Center of Mass Movement and Energy Transfer During Walking in Children With Cerebral Palsy

Factors associated with gait efficiency in children with cerebral palsy: association between gait abnormality and balance ability

[Purpose] Children with cerebral palsy require more gait energy than healthy children. The association between gait abnormalities and gait efficiency remains unclear. We investigated the association between gait abnormalities, balance, and maximum step length to determine contributors to gait efficiency in children with cerebral palsy. [Participants and Methods] The study included 33 patients with cerebral palsy, who could walk without the use of walking aids. All participants were instructed to walk for 6 min, and the Total Heart Beat Index was calculated as a measure of walking efficiency. The Edinburgh Visual Gait Score was used to assess gait abnormalities. Additionally, the maximum step length was recorded, and all participants performed the Berg Balance Scale. Correlation analysis and stepwise multiple regression analysis were used to confirm the association between the aforementioned parameters and the Total Heart Beat Index. [Results] The Edinburgh Visual Gait Score was correlated with the heel lift during the stance, knee position during the terminal swing of gait as factors associated with the Total Heartbeat Index. The Berg Balance Scale was correlated with turning 360°, standing with feet together. [Conclusion] Our findings emphasize the need for treatment strategies focused on gait abnormalities and balance.

Biomechanical Analysis of the Unaffected Limb While Using a Hands-Free Crutch

Basic human ambulation relies on a bipedal gait, which has been reported to be directly related to quality of life. However, injuries to the lower limb can cause an inability to walk and require non-weightbearing periods to heal. Among the many ambulatory aids, standard axillary crutches are prescribed. However, due to the disadvantages of having to use both hands, a slow gait, pain, nerve damage, and gait patterns that differ from that of healthy subjects, currently, a new generation of ambulatory aids has emerged. Among such aids, hands-free crutches (HFCs) are of particular interest due to their form factor, which does not require the use of the hands and facilitates a bipedal gait. In this study, we present an assessment of whether any different gait patterns, compared to overground gait, appeared on the unaffected limb during walking with an HFC. The spatiotemporal parameters, plantar force, lower-limb joint angles, and EMG patterns were evaluated. In conclusion, the results from 10 healthy subjects suggest that wearing an HFC causes only slight changes in the biomechanical gait patterns examined in the unaffected limb compared with overground walking without an HFC.

Simulation study on assist-as-needed control of a rehabilitation robotic walker

BACKGROUND

Along with China entering an aging society, the percentage of people that over 60 will reach 34.9% in 2050, resulted in a significant increase in stroke patients.

OBJECTIVE

This paper proposes a rehabilitation robotic walker for walking assistance during the daily life, and a control method for the motor relearning during the gait training. The walker consists of an omni-directional mobile platform (OMP) which ensures the walker can move on the ground, a body weight support system (BWS) which is capable of providing the desired unloading force, and a pelvic assist mechanism (PAM) to provide the user with four degrees of freedom and avoid the rigid impact. The study goal is to gain a better understanding of the assist-as-needed control strategy during the gait training.

METHODS

For the man-machine interaction control, the assist-as-needed control strategy is adopted to guide the users' motions and improve the interaction experience. To build the force field in the three-dimensional space, the dynamics of the system is derived to increase the accuracy of force control.

RESULTS

The simulation results show that the force field around the motion trajectory was generated in the three-dimensional space. In order to understand the force field, we designed the simulation on sagittal plane and the controller can generate the appropriate force field. The preliminary experiment results were consistent with the simulation results.

CONCLUSION

Based on the mathematical simulation and the preliminary test, the results demonstrate that the proposed system can provide the guide force around the target trajectory, the accuracy of force control still remains to be improved.

Energy analysis of gait in patients with down syndrome

Background

the primary aim of this study is to analyse the energy parameters of patients with Down syndrome compared to a control group and secondly to verify whether the sport activity leads to differences in energy expenditure.

Methods

3 groups of subjects were identified: 8 healthy subjects and 147 subjects with Down syndrome, of whom 14 played sports at least once a week. An energy index was calculated, given by the ratio between potential and kinetic energy. Next, kinetic ad potential energy parameters were extrapolated at 60% of the gait cycle (propulsion phase).

Findings

Down syndrome group was compared with the control group and emerged that the energy index was higher in the first one. No changes were found between Down syndrome and Down syndrome Sport groups. The analysis of the energy parameters showed that all parameters, except the medio-lateral kinetic energy, were higher in the control than in the Down syndrome groups. The potential energy, medio-lateral kinetic energy, and vertical were higher in the Down syndrome Sport group than in the Down syndrome group. The kinetic energy and the mean velocity were higher in the control group than in Down syndrome Sport group while the medio-lateral kinetic energy was lower.

Interpretation

sport modified the parameter of potential energy but not that of kinetic energy, which continued to be different compared to the healthy group and increased the oscillations in the medio-lateral plane, which were double compared to Down syndrome group. The increase in potential energy, found to be almost equal to that of control group, indicates an increase in vertical oscillations. This could be because subjects who practise sports have stronger muscles that allow a greater push-off ability, which therefore increases their potential energy.

Assessment methodology for human-exoskeleton interactions: Kinetic analysis based on muscle activation

During the development and assessment of an exoskeleton, many different analyzes need to be performed. The most frequently used evaluate the changes in muscle activations, metabolic consumption, kinematics, and kinetics. Since human-exoskeleton interactions are based on the exchange of forces and torques, the latter of these, kinetic analyzes, are essential and provide indispensable evaluation indices. Kinetic analyzes, however, require access to, and use of, complex experimental apparatus, involving many instruments and implicating lengthy data analysis processes. The proposed methodology in this paper, which is based on data collected via EMG and motion capture systems, considerably reduces this burden by calculating kinetic parameters, such as torque and power, without needing ground reaction force measurements. This considerably reduces the number of instruments used, allows the calculation of kinetic parameters even when the use of force sensors is problematic, does not need any dedicated software, and will be shown to have high statistical validity. The method, in fact, combines data found in the literature with those collected in the laboratory, allowing the analysis to be carried out over a much greater number of cycles than would normally be collected with force plates, thus enabling easy access to statistical analysis. This new approach evaluates the kinetic effects of the exoskeleton with respect to changes induced in the user's kinematics and muscular activation patterns and provides indices that quantify the assistance in terms of torque (AMI) and power (API). Following the User-Center Design approach, which requires driving the development process as feedback from the assessment process, this aspect is critical. Therefore, by enabling easy access to the assessment process, the development of exoskeletons could be positively affected.

