Intraoperative Quantification of MDS-UPDRS Tremor Measurements Using 3D Accelerometry: A Pilot Study.

The most frequently used method for evaluating tremor in Parkinson's disease (PD) is currently the internationally standardized Movement Disorder Society­Unified PD Rating Scale (MDS-UPDRS). However, the MDS-UPDRS is associated with limitations, such as its inherent subjectivity and reliance on experienced raters. Objective motor measurements using accelerometry may overcome the shortcomings of visually scored scales. Therefore, the current study focuses on translating the MDS-UPDRS tremor tests into an objective scoring method using 3D accelerometry. An algorithm to measure and classify tremor according to MDS-UPDRS criteria is proposed. For this study, 28 PD patients undergoing neurosurgical treatment and 26 healthy control subjects were included. Both groups underwent MDS-UPDRS tests to rate tremor severity, while accelerometric measurements were performed at the index fingers. All measurements were performed in an off-medication state. Quantitative measures were calculated from the 3D acceleration data, such as tremor amplitude and area-under-the-curve of power in the 4−6 Hz range. Agreement between MDS-UPDRS tremor scores and objective accelerometric scores was investigated. The trends were consistent with the logarithmic relationship between tremor amplitude and MDS-UPDRS score reported in previous studies. The accelerometric scores showed a substantial concordance (>69.6%) with the MDS-UPDRS ratings. However, accelerometric kinetic tremor measures poorly associated with the given MDS-UPDRS scores (R2 < 0.3), mainly due to the noise between 4 and 6 Hz found in the healthy controls. This study shows that MDS-UDPRS tremor tests can be translated to objective accelerometric measurements. However, discrepancies were found between accelerometric kinetic tremor measures and MDS-UDPRS ratings. This technology has the potential to reduce rater dependency of MDS-UPDRS measurements and allow more objective intraoperative monitoring of tremor.

Biomechanical effects of rocker shoes on plantar aponeurosis strain in patients with plantar fasciitis and healthy controls.

Plantar fasciitis is a frequently occurring overuse injury of the foot. Shoes with a stiff rocker profile are a commonly prescribed treatment modality used to alleviate complaints associated with plantar fasciitis. In rocker shoes the apex position was moved proximally as compared to normal shoes, limiting the progression of the ground reaction forces (GRF) and peak plantarflexion moments during gait. A stiff sole minimizes dorsiflexion of the toes. The aim of this study was to investigate whether the biomechanical effects of rocker shoes lead to minimization of plantar aponeurosis (PA) strain during gait in patients with plantar fasciitis and in healthy young adults. 8 patients with plantar fasciitis (1 male, 7 females; mean age 55.0 ± 8.4 years) and 8 healthy young adults (8 females; mean age 24.1 ± 1.6 years) participated in the study. Each participant walked for 1 minute on an instrumented treadmill while wearing consecutively in random order shoes with a normal apex position (61.2 ± 2.8% apex) with flexible insole (FN), normal apex position with stiff insole (SN), proximal apex position (56.1 ± 2.6% apex) with flexible insole (FR) and proximal apex position with stiff insole (SR). Marker position data of the foot and lower leg and GRF were recorded. An OpenSim foot model was used to compute the change in PA length based on changes in foot segment positions during gait. The changes in PA length due to increases in Achilles tendon forces were computed based on previous data of a cadaver study. PA strain computed from both methods was not statistically different between shoe conditions. Peak Achilles tendon force, peak first metatarsophalangeal (MTP1) joint angle and peak plantarflexion moment were significantly lower when walking with the rocker shoe with a proximal apex position and a stiff insole for all subjects (p<.05). Changes in Achilles tendon forces during gait accounted for 65 ± 2% of the total PA strain. Rocker shoes with a stiff insole reduce peak dorsiflexion angles of the toes and plantar flexion moments, but not PA strain because the effects of a proximal apex position and stiff insole do not occur at the same time, but independently affect PA strain at 80-90% and 90-100% of the stance phase. Rocker shoes with an apex position of ~56% are insufficient to significantly reduce peak PA strain values in patients with plantar fasciitis and healthy young adults.

