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Introduction: Asymmetrical sensorimotor function after stroke creates unique challenges for bipedal tasks such as walking or perturbation-induced reactive stepping. Preference for initiating steps with the less-involved (preferred) leg after a perturbation has been reported with limited information on the stepping response of the more-involved (non-preferred) leg. Understanding the capacity of both legs to respond to a perturbation would enhance the design of future treatment approaches. This pilot study investigated the difference in perturbation-induced stepping between legs in stroke participant and non-impaired controls. We hypothesized that stepping performance will be different between groups as well as between legs for post-stroke participants. Methods: Thirty-six participants (20 persons post-stroke, 16 age matched controls) were given an anterior perturbation from three stance positions: symmetrical (SS), preferred asymmetrical (PAS-70% body weight on the preferred leg), and non-preferred asymmetrical (N-PAS-70% body weight on the non-preferred leg). Kinematic and kinetic data were collected to measure anticipatory postural adjustment (APA), characteristics of the first step (onset, length, height, duration), number of steps, and velocity of the body at heel strike. Group differences were tested using the Mann-Whitney U-test and differences between legs tested using the Wilcoxon signed-rank test with an alpha level of 0.05. Results: Stepping with the more-involved leg increased from 11.5% of trials in SS and N-PAS up to 46% in PAS stance position for participants post-stroke. Post-stroke participants had an earlier APA and always took more steps than controls to regain balance. However, differences between post-stroke and control participants were mainly found when stance position was modified. Compare to controls, steps with the preferred leg (N-PAS) were earlier and shorter (in time and length), whereas steps with the non-preferred leg (PAS) were also shorter but took longer. For post-stroke participants, step duration was longer and utilized more steps when stepping with the more-involved leg compared to the less-involved leg. Conclusions: Stepping with the more-involved leg can be facilitated by unweighting the leg. The differences between groups, and legs in post-stroke participants illustrate the simultaneous bipedal role (support and stepping) both legs have in reactive stepping and should be considered for reactive balance training.

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.

Previous studies on handrim wheelchair-specific (an)aerobic exercise capacity in wheelchair athletes have used a diversity of participants, equipment, and protocols. Therefore, test results are difficult to compare among studies. The first aim of this scoping review is to provide an overview of the populations studied, the equipment and protocols used, and the reported outcomes from all laboratory-based studies on wheelchair-specific exercise capacity in wheelchair athletes. The second aim is to synthesize these findings into a standardized, yet individualized protocol. A scoping literature search resulted in 10 anaerobic and 38 aerobic protocols. A large variety in equipment, protocol design, and reported outcomes was found. Studies that systematically investigated the influence of protocol features are lacking, which makes it difficult to interpret and compare test outcomes among the heterogeneous group of wheelchair athletes. Protocol design was often dependent on a priori participant knowledge. However, specific guidelines for individualization were missing. However, the common protocol features of the different studies were united into guidelines that could be followed when performing standardized and individualized wheelchair-specific exercise capacity tests in wheelchair athletes. Together with guidelines regarding reporting of participant characteristics, used equipment, and outcome measures, we hope to work toward more international agreement in future testing.

This study investigated the effect of increased rolling resistance on wheelchair sprint performance and the concomitant force–velocity characteristics. Thirteen wheelchair rugby (WCR) athletes completed five 15 s wheelchair sprints in their own rugby wheelchair on an instrumented dual-roller wheelchair ergometer. The first sprint was performed against a close to overground resistance and in each of the following sprints, the resistance increased with 80% of that resistance. A repeated-measures ANOVA examined differences between sprints. Subsequently, linear regression analyses examined the individual force–velocity relations and then, individual parabolic power output curves were modeled. Increased rolling resistance led to significantly lower velocities (−36%), higher propulsion forces (+150%) and higher power outputs (+83%). These differences were accompanied by a lower push frequency, higher push time, yet a constant recovery time and contact angle. The modeled linear regressions (R2 = 0.71 ± 0.10) between force and velocity differed a lot in slope and intercept among individual athletes. The peak of the power output parabola (i.e., the optimal velocity) occurred on average at 3.1 ± 0.6 ms−1. These individual force–velocity profiles can be used for training recommendations or technological changes to better exploit power generation capabilities of the WCR athletes' musculoskeletal system.

A cyclist's performance depends critically on the generated average mechanical power output (AMPO). The instantaneous mechanical power output equals the product of crank angular velocity, crank length, and the tangential pedal force. Radial pedal forces do not contribute to mechanical power. It has been suggested that radial pedal forces arise from suboptimal pedaling technique and that limiting these would increase AMPO and efficiency. Here, we presented an optimal control musculoskeletal model of a cyclist (consisting of five segments driven by nine Hill-type muscle-tendon units) to predict maximal AMPO during sprint cycling at different levels of allowed radial pedal forces. Our findings showed that limiting radial pedal forces has a detrimental effect on maximal AMPO; it dropped from 1,115 W without a limit on radial forces to 528 W when no radial forces were allowed (both at 110 rpm). We explained that avoiding radial pedal forces causes ineffective use of muscles: muscles deliver less positive power and have a higher muscle power dissipation ratio (average mechanical power dissipated per unit of average positive power delivered). We concluded that radial pedal forces are an unavoidable by-product when optimizing for maximal AMPO and that limiting these leads to a performance decrease.NEW & NOTEWORTHY In the literature, but also in the "cycling field" [e.g., trainers, coaches, and (professional) cyclists], it is often suggested that trying to limit/avoid radial pedal forces enhances cycling technique and with that maximal average power output and efficiency. In this paper, we introduce an optimal control model of a human cyclists (consisting of five segments and driven by nine Hill-type muscle-tendon complex models). With that we not only show, but also explain why limiting radial forces is a bad idea: it will decrease maximal attainable AMPO and will decrease efficiency.

