment arms were measured with synchronized ultrasound and motion capture. The tendon wave speed-load relationship was calibrated at the typical walking speed and used to estimate tendon loading at other walking speeds.

RESULTS

Characteristic Achilles and patellar tendon wave speed trajectories exhibited two peaks over a gait cycle. Peak Achilles tendon force closely aligned with peak ankle plantarflexor moment during pushoff, though force exhibited less modulation with walking speed. A second peak in late swing Achilles loading, which was not evident from the ankle moment, increased significantly with walking speed (p < 0.001). The two peaks in patellar tendon loading occurred at 12 ± 1% and 68 ± 6% of the gait cycle, matching the timing of peak knee extension moment in early stance and early swing. Both patellar tendon load peaks increased significantly with walking speed (p < 0.05).

SIGNIFICANCE

This is the first study to use shear wave tensiometry to characterize Achilles and patellar tendon loading during gait in children. These data could serve as a normative comparison when using tensiometry to identify abnormal tendon loading patterns in individuals who exhibit equinus and/or crouch gait.

A spatio-temporal and kinematic description of self-selected walking in adults with Achondroplasia

BACKGROUND

Achondroplasia is characterised by a shorter appendicular limb to torso ratio, compared to age matched individuals of average stature (controls). Despite the well documented shorter leg length of individuals with compared to controls, there are few complete descriptions of gait kinematics reported for the population.

AIM

The aim of this study was to report the spatio-temporal and kinematic characteristics of self-selected walking (SSW) in a group with Achondroplasia (N = 10) and age matched group without Achondroplasia (controls, N = 17).

METHOD

Whole body 3D analysis of both groups was conducted using a 14 camera VICON system. Spatio-temporal and kinematic variables were determined through a Plug-in-Gait model. SSW was obtained from an average of three trials equating to a total of ∼120 m walking.

RESULTS

The group with Achondroplasia were 23 % slower (P < 0.001), had a 29 % shorter stride length (P < 0.001) and a 13 % higher stride frequency (P < 0.001) compared to controls. There were no differences in time normalised temporal measures of left toe off (P = 0.365), right heel contact (P = 0.442) or the duration of double support (P = 0.588) between groups. A number of discrete joint kinematic differences existed between groups, resulting in the group with Achondroplasia having more 'flexed' lower limbs than controls throughout the gait cycle.

CONCLUSION

Differences in absolute spatio-temporal variables between groups is likely due to the shorter leg length of the group with Achondroplasia, while their more flexed position of the lower limbs may facilitate toe-clearance during the swing phase.

Pendular energy transduction in the different phases of gait cycle in post-stroke subjects

MAIN: To analyze spatiotemporal gait parameters and the body center of mass (CoM) energy transduction at self-selected speed walking in a group of older patients with stroke.

METHODS

A cross-sectional study, fifteen subjects with 4.06 years post ̵stroke hemiparesis (eleven men and four women) and fifteen healthy subjects (four men and eleven women) participate in this study. Pendulum-like determining variables; Recovery (R) and Congruity percentage (%Cong) were analyzed in addition to immediate pendular re-conversion (Rint) during the phases in which the gait cycle is usually divided in clinical evaluations.

RESULTS

Healthy subjects walked faster that stroke group (p = 0.001). %Cong was significantly higher in post-stroke respect to healthy subjects (p = 0.05). Rint showed significant differences between the groups for all phases (p = 0.05). The relation between speed and R was confirmed, for healthy (r = 0.67, p = 0.006) and post-stroke subjects (r = 0.851, p = 0.001), %Cong y Rint (r = -0.79, p = 0.001), (r = -0.93, p = 0.001) and periods of double support (r = -0.76, p = 0.001), (r = 0.69, p = 0.004) respectively.

CONCLUSION

Alteration of pendular mechanism in subjects post-stroke is associated mainly with energy transduction; mechanical energy recovered during double support phases in healthy and post-stroke subjects follows a different trend, in post-stroke subjects, a longer duration of the double support is associated with less energy loss.

Self-reported factors contributing to fatigue and its management in adolescents and adults with cerebral palsy

PURPOSE

To explore the self-reported factors that generate fatigue and to describe fatigue self-management strategies from the perspectives of adolescents and adults with cerebral palsy (CP).

MATERIALS AND METHODS

Text responses to open-ended questions of the Fatigue Impact and Severity Self-Assessment from 160 participants (mean age 22.4 years) across all GMFCS levels were coded using inductive line-by-line coding and then grouped together to generate larger categories for each question. Frequency counts associated with each category were then summarized descriptively by Gross Motor Function Classification System level.

RESULTS

The most commonly reported contributors to fatigue included the following: activity-related factors, general demands of life, sleep/rest, general health concerns, CP-related factors, mental health concerns, and environmental factors. The top five strategies participants reported to manage fatigue included rest or relaxation, sleeping or napping, changing or limiting their activities, being physically active, or using specific adaptations or assistive devices.

CONCLUSIONS

Results from this study suggest that there are potentially modifiable factors, including activity level and sleep, that significantly contribute to fatigue for persons with CP; these could form the basis of interventions targeted at the prevention and management of fatigue.Implications for RehabilitationAs individuals with cerebral palsy who are physically active experience significant fatigue, clinicians need to address fatigue to enable these individuals to reap the health benefits of physical activity.Providing education and support to integrate self-management techniques, such as planning and pacing, may be an effective long-term strategy to support individuals to complete highly valued tasks.Interventions targeting modifiable fatigue-generating factors such as activity level, sleep, and mental health concerns are needed.

Management of the Knee Problems in Spastic Cerebral Palsy

Two common knee problems in cerebral palsy are increased knee flexion during stance phase and reduced knee flexion during the swing phase of gait. We reviewed the recent literature and based on that, we formed this review. Hamstring spasticity, quadriceps weakness, soleus weakness, and lever-arm dysfunction are few factors which lead to increased knee flexion during stance phase. Rectus spasticity diminishes knee flexion in the swing. Resulting gait-stiff knee gait interferes with ground clearance. Both gait patterns result into esthetically poor gait and increased energy consumption. Knee flexion gait may lead to pain in the knee. Natural history of knee flexion gait suggests deterioration over time. In the early stage, these gait abnormalities are managed by nonoperative treatment. Cases in which nonoperative measures fail or advance cases need surgical treatment. Various variables which are taken into consideration before selecting a particular treatment option are described. We also present an algorithm for decision-making. Nonsurgical options and surgical procedures are discussed.

Validity and reliability of ankle dorsiflexion measures in children with cerebral palsy

PURPOSE

We compared a goniometer method in a non-weight-bearing position with a tape measure method in a weight-bearing position to determine which was more reliable for assessing dorsiflexion range of motion (ROM) in children with cerebral palsy (CP).

METHODS

Ankle dorsiflexion ROM was measured using goniometer and tape measure methods in non-weight- and weight-bearing positions, respectively.