The repeatability and reproducibility of the Sheffield Features of Gait Tool.

Gait, the pattern or style in which locomotion is undertaken, has kinematic characteristics that may occur in varying proportions of a population and therefore have discriminatory potential. Forensic gait analysis is the analysis, comparison and evaluation of features of gait to assist the investigation of crime. While there have been recent developments in automated gait recognition systems, gait analysis presented in criminal court to assist in identification currently relies on observational analysis by expert witnesses. Observational gait analysis has been the focus of considerable research, and it has been shown that the adoption of a systematic approach to both the observation and recording of features of gait improves the reliability of the analysis. The Sheffield Features of Gait Tool was developed by forensic gait analysis practitioners based on their casework and trial experience, and consists of more than a hundred features of gait and variances. This paper reports the findings of a study undertaken to assess the repeatability and reproducibility of the Sheffield Features of Gait Tool. Fourteen participants, with experience in observational gait analysis, viewed footage of computer generated avatars walking, and completed the features of gait tool on multiple occasions. The repeatability scores varied between participants from a highest score of 42.59 out of a maximum possible score of 45 (94.65%), to a lowest score of 30.76 (68.35%), with a mean score of 35.79 (79.54%) and a standard deviation of 3.59 (7.98%). The reproducibility scores for the assessment of each avatar varied from a highest score of 137.73 out of the best possible score of 180 (76.52%), to a lowest score of 127.21 (70.67%), with a mean score of 132.21 (73.45) and a standard deviation of 3.82 (2.12%). The results demonstrated that the use of the Sheffield Features of Gait Tool by experienced analysists resulted in what could be considered to be good levels of both repeatability and reproducibility. Some variation was shown to occur both between the results produced by different analysts, and between those produced from the analysis of different avatars. An understanding of the probative value of gait analysis evidence is an important facet of its submission as evidence, and the design and testing of standardized methods of analysis and comparison are an essential element of developing that understanding. This study is the first to test a purpose designed features of gait tool for use in forensic gait analysis.

Transfer of improved movement technique after receiving verbal external focus and video instruction.

PURPOSE: It is unknown how movement patterns that are learned carry over to the field. The objective was to determine whether training during a jump-landing task would transfer to lower extremity kinematics and kinetics during sidestep cutting. METHODS: Forty healthy athletes were assigned to the verbal internal focus (IF, n = 10), verbal external focus (EF, n = 10), video (VI, n = 10) or control (CTRL, n = 10) group. A jump-landing task was performed as baseline followed by training blocks (TR1 and TR2) and a post-test. Group-specific instructions were given in TR1 and TR2. In addition, participants in the IF, EF and VI groups were free to ask for feedback after every jump during TR1 and TR2. Retention was tested after 1 week. Transfer of learned skill was determined by having participants perform a 45° unanticipated sidestep cutting task. 3D hip, knee and ankle kinematics and kinetics were the main outcome measures. RESULTS: During sidestep cutting, the VI group showed greater hip flexion ROM compared to the EF and IF groups (p < 0.001). The EF (p < 0.036) and VI (p < 0.004) groups had greater knee flexion ROM compared to the IF group. CONCLUSIONS: Improved jump-landing technique carried over to sidestep cutting when stimulating an external attentional focus combined with self-controlled feedback. Transfer to more sport-specific skills may demonstrate potential to reduce injuries on the field. Clinicians and practitioners are encouraged to apply instructions that stimulate an external focus of attention, of which visual instructions seem to be very powerful. LEVEL OF EVIDENCE: II.

RETENTION OF MOVEMENT TECHNIQUE: IMPLICATIONS FOR PRIMARY PREVENTION OF ACL INJURIES.

