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Calibration of instrumented treadmills is imperative for accurate measurement of ground reaction forces and center of pressure (COP). A protocol using an instrumented pole has been shown to considerably increase force and COP accuracy. This study examined how this protocol can be further optimized to maximize accuracy, by varying the measurement time and number of spots, using nonlinear approaches to calculate the calibration matrix and by correcting for potential inhomogeneity in the distribution of COP errors across the treadmill's surface. The accuracy increased with addition of spots and correction for the inhomogeneous distribution across the belt surface, decreased with reduction of measurement time, and did not improve by including nonlinear terms. Most of these methods improved the overall accuracy only to a limited extent, suggesting that the maximal accuracy is approached given the treadmill's inherent mechanical limitations. However, both correction for position dependence of the accuracy as well as its optimization within the walking area are found to be valuable additions to the standard calibration process. [ABSTRACT FROM AUTHOR]

Purpose: Stroke survivors are inclined to consciously control their movements, a phenomenon termed “reinvestment”. Preliminary evidence suggests reinvestment to impair patients’ motor recovery. To investigate this hypothesis, an instrument is needed that can reliably assess reinvestment post-stroke. Therefore, this study aimed to validate the Movement-Specific Reinvestment Scale (MSRS) within inpatient stroke patients. Method: One-hundred inpatient stroke patients (<1 year post-stroke) and 100 healthy peers completed the MSRS, which was translated to Dutch for the study purpose. To assess structural validity, confirmatory factor analysis determined whether the scale measures two latent constructs, as previously reported in healthy adults. Construct validity was determined by testing whether patients had higher reinvestment than controls. Reliability analyses entailed assessment of retest reliability (ICC), internal consistency (Cronbach’s alpha), and minimal detectable change. Results: Both structural and construct validity of the MSRS were supported. Retest reliability and internal consistency indices were acceptable to good. The minimal detectable change was adequate on group level, but considerable on individual level. Conclusions: The MSRS is a valid and reliable tool and suitable to assess the relationship between reinvestment and motor recovery in the first months post-stroke. Eventually, this may help therapists to individualize motor learning interventions based on patients’ reinvestment preferences.Implications for rehabilitationThis study showed that the Movement-Specific Reinvestment Scale (MSRS) is a valid and reliable tool to objectify stroke patients’ inclination for conscious motor control.The MSRS may be used to identify stroke patients who are strongly inclined to consciously control their movements, as this disposition may hinder their motor recovery.Eventually, the MSRS may enable clinicians to tailor motor learning interventions to stroke patients’ motor control preferences. [ABSTRACT FROM AUTHOR]

Instrumented treadmills are becoming more common in gait analysis. Due to their large and compliant structure, errors in force measurements are expected to be higher compared with conventional force plates. There is, however, no consistency in the literature on testing the performance of these treadmills. Therefore, we propose a standard protocol to assess and report error sources in instrumented treadmills. The first part of this protocol consists of assessment of the accuracy of forces and center of pressure (COP), including non-linearity, hysteresis and crosstalk. The second part consists of (novel) instrumented resonance testing and belt speed variability tests. The third part focuses on measurement variability over time, including drift, warming of the system and noise. The performance of two in-house instrumented treadmills with different dynamics was measured. Differences were found between the treadmills in COP accuracy (4.0 mm versus 6.5 mm), lowest eigen frequency (35 Hz versus 23 Hz) and noise level at 5 km/h (10 N versus 29 N). The loaded treadmills both showed a 3.3% belt speed variability at 5 km/h. Thus, the protocol was able to characterize strong and weak characteristics of the treadmills and allowed for a proper judgement on the validity of the instruments and their application in the domain of gait analysis. We propose to use this protocol when testing and reporting the performance of instrumented treadmills. [ABSTRACT FROM AUTHOR]