Background: Assessment of general movements (GMs) at three months is considered useful for prediction of adverse neurological outcome in high risk infants. Aims: To study the prevalence of abnormal GMs in infants born from women with early-onset hypertensive disorders of pregnancy and the association of GMs with neurodevelopmental outcome at one year. Study design: Prospective study, part of a randomised controlled trial of pre-birth management strategies. Subjects: Infants born from women with early-onset hypertensive disorders of pregnancy. Outcome measures: GMs observation and neurological examination at term and three months corrected age; at one year neurological examination and Bayley Scales of Infant Development. Results: From 216 women included, 175 of 178 surviving infants (mean gestational age 31.6 weeks [SD 2.3], mean birth weight 1346 grams [SD 458]), were examined at three months. At term age normal, mildly abnormal and definitely abnormal GMs were observed in 54%, 36% and 10% respectively; and at three months in 47%, 40% and 13%. Mildly or definitely abnormal GMs at three months were not associated with abnormal neurological examination at one year, however, they were associated with delayed psychomotor development at one year (p = 0.01). Conclusions: In this prospective study, including small for gestational age, preterm infants about half of them did not have normal GMs at term and three months. There was no association of GMs at term nor three months with neurological outcome at one year, but there was a significant association of GMs at three months with one year psychomotor development. © 2008 Elsevier Ireland Ltd. All rights reserved.

Objectives To evaluate the role of plasma volume expansion on 1-year infant outcome after severe hypertensive disorders of pregnancy and to determine prognostic factors for adverse neurodevelopmental infant outcome. Design Randomised controlled trial, observational prognostic study. Setting Two university hospitals in Amsterdam, The Netherlands. Population One hundred and seventy-two infants alive of 216 mothers with severe hypertensive disorders of pregnancy who were randomised for a temporising management strategy with or without plasma volume expansion. Methods At 1 year of corrected age, a neurological examination according to Bayley (mental development index [MDI] and psychomotor development index [PDI]) and Touwen was performed. Main outcome measures Adverse neurodevelopmental infant outcome was defined as a MDI/PDI score below 70 and/or an abnormal Touwen. Risk factors for adverse neurodevelopmental outcome were explored by univariate and multivariate analyses. Results Adverse neurodevelopmental infant outcome was observed in 31 infants (18%). There were no differences between the randomisation groups. In multivariate analysis, an association with abnormal umbilical artery/middle cerebral artery Doppler ratio higher than the median, major neonatal morbidity, higher education of the parents, multiparity and Caucasian ethnicity was observed. Conclusion Nearly 70% of the infants were alive at 1 year without adverse neurodevelopmental outcome. Maternal plasma volume expansion during pregnancy has no effect on 1-year infant outcome. The prediction of adverse outcome at 1 year by perinatal parameters is limited.

Contains fulltext : 71197.pdf (Publisher’s version ) (Closed access) In this study we investigated a family with paramyotonia (PC) congenita caused by a Gly1306Val mutation in the voltage-gated sodium-channel gene SCN4A. A previous study showed that exposure to cold aggravates the muscle stiffness in patients with this mutation. However, the mechanism behind cold sensitivity and the sodium-channel defect remained unclear. In order to gain a better understanding of sarcolemmal propagation in these patients, we measured muscle-fiber conduction velocity (MFCV) invasively. We studied four PC patients and four healthy subjects at room temperature. After the muscle was cooled, MFCV was measured again in the two PC patients and four control subjects. MFCV was significantly lower in the PC patients at room temperature, compatible with dysfunctional sodium channels. After cooling, MFCV was significantly lower in both groups as compared with room temperature. The relative slowing was 1.4% per degrees C for PC patients and 1.5% per degrees C for healthy subjects. These results indicate that, in these PC patients, mutant and wild-type sodium channels respond equally to cold exposure. Thus, MFCV is abnormal in these patients, but the aggravation of muscle stiffness cannot be explained by an abnormal sarcolemmal response to cold.

Contains fulltext : 51487.pdf (Publisher’s version ) (Open Access) Behavioral studies using motor preparation paradigms have revealed that increased expectancy of a response signal shortens reaction times (RTs). Neurophysiological data suggest that in such paradigms, not only RT but also neuronal activity in the motor structures involved is modulated by expectancy of behaviorally relevant events. Here, we directly tested whether expectancy of a response signal modulates excitability of the corticospinal system used in the subsequent movement. We combined single- and paired-pulse transcranial magnetic stimulation (TMS) over the primary motor cortex with a simple RT task with variable preparatory delays. We found that, in line with typical behavioral observations, the subjects' RTs decreased with increasing response signal expectancy. TMS results revealed a modulation of corticospinal excitability in correspondence with response signal expectancy. Besides an increased excitability over the time-course of the preparatory delay, corticospinal excitability transiently increased whenever a response signal was expected. Paired-pulse TMS showed that this modulation is unlikely to be mediated by excitability changes in interneuronal inhibitory or facilitatory networks in the primary motor cortex. Changes in corticospinal synchronization or other mechanisms involving spinal circuits are candidates mediating the modulation of corticospinal excitability by expectancy.