RESULTS

In the test-retest reliability of ankle dorsiflexion ROM using a universal goniometer, the intraclass correlation coefficient (ICC) varied from 0.75 to 0.96 and the overall ICC score was 0.91 (p< 0.001). In the test-retest reliability of ankle dorsiflexion ROM using a tape measure, ICC varied from 0.98 to 0.99 and the overall ICC score was 0.99 (p< 0.001). Ankle dorsiflexion ROM using a universal goniometer had a standard error of measurement (SEM) of 2.86 and a minimum detectable change (MDC) of 7.94. Ankle dorsiflexion ROM using a tape measure had an SEM of 1.01 and a MDC of 2.80.

CONCLUSIONS

The tape measure method in a weight-bearing position was more reliable than using a universal goniometer in a non-weight-bearing position in children with CP.

Physical Activity Promotion for Persons Experiencing Disability: The Importance of Interdisciplinary Research and Practice

This paper examines the need for interdisciplinary knowledge in the formation of public health models for health-promoting physical activity (PA) for people experiencing disability. PA promotion for people experiencing disability is a multifaceted endeavor and requires navigating a multitude of complicated and interactive factors. Both disability and health are multifaceted constructs and the relationship between PA and health is embedded within a complicated web of interactive influences. PA promotion must consider interacting biological and psychosocial factors within the person and in the sociopolitical environment. Models for research and practice need to evolve from value and belief systems that center on people experiencing disability without stigmatizing them. We argue that interdisciplinary research and practice is needed in navigating the intricacies of PA promotion toward improving the health of people experiencing disability and facilitating inclusion, empowerment, and dignity.

The Oxygen Consumption and Metabolic Cost of Walking and Running in Adults With Achondroplasia

The disproportionate body mass and leg length of Achondroplasic individuals may affect their net oxygen consumption (V͘O₂) and metabolic cost (C) when walking at running compared to those of average stature (controls). The aim of this study was to measure submaximal V͘O₂ and C during a range of set walking speeds (SWS; 0.56 – 1.94 m⋅s^-1, increment 0.28 m⋅s^-1), set running speeds (SRS; 1.67 – 3.33 m⋅s^-1, increment 0.28 m⋅s^-1) and a self-selected walking speed (SSW). V͘O₂ and C was scaled to total body mass (TBM) and fat free mass (FFM) while gait speed was scaled to leg length using Froude’s number (Fr). Achondroplasic V͘O_2TBM and V͘O_2FFM were on average 29 and 35% greater during SWS (P < 0.05) and 12 and 18% higher during SRS (P < 0.05) than controls, respectively. Achondroplasic C_TBM and C_FFM were 29 and 33% greater during SWS (P < 0.05) and 12 and 18% greater during SRS (P < 0.05) than controls, respectively. There was no difference in SSW V͘O_2TBM or V͘O_2FFM between groups (P > 0.05), but C_TBM and C_FFM at SSW were 23 and 29% higher (P < 0.05) in the Achondroplasic group compared to controls, respectively. V͘O_2TBM and V͘O_2FFM correlated with Fr for both groups (r = 0.984 – 0.999, P < 0.05). Leg length accounted for the majority of the higher V͘O_2TBM and V͘O_2FFM in the Achondroplasic group, but further work is required to explain the higher Achondroplasic C_TBM and C_FFM at all speeds compared to controls.

New and Noteworthy: There is a leftward shift of oxygen consumption scaled to total body mass and fat free mass in Achondroplasic adults when walking and running. This is nullified when talking into account leg length. However, despite these scalars, Achondroplasic individuals have a higher walking and metabolic cost compared to age matched non-Achondroplasic individuals, suggesting biomechanical differences between the groups.

Gait in patients with adolescent idiopathic scoliosis. Effect of surgery at 10 years of follow-up

PURPOSE

To assess radiological and gait biomechanical changes before, at one and 10 years after surgery in AIS patients.

METHODS

This clinical prospective study included fifteen adult women (mean[SD] age: 26 [1] years) diagnosed with thoraco-lumbar/lumbar AIS and operated 10 years ago. Clinical, radiological and gait variables, including kinematics, electromyography (EMG), mechanics and energetics were compared between presurgery (S0), 1 year (S1) and 10 years (S2) postsurgery period using a one way repeated measure ANOVA.

RESULTS

The Cobb angle of the scoliosis curve was reduced by 55% at 1 year postsugery but only by 37% at 10 years postsurgery suggesting a loss of 32% over time. Frontal plumb line C7-S1 distance was significantly improved by surgery (-44%) and remained stable at 10 years postsurgery. Lower limb kinematics was not affected by the surgery at long term. Excessive bilateral activation of lombo-pelvic muscles, observed before surgery, decreased significantly at S1 and S2 period. Mechanical energy increased significantly between S0, S1 and S2 session, without any change for the energetic variables.

CONCLUSIONS

Between 1 and 10 years post-surgery, thoraco-lumbar/lumbar AIS women showed a few decompensation of the curve without any change of the improved frontal body balance. Lower limbs and pelvic motion, during gait, was not affected by the surgery. But presurgical excessive EMG activity of the lumbo-pelvic muscle and reduced mechanical energy produced to walk get similar to normal patterns. Only the oxygen consumption remained excessive probably due to physical deconditioning or postural instability.

Effect of robotic-assisted gait rehabilitation on dynamic equilibrium control in the gait of children with cerebral palsy

Due to the intensity and repetition of movement, roboticassisted gait training therapy could have a beneficial effect on the recovery and improvement of postural and locomotor functions of the patient. This study sought to highlight the effects of robotic-assisted gait rehabilitation in gait of children with Cerebral Palsy (CP). We analyzed the different strategies before and after this rehabilitation which was used in order to generate forward motion while maintaining balance. Data were collected by a motion analysis system (Vicon® - Oxford Metrics, Oxford, UK). The children were divided into two groups in such a way as to obtain a randomized controlled population: i) a group of fourteen children (Treated Group) underwent 20 sessions of roboticassisted gait training therapy using the driven gait orthosis Lokomat®Pediatric (Hocoma AG, Volketswil, Switzerland) compared to ii) a group of sixteen children without sessions of Lokomat®Pediatric (Control Group). Significant differences are observed for the TG between the preand post-test values of the locomotor parameters and of the kinetic data of the propulsive forces of the Center of Mass (COM) and of the Center of Pressure (COP) dynamic trajectory. This first study, although performed on a limited number of patients, shows the usefulness of this robotic gait rehabilitation mainly in the balance control in gait. Indeed after this rehabilitation, these children improve their gait that is especially characterized by a more appropriate time lag between the time instant of COM-COP trajectory divergence and the time instant when the forward propulsive forces became apparent.

Mechanisms contributing to gait speed and metabolic cost in children with unilateral cerebral palsy

BACKGROUND

Gait speed and metabolic cost are indicators of functional capacity in children with cerebral palsy. Uncovering their mechanisms helps guide therapeutic actions.

OBJECTIVES

To investigate the contributions of energy-generating and energy-conserving mechanisms to gait speed and metabolic cost of children with unilateral cerebral palsy.

METHODS

Data on eccentric and concentric muscle work, co-contraction, elastic torque and vertical stiffness of the affected-limb, forcing torque of the non-affected limb, gait speed and metabolic cost were collected from 14 children with unilateral cerebral palsy, aged 6-12 years. Analyses included two groups of multiple regression models. The first group of models tested the association between each dependent variable (i.e., speed and metabolic cost) and the independent variables that met the input criteria. The second group verified the contribution of the non-selected biomechanical variables on the predictors of the first model.