Accelerometry can be used to objectively assess the walking ability of people with a lower-limb prosthesis inside and outside the laboratory setting. In this study, the validity of the DynaPort GaitMonitor software (McRoberts, The Hague, the Netherlands) for assessing spatiotemporal parameters of amputee gait was evaluated. Fourteen subjects with a lower-limb prosthesis walked on a straight level walkway at a self-selected walking speed over three different distances. During walking, we measured pelvis acceleration using a triaxial accelerometer (DynaPort MiniMod). Mean spa tiotemporal parameters were derived from these signals using the DynaPort GaitMonitor software. Similar parameters were simultaneously determined from video. Overall, the number of steps, mean step time, step length, and walking speed were detected accurately by the GaitMonitor software. No systematic deviation was found, and the accuracy of the different parameters was within 6.5%. However, step times measured separately for both the intact and prosthetic legs differed considerably between the GaitMonitor and the video. Step time was systematically underestimated by the GaitMonitor for the intact leg and overestimated for the prosthetic leg. We concluded that the DynaPort GaitMonitor is a valid instrument for assessing mean spatiotemporal parameters in amputee gait, although systematic errors in prosthetic and intact heel strike detection prevent a reliable analysis of walking symmetry. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to evaluate a Hill-based mathematical model of muscle energetics and to disclose inconsistencies in existing experimental data. For this purpose, we simulated iso-velocity contractions of mouse fast twitch EDL and slow twitch SOL fibers, and we compared the outcome to experimental results. The experimental results were extracted from two studies published in the literature, which were based on the same methodology but yielded different outcomes (B96 and B93). In the model, energy cost was modeled as the sum of heat and work. Parameters used to model heat rate were entirely independent of the experimental data-sets. Parameters describing the mechanical behavior were derived from both experimental studies. The model was found to accurately predict the muscle energetics and mechanical efficiency of data-set B96. The model could not, however, replicate the energetics and efficiency of SOL and EDL that were found in data-set B93. The model overestimated the shortening heat rate of EDL but, surprisingly, also the mechanical work rate for both muscles. This was surprising since mechanical characteristics of the model were derived directly from the experimental data. It was demonstrated that the inconsistencies in data-set B93 must have been due to some unexplained confounding artifact. It was concluded that the presented model of muscle energetics is valid for iso-velocity contractions of mammalian muscle since it accurately predicts experimental results of an independent data-set (B96). In addition, the model appeared to be helpful in revealing inconsistencies in a second data-set (B93). [Copyright &y& Elsevier]

PURPOSE: The introduction of the klapskate in speed skating confronts skaters with the question of how to adjust the position of the hinge in order to maximize performance. The purpose of this study was to reveal the constraint that klapskate hinge position imposes on push-off performance in speed skating. METHOD: For this purpose, a model of the musculoskeletal system was designed to simulate a simplified, two-dimensional skating push off. To capture the essence of a skating push off, this model performed a one-leg vertical jump, from a frictionless surface, while keeping its trunk horizontally. In this model, klapskate hinge position was varied by varying the length of the foot segment between 115 and 300 mm. With each foot length, an optimal control solution was found that resulted in the maximal amount of vertical kinetic and potential energy of the body's center of mass at take off (Weff). RESULTS: Foot length was shown to considerably affect push-off performance. Maximal Weff was obtained with a foot length of 185 mm and decreased by approximately 25% at either foot length of 115 mm and 300 mm. The reason for this decrease was that foot length affected the onset and control of foot rotation. This resulted in a distortion of the pattern of leg segment rotations and affected muscle work (Wmus) and the efficacy ratio (Weff/Wmus) of the entire leg system. CONCLUSION: Despite its simplicity, the model very well described and explained the effects of klapskate hinge position on push off performance that have been observed in speed-skating experiments. The simplicity of the model, however, does not allow quantitative analyses of optimal klapskate hinge position for speed-skating practice. [ABSTRACT FROM AUTHOR]

Background: Many stroke patients are inclined to consciously control their movements. This is thought to negatively affect patients' motor performance, as it disrupts movement automaticity. However, it has also been argued that conscious control may sometimes benefit motor performance, depending on the task or patientś motor or cognitive capacity.Aim: To assess whether stroke patients' inclination for conscious control is associated with motor performance, and explore whether the putative association differs as a function of task (single- vs dual) or patientś motor and cognitive capacity.Methods: Univariate and multivariate linear regression analysis were used to assess associations between patients' disposition to conscious control (i.e., Conscious Motor Processing subscale of Movement-Specific Reinvestment Scale; MSRS-CMP) and single-task (Timed-up-and-go test; TuG) and motor dual-task costs (TuG while tone counting; motor DTC%). We determined whether these associations were influenced by patients' walking speed (i.e., 10-m-walk test) and cognitive capacity (i.e., working memory, attention, executive function).Results: Seventy-eight clinical stroke patients (<6 months post-stroke) participated. Patients' conscious control inclination was not associated with single-task TuG performance. However, patients with a strong inclination for conscious control showed higher motor DTC%. These associations were irrespective of patients' motor and cognitive abilities.Conclusion: Patients' disposition for conscious control was not associated with single task motor performance, but was associated with higher motor dual task costs, regardless of patients' motor or cognitive abilities.Clinical Relevance: Therapists should be aware that patients' conscious control inclination can influence their dual-task performance while moving. Longitudinal studies are required to test whether reducing patients' disposition for conscious control would improve dual-tasking post-stroke. [ABSTRACT FROM AUTHOR]