Contains fulltext : 52187.pdf (Publisher’s version ) (Closed access) We analyzed the effects of gravitational unloading on muscular fatigability and the effectiveness of resistive vibration exercise to counteract these changes. Changes in knee extensor fatigability as a consequence of 8 weeks of horizontal bedrest with or without daily resistive vibration exercise were evaluated in 17 healthy male volunteers. Bedrest increased fatigability (% decrease in maximal voluntary isometric torque per minute exercise) from -7.2 +/- 0.5 to -10.2 +/- 1.0%/min (P < 0.05), which was accompanied by a decline (of 52.0 +/- 3.7%, P < 0.05) in muscle blood flow. Daily resistive vibration exercise training during bedrest prevented increases in fatigability (from -10.8 +/- 1.8 to -8.4 +/- 1.6%/min, P < 0.05), and mitigated the reduction in blood flow (decline of 26.1 +/- 5.1%, P < 0.05). Daily resistive exercise may thus be suggested as an effective countermeasure during spaceflight and illness-related prolonged bedrest to combat the detrimental changes in muscle endurance that result from gravitational unloading.

Contains fulltext : 49690.pdf (Publisher’s version ) (Closed access) Changes in the quadriceps femoris muscle with respect to anatomical cross sectional area (CSA), neural activation level and muscle strength were determined in 18 healthy men subjected to 8 weeks of horizontal bed rest (BR) with (n = 9) and without (n = 9) resistive vibration exercise (RVE). CSA of the knee extensor muscle group was measured with magnetic resonance imaging every 2 weeks during bed rest. In the control subjects (Ctrl), quadriceps femoris CSA decreased linearly over the 8 weeks of bed rest to -14.1 +/- 5.2% (P < 0.05). This reduction was significantly (P < 0.001) mitigated by the exercise paradigm (-3.5 +/- 4.2%; P < 0.05). Prior to and seven times during bed rest, maximal unilateral voluntary torque (MVT) values of the right leg were measured together with neural activation levels by means of a superimposed stimulation technique. For Ctrl, MVT decreased also linearly over time to -16.8 +/- 7.4% after 8 weeks of bed rest (P < 0.01), whereas the exercise paradigm fully maintained MVT during bed rest. In contrast to previous reports, the maximal voluntary activation remained unaltered for both groups throughout the study. For Ctrl, the absence of deterioration of the activation level might have been related to the repeated testing of muscle function during the bed rest. This notion was supported by the observation that for a subset of Ctrl subjects (n = 5) the MVT of the left leg, which was not tested during BR, was reduced by 20.5 +/- 10.1%, (P < 0.01) which was for those five subjects significantly (P < 0.05) more than the 11.1 +/- 9.2% (P < 0.01) reduction for the right, regularly tested leg.

Item does not contain fulltext The accuracy of predictions of muscle force based on electromyography (EMG) is an important issue in biomechanics and kinesiology. Since human skeletal muscles show a high diversity and heterogeneity in their fiber architecture, it is difficult to properly align electrodes to the muscle fiber direction. Against this background, we analyzed the effect of different bipolar configuration directions on EMG-based force estimation. In addition, we investigated whether principal component analysis (PCA) can improve this estimation. High-density surface-EMG from the triceps brachii muscle and the extension force of the elbow were measured in 11 subjects. The root mean square difference (RMSD) between predicted and measured force was determined. We found the best bipolar configuration direction to cause a 13% lower RMSD relative to the worst direction. Optimal results were obtained with electrodes aligned with the expected main muscle fiber direction. We found that PCA reduced RMSD by about 40% compared to conventional bipolar electrodes and by about 12% compared to optimally aligned multiple bipolar electrodes. Thus, PCA contributes to the accuracy of EMG-based estimation of muscle force when using a high-density EMG grid.

Contains fulltext : 50824.pdf (Publisher’s version ) (Closed access) High density-surface EMG (HD-sEMG) is a non-invasive technique to measure electrical muscle activity with multiple (more than two) closely spaced electrodes overlying a restricted area of the skin. Besides temporal activity HD-sEMG also allows spatial EMG activity to be recorded, thus expanding the possibilities to detect new muscle characteristics. Especially muscle fiber conduction velocity (MFCV) measurements and the evaluation of single motor unit (MU) characteristics come into view. This systematic review of the literature evaluates the clinical applications of HD-sEMG. Although beyond the scope of the present review, the search yielded a large number of "non-clinical" papers demonstrating that a considarable amount of work has been done and that significant technical progress has been made concerning the feasibility and optimization of HD-sEMG techniques. Twenty-nine clinical studies and four reviews of clinical applications of HD-sEMG were considered. The clinical studies concerned muscle fatigue, motor neuron diseases (MND), neuropathies, myopathies (mainly in patients with channelopathies), spontaneous muscle activity and MU firing rates. In principle, HD-sEMG allows pathological changes at the MU level to be detected, especially changes in neurogenic disorders and channelopathies. We additionally discuss several bioengineering aspects and future clinical applications of the technique and provide recommendations for further development and implementation of HD-sEMG as a clinical diagnostic tool.

Contains fulltext : 51351.pdf (Publisher’s version ) (Closed access)

New surface electromyogram (SEMG) techniques offer the potential to advance knowledge of healthy and diseased motor units. Conduction velocity (CV) estimates, obtained from indwelling electrodes, may provide diagnostic information, but the standard method of CV estimation from SEMG may be of only limited value. We developed a motor unit (MU) tracking algorithm to extract motor unit conduction velocity (MUCV) and motor unit action potential (MUAP) amplitude estimates from SEMG. The technique is designed to provide a noninvasive means of accessing fatigue and recruitment behavior of individual MUs. We have applied this MU tracking algorithm to SEMG data recorded during isometric fatiguing contractions of the tibialis anterior (TA) muscle in nine healthy subjects, at 30%-40% maximum voluntary contraction (MVC). The results reveal that MUCVs and MUAP amplitudes of individual MUs can be estimated and tracked across time. Time-related changes in the MU population may also be monitored. Thus, the SEMG technique employed provides insight into the behavior of the underlying muscle at the MU level by noninvasive means. © 2005 Wiley Periodicals, Inc.

