Effect of dual tasking on a dynamic balance task in children with and without DCD.

The purpose of this study was to compare performance of children with Developmental Coordination Disorder (DCD) and typically developing (TD) children in a dual task paradigm with a dynamic balance task on the Wii Fit as primary task and a concurrent cognitive (counting) or a concurrent bimanual fine motor task as secondary tasks. Using a cross-sectional design, 25 children with DCD and 38 TD children were assessed with the Movement Assessment Battery for Children, 2nd edition (MABC-2) and Divided Attention (DA) task of the KiTAP. Next, the single- and dual-tasks were performed and the level of interference or facilitation of the dual tasks was calculated. Regression analysis determined the predictive value of the DA and MABC-2 component balance outcomes on the dual task performance. On the motor and attentional tasks, the group of children with DCD scored significantly below the level of the TD children. The dual task effect showed similar interference and facilitation of tasks in the different dual-task conditions in both groups. In the dual task-cognitive condition, the divided attention abilities and the MABC-2 balance score predicted 25% of the Wii Fit dynamic balance task performance, whereas in the dual task-motor condition this was higher (31.6%). In both conditions, DA was a stronger predictor than MABC balance score and appears to be an important factor to consider when developing motor task training for children with DCD.

A new protocol for assessing action observation and imitation abilities in children with Developmental Coordination Disorder: A feasibility and reliability study.

AIMS: To develop a new protocol for the assessment of action observation (AO) abilities and imitation of meaningful and non-meaningful gestures, to examine its psychometric properties in children with DCD and typically developing (TD) children. BACKGROUND: For learning manual skills, AO and imitation are considered fundamental abilities. Knowledge about these modalities in children with DCD is scarce and an assessment protocol is lacking. METHOD: The protocol consists of 2 tests. The AO test consists of two assembly tasks. The imitation test includes 12 meaningful and 20 non-meaningful gestures. Items of both tests are rated on a 4-point scale. Twelve children with DCD (mean age 8y3m, SD, 1.30) and 11 TD children (mean age 8y2m, SD 1.52) were enrolled. For inter-rater reliability, intraclass correlation coefficients (ICC) were calculated for the total score, weighted kappa and percentage agreement for single items. Known group validity was assessed by comparison of DCD and TD group (Wilcoxon rank sum test). For construct validity, the mABC-2 test was used. The protocol was adapted and confirmed by an intra and inter-rater reliability study (new sample of 11 DCD children, mean age 7y5m, SD 1.37). RESULTS: Excellent ICCs were reported for intra and inter-rater reliability for the final protocol. A significant difference between DCD and TD group was found for AO abilities (p < .01), for nonmeaningful gestures (p < .001). A significant correlation was reported between the AO test and the mABC-2 test (r = 56;p ≤0.0001). No significant correlations were revealed for the imitation tests. DISCUSSION AND CONCLUSION: The results support the psychometric properties of this protocol. When fully validated, it may contribute to map the deficits in AO abilities and imitation, to evaluate treatment effects of imitation and AO interventions.

Movement Control Strategies in a Dynamic Balance Task in Children With and Without Developmental Coordination Disorder.

Our study aimed to analyze movement control strategies using predefined criteria for amplitude and differences in these strategies between children with and without DCD. Children with (n = 28) and without DCD (n = 15) were included. A video-observation-tool was used to score the moving body parts during a Wii Fit slalom task over multiple time points. Two-step cluster analysis was used to extract distinct movement strategies. Two different movement strategies were identified that were independently validated by a measure of task performance and a subjective mark of quality of the movement. Initial differences between groups and changes over time toward the more successful strategy were found in both groups, albeit in a different percentage. This study shows that the more efficient movement strategy is seen in the majority of the TD children and only in a small number of children with DCD, even after practice.

Qualities or skills discriminating under 19 rugby players by playing standards: a comparative analysis of elite, sub-elite and non-rugby players using the SCRuM test battery.