Dual-task performance is often impaired after stroke. This may be resolved by enhancing patients’ automaticity of movement. This study sets out to test the constrained action hypothesis, which holds that automaticity of movement is enhanced by triggering an external focus (on movement effects), rather than an internal focus (on movement execution). Thirty-nine individuals with chronic, unilateral stroke performed a one-leg-stepping task with both legs in single- and dual-task conditions. Attentional focus was manipulated with instructions. Motor performance (movement speed), movement automaticity (fluency of movement), and dual-task performance (dual-task costs) were assessed. The effects of focus on movement speed, single- and dual-task movement fluency, and dual-task costs were analysed with generalized estimating equations. Results showed that, overall, single-task performance was unaffected by focus (p = .341). Regarding movement fluency, no main effects of focus were found in single- or dual-task conditions (p’s ≥ .13). However, focus by leg interactions suggested that an external focus reduced movement fluency of the paretic leg compared to an internal focus (single-task conditions: p = .068; dual-task conditions: p = .084). An external focus also tended to result in inferior dual-task performance (β = -2.38, p = .065). Finally, a near-significant interaction (β = 2.36, p = .055) suggested that dual-task performance was more constrained by patients’ attentional capacity in external focus conditions. We conclude that, compared to an internal focus, an external focus did not result in more automated movements in chronic stroke patients. Contrary to expectations, trends were found for enhanced automaticity with an internal focus. These findings might be due to patients’ strong preference to use an internal focus in daily life. Future work needs to establish the more permanent effects of learning with different attentional foci on re-automating motor control after stroke. [ABSTRACT FROM AUTHOR]

Background: Holding a handrail or using a cane may decrease the energy cost of walking in stroke survivors. However, the factors underlying this decrease have not yet been previously identified. The purpose of the current study was to fill this void by investigating the effect of physical support (through handrail hold) and/or somatosensory input (through light touch contact with a handrail) on energy cost and accompanying changes in both step parameters and neuromuscular activity. Elucidating these aspects may provide useful insights into gait recovery post stroke. Methods: Fifteen stroke survivors participated in this study. Participants walked on a treadmill under three conditions: no handrail contact, light touch of the handrail, and firm handrail hold. During the trials we recorded oxygen consumption, center of pressure profiles, and bilateral activation of eight lower limb muscles. Effects of the three conditions on energy cost, step parameters and neuromuscular activation were compared statistically using conventional ANOVAs with repeated measures. In order to examine to which extent energy cost and step parameters/muscle activity are associated, we further employed a partial least squares regression analysis. Results: Handrail hold resulted in a significant reduction in energy cost, whereas light touch contact did not. With handrail hold subjects took longer steps with smaller step width and improved step length symmetry, whereas light touch contact only resulted in a small but significant decrease in step width. The EMG analysis indicated a global drop in muscle activity, accompanied by an increased constancy in the timing of this activity, and a decreased co-activation with handrail hold, but not with light touch. The regression analysis revealed that increased stride time and length, improved step length symmetry, and decreased muscle activity were closely associated with the decreased energy cost during handrail hold. Conclusion: Handrail hold, but not light touch, altered step parameters and was accompanied by a global reduction in muscle activity, with improved timing constancy. This suggests that the use of a handrail allows for a more economic step pattern that requires less muscular activation without resulting in substantial neuromuscular re-organization. Handrail use may thus have beneficial effects on gait economy after stroke, which cannot be accomplished through enhanced somatosensory input alone. [ABSTRACT FROM AUTHOR]