Assessment of gait quality and efficiency after undergoing a single-event multilevel surgery in children with cerebral palsy presenting an intoeing gait pattern

PURPOSE

The biomechanical impact of undergoing a single-event multilevel surgery (SEMLS) for children with cerebral palsy (CP) presenting an intoeing gait pattern has been widely documented. However, past studies mostly focused on gait quality rather than efficiency. Thus, there is a need to determine the impact of undergoing a SEMLS on gait quality and efficiency in children with CP presenting an intoeing gait pattern.

METHODS

Data from 16 children with CP presenting an intoeing gait pattern who underwent a SEMLS were retrospectively selected. Gait kinematics was quantified before (baseline) and at least 1 year after the surgery (follow-up). Gait quality was investigated with the Gait Profile Score (GPS), hip internal rotation angle and foot progression angle (FPA). Gait efficiency was analysed using clinically accessible variables, namely the normalised gait speed and medio-lateral and vertical centre of mass excursions (COMp). Dependent variables were compared between sessions with paired t-tests.

RESULTS

At the follow-up, children with CP exhibited a more outward FPA and GPS as well as a decreased hip internal rotation angle. No changes in normalised gait speed and vertical COMp excursion were observed, and medio-lateral COMp excursion was slightly decreased.

CONCLUSION

Children with CP presenting an intoeing gait pattern who underwent a SEMLS exhibited an increased gait quality, but gait efficiency was only minimally improved at the follow-up compared to baseline. Further studies are needed to identify contributors of gait efficiency in children with CP, and the best treatment modalities to optimise both their gait quality and efficiency.

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.

Analysis of center of mass and center of pressure displacement in the transverse plane during gait termination in children with cerebral palsy

BACKGROUND

While gait termination is challenging for children with spastic cerebral palsy (CCP), few studies have quantitatively assessed this issue.

RESEARCH QUESTION

What are the characteristics of center of mass (COM) and center of pressure (COP) displacement during gait termination in CCP, and how do they compare with those in children with typical development (CTD)?

METHODS

This cross-sectional study included 13 adults with typical development (19.85 ± 0.52 years), 12 CTD (10.41 ± 2.98 years), and 16 CCP (11.15 ± 2.71 years). Participants were instructed to immediately stop walking when a stop sign appeared on a screen, which was placed at the end of an 8-m walkway. COM and COP were determined via 3-dimensional motion analysis and force plate data. Differences between the groups were assessed using the two sample t-test or Wilcoxon rank sum test. The level of statistical significance was set at P < 0.05.

RESULTS

The normalized time for stopping in CCP (4.556 ± 0.602) was higher than that in CTD (3.617 ± 0.545, P < 0.001). The normalized COP displacement (P < 0.001) and divergence between COM and COP (P < 0.001) in the mediolateral (ML) direction were significantly higher in CCP than CTD. However, the normalized divergence between COM and COP in the anteroposterior (AP) direction in CCP was lower than that in CTD (P = 0.034).

SIGNIFICANCE

The more minor divergence between COM and COP in the AP direction and the more significant COP displacement in the ML direction cause difficulty to exert braking force during gait termination. Thus, CCP require a longer time for gait termination. This finding may facilitate the development of interventions for improving gait in CCP.

Self-selection of gestational lumbopelvic posture and bipedal evolution

BACKGROUND

Not all pregnant women seem to select the more curved lumbopelvic posture that their sexual dimorphic anatomy allows even though many previous researchers have assumed lumbopelvic curvature to be standard during pregnancy. This study is vital to understanding coevolution of lumbopelvic sexual dimorphism and bipedalism, and understanding some clinical implications of intervening in gestational posture changes.

RESEARCH QUESTIONS

Are there anthropometric changes that correspond with selection of lumbopelvic curvature change during pregnancy? What are the biomechanical costs and benefits of gestational lumbopelvic curvature change?

METHODS

Twenty pregnant women were tested at five different times in the 2nd and 3rd trimesters of pregnancy. Lumbopelvic posture, standing kinetics and gait kinetics were measured longitudinally. Additionally, we modeled the effects on standing and gait without lumbopelvic postural changes, but with anthropometric changes, for each individual.

RESULTS

We found greater lumbopelvic angulation to correspond with a shorter body height (6 cm difference between groups, p = 0.048) and deeper 2nd trimester abdomen (2 cm difference between groups, p = 0.013). Lumbopelvic angulation lowers support requirements (in standing and walking (6% lower support impulse, p = 0.056), but at the cost of shifting the propulsive actions to a less efficient pulling action rather than pushoff (13 % reduction in pushoff time, p = 0.001). We observed minimal effects on walking kinematics and balance control.

SIGNIFICANCE

Our findings suggest the evolutionary advantage of the female lumbopelvic unit is the adaptability it provides to adjust for the individual needs of the pregnant woman. We discuss multiple potential contributing factors that may have shaped hominin female lumbopelvic evolution and are involved in self-selecting lumbopelvic posture.

Pilot evaluation of changes in motor control after wearable robotic resistance training in children with cerebral palsy

Cerebral palsy (CP) is characterized by deficits in motor function due to reduced neuromuscular control. We leveraged the guiding principles of motor learning theory to design a wearable robotic intervention intended to improve neuromuscular control of the ankle. The goal of this study was to determine the neuromuscular and biomechanical response to four weeks of exoskeleton ankle resistance therapy (exo-therapy) in children with CP. Five children with CP (12 - 17 years, GMFCS I - II, two diplegic and three hemiplegic, four males and one female) were recruited for ten 20-minute sessions of exo-therapy. Surface electromyography, three-dimensional kinematics, and metabolic data were collected at baseline and after training was complete. After completion of training and with no device on, participants walked with decreased co-contraction between the plantar flexors and dorsiflexors (-29 ± 11%, p = 0.02), a more typical plantar flexor activation profile (33 ± 13% stronger correlation to a typical soleus activation profile, p = 0.01), and increased neural control complexity (7 ± 3%, p < 0.01 measured via muscle synergy analysis). These improvements in neuromuscular control led to a more mechanically efficient gait pattern (58 ± 34%, p < 0.05) with a reduced metabolic cost of transport (-29 ± 15%, p = 0.02). The findings from this study suggest that ankle exoskeleton resistance therapy shows promise for rapidly improving neuromuscular control for children with CP, and may serve as a meaningful rehabilitative complement to common surgical procedures.