OBJECTIVE: Although schoolboy rugby is growing in popularity and played at different competitive levels in Zimbabwe, the influence of playing standard on qualities or skills of older male adolescent rugby players is unknown. Utilising a cross-sectional design, this study determined anthropometric, physiological characteristics and rugby-specific game skills defining elite under 19 (U19) schoolboy rugby players. Following development and subsequent assessment of test-retest reliability of School Clinical Rugby Measure (SCRuM) test battery, this study compared performance outcomes of elite rugby players (n = 41), sub-elite rugby players (n = 46) and non-rugby athletes (n = 26) to identify qualities or skills discriminating (i) elite from sub-elite and non-rugby players, and concomitantly (ii) sub-elite from non-rugby players. RESULTS: 40 m speed test (p < 0.001, ES = 1.78) and 2 kg Medicine Ball Chest Throw test (p < 0.001, ES = 1.69) significantly discriminated elite U19 from sub-elite and non-rugby players. These tests further differentiated sub-elite from non-rugby athletes. Additionally, 1RM back squat (p = 0.009, ES = 0.57), 1RM bench press (p = 0.005, ES = 0.61), repeated high-intensity exercise test (p < 0.001, ES = 0.88) and passing ability test (p < 0.001, ES = 0.99) discriminated elite from sub-elite counterparts. These findings highlight important attributes linked to elite U19 schoolboy rugby in Zimbabwe. However, no significant differences were observed for sum of seven skinfold (p = 0.28), tackling (p = 0.08) and catching ability (p = 0.05).

Coaches' perceptions on qualities defining good adolescent rugby players and are important for player recruitment in talent identification programs: the SCRuM project.

OBJECTIVE: Competitive rugby is increasingly becoming popular among adolescent players even in countries hardly known for rugby such as Zimbabwe. Given the increased participation rates, burgeoning talent identification (TID) programs and the reportedly high injury-risk associated with competitive youth rugby, the minimal qualities or skills needed for effective performance by all young players need further clarification. Therefore, this qualitative study was conducted to explore the perceptions of high-school based rugby coaches on the key qualities or skills defining good adolescent rugby players and should be considered for player recruitment in TID programs. Currently, there is no consensus in literature from the coaches' perspective on these qualities. RESULTS: The final sample had 22 coaches (median age = 45.5 years) with years of coaching high-school rugby ranging from 6 to 17 years. Using the conventional approach to inductive content analysis four broad themes emerged suggesting the multifaceted nature of the requirements imperative for effective and optimal rugby performance among adolescent rugby players as perceived by the coaches. Themes identified included: physiological characteristics, anthropometric attributes, psychological qualities and game-specific skills. Possibly, training approaches or design of rugby-specific test-batteries should consider all these important qualities and be multi-dimensional in composition.

High-school adolescents' motivation to rugby participation and selection criteria for inclusion in school rugby teams: coaches' perspective (the SCRuM project).

OBJECTIVE: Despite increasing rugby popularity among schoolboys' worldwide, specific factors influencing their motivation to participate in rugby remain unclear. Therefore, this study was conducted in two parts with a dual purpose of exploring perceptions of rugby coaches on (i) factors motivating schoolboys to engage in competitive rugby, and (ii) criteria for selecting schoolboy rugby players for possible inclusion in school rugby teams. RESULTS: A qualitative study targeting Zimbabwean high school-based rugby coaches purposively-recruited during the 2017 Dairiboard Zimbabwe Rugby School Festival was conducted. Using the conventional approach to content analysis, the 22 recruited male coaches (median age = 45.5 years) felt that playing rugby is a choice largely influenced by either intrinsic or extrinsic motives for schoolboys. Additionally, coaches considered players' characteristics (performance during training, attitude, physical qualities and skills) and match-related factors when selecting schoolboys for possible inclusion in school rugby teams. To effectively promote competitive rugby participation among schoolboys and promote sustainable and effective talent identification programmes in Zimbabwe, more recognition should be paid to factors motivating schoolboys to participate in rugby and also on the factors coaches consider when assembling school rugby teams which indirectly informs on what coaches think should be trained among schoolboy rugby players.

