Task-specific training for improving propulsion symmetry and gait speed in people in the chronic phase after stroke: a proof-of-concept study.

BACKGROUND: After stroke, some individuals have latent, propulsive capacity of the paretic leg, that can be elicited during task-specific gait training. The aim of this proof-of-concept study was to investigate the effect of five-week robotic gait training for improving propulsion symmetry by increasing paretic propulsion in chronic stroke survivors. METHODS: Twenty-nine individuals with chronic stroke and impaired paretic propulsion (≥ 8% difference in paretic vs. non-paretic propulsive impulse) were enrolled. Participants received ten 60-min sessions of individual robotic gait training targeting paretic propulsion (five weeks, twice a week), complemented with home exercises (15 min/day) focusing on increasing strength and practicing learned strategies in daily life. Propulsion measures, gait kinematics and kinetics, self-selected gait speed, performance of functional gait tasks, and daily-life mobility and physical activity were assessed five weeks (T0) and one week (T1) before the start of intervention, and one week (T2) and five weeks (T3) after the intervention period. RESULTS: Between T0 and T1, no significant differences in outcomes were observed, except for a marginal increase in gait speed (+ 2.9%). Following the intervention, propulsion symmetry (+ 7.9%) and paretic propulsive impulse had significantly improved (+ 8.1%), whereas non-paretic propulsive impulse remained unchanged. Larger gains in propulsion symmetry were associated with more asymmetrical propulsion at T0. In addition, following the intervention significantly greater paretic trailing limb angles (+ 6.6%) and ankle plantarflexion moments (+ 7.1%) were observed. Furthermore, gait speed (+ 7.2%), 6-Minute Walk Test (+ 6.4%), Functional Gait Assessment (+ 6.5%), and daily-life walking intensity (+ 6.9%) had increased following the intervention. At five-week follow-up (T3), gains in all outcomes were retained, and gait speed had further increased (+ 3.6%). CONCLUSIONS: The post-intervention gain in paretic propulsion did not only translate into improved propulsion symmetry and gait speed, but also pertained to performance of functional gait tasks and daily-life walking activity levels. These findings suggest that well-selected chronic stroke survivors may benefit from task-specific targeted training to utilize the residual propulsive capacity of the paretic leg. Future research is recommended to establish simple baseline measures for identification of individuals who may benefit from such training and confirm benefits of the used training concepts in a randomized controlled trial. TRIAL REGISTRATION: Registry number ClinicalTrials.gov ( www.clinicaltrials.gov ): NCT04650802, retrospectively registered 3 December 2020.

Effect of assist-as-needed robotic gait training on the gait pattern post stroke: a randomized controlled trial.

BACKGROUND: Regaining gait capacity is an important rehabilitation goal post stroke. Compared to clinically available robotic gait trainers, robots with an assist-as-needed approach and multiple degrees of freedom (AANmDOF) are expected to support motor learning, and might improve the post-stroke gait pattern. However, their benefits compared to conventional gait training have not yet been shown in a randomized controlled trial (RCT). The aim of this two-center, assessor-blinded, RCT was to compare the effect of AANmDOF robotic to conventional training on the gait pattern and functional gait tasks during post-stroke inpatient rehabilitation. METHODS: Thirty-four participants with unilateral, supratentorial stroke were enrolled (< 10 weeks post onset, Functional Ambulation Categories 3-5) and randomly assigned to six weeks of AANmDOF robotic (combination of training in LOPES-II and conventional gait training) or conventional gait training (30 min, 3-5 times a week), focused on pre-defined training goals. Randomization and allocation to training group were carried out by an independent researcher. External mechanical work (WEXT), spatiotemporal gait parameters, gait kinematics related to pre-defined training goals, and functional gait tasks were assessed before training (T0), after training (T1), and at 4-months follow-up (T2). RESULTS: Two participants, one in each group, were excluded from analysis because of discontinued participation after T0, leaving 32 participants (AANmDOF robotic n = 17; conventional n = 15) for intention-to-treat analysis. In both groups, WEXT had decreased at T1 and had become similar to baseline at T2, while gait speed had increased at both assessments. In both groups, most spatiotemporal gait parameters and functional gait tasks had improved at T1 and T2. Except for step width (T0-T1) and paretic step length (T0-T2), there were no significant group differences at T1 or T2 compared to T0. In participants with a pre-defined goal aimed at foot clearance, paretic knee flexion improved more in the AANmDOF robotic group compared to the conventional group (T0-T2). CONCLUSIONS: Generally, AANmDOF robotic training was not superior to conventional training for improving gait pattern in subacute stroke survivors. Both groups improved their mechanical gait efficiency. Yet, AANmDOF robotic training might be more effective to improve specific post-stroke gait abnormalities such as reduced knee flexion during swing. Trial registration Registry number Netherlands Trial Register ( www.trialregister.nl ): NTR5060. Registered 13 February 2015.