Evaluation of Individualized Functional Electrical Stimulation-Induced Acute Changes during Walking: A Case Series in Children with Cerebral Palsy

Functional electrical stimulation (FES) walking interventions have demonstrated improvements to gait parameters; however, studies were often confined to stimulation of one or two muscle groups. Increased options such as number of muscle groups targeted, timing of stimulation delivery, and level of stimulation are needed to address subject-specific gait deviations. We aimed to demonstrate the feasibility of using a FES system with increased stimulation options during walking in children with cerebral palsy (CP). Three physical therapists designed individualized stimulation programs for six children with CP to target participant-specific gait deviations. Stimulation settings (pulse duration and current) were tuned to each participant. Participants donned our custom FES system that utilized gait phase detection to control stimulation to lower extremity muscle groups and walked on a treadmill at a self-selected speed. Motion capture data were collected during walking with and without the individualized stimulation program. Eight gait metrics and associated timing were compared between walking conditions. The prescribed participant-specific stimulation programs induced significant change towards typical gait in at least one metric for each participant with one iteration of FES-walking. FES systems with increased stimulation options have the potential to allow the physical therapist to better target the individual's gait deviations than a one size fits all device.

The effects of serial casting on lower limb function for children with Cerebral Palsy: a systematic review with meta-analysis

Background

Lower limb serial casting is commonly used therapeutically in paediatric clinical practice with some evidence to support its efficacy. This systematic review aimed to determine the effects of serial casting in isolation or combination with other therapies for the management of lower limb dysfunction in children with Cerebral Palsy (CP).

Methods

A systematic literature search was conducted in February 2019 across eight databases (PUBMED, EMBASE, CINAHL, PEDro, OTSeeker, Cochrane, Scopus and Proquest) using key terms ‘Cerebral Palsy’ and ‘serial casting’ and associated synonyms. A meta-synthesis and meta-analysis were undertaken when sufficient results were available showing the effect of serial casting on functional outcomes including: Ankle range of motion; neurological measures of hypertonicity and spasticity, functional gait measures and; gross motor function.

Results

Twenty-five articles from 3219 possible citations were included. Serial casting was found to be effective for: Improving ankle dorsiflexion (DF) passive range of motion (PROM) in the immediate to short-term, decreasing hypertonicity measured by Modified Ashworth Scale (MAS) in the short-term and, enhancing functional gait outcomes in the mid-term. Serial casting with or without botulinum toxin type-A (BTX-A) did not significantly affect gross motor capacity measured by Gross Motor Function Measure (GMFM). Serial casting with pharmacological intervention achieved significantly more DF PROM than serial casting alone (MD − 3.19 degrees; 95% CI − 5.76 to − 0.62; P = 0.01; I² = 0%), however the clinical importance of improving ankle DF PROM by an additional three degrees remains unclear.

Conclusions

Lower limb serial casting, improves several outcomes relevant to lower limb function supporting its clinical use for improving DF PROM, reducing hypertonicity and improving gait in children with CP. Further research using stronger methodological study designs, is indicated to explore long-term effects of serial casting on functional lower limb outcomes such as gross motor function in children with CP. Clinicians can use this information when developing individualised treatment plans for children who have CP during shared decision-making consultations.

Machine learning approach to predict center of pressure trajectories in a complete gait cycle: a feedforward neural network vs. LSTM network

Center of pressure (COP) trajectories of human can maintain regulation of forward progression and stability of lateral sway during walking. The insole pressure system can only detect COP trajectories of each foot during single stance. In this study, we developed artificial neural network models that could present COP trajectories in an integrated coordinate system during a complete gait cycle using pressure information of the insole system. A feed forward artificial neural network (FFANN) and a long short-term memory (LSTM) model were developed. For FFANN, among 198 pressure sensors from Pedar-X insoles, proper input variables were selected using sequential forward selection to reduce input dimension. The LSTM model used all 198 signals as inputs because of its self-learning characteristic. As results of cross-validation, the FFANN model showed correlation coefficients of 0.98-0.99 and 0.93-0.95 in anterior/posterior and medial/lateral directions, respectively. For the LSTM model, correlation coefficients were similar to those of FFANN. However, the relative root mean square error (12.5%) of the FFANN model was higher than that (9.8%) of the LSTM model in medial/lateral direction (p = 0.03). This study can be used for quantitative evaluation of clinical diagnosis and rehabilitation status for patient with various diseases through further training using varied databases. Graphical abstract Architectures of neural networks developed in this study (a feed forward artificial neural network; b LSTM network).

The Motion of Body Center of Mass During Walking: A Review Oriented to Clinical Applications

Human walking is usually conceived as the cyclic rotation of the limbs. The goal of lower-limb movements, however, is the forward translation of the body system, which can be mechanically represented by its center of mass (CoM). Lower limbs act as struts of an inverted pendulum, allowing minimization of muscle work, from infancy to old age. The plantar flexors of the trailing limbs have been identified as the main engines of CoM propulsion. Motion of the CoM can be investigated through refined techniques, but research has been focused on the fields of human and animal physiology rather than clinical medicine. Alterations in CoM motion could reveal motor impairments that are not detectable by clinical observation. The study of the three-dimensional trajectory of the CoM motion represents a clinical frontier. After adjusting for displacement due to the average forward speed, the trajectory assumes a figure-eight shape (dubbed the “bow-tie”) with a perimeter about 18 cm long. Its lateral size decreases with walking velocity, thus ensuring dynamic stability. Lateral redirection appears as a critical phase of the step, requiring precise muscle sequencing. The shape and size of the “bow-tie” as functions of dynamically equivalent velocities do not change from child to adulthood, despite anatomical growth. The trajectory of the CoM thus appears to be a promising summary index of both balance and the neural maturation of walking. In asymmetric gaits, the affected lower limb avoids muscle work by pivoting almost passively, but extra work is required from the unaffected side during the next step, in order to keep the body system in motion. Generally, the average work to transport the CoM across a stride remains normal. In more demanding conditions, such as walking faster or uphill, the affected limb can actually provide more work; however, the unaffected limb also provides more work and asymmetry between the steps persists. This learned or acquired asymmetry is a formerly unsuspected challenge to rehabilitation attempts to restore symmetry. Techniques of selective loading of the affected side, which include constraining the motion of the unaffected limb or forcing the use of the affected limb on split-belt treadmills which impose a different velocity and power to either limb, are now under scrutiny.