The validity and reliability of the Functional Strength Measurement (FSM) in children with intellectual disabilities.

BACKGROUND: There is lack of valid and reliable field-based tests for assessing functional strength in young children with mild intellectual disabilities (IDs). AIM: The aim of this study was to investigate the test-retest reliability and construct validity of the Functional Strength Measurement in children with ID (FSM-ID). METHOD: Fifty-two children with mild ID (40 boys and 12 girls, mean age 8.48 years, SD = 1.48) were tested with the FSM. Test-retest reliability (n = 32) was examined by a two-way interclass correlation coefficient for agreement (ICC 2.1A). Standard error of measurement and smallest detectable change were calculated. Construct validity was determined by calculating correlations between the FSM-ID and handheld dynamometry (HHD) (convergent validity), FSM-ID, FSM-ID and subtest strength of the Bruininks-Oseretsky test of motor proficiency - second edition (BOT-2) (convergent validity) and the FSM-ID and balance subtest of the BOT-2 (discriminant validity). RESULTS: Test-retest reliability ICC ranged 0.89-0.98. Correlation between the items of the FSM-ID and HHD ranged 0.39-0.79 and between FSM-ID and BOT-2 (strength items) 0.41-0.80. Correlation between items of the FSM-ID and BOT-2 (balance items) ranged 0.41-0.70. CONCLUSION: The FSM-ID showed good test-retest reliability and good convergent validity with the HHD and BOT-2 subtest strength. The correlations assessing discriminant validity were higher than expected. Poor levels of postural control and core stability in children with mild IDs may be the underlying factor of those higher correlations.

Changes in dynamic balance control over time in children with and without Developmental Coordination Disorder.

The aim of this study was to examine differences in underlying adaptations of dynamic balance in children with and without Developmental Coordination Disorder (DCD) during a Wii Fit game and to measure changes over time and after intervention. Twenty-eight children with DCD and 21 typically developing (TD) children participated in the study. Analyses of force plate variables showed that the TD group initially used a longer path length for the ski slope descent and tended toward more variation in Center of Pressure (CoP) displacement in lateral direction than the children with DCD. In contrast, the TD group showed a trend of fewer reversals per cm in both AP and lateral direction. After the nonintervention period, the TD group improved performance by decreasing the path length, while the DCD group improved by increasing the path length and by decreasing the number of reversals. After intervention, no changes were found in sway characteristics. Individual analyses within the DCD group showed that the path length per run fell more often within the 95% confidence Interval of the faultless runs. In conclusion both TD and DCD children modify the underlying kinetics of dynamic balance control, but in different ways and both lead to better performance.

The effect of a motor skills training program in the improvement of practiced and non-practiced tasks performance in children with developmental coordination disorder (DCD).

The purpose of the present study was to examine the effect of a group-based task oriented skills training program on motor and physical ability for children with DCD. It was also investigated if there was an effect on fine motor and handwriting tasks that were not specifically practiced during the training program. Forty-one children aged 6-10years took part in this study. Children were assigned to three groups: an experimental training group consisting of 14 children with DCD, a control non-training group consisted of 13 children with DCD and a control non-training group consisting of 14 typically developed children. The measurements included were, the Movement Assessment Battery for Children (MABC), the Modified Agility Test (MAT), the Triple Hop Distance (THD), the 5 Jump-test (5JT) and the Handwriting Performance Test. All measures were administered pre and post an 8-week training program. The results showed that 10 children of the DCD training-group improved their performance in MABC test, attaining a score above the 15th percentile after their participation in the training program. DCD training-group showed a significant improvement on all cluster scores (manual dexterity (t (13)=5.3, p<.001), ball skills (t (13)=2.73, p<.05) and balance (t (13)=5.13, p<.001). Significant performance improvements were also found in MAT, THD, 5JT (t (13)=-4.55; p<.01), handwriting quality (t (12)=-2.73; p<.05) and speed (t (12)=-4.2; p<.01) after the training program. In conclusion, improvement in both practiced and non-practiced skills, in the training program, may reflect improvement in motor skill but also transfer to other skills.