RESULTS

Gait speed (R²=0.80) was predicted by elastic torque (β=0.62; 95%CI: 0.60, 0.63), vertical stiffness (β=-0.477; 95%CI: -0.479, -0.474) and knee co-contraction (β=0.27; 95%CI: -1.96, 2.49). The production of eccentric work by the affected limb proved relevant in adjusting the vertical stiffness (R²=0.42; β=-0.64; 95%CI: 0.86, -0.42); elastic torque of the affected-leg was associated with impulsive torque of the non-affected leg (R²=0.31; β=0.55; 95%CI: 0.46, 0.64). Metabolic cost of gait (R²=0.48) was partially predicted by knee co-contraction (β=0.69; 95%CI: 0.685, 0.694).

CONCLUSIONS

The chain of associations revealed by the two steps models helped uncover the mechanisms involved in the locomotion of children with unilateral cerebral palsy. Intervention that changes specific energy conserving and generating mechanisms may improve gait of these children.

Decision Trees for Detection of Activity Intensity in Youth with Cerebral Palsy

PURPOSE

To develop and test decision tree (DT) models to classify physical activity (PA) intensity from accelerometer output and Gross Motor Function Classification System (GMFCS) classification level in ambulatory youth with cerebral palsy (CP) and compare the classification accuracy of the new DT models to that achieved by previously published cut points for youth with CP.

METHODS

Youth with CP (GMFCS levels I-III) (N = 51) completed seven activity trials with increasing PA intensity while wearing a portable metabolic system and ActiGraph GT3X accelerometers. DT models were used to identify vertical axis (VA) and vector magnitude (VM) count thresholds corresponding to sedentary (SED) (<1.5 METs), light-intensity PA (LPA) (≥1.5 and <3 METs) and moderate-to-vigorous PA (MVPA) (≥3 METs). Models were trained and cross-validated using the "rpart" and "caret" packages within R.

RESULTS

For the VA (VA_DT) and VM DT (VM_DT), a single threshold differentiated LPA from SED, whereas the threshold for differentiating MVPA from LPA decreased as the level of impairment increased. The average cross-validation accuracies for the VC_DT were 81.1%, 76.7%, and 82.9% for GMFCS levels I, II, and III. The corresponding cross-validation accuracies for the VM_DT were 80.5%, 75.6%, and 84.2%. Within each GMFCS level, the DT models achieved better PA intensity recognition than previously published cut points. The accuracy differential was greatest among GMFCS level III participants, in whom the previously published cut points misclassified 40% of the MVPA activity trials.

CONCLUSIONS

The GMFCS-specific cut points provide more accurate assessments of MVPA levels in youth with CP across the full spectrum of ambulatory ability.

Assistance magnitude versus metabolic cost reductions for a tethered multiarticular soft exosuit

When defining requirements for any wearable robot for walking assistance, it is important to maximize the user's metabolic benefit resulting from the exosuit assistance while limiting the metabolic penalty of carrying the system's mass. Thus, the aim of this study was to isolate and characterize the relationship between assistance magnitude and the metabolic cost of walking while also examining changes to the wearer's underlying gait mechanics. The study was performed with a tethered multiarticular soft exosuit during normal walking, where assistance was directly applied at the ankle joint and indirectly at the hip due to a textile architecture. The exosuit controller was designed such that the delivered torque profile at the ankle joint approximated that of the biological torque during normal walking. Seven participants walked on a treadmill at 1.5 meters per second under one unpowered and four powered conditions, where the peak moment applied at the ankle joint was varied from about 10 to 38% of biological ankle moment (equivalent to an applied force of 18.7 to 75.0% of body weight). Results showed that, with increasing exosuit assistance, net metabolic rate continually decreased within the tested range. When maximum assistance was applied, the metabolic rate of walking was reduced by 22.83 ± 3.17% relative to the powered-off condition (mean ± SEM).

VELOCIDADE AUTOSSELECIONADA E IDEAL DA CAMINHADA DE AMPUTADOS TRANSFEMORAIS: SOLO E ESTEIRA

RESUMO Introdução: A velocidade de progressão é, em geral, determinada em pesquisas na área da locomoção. Objetivo: Comparar as medidas de velocidade autosselecionada no solo, na esteira rolante e a velocidade ideal estimada pelo número de Froude em sujeitos amputados transfemorais. Método: Primeiramente foi determinada a velocidade no solo; em seguida, realizou-se o teste na esteira, e a velocidade ideal foi estimada a partir dos dados antropométricos. Todos os sujeitos utilizavam joelho hidráulico e pé em fibra de carbono. Para comparação entre as velocidades foi realizada ANOVA de duas vias. Resultados: A velocidade autosselecionada na esteira foi menor (22%) do que no solo. Tanto a velocidade autosselecionada na esteira como a do solo foram 44% e 22% menores do que a velocidade ideal estimada, respectivamente. Conclusão: As velocidades analisadas no presente estudo foram diferentes, provavelmente, devido à variação dos parâmetros cinemáticos.

An exploratory study of gait and functional outcomes after neuroprosthesis use in children with hemiplegic cerebral palsy

PURPOSE

To evaluate the immediate orthotic, total and therapeutic effects of functional electrical stimulation (FES) neuroprosthesis use on clinic based measures of gait and function in children with hemiplegic cerebral palsy.

METHODS

Eleven children (mean 9 years 11 months) participated in an FES neuroprosthesis (Ness L300) intervention (4 week accommodation period followed by 12 weeks of daily use) and were assessed at baseline and post in stimulation off and stimulation on conditions. Measures included clinic based outcomes of gait and function.

RESULTS

No significant immediate orthotic effects were observed. Significant (p < 0.01) total effects were noted for dorsiflexion at initial contact, Six-Minute Walk Test (6MWT), and walking speed. A significant therapeutic effect was found for steps off path on the Standardized Walking Obstacle Course (SWOC).

CONCLUSIONS

Results support previous findings of neuroprosthesis total effects on gait and provide some evidence for effects on function. Therapeutic effects remain unclear. Implications for Rehabilitation In this study, children with hemiplegic CP did not demonstrate immediate improvements in gait or function at their first clinic visit using the FES neuroprosthesis device suggesting one visit using the device is not sufficient to determine potential benefits. Over time with daily use of the FES neuroprosthesis, ankle dorsiflexion in swing and at initial contact, walking speed and endurance increased with the device worn. Overtime, no carryover effects in ankle dorsiflexion in swing and at initial contact were noted at the end of the intervention period with the device off. Clinicians should consider purchasing units to loan or rent to individuals to trial a device at home before determining long-term potential for benefit.

Energy expenditure during standing in children with cerebral palsy: A brief report1

PURPOSE

The aim of the study was to estimate the energy expenditure (EE) during a quiet standing task in children with bilateral spastic CP (BSCP) in comparison with typically developing (TD) children, using gas analyzer.