Three-dimensional path of the body centre of mass during walking in children: an index of neural maturation

Few studies have investigated the kinematic aspects of the body centre of mass motion, that is, its three-dimensional path during strides and their changes with child development. This study aimed to describe the three-dimensional path of the centre of mass in children while walking in order to disentangle the effect of age from that of absolute forward speed and body size and to define preliminary pediatric normative values. The three-dimensional path of the centre of mass during walking was compared across healthy children 5–6− years (n = 6), 7–8 years (n = 6), 9–10 years (n = 5), and 11–13 years of age (n = 5) and healthy adults (23–48 years, n = 6). Participants walked on a force-sensing treadmill at various speeds, and height normalization of speed was conducted with the dimensionless Froude number. The total length and maximal lateral, vertical, and forward displacements of the centre of mass path were calculated from the ground reaction forces during complete strides and were scaled to the participant’s height. The centre of mass path showed a curved figure-of-eight shape. Once adjusted for speed and participants’ height, as age increased, there was a decrease in the three-dimensional parameters and in the lateral displacement, with values approaching those of adults. At each step, lateral redirection of the centre of mass requires brisk transient muscle power output. The base of support becomes relatively narrower with increasing age. Skilled shortening of the lateral displacement of the centre of mass may therefore decrease the risk of falling sideways. The three-dimensional path of the centre of mass may represent maturation of neural control of gait during growth.

Mechanical work, kinematics, and kinetics during sit-to-stand in children with and without spastic diplegic cerebral palsy

BACKGROUND

Sit-to-stand (STS) is one of the most common fundamental activity in daily life. The pathology of the neuromuscular control system in children with spastic diplegic cerebral palsy (SDCP) could contribute to atypical movement patterns leading to the inefficiency performance including the STS task. However, there was also a lack of evidence about kinematics, kinetics, and especially mechanical work during the STS task in children with SDCP aged 7-12 years old.

RESEARCH QUESTION

What were the differences in mechanical work, kinematics and kinetics during STS task between children with SDCP and typically developing (TD) children?

METHODS

Eleven children with SDCP (GMFCS I-II) and eleven age and gender-matched control TD children with an age range of 7-12 years were enrolled. Motion analysis and force plate systems were used to collect data. All participants performed the STS task from an adjustable chair. Independent sample t-test and two-way analysis of variance were used in this study.

RESULTS

The children with SDCP took a longer time and used more mechanical work during STS than TD children. At the beginning of the STS task, children with SDCP showed more trunk flexion and posterior pelvic tilting; in addition, during the STS task they also presented more trunk, hip, and knee flexion than TD children. However, the children with SDCP showed less ankle dorsiflexion compared with TD children. For the kinetic variables, asymmetry was found in children with SDCP. The maximum hip and knee extension moment, plantar flexion moment, and peak vertical ground reaction force (GRF) of the non-dominant leg were higher than the values of the dominant leg in these children.

SIGNIFICANCE

Even though, children with SDCP who are able to independently STS. They were also a mechanically less efficient performance during STS task. Therefore, this task still needs to be trained during rehabilitation sessions.

Severity of equinus gait deviation on centre of mass trajectory in children with bilateral spastic cerebral palsy

Background/Aims:

To study the impact of severity of equinus gait on the vertical displacement of centre of mass and spatiotemporal parameters in children with bilateral spastic cerebral palsy.

Methods:

A total of 23 ambulant children with bilateral spastic cerebral palsy who had equinus gait and 16 typically developing children (controls) participated in this study. Children with cerebral palsy were categorised according to severity of equinus into two subgroups: children with peak dorsiflexion above 0° (positive group, n=11) and children with peak dorsiflexion below 0° (negative group, n=12). Three-dimensional gait analysis was conducted to measure the vertical displacement of centre of mass and spatiotemporal parameters of all participants.

Results:

There was a significantly greater increase in vertical displacement of centre of mass in equinus gait groups compared to the control group (P=0.007 for the positive group and P=0.011 for the negative group). Speed and step length were significantly reduced in the positive and negative groups compared to the control group, while cadence was non-significantly increased. No significant difference was found between the positive group and negative groups in any variables tested.

Conclusions:

Vertical centre of mass was significantly more displaced in children with bilateral spastic cerebral palsy with equinus compared to body mass index-matched typically developing children, regardless of the severity of equinus. The smooth transition of centre of mass and energy consumption might not be closely related to the degree of equinus.

Relationship between gait kinematics and walking energy expenditure during pregnancy in South African women

Background

Various musculoskeletal changes occurring during pregnancy may lead to the change in gait and contribute to the increase in walking energy expenditure. Previous research indicates that changes in gait mechanics may lead to the increase in mechanical work required during walking. However, there is little information to indicate if changes in gait mechanics during pregnancy have impact on active or total energy expenditure. Therefore, the primary aim of this study was to investigate the relationship between changes in gait kinematics and walking energy expenditure in pregnant women.

Methods

Thirty-five women (mean age = 27.5 ± 6.1 years) volunteered for the study during various stages of pregnancy (1st trimester average = 12.1 ± 2.2 weeks; 2nd trimester = 22.3 ± 2.6 weeks; 3rd trimester = 31.4 ± 2.6 weeks). 3D motion analysis was used to assess changes in kinematic parameters during walking at self-selected pace. Resting metabolic rate, and walking energy expenditure expressed in terms of rate and cost of O₂ were analysed with portable metabolic analyser.

Results

Only medio-lateral deviation of centre of gravity (COG_ML) increased 13.6% between the 1st and 2nd, and 39.3% between 2nd and 3rd trimester (p ≤ 0.001). However, self-selected walking speed depicted strong significant positive linear relationship with net O₂ rate (r = 0.70; p ≤ 0.001), and was strongly associated with the vertical excursion of the COG (r = 0.75, p ≤ 0.001).

Conclusions

Changes in gait mechanics during pregnancy may lead to an increase in walking energy expenditure. However, the consequent increase in walking energy cost may not be sufficient to offset the natural energy sparing mechanism.

On the Adaptation of Pelvic Motion by Applying 3-dimensional Guidance Forces Using TPAD

Pelvic movement is important to human locomotion as the center of mass is located near the center of pelvis. Lateral pelvic motion plays a crucial role to shift the center of mass on the stance leg, while swinging the other leg and keeping the body balanced. In addition, vertical pelvic movement helps to reduce metabolic energy expenditure by exchanging potential and kinetic energy during the gait cycle. However, patient groups with cerebral palsy or stroke have excessive pelvic motion that leads to high energy expenditure. In addition, they have higher chances of falls as the center ofmass could deviate outside the base of support. In this paper, a novel control method is suggested using tethered pelvic assist device (TPAD) to teach subjects to walk with a specified target pelvic trajectory while walking on a treadmill. In this method, a force field is applied to the pelvis to guide it to move on a target trajectory and correctional forces are applied, if the pelvis motion has excessive deviations from the target trajectory. Three different experimentswith healthy subjects were conducted to teach them to walk on a new target pelvic trajectory with the presented control method. For all three experiments, the baseline trajectory of the pelvis was experimentally determined for each participating subject. To design a target pelvic trajectory which is different from the baseline, Experiment I scaled up the lateral component of the baseline pelvic trajectory, while Experiment II scaled down the lateral component of the baseline trajectory. For both Experiments I and II, the controller generated a 2-D force field in the transverse plane to provide the guidance force. In this paper, seven subjects were recruited for each experiment who walked on the treadmill with suggested control methods and visual feedback of their pelvic trajectory. The results show that the subjects were able to learn the target pelvic trajectory in each experiment and also retained the training effects after the completion of the experiment. In Experiment III, both lateral and vertical components of the pelvic trajectory were scaled down from the baseline trajectory. The force field was extended to three dimensions in order to correct the vertical pelvic movement as well. Three subgroups (force feedback alone, visual feedback alone, and both force and visual feedback) were recruited to understand the effects of force feedback and visual feedback alone to distinguish the results from Experiments I and II. The results showthat a trainingmethod that combines visual and force feedback is superior to the training methods with visual or force feedback alone. We believe that the present control strategy holds potential in training and correcting abnormal pelvic movements in different patient populations.