Contains fulltext : 47637.pdf (Publisher’s version ) (Closed access) Surface EMG (SEMG) as non-invasive method is a valuable tool in functional studies of movement co-ordination. The interpolation of the SEMG power (EMG mapping) gives information about intra- and inter-muscular co-ordination. It has been shown that SEMG maps of low back pain patients and healthy subjects differ. The only major drawback to SEMG is that volume conduction of muscle tissue, fat, and skin decreases the spatial and temporal resolution of signals. To improve the interpretation of SEMG signals, we have applied high pass filtering of cross covariance functions, which has proved to be useful in increasing the spatial resolution, to SEMG data of the back region. Experimental data demonstrate that SEMG signals from the back extensors show only rarely signs of action potential propagation. This behaviour, also described in the literature, can be explained by a model assuming short, deep muscle fibres, having bipolar end effects, with overlapping positions parallel to the fibre direction. This condition is fulfilled by the mm. multifidii et rotatores which are part of the m. erector spinae. Although the model is simplistic, the agreement between simulations and experiments is good.

Contains fulltext : 48870.pdf (Publisher’s version ) (Closed access) High-density multichannel electromyography (EMG) recordings add spatial information to the temporal information content of the surface EMG (sEMG) signal. This study explores the potential value of such multichannel information at a single motor unit level, in particular for the improvement of motor unit number estimation (MUNE) techniques. It is shown that multichannel recordings make it easier to distinguish motor unit action potentials (MUAPs) and that MUAP combinations can be better resolved. Furthermore, the spatiotemporal information allows a quantitative assessment of the representativity of the mean of the recorded MUAPs in relation to the maximum CMAP, i.e., for the muscle as a whole. In general, this is practically impossible on the basis of temporal information alone. For these reasons, we expect that high-density sEMG has the potential to address several methodological limitations of single channel surface EMG recordings. This is specifically illustrated in this study for one of the MUNE techniques in use, the F-response method.

Item does not contain fulltext In the study of fatigue, several methods have been used to calculate the development of central activation failure (CAF) and peripheral fatigue (PF) in the course of a sustained maximal voluntary contraction (MVC). This paper presents a model that enables simultaneous determination of CAF and PF during sustained MVC by using only force registration and superimposed electrical stimulation. In the model, we explicitly use the assumption, which is virtually always made implicitly in earlier studies, that a constant relative fraction of maximal possible force is activated by the electrical stimulation. That fraction can be determined at the start and at the end of a sustained MVC. The model shows that in the course of a sustained MVC, CAF can be calculated by merely using 1) this fraction, 2) the amplitudes of the superimposed force responses to stimulation, and 3) the course of voluntary force. After CAF quantification, the development of PF during MVC becomes available as well. The present study first examines the model assumption with data of sustained MVCs of variable durations on six healthy subjects. Subsequently, it shows CAF values in a group of 27 healthy subjects determined with both the model and a method of linear interpolation for PF estimation. Model-based CAF values were significantly higher during, but not at the start and at the end of, a 2-min sustained MVC. Next to a well-justified CAF determination, the model has the advantage of simultaneously quantifying PF, which was not possible with the previous methods.

Contains fulltext : 48137.pdf (Publisher’s version ) (Closed access) The statistical method of motor unit number estimation (MUNE) uses the natural stochastic variation in a muscle's compound response to electrical stimulation to obtain an estimate of the number of recruitable motor units. The current method assumes that this variation follows a Poisson distribution. We present an alternative that instead assumes a binomial distribution. Results of computer simulations and of a pilot study on 19 healthy subjects showed that the binomial MUNE values are considerably higher than those of the Poisson method, and in better agreement with the results of other MUNE techniques. In addition, simulation results predict that the performance in patients with severe motor unit loss will be better for the binomial than Poisson method. The adapted method remains closer to physiology, because it can accommodate the increase in activation probability that results from rising stimulus intensity. It does not need recording windows as used with the Poisson method, and is therefore less user-dependent and more objective and quicker in its operation. For these reasons, we believe that the proposed modifications may lead to significant improvements in the statistical MUNE technique.

Item does not contain fulltext The speed of propagation of an action potential along a muscle fiber, its conduction velocity (CV), can be used as an indication of the physiological or pathological state of the muscle fiber membrane. The motor unit action potential (MUAP), the waveform resulting from the spatial and temporal summation of the individual muscle fiber action potentials of that motor unit (MU), propagates with a speed referred to as the motor unit conduction velocity (MUCV). This paper introduces a new algorithm, the MU tracking algorithm, which estimates MUCVs and MUAP amplitudes for individual MUs in a localized MU population using SEMG signals. By tracking these values across time, the electrical activity of the localized MU pool can be monitored. An assessment of the performance of the algorithm has been achieved using simulated SEMG signals. It is concluded that this analysis technique enhances the suitability of SEMG for clinical applications and points toward a future of noninvasive diagnosis and assessment of neuromuscular disorders.

Fitter police recruits are more likely to graduate, are less injury-prone, and fatigue less rapidly. Although most police academies implement fitness testing to ensure a minimum standard of job-specific fitness, academies may benefit from utilizing fitness tests that challenge recruits beyond the minimum fitness demand. The current study evaluated whether a fitness test called Professional Fit (ProfFit) of a police academy aligned with the academy’s purpose to challenge their recruits to become optimally fit. We evaluated whether the ProfFit measures an all-round range of fitness characteristics. Moreover, we evaluated whether the ProfFit measures higher fitness levels than the minimum fitness demand for duty. Police recruits ( N = 103) were tested on the ProfFit, six extra fitness tests known to measure one (isolated) aspect of fitness, and a standard practice job-specific fitness test. Results showed that the ProfFit measures an all-round range of fitness characteristics: anaerobic power, strength lower extremities, strength upper extremities, isometric strength, and muscular endurance of the trunk muscles. The results also showed that recruits indicated a higher rating of perceived exertion during the ProfFit than during the job-specific fitness test, indicating that they experienced the ProfFit as more demanding than the minimum fitness demand for duty. It was concluded that the ProfFit facilitates to challenge police recruits physically, as was the aim of the police academy. These findings provide empirical support for fitness tests that aim to improve police recruits’ fitness levels to be not just fit for duty, but rather optimally fit for duty.