Rocker shoes can be used to reduce foot pressure and adjust lower limb kinetics for various patient population, such as people with diabetic peripheral neuropathy. Selecting adequate properties of the rocker sole is of great importance for its efficacy. This study investigated the capability of human-in-the-loop optimization (HILO) to individually optimize apex position and angle of rocker shoe to reduce peak pressure and collision work simultaneously. Peak pressure, kinetic, and kinematic data were recorded from 10 healthy participants while walking at preferred speed wearing rocker shoes with adjustable apex position and angle. An evolutionary algorithm was used to find optimal apex parameters to reduce both peak pressure in medial forefoot and collision work. The optimized shoe (HILO shoe) was compared with generic optimal rocker settings (Chapman settings) and normal shoe. Compared to normal shoe, the HILO shoe had lower plantar pressure (p HILO = 0.007; p Chapman = 0.044) and Chapman shoe showed higher collision work (p HILO = 0.025; p Chapman = 0.014). Both HILO and Chapman shoe had smaller push-off work than normal shoe (p HILO = 0.001; p Chapman < 0.001) with the Chapman shoe exhibited earlier push-off onset (p HILO = 0.257; p Chapman = 0.016). The Human-in-the-loop optimization approach resulted in individualized apex settings which performed on average similar to Chapman settings but, were superior in selected cases. In these cases, medial forefoot could be further offloaded with apex angles larger than generic settings. The larger apex angle might increase the external ankle moment arm and push-off work. However, there is limited room for improvement on collision work compared to generic settings. • Human-in-the-loop optimization found individualized rocker shoe settings. • On group level the settings reduced plantar pressure similar to current standards. • On individual level medial forefoot was offloaded more than current gold standard. • Optimized apex position was similar to standard but with larger and varying angles. • Limited room to improve collision work was found while offloading the forefoot. [ABSTRACT FROM AUTHOR]

Highlights: [•] Lower muscle fatigability is observed in children with CP compared to TD children. [•] This is demonstrated by combining peak torque and EMG median frequency analyses. [•] Lower muscle fatigability coincides with lower muscle strength. [Copyright &y& Elsevier]

Highlights: [•] The effect of attentional focus on movement automatization was investigated. [•] We assessed automaticity with dual task costs, EMG activity, jerk, and sample entropy. [•] An external focus resulted in superior motor performance than an internal focus. [•] Focusing attention externally was found to enhance automatization of movement. [•] These results were in line with the predictions of the constrained action hypothesis. [ABSTRACT FROM AUTHOR]

Purpose. To evaluate the effects of a structured hand cycle training programme on physical capacity in subjects with spinal cord injury (SCI) during clinical rehabilitation. Method. Twenty subjects with SCI who followed hand cycle training were compared with matched control subjects from a Dutch longitudinal cohort study, who received usual care. Primary outcomes of physical capacity were peak power output (POpeak), peak oxygen uptake (VO2peak) and oxygen pulse during a hand rim wheelchair test. Secondary outcome measures were isometric peak muscle strength of the upper extremities and pulmonary function. Hand cycle capacity (POpeak and VO2peak) was evaluated in the training group only. Results. Strong tendencies for improvement were found in wheelchair capacity, reflected by POpeak and oxygen pulse after additional hand cycle training. Significant effects on shoulder exo- and endo-rotation and unilateral elbow flexion strength were found but no improvements on pulmonary function. Conclusions. Additional hand cycle training during clinical rehabilitation seems to show similar or slightly favourable results on wheelchair capacity and muscle strength compared with regular care. The heterogeneous subject group and large variation in training period may explain the limited effects of additional hand cycle training on wheelchair capacity. [ABSTRACT FROM AUTHOR]

Study design:Descriptive study.Objective:To examine the individual heart rate–oxygen uptake (HR–VO2) relationship during exercise in persons with tetraplegia (TP).Setting:Rehabilitation Centre Heliomare, Wijk aan Zee, The Netherlands.Methods:The HR–VO2 relationship was determined in untrained subjects with motor complete TP (C5 or C6, n=10 and C7 or C8, n=10) during a discontinuous graded exercise hand cycle test. The mean HR and VO2 of the final 60 s of 2-min exercise blocks were used for calculation of the individual correlation coefficient and the standard error of the estimate (SEE).Results:Two subjects of the C5–C6 group were not able to complete the test. Individual Pearson's correlation coefficients (r) ranged from 0.68 to 0.97 and SEE from 2.6 to 22.4% VO2-Reserve (VO2R). The mean Pearson's r and SEE were 0.81±0.12 and 10.6±5.6% VO2R in the C5–C6 group and 0.91±0.07 and 7.0±3.2% VO2R in the C7–C8 group, respectively. Two subjects of the C5–C6 group and six subjects of the C7–C8 group attained a linear HR–VO2 relationship with an acceptable SEE (6.0%) and r (>0.90).Conclusions:The HR–VO2 relationship appeared linear in only eight out of 18 subjects. An individual analysis of the HR–VO2 relationship is necessary to determine whether HR can be used to quantify exercise intensity. The use of HR to prescribe training intensity should be reconsidered in persons with TP.Sponsorship:This study is supported from a grant by ZON-MW.Spinal Cord (2007) 45, 104–111. doi:10.1038/sj.sc.3101946; published online 27 June 2006 [ABSTRACT FROM AUTHOR]