Immediate after-effects of robot-assisted gait with pelvic support or pelvic constraint on overground walking in healthy subjects.

BACKGROUND: Recovery of walking is a primary rehabilitation goal of most stroke survivors. Control of pelvic movements is one of the essential determinants of gait, yet surprisingly, conventional robot-assisted gait trainers constrain pelvic movements. Novel robot-assisted gait trainers, such as LOPES II, are able to support pelvic movements during gait. The aim of this cross-over study was to investigate the immediate after-effects of pelvic support (PS) or pelvic constraint (PC) gait training with LOPES II on overground walking in healthy subjects. METHODS: Thirteen able-bodied subjects (22.8 ± 2.1 years) participated in two 20-min gait training sessions with LOPES II; one with PS and one with PC. During the PS-training, the LOPES II actively guided the lateral displacement of the pelvis, while pelvic rotations were free. During the PC-condition, both lateral displacement and pelvic rotations were constrained and reduced to a minimum. The training sessions were separated by a 30-min resting period. Lateral displacement of the pelvis, hip and knee kinematics, and spatiotemporal parameters during overground walking were determined at baseline and immediately following the training using 3D gait analysis. RESULTS: During the PS-condition in LOPES II the lateral pelvic displacement was significantly greater (105.6 ± 0 .5 mm) than during the PC-condition (10.8 ± 0 .7 mm; p < 0.001). Analysis of the first five steps of overground walking immediately following PC-condition showed significantly smaller lateral displacements of the pelvis (32.3 ± 12.0 mm) compared to PS-condition (40.1 ± 9 .8 mm; p < 0.01). During the first five steps, step width was significantly smaller after PC-condition (0.17 ± 0. 04 m) compared to PS-condition (0.20 ± 0.04 m; p = 0.01) and baseline (0.19 ± 0. 03 m; p = 0.01). Lateral displacement of the pelvis and step width post training returned to baseline levels within 10 steps. PC- nor PS-condition affected kinematics, gait velocity, cadence, stride length or stance time. CONCLUSIONS: In healthy subjects, robot-assisted gait training with pelvic constraint had immediate negative after-effects on the overground walking pattern, as compared to robot-assisted gait training with pelvic support. Gait training including support of the lateral displacement of the pelvis better resembles the natural gait pattern. It remains to be identified whether pelvic support during robot-assisted gait training is superior to pelvic constraint to promote gait recovery in individuals with neurological disorders.

Assessment of the underlying systems involved in standing balance: the additional value of electromyography in system identification and parameter estimation.