The influence of task paradigm on motor imagery ability in children with Developmental Coordination Disorder.

Children with Developmental Coordination Disorder (DCD) have difficulty imagining movements such that they conform to the customary temporal constraints of real performance. We examined whether this ability is influenced by the choice of task used to elicit motor imagery (MI). Performance of typically developing (TD) (n=30) and children with DCD (n=30) was compared on two tasks: the Visually Guided Pointing Task (VGPT) and the Computerized Virtual Radial Fitts Task (C-VRFT). Since the VGPT places higher demands on executive functions like working memory but requires less spatial planning, we reasoned that the C-VRFT would provide a purer measure of motor imagery (or simulation). Based on our earlier work, we predicted that imagery deficits in DCD would more likely manifest on the C-VRFT. Results showed high correlations between tasks in terms of executed and imagined movement time suggest that both tasks measure MI ability. However, group differences were more pronounced in the imagined condition of the radial Fitts' task. Taken together, the more spatially complex C-VRFT appears to be a more sensitive measure of motor imagery, better discriminating between DCD and TD. Implications for theory and practice are discussed.

Children with Developmental Coordination Disorder are deficient in a visuo-manual tracking task requiring predictive control.

The aim of this study was to examine how feedback, or its absence, affects children with Developmental Coordination Disorder (DCD) during a visuo-manual tracking task. This cross-sectional study included 40 children with DCD and 40 typically developing (TD) children between 6 and 10 years old. Participants were required to track a target moving along a circular path presented on a monitor by moving an electronic pen on a digitizing tablet. The task was performed under two visibility conditions (target visible throughout the trajectory and target intermittently occluded) and at two different target velocities (30° and 60° per second). Variables reflecting tracking success and tracking behavior within the target were compared between groups. Results showed that children with DCD were less proficient in tracking a moving target than TD children. Their performance deteriorated even more when the target was occluded and when the target speed increased. The mean tracking speed of the DCD group exceeded the speed at which the target rotated which was attributed to accelerations and decelerations made during tracking. This suggests that children with DCD have significant difficulties in visuo-manual tracking especially when visual feedback is reduced. It appears that their impaired ability to predict together with impairments in fine-tuning arm movements may be responsible for poor performance in the intermittently occluded visuo-manual tracking task.

The effects of dual tasking on handwriting in patients with Parkinson's disease.

Previous studies have shown that patients with Parkinson's disease (PD) experience extensive problems during dual tasking. Up to now, dual-task interference in PD has mainly been investigated in the context of gait research. However, the simultaneous performance of two different tasks is also a prerequisite to efficiently perform many other tasks in daily life, including upper limb tasks. To address this issue, this study investigated the effect of a secondary cognitive task on the performance of handwriting in patients with PD. Eighteen PD patients and 11 age-matched controls performed a writing task involving the production of repetitive loops under single- and dual-task conditions. The secondary task consisted of counting high and low tones during writing. The writing tests were performed with two amplitudes (0.6 and 1.0cm) using a writing tablet. Results showed that dual-task performance was affected in PD patients versus controls. Dual tasking reduced writing amplitude in PD patients, but not in healthy controls (p=0.046). Patients' writing size was mainly reduced during the small-amplitude condition (small amplitude p=0.017; large amplitude p=0.310). This suggests that the control of writing at small amplitudes requires more compensational brain-processing recourses in PD and is as such less automatic than writing at large amplitudes. In addition, there was a larger dual-task effect on the secondary task in PD patients than controls (p=0.025). The writing tests on the writing tablet proved highly correlated to daily life writing as measured by the 'Systematic Screening of Handwriting Difficulties' test (SOS-test) and other manual dexterity tasks, particularly during dual-task conditions. Taken together, these results provide additional insights into the motor control of handwriting and the effects of dual tasking during upper limb movements in patients with PD.