Effects of Functional Electrical Stimulation on Reducing Falls and Improving Gait Parameters in Multiple Sclerosis and Stroke

BACKGROUND

Loss of neuromuscular control of the ankle joint is a common impairment in neurologic conditions, leading to abnormal gait and a greater risk of falling. Limited information, however, is available on the effectiveness of functional electrical stimulation (FES) on reducing falls, and no studies have investigated its usefulness in improving lower limbs kinematics related to foot clearance and energy recovery.

SETTING

Clinical setting.

STUDY DESIGN

Prospective longitudinal study.

PARTICIPANTS

Twenty-four subjects, 14 people with multiple sclerosis (mean age ± standard deviation 50.93 ± 8.72 years) and 10 people with stroke (55.38 ± 14.55 years).

METHODS

The number of falls was assessed at baseline and after 8 weeks, and a clinical assessment was performed at the baseline, 4-week, and 8-week time points. A subsample of the 24 subjects comprising 5 people with multiple sclerosis and 5 people with stroke performed a gait analysis assessment at baseline and after 4 weeks. After receiving the equipment and the training schedule, subjects performed daily home walking training using FES for 8 weeks.

MAIN OUTCOME MEASUREMENTS

The main outcomes were (1) the number of falls, (2) foot clearance, and (3) energy recovery.

RESULTS

A reduction in the number of falls was observed from baseline (n = 10) to the 8-week assessment (n = 2), P = .02. Foot clearance increased (+5.26 mm, P = .04) between the baseline without FES and at 4 weeks with FES (total effect). No statistically significant differences were found in energy recovery between baseline and 4 weeks.

CONCLUSIONS

The use of FES had an impact on gait, specifically reducing the number of falls and improving walking. A specific effect at the ankle joint was observed, increasing foot clearance during the swing phase of gait. This effect was not accompanied with a reduction in the energetic expenditure during walking in subjects with multiple sclerosis and stroke.

Transfer of mechanical energy during the shot put

The aim of this study was to analyse transfer of mechanical energy between body segments during the glide shot put. A group of eight elite throwers from the Polish National Team was analysed in the study. Motion analysis of each throw was recorded using an optoelectronic Vicon system composed of nine infrared camcorders and Kistler force plates. The power and energy were computed for the phase of final acceleration of the glide shot put. The data were normalized with respect to time using the algorithm of the fifth order spline and their values were interpolated with respect to the percentage of total time, assuming that the time of the final weight acceleration movement was different for each putter. Statistically significant transfer was found in the study group between the following segments: Right Knee - Right Hip (p = 0.0035), Left Hip - Torso (p = 0.0201), Torso - Right Shoulder (p = 0.0122) and Right Elbow - Right Wrist (p = 0.0001). Furthermore, the results of cluster analysis showed that the kinetic chain used during the final shot acceleration movement had two different models. Differences between the groups were revealed mainly in the energy generated by the hips and trunk.

Hip, Knee, and Ankle Osteoarthritis Negatively Affects Mechanical Energy Exchange

BACKGROUND

Individuals with osteoarthritis (OA) of the lower limb find normal locomotion tiring compared with individuals without OA, possibly because OA of any lower limb joint changes limb mechanics and may disrupt transfer of potential and kinetic energy of the center of mass during walking, resulting in increased locomotor costs. Although recovery has been explored in asymptomatic individuals and in some patient populations, the effect of changes in these gait parameters on center of mass movements and mechanical work in patients with OA in specific joints has not been well examined. The results can be used to inform clinical interventions and rehabilitation that focus on improving energy recovery.

QUESTIONS/PURPOSES

We hypothesized that (1) individuals with end-stage lower extremity OA would exhibit a decrease in walking velocity compared with asymptomatic individuals and that the joint affected with OA would differntially influence walking velocity, (2) individuals with end-stage lower extremity OA would show decreased energy recovery compared with asymptomatic individuals and that individuals with end-stage hip and ankle OA would have greater reductions in recovery than would individuals with end-stage knee OA owing to restrictions in hip and ankle motion, and (3) that differences in the amplitude and congruity of the center of mass would explain the differences in energy recovery that are observed in each population.

METHODS

Ground reaction forces at a range of self-selected walking speeds were collected from individuals with end-stage radiographic hip OA (n = 27; 14 males, 13 females; average age, 55.6 years; range, 41-70 years), knee OA (n = 20; seven males, 13 females; average age, 61.7 years; range, 49-74 years), ankle OA (n = 30; 14 males, 16 females; average age, 57 years; range, 45-70 years), and asymptomatic individuals (n = 13; eight males, five females; average age, 49.8 years; range, 41-67 years). Participants were all patients with end-stage OA who were scheduled to have joint replacement surgery within 4 weeks of testing. All patients were identified by the orthopaedic surgeon as having end-stage radiographic disease and to be a candidate for joint replacement surgery. Patients were excluded if they had pain at any other lower extremity joint, previous joint replacement surgery, or needed to use an assistive device for ambulation. Patients were enrolled if they met the study inclusion criteria. Our study was comparative and cohorts could be compared with each other, however, the asymptomatic group served to verify our methods and provided a recovery standard with which we could compare our patients. Potential and kinetic energy relationships (% congruity) and energy exchange (% recovery) were calculated. Linear regressions were used to examine the effect of congruity and amplitude of energy fluctuations and walking velocity on % recovery. Analysis of covariance was used to compare energy recovery between groups.