BACKGROUND: Closed loop system identification (CLSIT) is a method to disentangle the contribution of underlying systems in standing balance. We investigated whether taking into account lower leg muscle activation in CLSIT could improve the reliability and accuracy of estimated parameters identifying the underlying systems. METHODS: Standing balance behaviour of 20 healthy young participants was measured using continuous rotations of the support surface (SS). The dynamic balance behaviour obtained with CLSIT was expressed by sensitivity functions of the ankle torque, body sway and muscle activation of the lower legs to the SS rotation. Balance control models, 1) without activation dynamics, 2) with activation dynamics and 3) with activation dynamics and acceleration feedback, were fitted on the data of all possible combinations of the 3 sensitivity functions. The reliability of the estimated model parameters was represented by the mean relative standard errors of the mean (mSEM) of the estimated parameters, expressed for the basic parameters, the activation dynamics parameters and the acceleration feedback parameter. To investigate the accuracy, a model validation study was performed using simulated data obtained with a comprehensive balance control model. The accuracy of the estimated model parameters was described by the mean relative difference (mDIFF) between the estimated parameters and original parameters. RESULTS: The experimental data showed a low mSEM of the basic parameters, activation dynamics parameters and acceleration feedback parameter by adding muscle activation in combination with activation dynamics and acceleration feedback to the fitted model. From the simulated data, the mDIFF of the basic parameters varied from 22.2-22.4% when estimated using the torque and body sway sensitivity functions. Adding the activation dynamics, acceleration feedback and muscle activation improved mDIFF to 13.1-15.1%. CONCLUSIONS: Adding the muscle activation in combination with the activation dynamics and acceleration feedback to CLSIT improves the accuracy and reliability of the estimated parameters and gives the possibility to separate the neural time delay, electromechanical delay and the intrinsic and reflexive dynamics. To diagnose impaired balance more specifically, it is recommended to add electromyography (EMG) to body sway (with or without torque) measurements in the assessment of the underlying systems.

A gait paradigm reveals different patterns of abnormal cerebellar motor learning in primary focal dystonias.

Accumulating evidence points to a role of the cerebellum in the pathophysiology of primary dystonia. The aim of this study was to investigate whether the abnormalities of cerebellar motor learning in primary dystonia are solely detectable in more pure forms of cerebellum-dependent associative motor learning paradigms, or whether these are also present in other motor learning paradigms that rely heavily on the cerebellum but in addition require a more widespread sensorimotor network. Twenty-six patients with various forms of focal dystonia and 10 age-matched healthy controls participated in a motor learning paradigm on a split-belt treadmill. By using reflective markers, three-dimensional kinematics were recorded using a 6-camera motion analysis system. Adaptation walking parameters were analyzed offline, comparing the different dystonia groups and healthy controls. Patients with blepharospasm and writer's cramp were significantly impaired on various adaptation walking parameters. Whereas results of cervical dystonia patients did not differ from healthy controls in terms of adaptation walking parameters, differences in parameters of normal gait were found. We have here demonstrated abnormal sensorimotor adaptation with the split-belt paradigm in patients with blepharospasm and writer's cramp. This reinforces the current concept of cerebellar dysfunction in primary dystonia, and that this extends beyond more pure forms of cerebellum-dependent associative motor learning paradigms. However, the finding of normal adaptation in cervical dystonia patients indicates that the pattern of cerebellar dysfunction may be slightly different for the various forms of primary focal dystonia, suggesting that actual cerebellar pathology may not be a primary driving force in dystonia.

Obstacle course training can improve mobility and prevent falls in people with intellectual disabilities.