Many studies on ankle-foot orthoses investigated the optimal stiffness around the ankle, while the effect of footplate stiffness has been largely ignored. This study investigated the effects of ankle-foot orthosis footplate stiffness on ankle-foot push-off power during walking in able-bodied persons. Twelve healthy participants walked at a fixed speed (1.25 m·s−1) on an instrumented treadmill in four conditions: shod and with a posterior leaf-spring orthosis with a flexible, stiff or rigid footplate. For each trial, ankle kinematics and kinetics were averaged over one-minute walking. Separate contributions of the ankle joint complex and distal hindfoot to total ankle-foot power and work were calculated using a deformable foot model. Peak ankle joint power was significantly higher with the rigid footplate compared to the flexible and stiff footplate and not different from shod walking. The stiff footplate increased peak hindfoot power compared to the flexible and rigid footplate and shod walking. Total ankle-foot power showed a significant increase with increasing footplate stiffness, where walking with the rigid footplate was comparable to shod walking. Similar effects were found for positive mechanical work. A rigid footplate increases the lever of the foot, resulting in an increased ankle moment and energy storage and release of the orthosis' posterior leaf-spring as reflected in higher ankle joint power. This effect dominates the power generation of the foot, which was highest with the intermediate footplate stiffness. Future studies should focus on how tuning footplate stiffness could contribute to optimizing ankle-foot orthosis efficacy in clinical populations. • Ankle-foot orthosis footplate stiffness affects push-off power. • We were able to distinct the contribution of the ankle and foot to total power. • Contributions of both components are affected by orthosis footplate stiffness. • Ankle power increased with stiffer footplate due to increased mechanical advantage. • Footplate stiffness should be considered together with orthosis' ankle stiffness. [ABSTRACT FROM AUTHOR]

Purpose: Besides mechanical loading of the back, physiological strain is an important risk factor for low-back pain. Recently a passive exoskeleton (SPEXOR) has been developed to reduce loading on the low back. We aimed to assess the effect of this device on metabolic cost of repetitive lifting. To explain potential effects, we assessed kinematics, mechanical joint work, and back muscle activity.Methods: We recruited ten male employees, working in the luggage handling department of an airline company and having ample experience with lifting tasks at work. Metabolic cost, kinematics, mechanical joint work and muscle activity were measured during a 5-min repetitive lifting task. Participants had to lift and lower a box of 10 kg from ankle height with and without the exoskeleton.Results: Metabolic cost was significantly reduced by 18% when wearing the exoskeleton. Kinematics did not change significantly, while muscle activity decreased by up to 16%. The exoskeleton took over 18-25% of joint work at the hip and L5S1 joints. However, due to large variation in individual responses, we did not find a significant reduction of joint work around the individual joints.Conclusion: Wearing the SPEXOR exoskeleton decreased metabolic cost and might, therefore, reduce fatigue development and contribute to prevention of low-back pain during repetitive lifting tasks. Reduced metabolic cost can be explained by the exoskeleton substituting part of muscle work at the hip and L5S1 joints and consequently decreasing required back muscle activity. [ABSTRACT FROM AUTHOR]

Introduction: Regular rehabilitation therapies do not always strain patients enough to improve physical fitness. Therefore, Heliomare rehabilitation center introduced ‘Physical Profile’, a structured, progressive and intensive exercise programme for clinical patients. Objective: To describe the feasibility and the effects of 'Physical Profile’. Patients: Since April 2014, 108 patients were screened for the programme. A total of 43 patients trained in the programme for more than three weeks. The main reason for not starting or completing the programme was early discharge. Currently 26 patients have completed the programme, including pre- and postcardiopulmonary exercise test (CPET). This group consists of 15 people after stroke, six people with a lower limb amputation and five people with a spinal cord injury. Methods: Patients trained twice a week for one hour. Each training consisted of two high-intensity interval training blocks and three strength exercises. Training was progressively adapted to the patient’s fitness level. Progression was monitored at start and end of the using a CPET. Results: All patients showed an improved maximal power (Wpeak) after the training (median increase 18%; range 6%–80%). The majority of patients (19/26) also improved their maximal oxygen uptake (VO2peak). The median increase in VO2peak was 12% (range −13%–55%). Conclusion: Owing to logistic challenges and short rehabilitation stays not all patients completed the exercise programme. However, the group that did follow the programme showed an increase in Wmax and on average an increase in VO2peak. Clinical message: Despite logistic challenges, intensive physical training seems feasible and effective in a selective group of patients. [ABSTRACT FROM AUTHOR]