BACKGROUND: Retention of movement technique is crucial in anterior cruciate ligament (ACL) injury prevention programs. It is unknown if specific instructions or video instructions result in changes in kinematic and kinetic measures during a relatively short training session, and in a retention test one week later. HYPOTHESIS/PURPOSE: The purpose was to determine the effects of verbal external focus (EF), verbal internal focus (IF) and video instructions (VI) on landing technique (i.e. kinematics and kinetics) during training and retention. STUDY DESIGN: Randomized Controlled Trial. METHODS: This study compared verbal EF, verbal IF, VI and CTRL group. Forty healthy athletes were assigned to the IF (n=10), EF (n=10), VI (n=10) or CTRL group (n=10). A jump-landing task was performed as a baseline, followed by two training blocks (TR1 and TR2) and a post test. Group specific instructions were offered in TR1 and TR2. In addition, subjects in the IF, EF and VI groups were free to ask for feedback after every jump in TR1 and TR2. One week later, a retention test was conducted without specific instructions or feedback. Kinematics and kinetics were captured using an 8-camera motion analysis system. RESULTS: Males and females in the EF and VI instruction group showed beneficial results during and after the training session, in terms of improved landing technique. Retention was achieved after only a short training session. CONCLUSION: ACL injury prevention programs should include EF and/or VI instructions to improve kinematics and kinetics and achieve retention. LEVEL OF EVIDENCE: 3b.

Motor learning strategies in basketball players and its implications for ACL injury prevention: a randomized controlled trial.

PURPOSE: Adding external focus of attention (EF, focus on the movement effect) may optimize current anterior cruciate ligament (ACL) injury prevention programmes. The purpose of the current study was to investigate the effects of an EF, by a visual stimulus and an internal focus, by a verbal stimulus during unexpected sidestep cutting in female and male athletes and how these effects remained over time. METHODS: Ninety experienced basketball athletes performed sidestep cutting manoeuvres in three sessions (S1, S2 and S3). In this randomized controlled trial, athletes were allocated to three groups: visual (VIS), verbal (VER) and control (CTRL). Kinematics and kinetics were collected at the time of peak knee frontal plane moment. RESULTS: Males in the VIS group showed a larger vertical ground reaction force (S1: 25.4 ± 3.1 N/kg, S2: 25.8 ± 2.9 N/kg, S3: 25.2 ± 3.2 N/kg) and knee flexion moments (S1: -3.8 ± 0.9 Nm/kg, S2: -4.0 ± 1.2 Nm/kg, S3: -3.9 ± 1.3 Nm/kg) compared to the males in the VER and CTRL groups and to the females in the VIS group (p < 0.05). Additionally, the males in the VIS group reduced knee valgus moment and the females in the VER group reduced knee varus moment over time (n.s.). CONCLUSION: Male subjects clearly benefit from visual feedback. Females may need different feedback modes to learn a correct movement pattern. Sex-specific learning preferences may have to be acknowledged in day by day practice. Adding video instruction or feedback to regular training regimens when teaching athletes safe movement patterns and providing individual feedback might target suboptimal long-term results and optimize ACL injury prevention programmes. LEVEL OF EVIDENCE: I.

Cycling in the Absence of Task-Related Feedback: Effects on Pacing and Performance.

INTRODUCTION: To achieve personal goals in exercise task completion, exercisers have to regulate, distribute, and manage their effort. In endurance sports, it has become very commonplace for athletes to consult task-related feedback on external devices to do so. The aim of the present study was to explore the importance of the presence of this information by examining the influence of the absence of commonly available task-related feedback on effort distribution and performance in experienced endurance athletes. METHODS: A 20-km cycling time trial was performed. Twenty Participants from a homogenous cyclist population were appointed to a group that did not receive any feedback (NoF), or a group that could consult task-related feedback (i.e., speed, heart rate, power output, cadence, elapsed time, and elapsed distance) continuously during their trial (FF). RESULTS: The distribution of power output (PO) differed between groups. Most evident is the spurt at the end of the trial of FF, which was not incorporated by NoF. Nevertheless, no between-group differences were found in performance time (FF: 28.86 ± 3.68 vs. NoF: 30.95 ± 2.77 min) and mean PO controlled by body mass (FF: 3.61 ± 0.60 vs. NoF: 3.43 ± 0.38 W/kg). Also, no differences in rating of perceived exertion scores were found. CONCLUSION: The current study provides a first indication that prior knowledge of task demands together with reliance on bodily and environmental information can be sufficient for experienced athletes to come to comparable time trial performances. This questions the necessity of the presence of in-race instantaneous task-related feedback via external devices for maximizing performance. Moreover, it seems that different pacing strategies emerge depending on sources of information available to experienced athletes.