RESULTS

The results of this study support our hypothesis that individuals with OA walk at a slower velocity than asymptomatic individuals (1.4 ± 0.2 m/second, 1.2-1.5 m/second) and that the joint affected by OA also affects walking velocity (p < 0.0001). The cohort with ankle OA (0.9 ± 0.2 m/second, 0.77-0.94 m/second) walked at a slower speed relative to the cohort with hip OA (1.1 ± 0.2 m/second, 0.96-1.1 m/second; p = 0.002). However, when comparing the cohorts with ankle and knee OA (0.9 ± 0.2 m/second, 0.77-0.94 m/second) there was no difference in walking speed (p = 0.16) and the same was true when comparing the cohorts with knee and hip OA (p = 0.14). Differences in energy recovery existed when comparing the OA cohorts with the asymptomatic cohort and when examining differences between the OA cohorts. After adjusting for walking speeds these results showed that asymptomatic individuals (65% ± 3%, 63%-67%) had greater recovery than individuals with hip OA (54% ± 10%, 50%-58%; p = 0.014) and ankle OA (47% ± 13%, 40%-52%; p = 0.002) but were not different compared with individuals with knee OA (57% ± 10%, 53%-62%; p = 0.762). When speed was accounted for, 80% of the variation in recovery not attributable to speed was explained by congruity with only 10% being explained by amplitude.

CONCLUSIONS

OA in the hip, knee, or ankle reduces effective exchange of potential and kinetic energy, potentially increasing the muscular work required to control movements of the center of mass.

CLINICAL RELEVANCE

The fatigue and limited physical activity reported in patients with lower extremity OA could be associated with increased mechanical work of the center of mass. Focused gait retraining potentially could improve walking mechanics and decrease fatigue in these patients.

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.

The Effects of Varying Ankle Foot Orthosis Stiffness on Gait in Children with Spastic Cerebral Palsy Who Walk with Excessive Knee Flexion

Introduction

Rigid Ankle-Foot Orthoses (AFOs) are commonly prescribed to counteract excessive knee flexion during the stance phase of gait in children with cerebral palsy (CP). While rigid AFOs may normalize knee kinematics and kinetics effectively, it has the disadvantage of impeding push-off power. A spring-like AFO may enhance push-off power, which may come at the cost of reducing the knee flexion less effectively. Optimizing this trade-off between enhancing push-off power and normalizing knee flexion in stance is expected to maximize gait efficiency. This study investigated the effects of varying AFO stiffness on gait biomechanics and efficiency in children with CP who walk with excessive knee flexion in stance. Fifteen children with spastic CP (11 boys, 10±2 years) were prescribed with a ventral shell spring-hinged AFO (vAFO). The hinge was set into a rigid, or spring-like setting, using both a stiff and flexible performance. At baseline (i.e. shoes-only) and for each vAFO, a 3D-gait analysis and 6-minute walk test with breath-gas analysis were performed at comfortable speed. Lower limb joint kinematics and kinetics were calculated. From the 6-minute walk test, walking speed and the net energy cost were determined. A generalized estimation equation (p<0.05) was used to analyze the effects of different conditions. Compared to shoes-only, all vAFOs improved the knee angle and net moment similarly. Ankle power generation and work were preserved only by the spring-like vAFOs. All vAFOs decreased the net energy cost compared to shoes-only, but no differences were found between vAFOs, showing that the effects of spring-like vAFOs to promote push-off power did not lead to greater reductions in walking energy cost. These findings suggest that, in this specific group of children with spastic CP, the vAFO stiffness that maximizes gait efficiency is primarily determined by its effect on knee kinematics and kinetics rather than by its effect on push-off power.

Trial Registration

Dutch Trial Register NTR3418

Correlating mechanical work with energy consumption during gait throughout pregnancy

BACKGROUND

Measures of mechanical work may be useful in evaluating efficiency of walking during pregnancy. Various adaptations in the body during pregnancy lead to altered gait, consequently contributing to the total energy cost of walking. Measures of metabolic energy expenditure may not be reliable for measuring energetic cost of gait during pregnancy as pregnancy results in numerous metabolic changes resulting from foetal development. Therefore, the aim of this study is to determine if mechanical work prediction equations correlate with the metabolic energy cost of gait during pregnancy.

METHODS

Thirty-five (35) women (27.5 ± 6.1 years) gave informed consent for participation in the study at different weeks of gestation pregnancy. Gas exchange and gait data were recorded while walking at a fixed self-selected walking speed. External (Wext) work was estimated assuming no energy transfer between segments, while internal work (Wint) assumed energy transfer between segments. Hence total energy of the body (Wtot) was calculated based on the segmental changes relative to the surrounding, and relative to the centre of mass of the whole body. Equations for mechanical work were correlated with net and gross O2 rate, and O2 cost.

RESULTS

External, internal and total mechanical energy showed significant positive relationship with gross O2 rate (r = 0.48, r = 0.35; and r = 0.49 respectively), and gross O2 cost (r = 0.42; r = 0.70, and r = 0.62, respectively). In contrast, external, internal and total mechanical energy had no significant relationship with net O2 rate (r = 0.19, r = 0.24, and r = 0.24, respectively). Net O2 cost was significant related Wext (r = 0.49) Wint (r = 0.66) and Wtot (r = 0.62). Energy recovery improved with increase in gait speed.

CONCLUSIONS

Measures of mechanical work, when adjusted for resting energy expenditure, and walking speed may be useful in comparing metabolic energy consumption between women during pregnancy, or assessment or gait changes of the same individual throughout pregnancy.

Aging increases flexibility of postural reactive responses based on constraints imposed by a manual task

This study compared the effect of stability constraints imposed by a manual task on the adaptation of postural responses between 16 healthy elderly (mean age = 71.56 years, SD = 7.38) and 16 healthy young (mean age = 22.94 years, SD = 4.82) individuals. Postural stability was perturbed through unexpected release of a load attached to the participant’s trunk while performing two versions of a voluntary task: holding a tray with a cylinder placed with its flat side down (low constraint) or with its rolling round side down (high constraint). Low and high constraint tasks were performed in alternate blocks of trials. Results showed that young participants adapted muscular activation and kinematics of postural responses in association with previous experience with the first block of manual task constraint, whereas the elderly modulated postural responses based on the current manual constraint. This study provides evidence for flexibility of postural strategies in the elderly to deal with constraints imposed by a manual task.

Energy recovery in individuals with knee osteoarthritis

OBJECTIVE

Pathological gaits have been shown to limit transfer between potential (PE) and kinetic (KE) energy during walking, which can increase locomotor costs. The purpose of this study was to examine whether energy exchange would be limited in people with knee osteoarthritis (OA).

METHODS

Ground reaction forces during walking were collected from 93 subjects with symptomatic knee OA (self-selected and fast speeds) and 13 healthy controls (self-selected speed) and used to calculate their center of mass (COM) movements, PE and KE relationships, and energy recovery during a stride. Correlations and linear regressions examined the impact of energy fluctuation phase and amplitude, walking velocity, body mass, self-reported pain, and radiographic severity on recovery. Paired t-tests were run to compare energy recovery between cohorts.