METHODS

The study was an observational cross-sectional study of children with BSCP (Gross Motor Function Classification System [GMFCS] levels II and III; n = 30; 10 males, 20 females; mean weight 27.46 kgs; mean age 10 years) and TD children (n = 30; 16 males, 14 females; mean weight 25.35 kgs; mean age 9 years, 9 months). The energy expenditure during quiet standing task was measured by using Cosmed K4b2 gas analyzer and expressed in terms of peak oxygen consumption (VO2 max, ml/kg body weight/min).

RESULTS

Children with BSCP expended 1.4 times higher energy during standing than TD children (p< 0.0001).

CONCLUSION

We identified that standing puts an additional energy demand in ambulant children with BSCP. Findings suggest that both dependant and independent ambulating children with BSCP might need to exert more effort to maintain a static standing position. Therefore, clinicians must evaluate standing position for balance control and energy expenditure to evaluate the efficiency of physical therapy and rehabilitation.

A new method to calculate external mechanical work using force-platform data in ecological situations in humans: Application to Parkinson's disease

BACKGROUND AND AIM

To accurately quantify the cost of physical activity and to evaluate the different components of energy expenditure in humans, it is necessary to evaluate external mechanical work (WEXT). Large platform systems surpass other currently used techniques. Here, we describe a calculation method for force-platforms to calculate long-term WEXT.

METHODS

Each force-platform (2.46×1.60m and 3.80×2.48m) rests on 4 piezoelectric sensors. During long periods of recording, a drift in the speed of displacement of the center of mass (necessary to calculate WEXT) is generated. To suppress this drift, wavelet decomposition is used to low-pass filter the source signal. By using wavelet decomposition coefficients, the source signal can be recovered. To check the validity of WEXT calculations after signal processing, an oscillating pendulum system was first used; then, 10 healthy subjects performed a standardized exercise (squatting exercise). A medical application is also reported in eight Parkinsonian patients during the timed "get-up and go" test and compared with the same test in ten healthy subjects.

RESULTS

Values of WEXT with the oscillating pendulum showed that the system was accurate and reliable. During the squatting exercise, the average measured WEXT was 0.4% lower than theoretical work. WEXT and mechanical work efficiency during the "get-up and go" test in Parkinson's disease patients in comparison with that of healthy subjects were very coherent.

CONCLUSIONS

This method has numerous applications for studying physical activity and mechanical work efficiency in physiological and pathological conditions.

External Mechanical Work and Pendular Energy Transduction of Overground and Treadmill Walking in Adolescents with Unilateral Cerebral Palsy

PURPOSE

Motor impairments affect functional abilities and gait in children and adolescents with cerebral palsy (CP). Improving their walking is an essential objective of treatment, and the use of a treadmill for gait analysis and training could offer several advantages in adolescents with CP. However, there is a controversy regarding the similarity between treadmill and overground walking both for gait analysis and training in children and adolescents. The aim of this study was to compare the external mechanical work and pendular energy transduction of these two types of gait modalities at standard and preferred walking speeds in adolescents with unilateral cerebral palsy (UCP) and typically developing (TD) adolescents matched on age, height and body mass.

METHODS

Spatiotemporal parameters, external mechanical work and pendular energy transduction of walking were computed using two inertial sensors equipped with a triaxial accelerometer and gyroscope and compared in 10 UCP (14.2 ± 1.7 year) and 10 TD (14.1 ± 1.9 year) adolescents during treadmill and overground walking at standard and preferred speeds.

RESULTS

The treadmill induced almost identical mechanical changes to overground walking in TD adolescents and those with UCP, with the exception of potential and kinetic vertical and lateral mechanical works, which are both significantly increased in the overground-treadmill transition only in UCP (P < 0.05).

CONCLUSIONS

Adolescents with UCP have a reduced adaptive capacity in absorbing and decelerating the speed created by a treadmill (i.e., dynamic stability) compared to TD adolescents. This may have an important implication in rehabilitation programs that assess and train gait by using a treadmill in adolescents with UCP.

Toe walking: causes, epidemiology, assessment, and treatment

PURPOSE OF REVIEW

The present review includes the most up-to-date literature on the causes, epidemiology, diagnosis, and treatment of toe walking.

RECENT FINDINGS

The prevalence of toe walking at age 5.5 years is 2% in normally developing children, and 41% in children with a neuropsychiatric diagnosis or developmental delays. A recent systematic review concluded that there is good evidence for casting and surgery in the treatment of idiopathic toe walking, with only surgery providing long-term results beyond 1 year. Botox combined with casting does not provide better outcomes compared with casting alone. Ankle-foot-orthoses restrict toe walking when worn, but children revert to equinus gait once the orthosis is removed.

SUMMARY

Toe walking can occur because of an underlying anatomic or neuromuscular condition, but in the majority of cases toe walking is idiopathic, without a discernable underlying cause. For some families, toe walking may simply be a cosmetic concern, whereas in other cases it can cause pain or functional issues. Treatment for toe walking is based on age, underlying cause, and the severity of tendon contracture. Described treatments include casting, chemical denervation, orthotics, physical therapy, and surgical lengthening of the gastroc-soleus-Achilles complex. A careful history, clinical exam, and selective diagnostic testing can be used to differentiate between different types of toe walking and determine the most appropriate treatment for each child.

Kinematic foot types in youth with equinovarus secondary to hemiplegia

BACKGROUND

Elevated kinematic variability of the foot and ankle segments exists during gait among individuals with equinovarus secondary to hemiplegic cerebral palsy (CP). Clinicians have previously addressed such variability by developing classification schemes to identify subgroups of individuals based on their kinematics.

OBJECTIVE

To identify kinematic subgroups among youth with equinovarus secondary to CP using 3-dimensional multi-segment foot and ankle kinematics during locomotion as inputs for principal component analysis (PCA), and K-means cluster analysis.

METHODS

In a single assessment session, multi-segment foot and ankle kinematics using the Milwaukee Foot Model (MFM) were collected in 24 children/adolescents with equinovarus and 20 typically developing children/adolescents.

RESULTS

PCA was used as a data reduction technique on 40 variables. K-means cluster analysis was performed on the first six principal components (PCs) which accounted for 92% of the variance of the dataset. The PCs described the location and plane of involvement in the foot and ankle. Five distinct kinematic subgroups were identified using K-means clustering. Participants with equinovarus presented with variable involvement ranging from primary hindfoot or forefoot deviations to deformtiy that included both segments in multiple planes.

CONCLUSION

This study provides further evidence of the variability in foot characteristics associated with equinovarus secondary to hemiplegic CP. These findings would not have been detected using a single segment foot model. The identification of multiple kinematic subgroups with unique foot and ankle characteristics has the potential to improve treatment since similar patients within a subgroup are likely to benefit from the same intervention(s).

Decrease in ankle-foot dorsiflexion range of motion is related to increased knee flexion during gait in children with spastic cerebral palsy

PURPOSE

To determine the effects of decreased ankle-foot dorsiflexion (A-Fdf) range of motion (ROM) on gait kinematics in children with spastic cerebral palsy (SCP).