Staying in dynamic balance on a prosthetic limb: A leg to stand on?

With the loss of a lower limb, amputees lack the active muscle empowered control of the ankle that is important for balance control. We examined single-leg stance on prosthesis vs. sound limb balancing on narrow ridges in transtibial amputees. When balancing on the prosthetic limb, the lateral displacement of the center of pressure was reduced and was compensated by an increase in counter-rotation. We show that single-leg stance on a prosthetic limb can be compared to balancing on a narrow ridge. Standing on a prosthetic limb involves the same balance mechanisms as balancing on narrow ridges of 40-mm to 20-mm width. Yet, the ability to balance on a narrow ridge with the sound limb was only a weak predictor for an amputee's ability to stand on the prosthetic limb. Balancing in single-leg stance on a prosthetic limb is not a common activity. The ability to compensate with the sound limb may therefore be functionally more important than the ability to stay in dynamic balance on the prosthetic limb.

Recovery of motor imagery ability in the first year after stroke.

The aim of this study was to examine the level and recovery of motor imagery ability (MIA) in the first year after stroke and whether the recovery of MIA is related to that of arm/hand function. Twenty-three patients with diminished arm/hand function were included. The accuracy score on the hand laterality judgment task was used to assess MIA and the Fugl-Meyer Assessment was used to evaluate the recovery of arm/hand function. The patients were assessed 3, 6, 16, 26, and 52 weeks after stroke. In the first year after stroke, the percentage of patients with moderate to good MIA improved from 78% after 3 weeks to 94% after 1 year. The recovery of MIA took place in the first 6 weeks after stroke. No correlation was found between the recovery of MIA and arm/hand function, despite the fact that the greatest improvement in both occurred in the first 6 weeks.

Enhanced retention of drop vertical jump landing technique: A randomized controlled trial.

External focus instructions have been shown to result in superior motor performance compared to internal focus instructions. Using an EF may help to optimize current anterior cruciate ligament (ACL) injury prevention programs. The purpose of the current study was to investigate the effects of instructions on landing technique and performance by comparing an external focus (EF), internal focus (IF), video (VI) and control (CTRL) group. Subjects (age 22.50±1.62years, height 179.70±10.43cm, mass 73.98±12.68kg) were randomly assigned to IF (n=10), EF (n=10), VI (n=10) or CTRL group (n=10). Landing was assessed from a drop vertical jump (DVJ) in five sessions: pretest, two training blocks (TR1 and TR2) and directly after the training sessions (post test) and retention test 1week later. Group specific instructions were offered in TR1 and TR2. Landing technique was assessed with the Landing Error Scoring System (LESS) and jump height was taken as performance measure. The results show that males in the VI group and females both in the VI and EF groups significantly improved jump-landing technique. Retention was achieved and jump height was maintained for males in the VI group and females both in the VI and EF groups. It is therefore concluded that EF and VI instructions have great potential in ACL injury prevention.

Activities of Daily Living in Children With Developmental Coordination Disorder: Performance, Learning, and Participation.