BACKGROUND: Persons with intellectual disabilities (ID) constitute a special-needs population at high risk of falling. This is the first study to evaluate whether obstacle course training can improve mobility and prevent falls in this population. METHODS: The intervention was implemented as part of an institution-wide health care improvement plan aimed at reducing falls at a residential facility for people with ID. It comprised an annual screening of each resident for his or her individual fall risk. Subsequently, the group of ambulatory persons with a moderate to high fall risk (n = 39) were offered 10-session obstacle course training to improve their balance and gait abilities. Mobility was assessed pre-intervention, mid-term and post-intervention with the Performance Oriented Mobility Assessment (POMA), the Timed Up and Go (TUG) and the 10-meter walking test. The number of falls was compared between the year before and after intervention. RESULTS: The number of falls decreased by 82% (P < 0.001). POMA scores significantly improved from pre-intervention to mid-term (mean difference ± SD, 1.8 ± 2.9, P = 0.001), from mid-term to post-intervention (2.0 ± 2.9, P < 0.001), and from pre-intervention to post-intervention (3.8 ± 4.3, P < 0.001). Participants completed the 10-meter walking test faster at the post-intervention compared with the pre-intervention assessment (difference ± SD, 2.1 ± 5.1 s, P = 0.022). TUG scores did not improve significantly. CONCLUSIONS: The present study provides preliminary evidence for the effectiveness of obstacle course training in improving mobility and preventing falls in people with ID. As falls are a significant health concern in this population, further research is advocated to provide conclusive evidence for the suggested beneficial effects of exercise interventions.

Falls in older persons with intellectual disabilities: fall rate, circumstances and consequences.

BACKGROUND: Falling is a common cause of injuries and reduced quality of life. Persons with intellectual disabilities (ID) are at increased risk for falls and related injuries. As the number of elderly persons with ID is growing rapidly, it is imperative to gain insight into the quantity of the problem of falling, the circumstances that precipitate falls and to better understand their aetiology in persons with ID. This is the first study to prospectively investigate fall rate, circumstances and fall consequences in older adults with mild to moderate ID. METHOD: Eighty-two individuals with mild to moderate ID, 50 years and over [mean age 62.3 (SD = 7.6), 34 male], participated in this study, which was conducted at three service providers for persons with ID in the Netherlands. Falls were registered for 1 year with monthly fall registration calendars to determine the fall rate (mean number of falls per person per year). Information on fall circumstances and consequences was obtained from questionnaires completed by caregivers and study participants after each fall. RESULTS: We determined that the fall rate in this sample was 1.00 fall per person per year. Thirty-seven participants reported at least one fall (range 1-6). Sex and age were not related to falls. Most falls occurred while walking (63.3%), outside (61.7%) and in familiar environments (88.9%). Importantly, 11.5% of falls resulted in severe injuries, approximately half of which were fractures. CONCLUSION: The circumstances and consequences of falls in persons with ID are comparable to those of the general elderly population, but the rate is substantially higher. As such, appropriate fall prevention strategies must be developed for individuals with ID.

Martial arts fall training to prevent hip fractures in the elderly.

UNLABELLED: Hip fractures are a common and serious consequence of falls. Training of proper fall techniques may be useful to prevent hip fractures in the elderly. The results suggested that martial arts fall techniques may be trainable in older individuals. Better performance resulted in a reduced impact force. INTRODUCTION: Hip fractures are a common and serious consequence of falls. Fall training may be useful to prevent hip fractures in the elderly. This pilot study determined whether older individuals could learn martial arts (MA) fall techniques and whether this resulted in a reduced hip impact force during a sideways fall. METHODS: Six male and nineteen female healthy older individuals completed a five-session MA fall training. Before and after training, force and kinematic data were collected during volitional sideways falls from kneeling position. Two MA experts evaluated the fall performance. Fear of falling was measured with a visual analog scale (VAS). RESULTS: After fall training, fall performance from a kneeling position was improved by a mean increase of 1.6 on a ten-point scale (P < 0.001). Hip impact force was reduced by a mean of 8% (0.20 N/N, P = 0.016). Fear of falling was reduced by 0.88 on a VAS scale (P = 0.005). CONCLUSION: MA techniques may be trainable in older individuals, and a better performance may reduce the hip impact force in a volitional sideways fall from a kneeling position. The additional reduction of fear of falling might result in the prevention of falls and related injuries.

Effectiveness of rehabilitation interventions to improve paretic propulsion in individuals with stroke - A systematic review.