The efficacy of two task-orientated interventions for children with Developmental Coordination Disorder: Neuromotor Task Training and Nintendo Wii Fit Training.

Neuromotor Task Training (NTT) and Nintendo Wii Fit Training (Wii training) are both task-based interventions used to improve performance in children with motor coordination problems. The aim of this study was to compare the efficacy of these two interventions on the motor performance, isometric strength and cardiorespiratory fitness (aerobic and anaerobic capacity) of children with Developmental Coordination Disorder (DCD) attending mainstream schools in a low-income setting. A pragmatic, quasi-experimental study design was utilized. Children between the ages of 6-10 years, who scored at or below the 16th percentile on the Movement Assessment Battery for Children-2 (MABC-2) and whose teacher reported a functional motor problem, were allocated to either NTT (n=37) or Wii training (n=19) groups depending on school of attendance. The MABC-2, a hand-held dynamometer, the Functional Strength Measure, the Muscle Power Sprint Test and the 20m Shuttle Run Test were used to assess performance at baseline and after the intervention. The main findings show that the mean motor performance scores of both groups improved over the study period. However, significant differences in improvement were detected between groups, with the NTT group showing greater improvement in motor performance, functional strength and cardiorespiratory fitness. No improvements in isometric strength were seen in either group. The Wii training group showed significant improvement in anaerobic performance. This study provides evidence to support the use of both the Wii Training and NTT for children with DCD. However, in comparison to Wii training, the NTT approach yields superior results across measures of motor proficiency, cardiorespiratory fitness and functional strength. The decision to use either approach may be influenced by resources and time constraints.

Bimanual force coordination in children with spastic unilateral cerebral palsy.

In this study bimanual grip-force coordination was quantified using a novel "Gripper" system that records grip forces produced while holding a lower and upper unit, in combination with the lift force necessary to separate these units. Children with unilateral cerebral palsy (CP) (aged 5-14 years, n=12) were compared to age matched typically developing (TD) children (n=23). Compared to TD, the CP-group is much slower and takes 50% more time to generate grip and lift forces with more fixating force before lifting the upper unit. In addition the coordination between forces in both hands is reduced. The CP-group increases the lift force in the upper hand 2.5 times more than the holding force when pulling the two units apart, while this is only 1.5 times in TD. Moreover, the correlation between forces generated in both hands in the CP-group is lower. The lack of fine tuning of the forces, measured by the linearity error is increased, especially when the magnet load keeping the unit together is low. The results indicate an impaired pull-hold synergy between upper and lower hand and the lift force. Bimanual tasks evaluating bimanual grip and lift forces in children with CP and can give us new insights in the underlying force control mechanisms of the spastic hand.

Brain-behavior relationships in young traumatic brain injury patients: fractional anisotropy measures are highly correlated with dynamic visuomotor tracking performance.

Traumatic brain injury (TBI) patients have a high incidence of eye-hand coordination deficits. Diffuse axonal injury is common in TBI and is presumed to contribute to persistent motor problems. Using Diffusion Tensor Imaging (DTI), this study sought to identify changes in (sensori)motor white matter (WM) pathways/regions in a TBI group during the chronic recovery stage. A secondary objective was to examine the relationship between WM integrity and upper-limb visuomotor tracking performance. A young TBI (n=17) and control (n=14) group performed a dynamic tracking task, characterized by increasing information processing speed and predictive movement control. DTI scans were administered along with standard anatomical scans. The TBI group was found to perform inferior to the control group on the tracking task. Decreased fractional anisotropy was found in the TBI group in dedicated pathways involved in transmission of afferent and efferent information, i.e., corticospinal tract, posterior thalamic radiation, and optic radiation, due to increased diffusivity parallel and perpendicular to axonal fibre direction. This decrease in WM integrity was associated with inferior visuomotor tracking performance. Moreover, discriminant function analysis demonstrated that the model, based on the combined application of DTI and behavioral measures, was the most effective in distinguishing between TBI patients and controls. This study shows that specific eye-hand coordination deficits in a young TBI group are related to microstructural abnormalities in task-specific cerebral WM structures. Measures of white matter integrity are potentially important biomarkers for TBI that may support prognosis of motor deficits.