BACKGROUND: Children with developmental coordination disorder (DCD) face evident motor difficulties in daily functioning. Little is known, however, about their difficulties in specific activities of daily living (ADL). OBJECTIVE: The purposes of this study were: (1) to investigate differences between children with DCD and their peers with typical development for ADL performance, learning, and participation, and (2) to explore the predictive values of these aspects. DESIGN: This was a cross-sectional study. METHODS: In both a clinical sample of children diagnosed with DCD (n=25 [21 male, 4 female], age range=5-8 years) and a group of peers with typical development (25 matched controls), the children's parents completed the DCDDaily-Q. Differences in scores between the groups were investigated using t tests for performance and participation and Pearson chi-square analysis for learning. Multiple regression analyses were performed to explore the predictive values of performance, learning, and participation. RESULTS: Compared with their peers, children with DCD showed poor performance of ADL and less frequent participation in some ADL. Children with DCD demonstrated heterogeneous patterns of performance (poor in 10%-80% of the items) and learning (delayed in 0%-100% of the items). In the DCD group, delays in learning of ADL were a predictor for poor performance of ADL, and poor performance of ADL was a predictor for less frequent participation in ADL compared with the control group. LIMITATIONS: A limited number of children with DCD were addressed in this study. CONCLUSIONS: This study highlights the impact of DCD on children's daily lives and the need for tailored intervention.

Optimization of the anterior cruciate ligament injury prevention paradigm: novel feedback techniques to enhance motor learning and reduce injury risk.

SYNOPSIS: Primary anterior cruciate ligament (ACL) injury prevention programs effectively reduce ACL injury risk in the short term. Despite these programs, ACL injury incidence is still high, making it imperative to continue to improve current prevention strategies. A potential limitation of current ACL injury prevention training may be a deficit in the transfer of conscious, optimal movement strategies rehearsed during training sessions to automatic movements required for athletic activities and unanticipated events on the field. Instructional strategies with an internal focus of attention have traditionally been utilized, but may not be optimal for the acquisition of the control of complex motor skills required for sports. Conversely, external-focus instructional strategies may enhance skill acquisition more efficiently and increase the transfer of improved motor skills to sports activities. The current article will present insights gained from the motor-learning domain that may enhance neuromuscular training programs via improved skill development and increased retention and transfer to sports activities, which may reduce ACL injury incidence in the long term.

Novel methods of instruction in ACL injury prevention programs, a systematic review.

Anterior cruciate ligament (ACL) injury prevention programs have been successful in the short term. Motor learning strategies with an internal focus (IF) to body movements have traditionally been utilized, but may be less suitable than an external focus (EF) for the acquisition and control of complex motor skills required for sport. To investigate the available literature and provide an overview of the effect of IF and EF instructions on jump landing technique. Systematic searches were conducted in PubMed (1966 to May 2014), CINAHL (1981 to May 2014) and PsycInfo (1989 to May 2014). A priori defined inclusion criteria were: (i) full text; (ii) published in English, German or Dutch; (iii) healthy adult subjects (mean age ≥18 years); (iv) jump and landing performance tested and (v) study used comparison between an EF and IF. Performance (jump height and distance) and technique (kinematics and kinetics) were the primary outcome variables of interest. Nine papers were included. Significant better motor performance and movement technique was found with an EF compared to an IF. Considering the beneficial results in the included studies when utilizing an EF, it is suggested to implement these strategies into ACL injury prevention programs.

The effects of attentional focus on jump performance and knee joint kinematics in patients after ACL reconstruction.

OBJECTIVES: The purpose of this study was to determine the effect of an internal and external attentional focus on single leg hop jump distance and knee kinematics in patients after ACL reconstruction (ACLR). DESIGN: Experimental. SETTING: Outpatient physical therapy facility. PARTICIPANTS: Sixteen patients after ACLR. MAIN OUTCOME MEASURES: Patients received either an instruction with an internal focus or an external focus before performing a single leg hop jump. The jump distance, knee valgus angle at initial contact, peak knee valgus angle, knee flexion angle at initial contact, peak knee flexion angle, total ROM and time to peak angles for the injured and non-injured legs were recorded. A repeated measures MANOVA was used to determine significance between the experimental conditions with the primary outcome measures as dependent variables. RESULTS: The external focus group had significant larger knee flexion angles at initial contact, peak knee flexion, total ROM and time to peak knee flexion for the injured legs. CONCLUSIONS: This study demonstrates the applicability of using an external focus during rehabilitation of patients after ACLR to enhance safer movement patterns compared to an internal focus of attention and subsequently may help to reduce second ACL injury risk.

Psychometric properties of the DCDDaily-Q: a new parental questionnaire on children's performance in activities of daily living.