BACKGROUND: Stroke survivors often show reduced walking velocity and gait asymmetry. These gait abnormalities are associated with reduced propulsion of the paretic leg. This review aimed to provide an overview of the potential effectiveness of post-stroke rehabilitation interventions to improve paretic propulsion, ankle kinetics and walking velocity. METHODS: A systematic search was performed in Pubmed, Web of Science, Embase, and Pedro. Studies were eligible if they reported changes in propulsion measures (impulse, peak value and symmetry ratios) or ankle kinetics (moment and power) following intervention in stroke survivors (group size ≥10). Study selection, data extraction and quality assessment were performed independently by two authors. FINDINGS: A total of 28 studies were included, of which 25 studies applied exercise interventions, two studies focused on surgical interventions, and one on non-invasive brain stimulation. The number of high-quality trials was limited (N = 6; score Downs and Black scale ≥19). Propulsion measures were the primary outcome in eight studies. In general, mixed results were reported with 14 interventions yielding improvements in propulsion and ankle kinetics. In contrast, gains in walking velocity were observed in the vast majority of studies (N = 20 out of 23). INTERPRETATION: Interventions that yielded gains in propulsion appeared to have in common that they challenged and/or enabled the utilization of latent propulsive capacity of the paretic leg during walking. Walking speed generally increased, regardless of the observed change in propulsion, suggesting the use of compensatory mechanisms. Findings should, however, be interpreted with some caution, as the evidence base for this emerging focus of rehabilitation is limited.

Estimating ankle torque and dynamics of the stabilizing mechanism: No need for horizontal ground reaction forces.

Changes in human balance control can objectively be assessed using system identification techniques in combination with support surface translations. However, large, expensive and complex motion platforms are required, which are not suitable for the clinic. A treadmill could be a simple alternative to apply support surface translations. In this paper we first validated the estimation of the joint stiffness of an inverted pendulum using system identification methods in combination with support surface translations, by comparison with the joint stiffness calculated using a linear regression method. Second, we used the system identification method to investigate the effect of horizontal ground reaction forces on the estimation of the ankle torque and the dynamics of the stabilizing mechanism of 12 healthy participants. Ankle torque and resulting frequency response functions, which describes the dynamics of the stabilizing mechanism, were calculated by both including and excluding horizontal ground reaction forces. Results showed that the joint stiffness of an inverted pendulum estimated using system identification is comparable to the joint stiffness estimated by a regression method. Secondly, within the induced body sway angles, the ankle torque and frequency response function of the joint dynamics calculated by both including and excluding horizontal ground reaction forces are similar. Therefore, the horizontal ground reaction forces play a minor role in calculating the ankle torque and frequency response function of the dynamics of the stabilizing mechanism and can thus be omitted.

Exercise interventions to reduce fall-related fractures and their risk factors in individuals with low bone density: a systematic review of randomized controlled trials.

SUMMARY: Exercise can reduce falls and fall-related fractures in healthy individuals; however, evidence for individuals with low BMD is limited. The results from this systematic review indicate that exercise interventions for individuals with low BMD to reduce falls and fractures should include balance, muscle strengthening, and weight-bearing exercises. INTRODUCTION: The purpose of this systematic review was to investigate which exercise interventions are effective in individuals with low bone mineral density (BMD; osteopenia or osteoporosis) in reducing (1) falls and fractures and (2) risk factors for falls and fractures. METHODS: Databases were searched for relevant studies between 1996 and June 2008. Methodological quality was assessed with the Jadad score and the PEDro scale. RESULTS: Of the 1,369 publications found, 23 met the inclusion criteria. Five additional articles were included after checking reference lists and searching author's names and related articles. Interventions with balance exercises reduced falls or fall-related fractures and improved balance in the majority of the studies. Muscle strengthening exercises were effective in improving lower extremity strength and back extensor strength; however, not all RCT's reported positive effects. Bone strength was improved by weight-bearing aerobic exercise with or without muscle strengthening exercise when the duration of the intervention was at least a year. CONCLUSIONS: Exercise can reduce falls, fall-related fractures, and several risk factors for falls in individuals with low BMD. Exercise interventions for patients with osteoporosis should include weight-bearing activities, balance exercise, and strengthening exercises to reduce fall and fracture risk.