Background: Prosthetic alignment is used to optimize prosthetic functioning and comfort. Spatio-temporal and kinematic gait parameters are generally observed to guide this process. However, they have been shown to be influenced by compensations, which reduces their sensitivity to changes in alignment. Alternatively, the use of moments working at the base of the prosthetic socket, external socket reaction moments (ESRM), has been proposed to quantify prosthetic alignment.Research Question: To investigate if a predetermined kinetic alignment criterion, 0Nm averaged over the stance phase, can be used to fine-tune prosthetic alignment.Methods: 10 transtibial amputees were included in this intervention study. Firstly, their prostheses were aligned using conventional alignment procedures. Kinetic parameters and Socket Comfort Score (SCS) were measured in this initial alignment (IA) condition. Subsequently, the coronal plane ESRM during gait was presented to the prosthetist in real time using a Gait Real-time Analysis Interactive Lab. The prosthetist iteratively adapted the prosthetic alignment towards a predetermined average ESRM during the stance phase of 0 Nm. At the Final Alignment (FA), kinetic parameters and SCS were measured again and a paired sample t-test was performed to compare ESRMs and SCSs between alignments.Results: A significant (p < 0.001) change was found in the absolute coronal plane ESRM (mean ± SD) from IA (|0.104| ± 0.058 Nm/kg) to FA (|0.012| ± 0.015 Nm/kg). In addition a significant (p < 0.001) change of the external coronal adduction knee moments was observed from IA (-0,127 ± 0.079 Nm/kg) to FA (-0.055 ± 0.089 Nm/kg), however this change was more variable among participants. On average, no significant (p = 0.37) change in the SCS was observed.Significance: While this study shows the potential of quantifying and guiding alignment with the assistance of kinetic criteria, it also suggests that a sole reliance on the ESRM as a single alignment criterion might be too simple. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the effect of a passive trunk exoskeleton on functional performance for various work related tasks in healthy individuals. 18 healthy men performed 12 tasks. Functional performance in each task was assessed based on objective outcome measures and subjectively in terms of perceived task difficulty, local and general discomfort. Wearing the exoskeleton tended to increase objective performance in static forward bending, but decreased performance in tasks, such as walking, carrying and ladder climbing. A significant decrease was found in perceived task difficulty and local discomfort in the back in static forward bending, but a significant increase of perceived difficulty in several other tasks, like walking, squatting and wide standing. Especially tasks that involved hip flexion were perceived more difficult with the exoskeleton. Design improvements should include provisions to allow full range of motion of hips and trunk to increase versatility and user acceptance. [ABSTRACT FROM AUTHOR]

Stretching is applied to lengthen shortened muscles in pathological conditions such as joint contractures. We investigated (i) the acute effects of different types of stretching, i.e. constant length (CL) and constant force (CF) stretching, on acute deformations and changes in passive mechanical properties of medial gastrocnemius muscle (MG) and (ii) the association of acute muscle–tendon deformations or changes in mechanical properties with the impulse or maximal strain of stretching. Forty-eight hindlimbs from 13 male and 12 female Wistar rats (13 weeks old, respectively 424.6 ± 35.5 and 261.8 ± 15.6 g) were divided into six groups (n = 8 each). The MG was initially stretched to a length at which the force was 75%, 95%, or 115% of the force corresponding to estimated maximal dorsiflexion and held at either CF or CL for 30 min. Before and after the stretching protocol, the MG peak force and peak stiffness were assessed by lengthening the passive muscle to the length corresponding to maximal ankle dorsiflexion. Also, the muscle belly length and tendon length were measured. CF stretching affected peak force, peak stiffness, muscle belly length, and tendon length more than CL stretching (p < 0.01). Impulse was associated only with the decrease in peak force, while maximal strain was associated with the decrease in peak force, peak stiffness, and the increase in muscle belly length. We conclude that CF stretching results in greater acute deformations and changes in mechanical properties than CL stretching, which appears to be dependent predominantly on the differences in imposed maximal strain. [ABSTRACT FROM AUTHOR]