METHODS

All participants were children with spastic cerebral palsy (n = 10) who walked with knee flexion in midstance. Data were collected over 2-5 sessions, at 3-monthly intervals. A-Fdf ROM was quantified using a custom-designed hand-held ankle dynamometer that exerted 4 Nm at the ankle. Ankle-foot and knee angles during gait were quantified on sagittal video recordings. Linear regression (cross-sectional analysis) and General Estimation Equation analysis (longitudinal analysis) were performed to assess relationships between (change in) A-Fdf ROM and (change in) ankle-foot and knee angle during gait.

RESULTS

Cross-sectional analysis showed a positive relationship between A-Fdf ROM and both ankle-foot angle in midstance and terminal swing. Longitudinal analysis showed a positive relationship between individual decreases in A-Fdf ROM and increases of knee flexion during gait (lowest knee angle in terminal stance and angle in terminal swing).

CONCLUSION

For this subgroup of SCP children, our results indicate that while changes in ankle angles during gait are unrelated to changes in A-Fdf ROM, changes in knee angles are related to changes in A-Fdf ROM.

Center of mass mechanics of chimpanzee bipedal walking

Center of mass (CoM) oscillations were documented for 81 bipedal walking strides of three chimpanzees. Full-stride ground reaction forces were recorded as well as kinematic data to synchronize force to gait events and to determine speed. Despite being a bent-hip, bent-knee (BHBK) gait, chimpanzee walking uses pendulum-like motion with vertical oscillations of the CoM that are similar in pattern and relative magnitude to those of humans. Maximum height is achieved during single support and minimum height during double support. The mediolateral oscillations of the CoM are more pronounced relative to stature than in human walking when compared at the same Froude speed. Despite the pendular nature of chimpanzee bipedalism, energy recoveries from exchanges of kinetic and potential energies are low on average and highly variable. This variability is probably related to the poor phasic coordination of energy fluctuations in these facultatively bipedal animals. The work on the CoM per unit mass and distance (mechanical cost of transport) is higher than that in humans, but lower than that in bipedally walking monkeys and gibbons. The pronounced side sway is not passive, but constitutes 10% of the total work of lifting and accelerating the CoM. CoM oscillations of bipedally walking chimpanzees are distinctly different from those of BHBK gait of humans with a flat trajectory, but this is often described as "chimpanzee-like" walking. Human BHBK gait is a poor model for chimpanzee bipedal walking and offers limited insights for reconstructing early hominin gait evolution.

Validity of an activity monitor in young people with cerebral palsy gross motor function classification system level I

The activPAL™ activity monitor has potential for use in youth with Cerebral Palsy (CP) as it has demonstrated acceptable validity for the assessment of sedentary and physical activity in other populations. This study determined the validity of the activPAL™ activity monitor for the measurement of sitting, standing, walking time, transitions and step count for both legs in young people with hemiplegic and asymmetric diplegic CP. Seventeen participants with CP Gross Motor Function Classification System level I completed two video recorded test protocols that involved wearing an activPAL™ activity monitor on alternate legs. Agreement between observed video recorded data and activPAL™ activity monitor data was assessed using the Bland and Altman (BA) method and intraclass correlation coefficients (ICC 3,1). There was perfect agreement for transitions and high agreement for sitting (BA mean differences (MD): -1.8 and -1.8 s; ICCs: 0.49 and 0.95) standing (MD: 0.8 and 0.1 s; ICCs: 0.59 and 0.98) walking (MD: 1 and 1.1 s; ICCs: 0.99 and 0.94) timings and low agreement for step count (MD: 4.1 and 2.8 steps; ICCs: 0.96 and 0.95) for both legs. This study found clinically acceptable agreement with direct observation for all activPAL™ activity monitor functions, except for step count measurement with respect to the range of measurement values obtained for both legs in this study population.

Mechanical work and energy consumption in children with cerebral palsy after single-event multilevel surgery

Multilevel surgery is commonly performed to improve walking in children with cerebral palsy (CP). Classical gait analysis (kinetics, kinematics) demonstrated positive outcomes after this intervention, however it doesn't give global indication about gait's features. The assessment of energy cost and mechanical work of locomotion can provide an overall description of walking functionality. Therefore, we propose to describe the effects of multilevel surgery in children with CP, considering energetics, mechanical work, kinetic and kinematic of walking. We measured external, internal, total work, energy cost, recovery, efficiency, kinetic and kinematic of walking in 10 children with CP (4 girls, 6 boys; 13 years ± 2) before and 1 year after multilevel surgery. Kinetic and kinematic results are partially comparable to previous findings, energy cost of walking is significantly reduced (p < 0.05); external, internal, total work, recovery, efficiency are not significantly different (p = 0.129; p = 0.147; p = 0.795; p = 0.119; p = 0.21). The improvement of the walking's energy consumption is not accompanied by a corresponding improvement of mechanical work. Therefore it is conceivable that the improvement of walking economy depend on a reduced effort of the muscle to maintain the posture, rather then to an improvement of the mechanism of energy recovery typical of human locomotion.

Flexed-knee gait in children with cerebral palsy: a 10-year follow-up study

BACKGROUND

While several studies have evaluated the short-term effectiveness of conservative and surgical treatment of flexed-knee gait in children with cerebral palsy (CP), few have explored the long-term outcomes using gait analysis. The purpose of this study was to examine, through gait analysis, the 10-year outcomes of flexed-knee gait in children with CP.

METHODS

Ninety-seven children with spastic CP who walked with a flexed-knee gait underwent two gait evaluations [age 6.1 ± 2.1 and 16.2 ± 2.3 years, Gross Motor Function Classification System (GMFCS) I (12), II (45), III (37), IV (3)]. Limbs with knee flexion at initial contact >15° were considered walking with a flexed-knee gait and were included in the study (n = 185). Kinematic data were collected using an eight-camera motion analysis system (Motion Analysis, Santa Rosa, CA). Surgical and therapeutic interventions were not controlled.

RESULTS

A comparison between the two gait studies showed an overall improvement in gait at 10 years follow-up. Significant improvements were seen in knee flexion at initial contact, Gait Deviation Index (GDI), Gross Motor Function Measure (GMFM), and gait speed (P < 0.01 for all). Outcome was also evaluated based on the severity of flexed-knee gait at the initial visit, with functional skills and overall gait (GDI) improving in all groups (P < 0.01 for all). The group with a severe flexed-knee gait exhibited the most improvement, while subjects with a mild flexed-knee improved the least.

CONCLUSIONS

Children at a specialty hospital whose orthopedic care included gait analysis and multi-level surgery showed improvement of flexed-knee gait and gross motor function over a 10-year course, regardless of the initial severity.