Obstacle avoidance in persons with rheumatoid arthritis walking on a treadmill.

OBJECTIVE: Patients with rheumatoid arthritis (RA) are at increased risk of falling. In healthy elderly persons with a history of falling, a reduced ability to avoid obstacles while walking has been shown to relate to increased fall risk. The aim of this study was to determine whether this potential risk factor for falls would also be present in persons with RA. METHODS: Twelve RA patients and twelve controls performed an obstacle avoidance task on a treadmill. The obstacle was released during three different phases of the gait cycle (late stance, early swing and mid swing) to create increasing difficulty levels. The primary outcome measure was failure rate. RESULTS: Overall, the RA patients had significantly higher obstacle avoidance failure rates. To avoid an obstacle, a long or a short stride strategy can be used, the choice of which depends on the phase of obstacle release. There were no significant group differences in the distribution of obstacle avoidance strategies. However, the RA patients made significantly more failures when performing a short stride strategy in mid swing obstacle release trials (the condition which gave the patients the least time to react; available response time). In addition, compared to the controls, the RA group approached the obstacle more closely prior to obstacle crossing (shorter toe distance), thereby increasing the risk of stumbling. CONCLUSION: Obstacle avoidance performance in persons with RA is significantly deteriorated compared to age- and gender-matched controls, especially when available response time is low. This deficit may contribute to their higher fall risk.

Excessive short-latency stretch reflexes in the calf muscles do not cause postural instability in patients with hereditary spastic paraplegia.

OBJECTIVE: To identify the role of hyperexcitable short-latency stretch reflexes (SLRs) on balance control in people with hereditary spastic paraplegia (PwHSP). METHODS: Sixteen PwHSP with triceps surae spasticity and 9 healthy control subjects were subjected to toes-up support-surface perturbations. EMG data were recorded from gastrocnemius, soleus and tibialis anterior. Furthermore, center-of-mass trajectories were recorded. RESULTS: PwHSP were less able to withstand the perturbations. Triceps surae SLRs (40-80 ms post perturbation) in PwHSP were increased compared to healthy subjects. Furthermore, a sustained triceps surae EMG activity at 220-320 ms post perturbation was observed in PwHSP, whereas control subjects demonstrated suppression of triceps surae activity. Center of mass trajectories started to diverge between PwHSP and controls only after ∼500 ms, with greater excursions being observed in the PwHSP. CONCLUSIONS: The present results confirm that balance control is impaired in PwHSP. However, the late instant of center of mass divergence argues against a direct, causative role of hyperexcitable SLRs in the triceps surae. SIGNIFICANCE: We postulate that enhanced short-latency stretch reflexes of the triceps surae do not underlie poor balance control in PwHSP. Instead, we suggest the lack of suppression of later triceps surae activity to be the main cause.

Proprioceptive perturbations of stability during gait.

Through recent studies, the role of proprioceptors in reactions to perturbations during gait has been finally somewhat better understood. The input from spindle afferents has been investigated with tendon taps, vibration and other forms of muscle stretches, including some resembling natural perturbations (stumbling, slips, and ankle inversions). It was found that activation of spindle afferents produces short-latency response (SLR), consistent with a fast spinal pathway. These reflexes induce relatively minor activation in the stretched muscles. A central question is whether stretch reflexes can occur for stimuli that are quite remote. Thus, a new study was made to examine whether foot sole vibration is able to elicit reflex responses in upper-leg muscles, for example by conduction of vibrations throughout the whole leg. SLR responses were indeed found not only in lower- but also in upper-leg muscles. Similarly during stumbling, SLR are observed throughout the whole limb, although the primary perturbation occurs at foot level. After the SLR, much stronger activations usually occur, with latencies (85 or 120ms) well below those seen in voluntary contractions. These late responses are much more selective and presumably linked to the maintenance of stability. The role of the I(b) afferents from the Golgi tendon organs (GTO) is less clear. From animal work, it is known that these afferents are very sensitive to active muscle contraction and that they play a role in providing reinforcing feedback to extensors during the stance phase. The available evidence supports this notion in humans but lack of selective activation methods precludes more conclusive confirmation.