RESULTS

Symptomatic knee OA subjects displayed lower energetic recovery during self-selected walking speeds than healthy controls (P = 0.0018). PE and KE phase relationships explained the majority (66%) of variance in recovery. Recovery had a complex relationship with velocity and its change across speeds was significantly influenced by the self-selected walking speed of each subject. Neither radiographic OA scores nor subject self-reported measures demonstrated any relationship with energy recovery.

CONCLUSIONS

Knee OA reduces effective exchange of PE and KE, potentially increasing the muscular work required to control movements of the COM. Gait retraining may return subjects to more normal patterns of energy exchange and allow them to reduce fatigue.

Dance recognition system using lower body movement

The current means of locating specific movements in film necessitate hours of viewing, making the task of conducting research into movement characteristics and patterns tedious and difficult. This is particularly problematic for the research and analysis of complex movement systems such as sports and dance. While some systems have been developed to manually annotate film, to date no automated way of identifying complex, full body movement exists. With pattern recognition technology and knowledge of joint locations, automatically describing filmed movement using computer software is possible. This study used various forms of lower body kinematic analysis to identify codified dance movements. We created an algorithm that compares an unknown move with a specified start and stop against known dance moves. Our recognition method consists of classification and template correlation using a database of model moves. This system was optimized to include nearly 90 dance and Tai Chi Chuan movements, producing accurate name identification in over 97% of trials. In addition, the program had the capability to provide a kinematic description of either matched or unmatched moves obtained from classification recognition.

Estimating energy expenditure for different assistive devices in the school setting

PURPOSE

This case report describes a simple means of estimating energy costs for a child with cerebral palsy using different assistive devices within a school setting.

KEY POINTS

A 9-year-old boy, Gross Motor Function Classification Scale level III, was assessed over 8 ambulation trials using a posterior walker and using forearm crutches. Each trial was followed by a fine motor accuracy task. An energy expenditure index (EEI) was calculated for each device. For the posterior walker, EEI was 47% higher overall compared with forearm crutches. Fine motor accuracy and task completion time were similar for both devices.

CONCLUSION

EEI was a straightforward method of estimating the energy costs of different assistive devices. Measurement procedures described in this case were time efficient in the field and provided a reasonable estimation of energy expenditure to help decide objectively which assistive device would best fit the needs of the student.

VIDEO ABSTRACT

For more insights from the authors, see Supplemental Digital Content 1, available at http://links.lww.com/PPT/A63.

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.

Effects of vertical motion of the centre of mass on walking efficiency in the early stages after total hip arthroplasty

PURPOSE

The purpose of this study was to identify factors related to walking efficiency in the early postoperative period of total hip arthroplasty (THA).

METHODS

The subjects of this study were 18 women who had undergone unilateral THA 4 weeks before and 18 healthy women as control. Using a force plate and a 3-D motion analyser, we measured: 1) gait speed, stride length, cadence; 2) centre of mass displacement in the three directions; 3) asymmetry of the centre of mass movement in vertical direction; and 4) the total internal work per unit mass and distance walked (a negative index of walking efficiency).

RESULTS

Compared with healthy persons, THA patients showed significantly greater total internal work per unit mass and distance walked. The vertical centre of mass motion of the THA patients demonstrated an asymmetrical pattern. In THA patients, the stepwise multiple regression analysis selected the displacement and the asymmetrical vertical motion of centre of mass as the sole significant variable affecting walking efficiency (R2 = 0.81).

CONCLUSIONS

Our findings indicated that rehabilitation programs that control the vertical movement of the centre of mass during gait are important to improve walking ability in the early post-operative phase after THA.

Assessing postural asymmetry with a podoscope in infants with Central Coordination Disturbance

The aim of this study was to digitally evaluate the incidence and severity of postural asymmetry in infants with Central Coordination Disturbance (CCD) by using a computer-aided podoscope (PodoBaby) from CQ Elektronik System. A sample of 120 infants aged from 3 months (± 1 week) to 6 months (± 1 week) took part in the study, of which 60 were diagnosed with CCD by a neurologist using Vojta's method and the remaining half healthy, non-afflicted infants. The relationships between Vojta's method, as a subjective clinical diagnostic tool for assessing the functional performance of infants with CCD, and the postural asymmetry results recorded with the podoscope, were also defined. Each infant was placed on the podoscope and photographed underneath in two positions: first lying on their back and then on their stomach. A symmetry index was used to calculate body asymmetry, i.e., the percent difference of abnormal body posture by favoring one side of the body to the other. The results confirmed that postural asymmetry assessed by the PodoBaby was in line with the earlier clinical diagnosis using Vojta's method. Statistically significant differences in postural asymmetry were also found between the healthy infants and infants with CCD. In addition, significant relationships were demonstrated in the magnitude and direction of asymmetry in the stomach and back positions.

Walking deterioration and gait analysis in adults with spastic bilateral cerebral palsy

Walking deterioration occurs frequently in adults with spastic bilateral cerebral palsy (CP), but their gait characteristics are largely unknown. The study aims were (1) to compare selected gait analysis variables between those reporting and those not reporting walking deterioration, and (2) to characterise the overall gait deviations and classify the gait patterns. Participants (N=16) were recruited from a follow-up study, had spastic bilateral CP, <40 years in 2006, GMFCS levels I-III, and could walk at least 10 m without support. Eight reported walking deterioration (cases) and eight did not (controls). A theoretical framework linking work of walking, fatigue and deterioration in walking was developed. It was hypothesised that higher energy requirements during gait and larger gait deviations would be associated with deterioration in walking. Three-dimensional gait analysis was used to obtain centre of mass work, mechanical joint work, lower limb kinematics, movement analysis profile (MAP), and gait profile scores (GPS). There were no differences between the cases and controls in centre of mass work, joint work, or in the GPS. The largest MAP deviations were seen in sagittal pelvis, hip, and knee angles and foot progression. Crouch and asymmetric gait were common patterns. Walking deterioration could not be explained by these work and kinematic variables. An individual's perception of deterioration in walking is subjective, and may be experienced and interpreted differently across people. Larger, longitudinal studies on the natural history of walking in spastic CP are needed. Qualitative studies on the subjective experiences of walking deterioration are also warranted.