Motion of the center of mass in children with spastic hemiplegia: balance, energy transfer, and work performed by the affected leg vs. the unaffected leg

Asymmetry between limbs in people with spastic hemiplegic cerebral palsy (HEMI) adversely affects limb coordination and energy generation and consumption. This study compared how the affected leg and the unaffected leg of children with HEMI would differ based on which leg trails. Full-body gait analysis data and force-plate data were analyzed for 31 children (11.9 ± 3.8 years) with HEMI and 23 children (11.1 ± 3.1 years) with typical development (TD). Results showed that peak posterior center of mass-center of pressure (COM-COP) inclination angles of HEMI were smaller than TD when the affected leg trailed but not when the unaffected leg trailed. HEMI showed greater peak medial COM-COP inclination angles and wider step width than TD, no matter which leg trailed. More importantly, when the affected leg of HEMI trailed, it did not perform enough positive work during double support to propel COM motion. Consequently, the unaffected leg had to perform additional positive work during the early portion of single support, which costs more energy. When the unaffected leg trailed, the affected leg performed more negative work during double support; therefore, more positive work was still needed during early single support, but energy efficiency was closer to that of TD. Energy recovery factor was lower when the affected leg trailed than when the unaffected leg trailed; both were lower than TD. These findings suggest that the trailing leg plays a significant role in propelling COM motion during double support, and the 'unaffected' side of HEMI may not be completely unaffected. It is important to strengthen both legs.

Optimising Ankle Foot Orthoses for children with cerebral palsy walking with excessive knee flexion to improve their mobility and participation; protocol of the AFO-CP study

Background

Ankle-Foot-Orthoses with a ventral shell, also known as Floor Reaction Orthoses (FROs), are often used to reduce gait-related problems in children with spastic cerebral palsy (SCP), walking with excessive knee flexion. However, current evidence for the effectiveness (e.g. in terms of walking energy cost) of FROs is both limited and inconclusive. Much of this ambiguity may be due to a mismatch between the FRO ankle stiffness and the patient’s gait deviations.

The primary aim of this study is to evaluate the effect of FROs optimised for ankle stiffness on the walking energy cost in children with SCP, compared to walking with shoes alone. In addition, effects on various secondary outcome measures will be evaluated in order to identify possible working mechanisms and potential predictors of FRO treatment success.

Method/Design

A pre-post experimental study design will include 32 children with SCP, walking with excessive knee flexion in midstance, recruited from our university hospital and affiliated rehabilitation centres. All participants will receive a newly designed FRO, allowing ankle stiffness to be varied into three configurations by means of a hinge. Gait biomechanics will be assessed for each FRO configuration. The FRO that results in the greatest reduction in knee flexion during the single stance phase will be selected as the subject’s optimal FRO. Subsequently, the effects of wearing this optimal FRO will be evaluated after 12–20 weeks. The primary study parameter will be walking energy cost, with the most important secondary outcomes being intensity of participation, daily activity, walking speed and gait biomechanics.

Discussion

The AFO-CP trial will be the first experimental study to evaluate the effect of individually optimised FROs on mobility and participation. The evaluation will include outcome measures at all levels of the International Classification of Functioning, Disability and Health, providing a unique set of data with which to assess relationships between outcome measures. This will give insights into working mechanisms of FROs and will help to identify predictors of treatment success, both of which will contribute to improving FRO treatment in SCP in term.

Trial registration

This study is registered in the Dutch Trial Register as NTR3418.

Mesh Achilles tendon lengthening--a new method to treat equinus deformity in patients with spastic cerebral palsy: surgical technique and early results

Equinus of the ankle is a common deformity in spastic cerebral palsy. Many methods have been developed to lengthen the Achilles tendon to correct the deformity. A new mesh Achilles tendon lengthening (ATL) procedure that might decrease immobilization and promote recovery was performed in 36 tendons with equinus deformity (22 patients, average age=6.2). The results were compared with those of two other methods: the Vulpius group and the Z-lengthening group. The corrected dorsiflexion angle of the ankle at a subsequent 2-year follow-up of the mesh ATL and Vulpius groups matched (25.5±3.0 and 27.1±3.5°, respectively), whereas that of the Z-lengthening group was higher (33.9±3.8°). Nevertheless, statistics of the timing of each patient's readiness to begin rehabilitation and walking as well as gaining better stability for running and one-legged hopping indicated that the mesh ATL group recovered significantly quicker than the Vulpius and Z-lengthening groups. The mesh ATL procedure achieves a successful correction of the equinus deformity in spastic cerebral palsy comparable with that of the Vulpius procedure, with the advantage of preserving the gastrocnemius without a complete section. This confers greater antigravity stability and quicker recovery in patients.

Increased mechanical cost of walking in children with diplegia: the role of the passenger unit cannot be neglected

Gait efficiency in children with cerebral palsy is decreased. To date, most research did not include the upper body as a separate functional unit when exploring these changes in gait efficiency. Since children with spastic diplegia often experience problems with trunk control, they could benefit from separate evaluation of the so-called 'passenger unit'. Therefore, the aim of the current study was to improve insights in the role of the passenger unit in decreased gait efficiency in children with diplegia. Mechanical cost of walking was investigated by calculating work by the integrated joint power approach in 18 children with diplegia and 25 age-related typical developing controls. The total mechanical work in children with diplegia was 1.5 times higher than in typical children. In children with diplegia work at the lower limbs was increased by 37% compared to typical children. Substantially higher increases, up to 222%, were noted at the passenger unit. Trunk and head were the main contributors to the increased work of the passenger unit, but the role of the arms cannot be neglected. Due to these disproportional increases in locomotor and passenger unit, the demands of the passenger unit in pathological gait can no longer be considered minor, as in typical gait. Therefore, the role of the passenger unit must be recognized in the decrease of gait efficiency in children with spastic diplegia and should be part of the evaluation of gait efficiency in clinical practice.

A unified deformable (UD) segment model for quantifying total power of anatomical and prosthetic below-knee structures during stance in gait

Anatomically-relevant (AR) biomechanical models are traditionally used to quantify joint powers and segmental energies of lower extremity structures during gait. While AR models contain a series of rigid body segments linked together via mechanical joints, prosthetic below-knee structures are often deformable objects without a definable ankle joint. Consequently, the application of AR models for the study of prosthetic limbs has been problematic. The purpose of this study was to develop and validate a unified deformable (UD) segment model for quantifying the total power of below-knee structures. Estimates of total below-knee power derived via the UD segment model were compared to those derived via an AR model during stance in gait of eleven healthy subjects. The UD segment model achieved similar results to the AR model. Differences in peak power, total positive work, and total negative work were 1.91±0.31%, 3.97±0.49%, and 1.39±0.33%, relative to the AR model estimates. The main advantage of the UD segment model is that it does not require the definition of an ankle joint or foot structures. Therefore, this technique may be valuable for facilitating direct comparisons between anatomical and disparate prosthetic below-knee structures in future studies.

Fatigue in cerebral palsy: a critical review

OBJECTIVE

Fatigue contributes to the deterioration or cessation of walking ability in adults with cerebral palsy (CP). However, conflict exists as to its role. Studies involving functional tasks reported increased, and earlier onset of, fatigue in CP, whereas laboratory studies have reported individuals with CP to be more fatigue-resistant than their peers.

METHODS

A critical review of the literature related to fatigue in CP was conducted.

RESULTS

This review describes factors that contribute to the observed fatigue resistance in laboratory tasks and how a decreased force-production in CP can result in higher energy expenditure to perform the same amount of work as their peers.

CONCLUSION

More research regarding the process of fatigue and recovery for individuals with CP is needed; specifically studies that focus on functional movements requiring the integration of the whole body, thereby stressing the neuromuscular system in a different way than previously explored.