The relation between hip impact velocity and hip impact force differs between sideways fall techniques.

Fall techniques that reduce fall severity may decrease the risk of hip fractures. A fundamental variable for fall severity is impact force, but impact velocity is also used. The purpose of the study was to determine whether impact velocity is valid to determine differences in fall severity between different techniques. Five young adults with martial arts (MA) experience performed sideways falls from kneeling height using three techniques: Block with arm (Block) and MA techniques with and without use of the arm to break the fall. In addition, one subject also performed MA falls from standing height. Linear regression analysis showed a moderate relation between hip impact velocity and force, which was depended on technique. In falls with comparable impact velocities, forces in MA falls were lower than forces in Block falls. Hence, differences in impact force could not be predicted by velocity. In conclusion, hip impact velocity may be useful to make an approximate prediction of impact force within fall techniques. However, to determine differences between techniques it was not always a valid predictor. When direct impact force measurements are not possible, methods combining impact velocity with energy estimates before and after impact might be more valid.

Martial arts fall techniques reduce hip impact forces in naive subjects after a brief period of training.

Hip fractures are among the most serious consequences of falls in the elderly. Martial arts (MA) fall techniques may reduce hip fracture risk, as they are known to reduce hip impact forces by approximately 30% in experienced fallers. The purpose of this study was to investigate whether hip impact forces and velocities in MA falls would be smaller than in a 'natural' fall arrest strategy (Block) in young adults (without any prior experience) after a 30-min training session in sideways MA fall techniques. Ten subjects fell sideways from kneeling height. In order to identify experience-related differences, additional EMG data of both fall types were collected in inexperienced (n=10) and experienced fallers (n=5). Compared to Block falls, MA falls had significantly smaller hip impact forces (-17%) and velocities (-7%). EMG results revealed experience-related differences in the execution of the MA fall, indicative of less pronounced trunk rotation in the inexperienced fallers. This may explain their smaller reduction of impact forces compared to experienced fallers. In conclusion, the finding that a substantial reduction in impact forces can be achieved after a short training in MA techniques is very promising with respect to their use in interventions to prevent fall injuries.

Martial arts fall techniques decrease the impact forces at the hip during sideways falling.

Falls to the side and those with impact on the hip are risky for hip fractures in the elderly. A previous study has indicated that martial arts (MA) fall techniques can reduce hip impact force, but the underlying mechanism is unknown. Furthermore, the high impact forces at the hand used to break the fall have raised concerns because of the risk for wrist fractures. The purpose of the study was to get insight into the role of hand impact, impact velocity, and trunk orientation in the reduction of hip impact force in MA techniques. Six experienced judokas performed sideways falls from kneeling height using three fall techniques: block with arm technique (control), MA technique with use of the arm to break the fall (MA-a), and MA technique without use of the arm (MA-na). The results showed that the MA-a and MA-na technique reduced the impact force by 27.5% and 30%, respectively. Impact velocity was significantly reduced in the MA falls. Trunk orientation was significantly less vertical in the MA-a falls. No significant differences were found between the MA techniques. It was concluded that the reduction in hip impact force was associated with a lower impact velocity and less vertical trunk orientation. Rolling after impact, which is characteristic for MA falls, is likely to contribute to the reduction of impact forces, as well. Using the arm to break the fall was not essential for the MA technique to reduce hip impact force. These findings provided support for the incorporation of MA fall techniques in fall prevention programs for elderly.