OBJECTIVE: To compare handrim wheelchair propulsion technique between individuals with spinal cord injury (SCI) with and without shoulder pain.DESIGN: A cross-sectional study including 38 experienced handrim wheelchair users with SCI. Participants were divided in a 'shoulder pain' (n = 15) and 'no-shoulder pain' (n = 23) group using the Local Musculoskeletal Discomfort scale. Kinetic and spatiotemporal aspects of handrim wheelchair propulsion during submaximal exercise on a motor-driven treadmill were analyzed. Data were collected using a measurement wheel instrumented with 3D force sensors.RESULTS: After correction for confounders (time since injury and body height), linear regression analyses showed the pain group had a 0.30 s (95% CI, -0.5 to -0.1) shorter cycle time, 0.22 s (95% CI, -0.4 to -0.1) shorter recovery time, 15.6° (95% CI, -27.4 to -3.8) smaller contact angle and 8% (95% CI, -15 to 0) lower variability in the work per push compared to the no-pain group. Other parameters did not differ between groups.CONCLUSIONS: This study indicates that individuals with SCI who experience shoulder pain propel their handrim wheelchair kinematically different from individuals with SCI without shoulder pain. This difference in propulsion technique might be a pain-avoiding mechanism aimed at decreasing shoulder range of motion.

The effects of fatigue emerge from the beginning of sustained submaximal contractions, as shown by an increase in the amplitude of the surface electromyogram (EMG). The increase in EMG amplitude is attributed to an augmentation of the excitatory drive to the motor neuron pool that, more importantly than increasing discharge rates, recruits additional motor units for the contraction. The aim of this study was to determine whether the spatiotemporal distribution of biceps brachii (BB) activity becomes more or less heterogeneous during a fatiguing isometric contraction sustained at a submaximal target force. Multiple electrodes were attached over the entire BB muscle, and principal component analysis (PCA) was used to extract the representative information from multiple monopolar EMG channels. The development of heterogeneity during the fatiguing contraction was quantified by applying a cluster algorithm on the PCA-processed EMG amplitudes. As shown previously, the overall EMG amplitude increased during the sustained contraction, whereas there was no change in coactivation of triceps brachii. However, EMG amplitude did not increase in all channels and even decreased in some. The change in spatial distribution of muscle activity varied across subjects. As found in other studies, the spatial distribution of EMG activity changed during the sustained contraction, but the grouping and size of the clusters did not change. This study showed for the first time that muscle activation became more heterogeneous during a sustained contraction, presumably due to a decrease in the strength of common inputs with the recruitment of additional motor units. electromyography; monopolar signals; muscle fatigue; principal component analysis; cluster algorithm; motor control. © 2014 the American Physiological Society.

Assessment of metabolic energy expenditure from indirect calorimetry is currently limited to sustained (>4 min) cyclic activities, because of steady-state requirements. This is problematic for patient populations who are unable to perform such sustained activities. Therefore, this study explores validity and reliability of a method estimating metabolic energy expenditure based on oxygen consumption (V̇O2) during short walking bouts. Twelve able-bodied adults twice performed six treadmill walking trials (1, 2 and 6 min at 4 and 5 km/h), while V̇O2 was measured. Total V̇O2 was calculated by integrating net V̇O2 over walking and recovery. Concurrent validity with steady-state V̇O2 was assessed with Pearson’s correlations. Test-retest reliability was assessed using intra-class correlation coefficients (ICC) and Bland-Altman analyses. Total V̇O2 was strongly correlated with steady-state V̇O2 (r=0.91–0.99), but consistently higher. Test-retest reliability of total V̇O2 (ICC=0.65–0.92) was lower than or comparable to steady-state V̇O2 (ICC=0.83–0.92), with lower reliability for shorter trials. Total V̇O2 discriminated between gait speeds. Total oxygen uptake provides a useful measure to estimate metabolic load of short activities from oxygen consumption. Although estimates are less reliable than steady-state measurements, they can provide insight in the yet unknown metabolic demands of daily activities for patient populations unable to perform sustained activities.

Background Patients with a transient ischemic attack (TIA) or ischemic stroke are at increased risk of developing cognitive impairment in the subacute phase. At present, the effects of exercise on cognitive functioning following a TIA or stroke are not fully known. The purpose of this trial was to investigate the effect of exercise on global cognition. Methods The MoveIT trial is a single-centre, observer-blinded, randomized controlled trial involving a 1-year exercise intervention consisting of a 12-week group exercise program, combined with three counselling visits to the physiotherapists over a 9-month period. The control group received standard care. The primary outcome was global cognitive functioning, assessed at one year, using the Montreal Cognitive Assessment (MoCA). Secondary outcomes included cardiorespiratory fitness, the cardiovascular profile, and attainment of secondary prevention targets, anxiety, depression and fatigue at one and two years. Results The experimental group consisted of 60 patients, while the control group consisted of 59 patients. The mean age was 64.3 years and 41% were female. No between-group differences were found on global cognitive functioning (MD, 0.7 out of 30, 95% CI, − 0.2 to 1.6) or on secondary outcome measures at 12 months. The only significant between-group difference was found for fatigue, in favour of the experimental group at 12 months (MD, 0.6 out of 63, 95% CI, 0.1 to 1.1). Conclusions No benefit of this exercise intervention was found regarding global cognition. Future studies need to focus on optimizing rehabilitation strategies for this vulnerable group of patients. Trial registration http://www.trialregister.nl. Unique identifier: NL3721. Date first registration: 06-03-2013.