Energetic cost of walking with increased step variability

Step-by-step variations occur during normal human walking, induced in part by imperfect sensorimotor control and naturally occurring random perturbations. These effects might increase energy expenditure during walking, because they differ from the nominal preferred gait, which is typically the most economical, and because of the cost of making active feedback adjustments to maintain gait stability. We tested this hypothesis by artificially inducing greater step variability through visual perturbations from a virtual reality display, and measuring the effect on energy expenditure. Young healthy adult subjects (N=11) walked on a treadmill while viewing a virtual hallway, to which virtual perturbations were applied in fore-aft or medio-lateral directions. The greatest effect on gait was achieved with medio-lateral visual perturbations, which resulted in a 65% increase in step width variability and a 5.9% increase (both P<0.05) in net metabolic rate compared to walking without perturbations. Perturbations generally induced greater variability in both step width and (to a lesser degree) step length, and also induced slightly wider and (to a lesser degree) shorter mean steps. Each of these measures was found to correlate significantly with each other, regardless of perturbation direction and magnitude. They also correlated with metabolic rate (P<0.05 for each separate measure), despite explaining only a modest proportion of overall energetic variations (R(2)<0.40). Step variability increases with some gait disorders and with increasing age. Our results suggest that imperfect sensorimotor control may contribute to the increased metabolic cost of walking observed with such conditions.

Splint: the efficacy of orthotic management in rest to prevent equinus in children with cerebral palsy, a randomised controlled trial

BACKGROUND

Range of motion deficits of the lower extremity occur in about the half of the children with spastic cerebral palsy (CP). Over time, these impairments can cause joint deformities and deviations in the children's gait pattern, leading to limitations in moblity. Preventing a loss of range of motion is important in order to reduce secondary activity limitations and joint deformities. Sustained muscle stretch, imposed by orthotic management in rest, might be an effective method of preventing a decrease in range of motion. However, no controlled study has been performed.

METHODS

A single blind randomised controlled trial will be performed in 66 children with spastic CP, divided over three groups with each 22 participants. Two groups will be treated for 1 year with orthoses to prevent a decrease in range of motion in the ankle (either with static or dynamic knee-ankle-foot-orthoses) and a third group will be included as a control group and will receive usual care (physical therapy, manual stretching). Measurements will be performed at baseline and at 3, 6, 9 and 12 months after treatment allocation. The primary outcome measure will be ankle dorsiflexion at full knee extension, measured with a custom designed hand held dynamometer. Secondary outcome measures will be i) ankle and knee flexion during gait and ii) gross motor function. Furthermore, to gain more insight in the working mechanism of the orthotic management in rest, morphological parameters like achilles tendon length, muscle belly length, muscle fascicle length, muscle physiological cross sectional area length and fascicle pennation angle will be measured in a subgroup of 18 participants using a 3D imaging technique.

DISCUSSION

This randomised controlled trial will provide more insight into the efficacy of orthotic management in rest and the working mechanisms behind this treatment. The results of this study could lead to improved treatments.

TRIAL REGISTRATION NUMBER

Nederlands Trial Register NTR2091.

Mechanical energy estimation during walking: validity and sensitivity in typical gait and in children with cerebral palsy

Gait efficiency in children with cerebral palsy is usually quantified by metabolic energy expenditure. Mechanical energy estimations, however, can be a valuable supplement as they can be assessed during gait analysis and plotted over the gait cycle, thus revealing information on timing and sources of increases in energy expenditure. Unfortunately, little information on validity and sensitivity exists. Three mechanical estimation approaches: (1) centre of mass (CoM) approach, (2) sum of segmental energies (SSE) approach and (3) integrated joint power approach, were validated against oxygen consumption and each other. Sensitivity was assessed in typical gait and in children with diplegia. CoM approach underestimated total energy expenditure and showed poor sensitivity. SSE approach overestimated energy expenditure and showed acceptable sensitivity. Validity and sensitivity were best in the integrated joint power approach. This method is therefore preferred for mechanical energy estimation in children with diplegia. However, mechanical energy should supplement, not replace metabolic energy, as total energy expended is not captured in any mechanical approach.

The gait of children with and without cerebral palsy: work, energy, and angular momentum

This paper describes a method to characterize gait pathologies like cerebral palsy using work, energy, and angular momentum. For a group of 24 children, 16 with spastic diplegic cerebral palsy and 8 typically developed, kinematic data were collected at the subjects self selected comfortable walking speed. From the kinematics, the work-internal, external, and whole body; energy-rotational and relative linear; and the angular momentum were calculated. Our findings suggest that internal work represents 53% and 40% respectively of the whole body work in gait for typically developed children and children with cerebral palsy. Analysis of the angular momentum of the whole body, and other subgroupings of body segments, revealed a relationship between increased angular momentum and increased internal work. This relationship allows one to use angular momentum to assist in determining the kinetics and kinematics of gait which contribute to increased internal work. Thus offering insight to interventions which can be applied to increase the efficiency of bipedal locomotion, by reducing internal work which has no direct contribution to center of mass motion, in both normal and pathologic populations.

A multivariate model of determinants of change in gross-motor abilities and engagement in self-care and play of young children with cerebral palsy

A multivariate model of determinants of change in gross-motor ability and engagement in self-care and play provides physical and occupational therapists a framework for decisions on interventions and supports for young children with cerebral palsy and their families. Aspects of the child, family ecology, and rehabilitation and community services may influence children's activity and participation. Aspects of the child include primary and secondary impairments, associated and comorbid health conditions, and adaptive behaviors. Literature support for the model is reviewed. A clinical scenario illustrates the use of the model as a framework for practice. The model encourages therapists to broaden the focus of rehabilitation services for young children with CP to include not only development of motor abilities but also comprehensive interventions and supports to enhance participation in daily activities and routines. Therapists are encouraged to consider how child, family, and service factors interact when planning interventions and evaluating outcomes.

Gait in thoracolumbar/lumbar adolescent idiopathic scoliosis: effect of surgery on gait mechanisms