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.

Neural correlates of motor dysfunction in children with traumatic brain injury: exploration of compensatory recruitment patterns.

Traumatic brain injury (TBI) is a common form of disability in children. Persistent deficits in motor control have been documented following TBI but there has been less emphasis on changes in functional cerebral activity. In the present study, children with moderate to severe TBI (n = 9) and controls (n = 17) were scanned while performing cyclical movements with their dominant and non-dominant hand and foot according to the easy isodirectional (same direction) and more difficult non-isodirectional (opposite direction) mode. Even though the children with TBI were shown to be less successful on various items of a clinical motor test battery than the control group, performance on the coordination task during scanning was similar between groups, allowing a meaningful interpretation of their brain activation differences. fMRI analysis revealed that the TBI children showed enhanced activity in medial and anterior parietal areas as well as posterior cerebellum as compared with the control group. Brain activation generally increased during the non-isodirectional as compared with the isodirectional mode and additional regions were involved, consistent with their differential degree of difficulty. However, this effect did not interact with group. Overall, the findings indicate that motor impairment in TBI children is associated with changes in functional cerebral activity, i.e. they exhibit compensatory activation reflecting increased recruitment of neural resources for attentional deployment and somatosensory processing.

Deficits in executed and imagined aiming performance in brain-injured children.

Motor disorders are a frequent consequence of acquired brain injury (ABI) in children and much effort is currently invested in alleviating these deficits. The aim of the present study was to test motor imagery (MI) capabilities in children with ABI (n=25) and an age- and gender-matched control group (n=25). A computerized Virtual Radial Fitts Task (VRFT) was used to investigate the speed-accuracy trade-offs (or Fitts' law) that occur as target size is varied for both executed and imagined performance. In the control group, the speed for accuracy trade-off for both executed and imagined performance conformed to Fitts' law. In the ABI group, only executed movements conformed to Fitts' law. These findings suggest that children with ABI show an inferior ability to imagine the time needed to complete goal-directed movements with differential difficulty levels.

Botulinum toxin-a in children with congenital spastic hemiplegia does not improve upper extremity motor-related function over rehabilitation alone: a randomized controlled trial.

BACKGROUND: Rehabilitation of the upper extremity in children with hemiplegic cerebral palsy has not been compared to the same intensity of therapy combined with injected botulinum toxin (BTX). OBJECTIVE: To measure the short-term (2 weeks) and long-term (6 and 9 months) effects of a standardized functional training program versus without the addition of chemodenervation of forearm and hand muscles. METHODS: Twenty children with spastic hemiplegia, aged 4 to 16 years, were matched for baseline characteristics and then randomized to standardized functional physical and occupational therapies for 6 months (PT/OT group) or to the same therapies plus multimuscle BTX-A (BTX+ group). MAIN OUTCOME MEASURES: were isometric generated force, overshoot and undershoot (force production error), active and passive range of motion by goniometry (ROM), stretch restricted angle (SRA) of joints, Ashworth scores at the elbow and wrist, and the Melbourne assessment of unilateral upper limb function. All measures were performed at baseline, 2 weeks after BTX-A, 6 months (end of therapy), and then 3 months after termination of the therapy. RESULTS: Clinical measures (muscle tone, active ROM of wrist and elbow) showed improvement in both groups. However, no significant differences emerged between groups on functional measures. Generated force decreased directly after the BTX-A injection but increased during the therapy period. The PT/OT group, however, showed a significantly higher increase in force and accuracy with therapy compared with the BTX+ therapy group. CONCLUSIONS: Functional rehabilitation therapies for the upper extremity increase manual isometric flexor force at the wrist and ROM, but BTX injections cause weakness and do not lead to better outcomes than therapy alone.

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.