Shoulder disorders are very common musculoskeletal conditions. Few studies have focused on the costs associated with shoulder disorders, and the economic burden has never been established in a nationwide cost-of-illness study. We aimed to evaluate the healthcare costs and costs of productivity loss (sick leave), and to evaluate if costs were higher for specific subgroups. Using national Danish registers, we identified individuals with shoulder disorders (subacromial pain, stiffness, fracture or dislocation) diagnosed between 2005 and 2017 and controls matched on age and gender without shoulder disorders. Health care usage, sick leave and related costs were estimated. During the 13-year inclusion period, 617,334 unique individuals were identified and the incidence rate was 1,215 per 100,000 person years in 2017. The expected additional societal costs were €1.21 billion annually. The mean additional total costs for the 6-years period were €11,334 (11,014; 11,654) for individuals aged ≥65 years and €25,771 (25,531; 26,012) for individuals aged

It is generally accepted that most of the energy transferred to the ball during a baseball pitch is generated in the trunk and lower extremities. Therefore, purpose of this study was to assess the energy flow through the lower extremities during a baseball pitch. It was hypothesised that the (stabilising) leading leg mainly transfers energy in a distal-to-proximal order as a kinetic chain while the (driving) trailing leg generates most energy, primarily at the hip. A joint power analysis was used to determine the rates of energy (power) transfer and generation in the ankles, knees, hips and lumbosacral joint (L5-S1) for 22 youth pitchers. Analyses showed that the leading leg mainly transfers energy upwards in a distal-to-proximal order just before stride foot contact. Furthermore, energy generation was higher in the trailing leg and primarily arose from the trailing hip. In conclusion, the legs contribute differently to the energy flow where the leading leg acts as an initial kinetic chain component and the trailing leg drives the pitch by generating energy. The actions of both legs are combined in the pelvis and passed on to the subsequent, more commonly discussed, open kinetic chain starting at L5-S1.

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

Made available in DSpace on 2022-05-01T05:29:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-07-19 It is challenging for people with Parkinson's disease (PwPD) to adjust their gait to perturbations, including fatigue. Obstacle negotiation increases the risk of tripping and falling in PD. Being physically active can improve gait control and the ability to negotiate obstacles while walking under fatigue state. We thus determined the effects of Parkinson's disease, fatigue, and level of physical activity on gait during the approach to and crossing an obstacle during gait. Forty participants were stratified to people with Parkinson's disease active and inactive, and control individuals active and inactive. Participants walked on an 8 m walkway and stepped over an obstacle placed at the middle (4 m). They performed three trials before and after repeated sit-to-stand (rSTS)-induced fatigue state. Maximum voluntary force was assessed before and after rSTS. We measured the length, width, duration, and velocity of the approach (stride before obstacle) and crossing (step over the obstacle) phases and the leading and trailing placements and clearance during crossing phase. Fatigue trait was determined by multidimensional fatigue inventory. Before rSTS, people with Parkinson's disease inactive vs. other subgroups approached the obstacle using 18–28% shorter, wider and slower steps and crossed the obstacle slower (all p < 0.04). After rSTS, people with Parkinson's disease inactive increased (23–34%) stride length and velocity and decreased (-21%) the step width (p < 0.01). People with Parkinson's disease approached the obstacle similarly to control individuals. Physical activity minimizes Parkinson's disease-typical gait impairments during obstacle negotiation and affords a protective effect against fatigue-effects on obstacle negotiation. São Paulo State University (UNESP) Graduate Program in Movement Sciences Institute of Biosciences Posture and Gait Studies Laboratory (LEPLO) São Paulo State University (UNESP) Graduate Program in Movement Sciences Department of Physical Education Human Movement Research Laboratory (MOVI-LAB) University of Groningen University Medical Center Groningen Center for Human Movement Sciences Institute of Sport Sciences and Physical Education Faculty of Sciences University of Pécs Somogy County Kaposi Mór Teaching Hospital São Paulo State University (UNESP) Graduate Program in Movement Sciences Institute of Biosciences Posture and Gait Studies Laboratory (LEPLO) São Paulo State University (UNESP) Graduate Program in Movement Sciences Department of Physical Education Human Movement Research Laboratory (MOVI-LAB)

To describe physical strain during activities of daily living (ADL), 44 men with spinal cord injuries (C4-L5) performed a set of standardised tasks. The physical strain was defined as the highest heart rate response expressed as a percentage of the individual heart rate reserve (%HRR). The physical strain averaged over the subjects who performed all tasks (n = 24) was (mean +/- SD): 20.2 +/- 7.2 %HRR (washing hands), 20.4 +/- 7.3 %HRR (passing a side-hung door), 28.8 +/- 10.8 %HRR (transfer to a toilet), 31.2 +/- 13.1 %HRR (ascending an 8 cm curb). 33.9 +/- 12.0 %HRR (transfer to a shower seat), 35.1 +/- 10.5 %HRR (transfer to bed), 36.4 +/- 13.3 %HRR (preparing lunch), 37.1 +/- 12.0 %HRR (washing up), 38.7 +/- 14.9 %HRR (ascending a ramp), 39.8 +/- 15.6 %HRR (transfer to a shower wheelchair), 41.4 +/- 12.1 %HRR (changing sheets), and 45.9 +/- 10.4 %HRR (entering a car). Physical strain could be notably high, but large variations among subjects were present. During all tasks, subjects with tetraplegia had significantly higher levels of strain than subjects with low (T6-L5) lesions. Physical strain was inversely related to parameters of physical capacity: isometric strength (r: -0.34 to -0.72), sprint power (r: -0.34 to -0.69), peak oxygen uptake (r: -0.41 to -0.81) and maximal power output (r: -0.52 to -0.82). Parameters of physical capacity were better predictors of physical strain than was the lesion level, and explained 37-71% of the variance in strain during ADL. It was also concluded that the method used in this study provides a quantitative and objective estimation of physical strain and may therefore be a useful tool to identify task difficulty during rehabilitation and to evaluate the results of task and physical training on the physical strain during ADL.