For patients whose scoliosis progresses, surgery remains the ultimate way to correct and stabilise the deformity while maintaining as many mobile spinal segments as possible. In thoracolumbar/lumbar adolescent idiopathic scoliosis (AIS), the spinal fusion has to be extended to the lumbar spine. The use of anterior spinal fusion (ASF) instead of the classic posterior fusion (PSF) may preserve more distal spinal levels in attempt to limit the consequences of surgery on trunk mobility. The effects of surgery on body shape, pain and the decompensation phenomenon have all been well evaluated. Very few studies have addressed the effect of ASF or PSF on basic activities, such as walking. Before any treatment, AIS patients already have reduced pelvis, hip and shoulder motion when walking at a normal speed compared with adolescents without scoliosis (control group). Additionally, they have longer contraction time of the lumbar and pelvic muscles leading to an excessive energy cost and reduced muscle efficiency. In addition, if these changes are associated with spinal stiffness, spinal fusion could further negatively affect this pre-surgical inefficient walk. The goals of this study were (a) to compare pre- and 1-year post-surgery conditions in order to assess the effects of spinal arthrodesis on gait parameters and (b) to compare the anterior versus the posterior surgical approaches. Nineteen young females with thoracolumbar/lumbar AIS were assessed by radiological and clinical examination and by conventional gait analysis before surgery and at almost 12 months after surgery. Seven subjects underwent surgery using ASF and 12 using PSF. Three-dimensional gait analysis was performed on a motor-driven treadmill at spontaneous self-selected speed to record kinematic, electromyographic (EMG), mechanical and energetic measurements synchronously. Although it was expected that the instrumentation would modify the characteristics of normal walking, this study showed that surgery does not induce asymmetric gait or any significant differences between the ASP and the PSF surgery groups. One year after surgery, the changes observed consisted of improvements in the gait and mechanical parameters. In the PSF group, 11-14 vertebrae were fused while only 3-4 were fused in the ASF group. In both AIS groups, step length was increased by 4% and cadence reduced by 2%. There was a slight increase in pelvis and hip frontal motion. Only the transverse shoulder motion was mildly decreased by 1.5 degrees . All the other gait parameters were left unchanged or were improved by surgery. Notably, the EMG timing activity did not change. The total muscular mechanical work (W (tot)) increased by 6% mainly due to the external work (W (ext)), i.e. the work performed by the body muscles to move the body in its surroundings. The energy cost, although showing a tendency towards a reduction, remained globally excessive, probably due to the excessive co-contraction of the lumbo-pelvic muscles.

Walking economy in people with Parkinson's disease

Gait dysfunction is an early problem identified by patients with Parkinson's disease (PD). Alterations in gait may result in an increase in the energy cost of walking (i.e., walking economy). The purpose of this study was to determine whether walking economy is atypical in patients with PD when compared with healthy controls. A secondary purpose was to evaluate the associations of age, sex, and level of disease severity with walking economy in patients with PD. The rate of oxygen consumption (VO(2)) and other responses to treadmill walking were compared in 90 patients (64.4 +/- 10.3 years) and 44 controls (64.6 +/- 7.3 years) at several walking speeds. Pearson correlation coefficients (r) were calculated to determine relationships of age, sex, and disease state with walking economy in PD patients. Walking economy was significantly worse in PD patients than in controls at all speeds above 1.0 mph. Across all speeds, VO(2) was 6 to 10% higher in PD patients. Heart rate, minute ventilation, respiratory exchange ratio, and rating of perceived exertion were correspondingly elevated. No significant relationship of age, sex, or UPDRS score with VO(2) was found for patients with PD. The findings suggest that the physiologic stress of daily physical activities is increased in patients with early to mid-stage PD, and this may contribute to the elevated level of fatigue that is characteristic of PD.

Gait in adolescent idiopathic scoliosis: energy cost analysis

Walking is a very common activity for the human body. It is so common that the musculoskeletal and cardiovascular systems are optimized to have the minimum energetic cost at 4 km/h (spontaneous speed). A previous study showed that lumbar and thoracolumbar adolescent idiopathic scoliosis (AIS) patients exhibit a reduction of shoulder, pelvic, and hip frontal mobility during gait. A longer contraction duration of the spinal and pelvic muscles was also noted. The energetic cost (C) of walking is normally linked to the actual mechanical work muscles have to perform. This total mechanical work (W(tot)) can be divided in two parts: the work needed to move the shoulders and lower limbs relative to the center of mass of the body (COM(b)) is known as the internal work (W(int)), whereas additional work, known as external work (W(ext)), is needed to accelerate and lift up the COM(b) relative to the ground. Normally, the COM(b) goes up and down by 3 cm with every step. Pathological walking usually leads to an increase in W (tot) (often because of increased vertical displacement of the COM(b)), and consequently, it increases the energetic cost. The goal of this study is to investigate the effects of scoliosis and scoliosis severity on the mechanical work and energetic cost of walking. Fifty-four female subjects aged 12 to 17 were used in this study. Thirteen healthy girls were in the control group, 12 were in scoliosis group 1 (Cobb angle [Cb] < or = 20 degrees), 13 were in scoliosis group 2 (20 degrees < Cb < 40 degrees), and 16 were in scoliosis group 3 (Cb > or = 40 degrees). They were assessed by physical examination and gait analysis. The 41 scoliotic patients had an untreated progressive left thoracolumbar or lumbar AIS. During gait analysis, the subject was asked to walk on a treadmill at 4 km h(-1). Movements of the limbs were followed by six infrared cameras, which tracked markers fixed on the body. W(int) was calculated from the kinematics. The movements of the COM(b) were derived from the ground reaction forces, and W(ext) was calculated from the force signal. W(tot) was equal to W(int) + W(ext). Oxygen consumption VO2 was measured with a mask to calculate energetic cost (C) and muscular efficiency (W(tot)/C). Statistical comparisons between the groups were performed using an analysis of variance (ANOVA). The external work (W(ext)) and internal work (W(int)) were both reduced from 7 to 22% as a function of the severity of the scoliosis curve. Overall, the total muscular mechanical work (W(tot)) was reduced from 7% to 13% in the scoliosis patients. Within scoliosis groups, the W(ext) for the group 1 (Cb > or = 20 degrees) and 2 (20 < or = Cb < or = 40 degrees) was significantly different from group 3 (Cb > or = 40 degrees). No significant differences were observed between scoliosis groups for the W(int). The W(tot) did not showed any significant difference between scoliosis groups except between group 1 and 3. The energy cost and VO2 were increased by around 30%. As a result Muscle efficiency was significantly decreased by 23% to 32%, but no significant differences related to the severity of the scoliosis were noted. This study shows that scoliosis patients have inefficient muscles during walking. Muscle efficiency was so severely decreased that it could be used as a diagnostic tool, since every scoliosis patient had an average muscle efficiency below 27%, whereas every control had an average muscle efficiency above 27%. The reduction of mechanical work found in scoliotic patients has never been observed in any pathological gait, but it is interpreted as a long term adaptation to economize energy and face poor muscle efficiency. With a relatively stiff gait, scoliosis patients also limit vertical movement of the COM(b) (smoothing the gait) and consequently, reduce W(ext) and W(int). Inefficiency of scoliosis muscles was obvious even in mild scoliosis (group 1, Cb < 20 degrees) and could be related to the prolonged muscle contraction time observed in a previous study (muscle co-contraction).

Using cognitive interviewing for test items to assess physical function in children with cerebral palsy

PURPOSE

The purpose of this study was to assess the content, format, and comprehension of test items and responses developed for use in a computer adaptive test (CAT) of physical function for children with cerebral palsy (CP).

METHODS

After training in cognitive interviewing techniques, investigators defined item intent and developed questions for each item. Parents of children with CP (n = 27) participated in interviews probing item meaning, item wording, and response choice adequacy and appropriateness.

RESULTS

Qualitative analysis identified 3 themes: item clarity; relevance, context, and attribution; and problems with wording or tone. Parents reported the importance of delineating task components, assistance amount, and environmental context.

CONCLUSION

Cognitive interviewing provided valuable information about the validity of new items and insight to improve relevance and context. We believe that the development of CATs in pediatric rehabilitation may ultimately reduce the impact of the issues identified.