Background Knowledge on lower extremity strength is imperative to informed decision making for children with cerebral palsy (CP) with mobility problems. However, a functional and clinically feasible test is not available. We aimed to determine whether the squat test is suitable for this purpose by investigating test performance and execution in children with cerebral palsy and typically developing (TD) peers. Methods Squat test performance, defined by the number of two-legged squats until fatigue (max 20), was assessed in twenty children with bilateral CP (6–19 years; gross motor function classification system I–III) and sixteen TD children (7–16 years). Muscle fatigue was assessed from changes in electromyography (EMG). Joint range-of-motion and net torque were calculated for each single squat, to investigate differences between groups and between the 2nd and last squat. Findings Fifteen children with CP performed < 20 squats (median = 13, IQR = 7–19), while all TD children performed the maximum of 20 squats. Median EMG frequency decreased and amplitude increased in mm. quadriceps of both groups. Ankle and knee range-of-motion were reduced in children with CP during a single squat by 10 to 15°. No differences between 2nd and last squat were observed, except for knee range-of-motion which increased in TD children and decreased in children with CP. Interpretation Squat test performance was reduced in children with CP, especially in those with more severe CP. Muscle fatigue was present in both children with CP and TD peers, confirming that endurance of the lower extremity was tested. Minor execution differences between groups suggest that standardized execution is important to avoid compensation strategies. It is concluded that the squat test is feasible to test lower extremity strength in children with CP in a clinically meaningful way. Further clinimetric evaluation is needed before clinical implementation. [ABSTRACT FROM AUTHOR]

Many stroke patients experience difficulty with performing dual-tasks. A promising intervention to target this issue is implicit motor learning, as it should enhance patients’ automaticity of movement. Yet, although it is often thought that implicit motor learning is preserved post-stroke, evidence for this claim has not been systematically analysed yet. Therefore, we systematically reviewed whether implicit motor learning is preserved post-stroke, and whether patients benefit more from implicit than from explicit motor learning. We comprehensively searched conventional (MEDLINE, Cochrane, Embase, PEDro, PsycINFO) and grey literature databases (BIOSIS, Web of Science, OpenGrey, British Library, trial registries) for relevant reports. Two independent reviewers screened reports, extracted data, and performed a risk of bias assessment. Overall, we included 20 out of the 2177 identified reports that allow for a succinct evaluation of implicit motor learning. Of these, only 1 study investigated learning on a relatively complex, whole-body (balance board) task. All 19 other studies concerned variants of the serial-reaction time paradigm, with most of these focusing on learning with the unaffected hand (N = 13) rather than the affected hand or both hands (both: N = 4). Four of the 20 studies compared explicit and implicit motor learning post-stroke. Meta-analyses suggest that patients with stroke can learn implicitly with their unaffected side (mean difference (MD) = 69 ms, 95% CI[45.1, 92.9], p < .00001), but not with their affected side (standardized MD = -.11, 95% CI[-.45, .25], p = .56). Finally, implicit motor learning seemed equally effective as explicit motor learning post-stroke (SMD = -.54, 95% CI[-1.37, .29], p = .20). However, overall, the high risk of bias, small samples, and limited clinical relevance of most studies make it impossible to draw reliable conclusions regarding the effect of implicit motor learning strategies post-stroke. High quality studies with larger samples are warranted to test implicit motor learning in clinically relevant contexts. [ABSTRACT FROM AUTHOR]

Abstract: The energy cost of walking could be attributed to energy related to the walking movement and energy related to balance control. In order to differentiate between both components we investigated the energy cost of walking an enforced step pattern, thereby perturbing balance while the walking movement is preserved. Nine healthy subjects walked three times at comfortable walking speed on an instrumented treadmill. The first trial consisted of unconstrained walking. In the next two trials, subject walked while following a step pattern projected on the treadmill. The steps projected were either composed of the averaged step characteristics (periodic trial), or were an exact copy including the variability of the steps taken while walking unconstrained (variable trial). Metabolic energy cost was assessed and center of pressure profiles were analyzed to determine task performance, and to gain insight into the balance control strategies applied. Results showed that the metabolic energy cost was significantly higher in both the periodic and variable trial (8% and 13%, respectively) compared to unconstrained walking. The variation in center of pressure trajectories during single limb support was higher when a gait pattern was enforced, indicating a more active ankle strategy. The increased metabolic energy cost could originate from increased preparatory muscle activation to ensure proper foot placement and a more active ankle strategy to control for lateral balance. These results entail that metabolic energy cost of walking can be influenced significantly by control strategies that do not necessary alter global gait characteristics. [Copyright &y& Elsevier]