Background. To improve maternal health, studies of maternal morbidity are increasingly being used to evaluate the quality of maternity care, in addition to studies of mortality. While South Africa (SA) has a well-established confidential enquiry into maternal deaths, there is currently no structure in place to systematically collect and analyse maternal near-misses (MNMs) at national level.Objectives. To synthesise MNM indicators and causes in SA by performing a systematic literature search, and to investigate perceived needs for data collection related to MNMs and determine whether the MNM tool from the World Health Organization (WHO-MNM) would require adaptations in order to be implemented.Methods. The study used a mixed-methods approach. A systematic literature search was conducted to find all published data on MNM audits in SA. Semi-structured interviews were conducted virtually with maternal health experts throughout the country who had been involved in studies of MNMs, and main themes arising in the interviews were synthesised. A method for MNM data collection for SA use was discussed with these experts.Results. The literature search yielded 797 articles, 15 of which met the WHO-MNM or Mantel et al. severe acute maternal morbidity criteria. The median (interquartile range) MNM incidence ratio in SA was 8.4/1 000 (5.6 - 8.7) live births, the median maternal mortality ratio was 130/100 000 (71.4 - 226) live births, and the median mortality index was 16.6% (11.7 - 18.8). The main causes of MNMs were hypertensive disorders of pregnancy and obstetric haemorrhage. Eight maternal health experts were interviewed from May 2020 to February 2021. All participants focused on the challenges of implementing a national MNM audit, yet noted the urgent need for one. Recognition of MNMs as an indicator of quality of maternity care was considered to lead to improved management earlier in the chain of events, thereby possibly preventing mortality. Obtaining qualitative information from women with MNMs was perceived as an important opportunity to improve the maternity care system. Participants suggested that the WHO-MNM tool would have to be adapted into a simplified tool with more clearly defined criteria and a number of specific diagnoses relevant to the SA setting. This ‘Maternal near-miss: Inclusion criteria and data collection form’ is provided as a supplementary file.Conclusion. Adding MNMs to the existing confidential maternal death enquiry could potentially contribute to a more robust audit with data that may inform health systems planning. This was perceived by SA experts to be valuable, but would require context-specific adaptations to the WHO-MNM tool. The available body of evidence is sufficient to justify moving to implementation.

IntroductionSurgery is not a viable treatment for all patients with hip dysplasia. Currently, usual care for these patients is limited to a consultation on self-management. We have shown that an exercise and patient education intervention is a feasible and acceptable intervention for patients not receiving surgery. Therefore, we aim to investigate whether patients with hip dysplasia randomised to exercise and patient education have a different mean change in self-reported pain compared with those randomised to usual care over 6 months. Furthermore, we aim to evaluate the cost-effectiveness and perform a process evaluation.Methods and analysisIn a randomised controlled trial, 200 young and middle-aged patients will be randomised to either exercise and patient education or usual care at a 1:1 ratio through permuted block randomisation. The intervention group will receive exercise instruction and patient education over 6 months. The usual care group will receive one consultation on self-management of hip symptoms. The primary outcome is the self-reported mean change in the pain subscale of the Copenhagen Hip and Groin Outcome Score (HAGOS). Secondary outcomes include mean changes in the other HAGOS subscales, in the Short Version of the International Hip Outcome Tool, in performance, balance and maximal hip muscle strength. Between-group comparison from baseline to 6-month follow-up will be made with intention-to-treat analyses with a mixed-effects model. Cost-effectiveness will be evaluated by relating quality-adjusted life years and differences in HAGOS pain to differences in costs over 12 months. The functioning of the intervention will be evaluated as implementation, mechanisms of change and contextual factors.Ethics and disseminationThe study protocol was approved by the Committee on Health Research Ethics in the Central Denmark Region and registered at ClinicalTrials. Positive, negative and inconclusive findings will be disseminated through international peer-reviewed scientific journals and international conferences.Trial registration numberNCT04795843.

The goal of this study was to evaluate the technical and physical adaptations to a data-driven 12-weeks training programs that incorporated recent findings from biomechanical studies on the diving save. Three-dimensional kinematics and kinetics were collected and analysed from 11 goalkeepers diving to save high (190 cm) and low (30 cm) balls at three occasions: twice pre-training and once post-training. Intraclass correlation coefficients were found to be excellent (>.7) between the pre-training tests, and there were no learning effects between them. Three-way repeated measures ANOVAs were used to evaluate the effect of dive side, dive height and training programme (pre- vs post-training) on normalised dive time [s·m -1], average centre of mass (CoM) horizontal velocity [m·s -1] and total power [W] generated at contralateral and ipsilateral push-offs. Compared to pre-training, the post-training results revealed greater average CoM horizontal velocity (+.82 m·s -1, 95% CI = [.62, 1.02]) and power (+523 W, 95% CI = [313, 732]) at contralateral push-off. These adaptations caused a reduction in normalised dive time (- .008 s·m -1, 95% CI = [- .014, - .002]) at post-training compared to pre-training. This translates to 42 cm more goal area coverage in a penalty situation.