Estimating severity of sideways fall using a generic multi linear regression model based on kinematic input variables.

Many research groups have studied fall impact mechanics to understand how fall severity can be reduced to prevent hip fractures. Yet, direct impact force measurements with force plates are restricted to a very limited repertoire of experimental falls. The purpose of this study was to develop a generic model for estimating hip impact forces (i.e. fall severity) in in vivo sideways falls without the use of force plates. Twelve experienced judokas performed sideways Martial Arts (MA) and Block ('natural') falls on a force plate, both with and without a mat on top. Data were analyzed to determine the hip impact force and to derive 11 selected (subject-specific and kinematic) variables. Falls from kneeling height were used to perform a stepwise regression procedure to assess the effects of these input variables and build the model. The final model includes four input variables, involving one subject-specific measure and three kinematic variables: maximum upper body deceleration, body mass, shoulder angle at the instant of 'maximum impact' and maximum hip deceleration. The results showed that estimated and measured hip impact forces were linearly related (explained variances ranging from 46 to 63%). Hip impact forces of MA falls onto the mat from a standing position (3650±916N) estimated by the final model were comparable with measured values (3698±689N), even though these data were not used for training the model. In conclusion, a generic linear regression model was developed that enables the assessment of fall severity through kinematic measures of sideways falls, without using force plates.

Dynamic stability during level walking and obstacle crossing in persons with facioscapulohumeral muscular dystrophy.

Patients with FSHD suffer from progressive skeletal muscle weakness, which is associated with an elevated fall risk. To obtain insight into fall mechanisms in this patient group, we aimed to assess dynamic stability during level walking and obstacle crossing in patients at different disease stages. Ten patients with at least some lower extremity weakness were included, of whom six were classified as moderately affected and four as mildly affected. Ten healthy controls were also included. Level walking at comfortable speed was assessed, as well as crossing a 10 cm high wooden obstacle. We assessed forward and lateral dynamic stability, as well as spatiotemporal and kinematics variables. During level walking, the moderately affected group demonstrated a lower walking speed, which was accompanied by longer step times and smaller step lengths, yet dynamic stability was unaffected. When crossing the obstacle, however, the moderately affected patients demonstrated reduced forward stability margins during the trailing step, which was accompanied by an increased toe clearance and greater trunk and hip flexion. This suggests that during level walking, the patients effectively utilized compensatory strategies for maintaining dynamic stability, but that the moderately affected group lacked the capacity to fully compensate for the greater stability demands imposed by obstacle crossing, rendering them unable to maintain optimal stability levels. The present results highlight the difficulties that FSHD patients experience in performing this common activity of daily living and may help explain their propensity to fall in the forward direction.

Incorporating in vivo fall assessments in the simulation of femoral fractures with finite element models.

Femoral fractures are a major health issue. Most experimental and finite element (FE) fracture studies use polymethylmethacrylate cups on the greater trochanter (GT) to simulate fall impact loads. However, in vivo fall studies showed that the femur is loaded distally from the GT. Our objective was to incorporate in vivo fall data in FE models to determine the effects of loading position and direction, and size of simulated impact site on the fracture load and fracture type for a healthy and an osteoporotic femur. Twelve sets of loading position and angles were applied through 'near point loads' on the models. Additional simulations were performed with 'cup loads' on the GT, similar to the literature. The results showed no significant difference between fracture loads from simulations with near point loads distally from the GT and those with cup loads on the GT. However, simulated fracture types differed, as near point loads distally from the GT generally resulted in various neck fractures, whilst cup load simulations predicted superior neck and trochanteric fractures only. This study showed that incorporating in vivo fall assessments in FE models by loading the models distally from the GT results in prediction of realistic fracture loads and fracture types.