Background: This study examined metabolic energy cost and external mechanical work for step-to-step transitions after tibiotalar arthrodesis, and the effect of MBT rocker bottom shoes. Methods: Oxygen uptake, forceplate and kinematic data were recorded in 18 controls and 15 patients while walking at a fixed speed of 1.25m/s in three walking conditions: barefoot, normal walking shoes and MBT rocker bottom shoes. Metabolic energy cost, external mechanical work, and the roll-over shape of the ankle–foot complex were analyzed. Findings: Tibiotalar arthrodesis leads to higher metabolic energy cost during walking. During step-to-step transitions positive work during push-off with the impaired ankle was decreased but negative work during collision was not affected. The roll-over shape of the ankle–foot complex did not differ between groups and shoe conditions. However, both in patients and controls rocker bottom shoes did lead to decreased positive work at push-off and increased negative work at collision and consequently higher metabolic energy cost of walking. Interpretation: External mechanical work for step-to-step transitions is not different between patients and controls and could not account for the higher metabolic energy cost in patients. Apparently, patients adopt a different walking strategy that limits step-to-step transition cost but nevertheless induces a higher metabolic energy cost. Despite restricted ankle movement, patients retain a normal roll-over shape of the ankle–foot complex. MBT shoes do not affect roll-over shape and appear to have a counterproductive effect on step-to-step transition cost and walking economy. [Copyright &y& Elsevier]

Objective: To review the influence of physical capacity on regaining walking ability and the development of walking ability after lower limb amputation. Design: A systematic search of literature was performed. The quality of all relevant studies was evaluated according to a checklist for statistical review of general papers. Subjects: Lower limb amputees. Main measures: Physical capacity (expressed by aerobic capacity, anaerobic capacity, muscle force, flexibility and balance) and walking ability (expressed by the walking velocity and symmetry). Results: A total of 48 studies that complied with the inclusion criteria were selected. From these studies there is strong evidence for deterioration of two aspects of physical capacity (muscle strength and balance) and of two aspects of walking ability (walking velocity and symmetry) after lower limb amputation. Strong evidence was found for a relation between balance and walking ability. Conclusion: Strong evidence was only found for a relation between balance and walking ability. Evidence about a relation between other elements of physical capacity and walking ability was insufficient. Training of physical capacity as well as walking ability during rehabilitation following lower limb amputation should not be discouraged since several parameters have been shown to be reduced after amputation, although their relation to regaining walking ability and to the development of walking ability remains unclear. [ABSTRACT FROM AUTHOR]

Introduction: Clinical decision making for children with cerebral palsy (CP) with mobility problems requires valid assessment of their ability to repetitively generate forces, here muscle endurance. Unfortunately, a generally accepted and validated clinical test is not available. Objective: We aimed to determine whether a squat test is suitable to measure muscle endurance by evaluating test performance, muscle fatigue and execution in children with CP and typically developing (TD) peers. Patients: Twenty children with bilateral spastic CP (6–19 years; GMFCSI/II/III: N = 5/13/2) and 16 TD peers (7–16 years). Methods: Test performance was measured as the number of two-legged squats until fatigue (max. 20). Muscle fatigue was assessed from changes in electromyography (EMG). Joint range of motions (ROM) and net torques were calculated at the beginning and end of the test. Results: Test performance differed between CP and TD children. Seventeen CP children performed less than 20 squats (median = 13; IQR = 7–19), while all TD children performed the maximum of 20. EMG median frequency decreased and EMG amplitude increased in quadriceps of both groups, indicating presence of muscle fatigue. No differences were observed between the beginning and end, except for knee ROM, which increased in TD and decreased in CP. Discussion and conclusions: Squat test performance was reduced in children with CP compared with TD. Quadriceps muscle fatigue in both groups confirms that the squat test assesses muscle endurance. Minor differences in execution indicate the importance to closely monitor test execution. Clinical message: The squat test is a clinically feasible and valid assessment of muscle endurance in children with CP. [ABSTRACT FROM AUTHOR]