Changes in kinematics, metabolic cost and external work during walking with a forward assistive force

We examined how the application of a forward horizontal force applied at the waist alters the metabolic cost, kinematics, and external work of gait. Horizontal assist forces of 4%, 8% and 12% of a subject's body weight were applied via our testing apparatus while subjects walked at comfortable walking speed on a level treadmill. Kinematic and metabolic parameters were measured using motion capture and ergospirometry respectively on a group of 10 healthy male subjects. Changes in kinematic and metabolic parameters were quantified and found similar to walking downhill at varying grades. A horizontal assist force of 8% resulted in the greatest reduction of metabolic cost. Changes in recovery factor, external work, and center of mass (COM) movement did not correlate with changes in metabolic rate and therefore were not driving the observed reductions in cost. The assist force may have performed external work by providing propulsion as well as raising the COM as it pivots over the stance leg. Assist forces may decrease metabolic cost by reducing the concentric work required for propulsion while increasing the eccentric work of braking. These findings on the effects of assist forces suggest novel mobility aids for individuals with gait disorders and training strategies for athletes.

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.

The interaction of postural and voluntary strategies for stability in Parkinson's disease

This study assessed the effects of stability constraints of a voluntary task on postural responses to an external perturbation in subjects with Parkinson's disease (PD) and healthy elderly participants. Eleven PD subjects and twelve control subjects were perturbed with backward surface translations while standing and performing two versions of a voluntary task: holding a tray with a cylinder placed with the flat side down [low constraint (LC)] or with the rolling, round side down [high constraint (HC)]. Participants performed alternating blocks of LC and HC trials. PD participants accomplished the voluntary task as well as control subjects, showing slower tray velocity in the HC condition compared with the LC condition. However, the latency of postural responses was longer in the HC condition only for control subjects. Control subjects presented different patterns of hip-shoulder coordination as a function of task constraint, whereas PD subjects had a relatively invariant pattern. Initiating the experiment with the HC task led to 1) decreased postural stability in PD subjects only and 2) reduced peak hip flexion in control subjects only. These results suggest that PD impairs the capacity to adapt postural responses to constraints imposed by a voluntary task.

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.

Generation, absorption, and transfer of mechanical energy during walking in children

The purpose of this study was to characterize the manner in which net joint moments and non-muscular forces generate, absorb, and transfer mechanical energy during walking in able-bodied children. Standard gait data from seven healthy subjects between 6 and 17 years of age were combined with a dynamic model of the whole body to perform a power analysis based on induced acceleration techniques. These data were used to determine how each moment and force generates energy to, absorbs energy from, and transfers energy among the major body segments. The joint moments were found to induce transfers of mechanical energy between body segments that generally exceeded the magnitudes of energy generation and absorption. The amount of energy transferred by gravitational and velocity-dependent forces was considerably less than for the joint moments. The hip and ankle joint moments had relatively simple power patterns that tended to oppose each other, particularly over the stance phase. The knee joint moment had a more complex power pattern that appeared distinct from the hip and ankle moments. The general patterns of mechanical energy flow were similar to previous reports in adults. The approach described in this paper should provide a useful complement to standard clinical gait analysis procedures.

The reasons why stroke patients expend so much energy to walk slowly

BACKGROUND

The energy consumed per covered distance (C) is increased in hemiparetic stroke adults during walking.

OBJECTIVE

To ascertain if increased C in stroke patients is a result of increased mechanical work, of decreased efficiency of work production by muscles or of slow walking speed.

METHODS

C and mechanical work were computed in 20 patients walking on a force measuring treadmill at speeds ranging from 1 km h(-1) to their own maximum speed (WS(MAX)). Works done by healthy and pathological limbs were computed separately.

RESULTS

For hemiparetic patients, C was around 1.7 times greater than normal. When these patients had a slower WS(MAX), they had greater C and mechanical work (r=-0.44 and -0.57, respectively). The increased C was related to the external work performed to lift the center of body mass when the healthy limb was supporting the body weight (r=0.77).

CONCLUSIONS

The increase of C in stroke patients is more pronounced when WS(MAX) is slow. Moreover, this increase is related to increased mechanical work done by muscles and is not related to slow walking speed or decreased efficiency. As in healthy subjects, C and external work presented optimum speeds, indicating a preserved pendular mechanism of walking.

BALANCE CONTROL DURING LEVEL WALKING IN CHILDREN WITH SPASTIC DIPLEGIC CEREBRAL PALSY

Children with cerebral palsy (CP) have been reported to have various levels of deficits in balance control, which can be described using the relationship between the body's centre of mass (COM) and the centre of pressure (COP). This study aimed to investigate the balance control of children with spastic diplegic CP during level walking. The COM-COP inclination angles and angular velocities, as well as temporal-spatial variables from 12 children with spastic diplegic CP (seven girls and five boys, aged 12.4 ± 4.4 years) and 12 normal controls (eight girls and four boys, aged 11.2 ± 4.4 years) were obtained using a motion analysis system and two forceplates. With compromised balance control as a result of neuromusculoskeletal pathologies, the CP group walked with reduced walking speed and stride length (p < 0.05), but increased stride time and step width (p < 0.05), indicating reduced gait efficiency. They also showed significantly reduced anterioposterior COM-COP inclination angles and angular velocities (p < 0.05), but increased mediolateral COM-COP inclination angles and angular velocities (p < 0.05) when compared to the normal controls. The latter phenomenon may be related to an increased risk of falling in these patients. Therefore, it appears that programs and/or devices for preventing falls are needed for children with spastic diplegic CP.

The effects of ankle foot orthoses on energy recovery and work during gait in children with cerebral palsy

BACKGROUND

Studies suggest that 50% of children with cerebral palsy are prescribed ankle foot orthoses. One of the aims of ankle foot orthosis use is to aid in walking. This research examined the effects that ankle foot orthoses have on the energy recovery and the mechanical work performed by children with cerebral palsy during walking.

METHODS

Twenty-one children with spastic diplegia walked with and without their prescribed bilateral ankle foot orthoses. Ten of the subjects wore articulated (hinged) orthoses and 11 subjects wore solid orthoses. Three dimensional kinematic data were collected and between and within group repeated measures ANOVAs were applied to the dependent measures.

FINDINGS

The results were similar for both groups. There was an increase in stride length, energy recovery, and potential energy and the kinetic energy variation. There was no change in the mechanical work performed to walk or the normalized center of mass vertical excursion. Unfortunately, the increase in energy recovery did not alter the external work, as it was offset by increased variation in the potential and kinetic energies of the center of mass. There was a great deal of variability in the measured work, with both large increases and decreases in the work of individual subjects when wearing orthoses.

INTERPRETATION

These results suggest that current ankle foot orthoses can reduce the work to walk, but do not do so for many children with cerebral palsy. This research suggests that ankle foot orthosis prescription could be aided by measuring the mechanical work during walking.

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.