Difficulties in the performance of activities of daily living (ADL) are a key feature of developmental coordination disorder (DCD). The DCDDaily-Q was developed to address children's motor performance in a comprehensive range ADL. The aim of this study was to investigate the psychometric properties of this parental questionnaire. Parents of 218 five to eight year-old children (DCD group: N=25; reference group: N=193) completed the research version of the new DCDDaily-Q and the Movement Assessment Battery for Children-2 (MABC2) Checklist and Developmental Coordination Disorder Questionnaire (DCDQ). Children were assessed with the MABC2 and DCDDaily. Item reduction analyses were performed and reliability (internal consistency and factor structure) and concurrent, discriminant, and incremental validity of the DCDDaily-Q were investigated. The final version of the DCDDaily-Q comprises 23 items that cover three underlying factors and shows good internal consistency (Cronbach's α>.80). Moderate correlations were found between the DCDDaily-Q and the other instruments used (p<.001 for the reference group; p>.05 for the DCD group). Discriminant validity of the DCDDaily-Q was good for DCDDaily-Q total scores (p<.001) and all 23 item scores (p<.01), indicating poorer performance in the DCD group. Sensitivity (88%) and specificity (92%) were good. The DCDDaily-Q better predicted DCD than currently used questionnaires (R(2)=.88). In conclusion, the DCDDaily-Q is a valid and reliable questionnaire to address children's ADL performance.

Motor imagery ability in stroke patients: the relationship between implicit and explicit motor imagery measures.

There is little consensus on how motor imagery ability should be measured in stroke patients. In particular it is unclear how two methods tapping different aspects of the motor imagery process relate to each other. The aim of this study was to investigate the relationship between implicit and explicit motor imagery ability by comparing performance of stroke patients and controls on a motor imagery questionnaire and a hand laterality judgment task (HLJT). Sixteen ischemic stroke patients (36 ± 13 weeks post-stroke) and 16 controls, matched by age (51 ± 10 years), gender (7 females) and handedness (3 left-handed), performed a HLJT and completed a motor imagery questionnaire. Our study shows that neither in the healthy controls nor in patients, a correlation is found between the HLJT and the motor imagery questionnaire. Although the patient group scored significantly lower than the control group on the visual motor imagery component (U = 60; p = 0.010) and the kinesthetic motor imagery component (U = 63.5; p = 0.015) of the questionnaire, there were no significant differences between patients and controls on accuracy scores of the HLJT. Analyses of the reaction time profiles of patients and controls showed that patient were still able to use an implicit motor imagery strategy in the HLJT task. Our results show that after stroke performance on tests that measure two different aspects of motor imagery ability, e.g., implicit and explicit motor imagery, can be differently affected. These results articulate the complex relation phenomenological experience and the different components of motor imagery have and caution the use of one tool as an instrument for use in screening, selecting and monitoring stroke patients in rehabilitation settings.

Development and psychometric properties of the DCDDaily: a new test for clinical assessment of capacity in activities of daily living in children with developmental coordination disorder.

OBJECTIVE: To develop the DCDDaily, an instrument for objective and standardized clinical assessment of capacity in activities of daily living (ADL) in children with developmental coordination disorder (DCD), and to investigate its usability, reliability, and validity. SUBJECTS: Five to eight-year-old children with and without DCD. MAIN MEASURES: The DCDDaily was developed based on thorough review of the literature and extensive expert involvement. To investigate the usability (assessment time and feasibility), reliability (internal consistency and repeatability), and validity (concurrent and discriminant validity) of the DCDDaily, children were assessed with the DCDDaily and the Movement Assessment Battery for Children-2 Test, and their parents filled in the Movement Assessment Battery for Children-2 Checklist and Developmental Coordination Disorder Questionnaire. RESULTS: 459 children were assessed (DCD group, n = 55; normative reference group, n = 404). Assessment was possible within 30 minutes and in any clinical setting. For internal consistency, Cronbach's α = 0.83. Intraclass correlation = 0.87 for test-retest reliability and 0.89 for inter-rater reliability. Concurrent correlations with Movement Assessment Battery for Children-2 Test and questionnaires were ρ = -0.494, 0.239, and -0.284, p < 0.001. Discriminant validity measures showed significantly worse performance in the DCD group than in the control group (mean (SD) score 33 (5.6) versus 26 (4.3), p < 0.001). The area under curve characteristic = 0.872, sensitivity and specificity were 80%. CONCLUSIONS: The DCDDaily is a valid and reliable instrument for clinical assessment of capacity in ADL, that is feasible for use in clinical practice.