Objective: The incidence of maternal mortality due to hypertensive disorders of pregnancy in the Netherlands is greater than in other Western countries. We aimed to confirm and explain this difference by assessing incidence, risk factors, and substandard care of eclampsia in the Netherlands. Methods: In a nationwide population-based cohort study, all cases of eclampsia were prospectively collected during a 2-year period (2004-2006). All pregnant women in the Netherlands in the same period acted as reference cohort (n=371,021). Substandard care was assessed in all cases. A selection of cases was extensively audited by an expert panel. Main outcome measures were incidence, case fatality rate, possible risk factors, and substandard care. Results: All 98 Dutch maternity units participated (100%). There were 222 cases of eclampsia, for an incidence of 6.2 per 10,000 deliveries. Three maternal deaths occurred; the case fatality rate was 1 in 74. Risk factors in univariable analysis included multiple pregnancy, primiparity, young age, ethnicity, and overweight. Prophylactic magnesium sulfate was given in 10.4% of women, and antihypertensive medication was given in 39.6% of women with a blood pressure on admission at or above 170/110 mm Hg. Additionally, substandard care was judged to be present by an expert panel in 15 of 18 audited cases (83%). Conclusion: The incidence of eclampsia in the Netherlands is markedly increased as compared with other Western European countries. Substandard care was identified in many cases, indicating the need for critical evaluation of the management of hypertensive disease in the Netherlands.

SummaryIt was the objective of this study to analyse the influence of confounders, such as ethnicity, severity of illness and method of testing, in articles concerning the still moot relationship of thrombophilias to adverse pregnancy outcome (APO). Relevant casecontrol studies were identified using Medline and EMBASE databases between 1966 and 2006. Search terms were recurrent fetal loss, intrauterine fetal death, preeclampsia, HELLP-syndrome, eclampsia, fetal growth restriction, abruptio placentae, combined with maternal thrombophilias. Data was extracted from the articles per subgroup ofAPO regardless of confounder. These subgroups were tested if they fulfilled the heterogeneity testing criterion (I2 > 35%) to weigh the influence of the confounder. Confounders were selected and examined with Mantel- Haenszel method. Increased thrombophilia prevalence was confirmed in most adverse pregnancy outcomes. Ethnicity, genetic testing only and severity of illness were confounders in the various forms of APO. Stronger relationships between factor V Leiden and severity of disease were found in 2nd and 3rd trimester than 1st trimester recurrent fetal loss, in preeclampsia with: blood pressure ≥160/110 mmHg than ≥140/90 mmHg; proteinuria ≥5 grams per day than < 5 grams; onset before than after 28 weeks, in fetal growth restriction

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Objective: To assess incidence, case fatality rate, risk factors and substandard care in severe maternal morbidity in the Netherlands. Design: Prospective population-based cohort study. Setting: All 98 maternity units in the Netherlands. Population: All pregnant women in the Netherlands. Methods: Cases of severe maternal morbidity were collected during a 2-year period. All pregnant women in the Netherlands in the same period acted as reference cohort (n = 371 021). As immigrant women are disproportionately represented in Dutch maternal mortality statistics, special attention was paid to the ethnic background. In a subset of 2.5% of women, substandard care was assessed through clinical audit. Main outcome measures: Incidence, case fatality rates, possible risk factors and substandard care. Results: Severe maternal morbidity was reported in 2552 women, giving an overall incidence of 7.1 per 1000 deliveries. Intensive care unit admission was reported in 847 women (incidence 2.4 per 1000), uterine rupture in 218 women (incidence 6.1/10 000), eclampsia in 222 women (incidence 6.2/10 000) and major obstetric haemorrhage in 1606 women (incidence 4.5 per 1000). Non-Western immigrant women had a 1.3-fold increased risk of severe maternal morbidity (95% CI 1.2-1.5) when compared with Western women. Overall case fatality rate was 1 in 53. Substandard care was found in 39 of a subset of 63 women (62%) through clinical audit. Conclusions: Severe maternal morbidity complicates at least 0.71% of all pregnancies in the Netherlands, immigrant women experiencing an increased risk. Since substandard care was found in the majority of assessed cases, reduction of severe maternal morbidity seems a mandatory challenge. © 2008 The Authors.

Contains fulltext : 51651.pdf (Publisher’s version ) (Closed access) Recently, high-density surface EMG electrode grids and multi-channel amplifiers became available for non-invasive recording of human motor units (MUs). We present a way to decompose surface EMG signals into MU firing patterns, whereby we concentrate on the importance of two-dimensional spatial differences between the MU action potentials (MUAPs). Our method is exemplified with high-density EMG data from the vastus lateralis muscle of a single subject. Bipolar and Laplacian spatial filtering was applied to the monopolar raw signals. From the single recording in this subject six different simultaneously active MUs could be distinguished using the spatial differences between MUAPs in the direction perpendicular to the muscle fiber direction. After spike-triggered averaging, 125-channel two-dimensional MUAP templates were obtained. Template-matching allowed tracking of all MU firings. The impact of spatial information was measured by using subsets of the MUAP templates, either in parallel or perpendicular to the muscle fiber direction. The use of one-dimensional spatial information perpendicular to the muscle fiber direction was superior to the use of a linear array electrode in the longitudinal direction. However, to detect the firing events of the MUs with a high accuracy, as needed for instance for estimation of firing synchrony, two-dimensional information from the complete grid electrode appears essential.

compared with most neurophysiological phenomena, muscle contraction is a slow process. After an action potential has arrived at the muscle fiber membrane, it takes some 30 ms to fully start up the contractile machinery, and it takes even longer to stop it, i.e., to relax force. The contractile