Controlling horizontal deceleration during gait termination in transfemoral amputees: measurements and simulations.

In this study we investigated how leading limb angles combined with active ankle moments of a sound ankle or passive stiffness of a prosthetic ankle, influence the center of mass (CoM) velocity during the single limb support phase in gait termination. Also, we studied how the trailing limb velocity influences the CoM velocity during this phase. We analyzed force plate data from a group of experienced transfermoral (TF) amputee subjects using a prosthetic limb, and the outcome from a two-dimensional mathematical forward dynamics model. We found that when leading with the sound limb, the subjects came almost to a full stop in the single limb support phase, without the use of the prosthetic limb. When leading with the prosthetic limb, the CoM deceleration was less in a relatively short single limb support phase, with a fast forward swing of the trailing sound limb. Slowing down the heavier trailing sound limb, compared to the prosthetic limb, results in a relatively larger braking force at the end of the swing phase. The simulations showed that only narrow ranges of leading limb angle and ankle moments could be used to achieve the same CoM velocities with the mathematical model as the average start and end velocities of the prosthetic limb user. We conclude that users of prosthetic limbs have a narrow range of options for the dynamics variables to achieve a target CoM velocity. The lack of active control in the passive prosthetic ankle prevents the TF amputee subjects from producing sufficient braking force when terminating gait with the prosthetic limb leading, forcing the subjects to use both limbs as a functional unit, in which the sound limb is mostly responsible for the gait termination.

The relative contributions of the prosthetic and sound limb to balance control in unilateral transtibial amputees.

In unilateral transtibial amputees maintenance of standing balance is compromised due to the lack of active ankle control in the prosthetic limb. The purpose of this study is to disentangle the contribution of the prosthetic and sound limb to balance control following waist-pull perturbations. We compared the contribution of the hip and ankle joints to balance control of 15 unilateral transtibial amputees and 13 able-bodied controls after been externally perturbed through release of a pulling force. Perturbations were applied in four different directions. Outcome measure was the proportion of joint moment integrated over time generated by the hip and ankle joints in order to restore static stability after perturbation. Analyses revealed that perturbations in backward/forward direction were recovered mainly by the ankle strategy. The amputees compensated for the absence of active ankle control in the prosthetic limb by increasing the ankle moment in the sound limb. Interestingly, the passive properties of the prosthetic foot contributed to balance control, which has important implications for prosthetic fitting and standing stability in lower limb amputees. Amputees and controls resisted perturbations in medio-lateral direction by generating the necessary hip moments. Finally, these findings are discussed with respect to prosthetic design and rehabilitation processes.

Stabilizing moments of force on a prosthetic knee during stance in the first steps after gait initiation.

In this study, the occurrences of stabilizing and destabilizing external moments of force on a prosthetic knee during stance, in the first steps after gait initiation, in inexperienced users were investigated. Primary aim was to identify the differences in the external moments during gait initiation with the sound leg leading and the prosthetic leg leading. A prosthetic leg simulator device, with a flexible knee, was used to test able-bodied subject, with no walking aid experience. Inverse dynamics calculations were preformed to calculate the external moments. The subjects learned to control the prosthetic leg within 100 steps, without walking aids, evoking similar patterns of external moments of force during the steps after the gait initiation, either with their sound leg loading or prosthetic leg leading. Critical phases in which a sudden flexion of the knee can occur were found just after heelstrike and just before toe off, in which the external moment of force was close to the internal moment produced by a knee extension aiding spring in the opposite direction.