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Purpose: This study modified established clinical balance and walking measures and estimated the reliability, validity, and feasibility of using these measures to assess people post-stroke via videoconferencing. Method: Twenty-eight people with chronic stroke were recruited and completed the in-person balance and mobility tests. Five clinical measures were modified as virtual assessments over videoconferencing. Feasibility was evaluated by task completion rate, occurrence of adverse events, and technical difficulties. Test–retest reliability and agreement were examined by intra-class correlations and standard error of measurement between two testing days. Convergent validity was examined by the magnitude of associations between in-person and virtual assessments using Pearson or Spearman rank correlation. Results: Twenty-one participants (52% female) participated in both in-person and virtual assessments. No adverse events occurred. Technical challenges were experienced by eight participants. Test–retest reliability for timed up and go test, 30-seconds sit-to-stand, five-times sit-to-stand, functional reach test, and tandem stance resulted in intra-class coefficients of 0.97, 0.90, 0.77, 0.54, and 0.50 respectively. The standard error of measurement was low across all virtual assessments. The timed up and go test, five-times sit-to-stand, and 30-seconds sit-to-stand showed relationship with in-person assessments ( r = −0.55 to −0.81). Conclusion: Virtual assessment of walking and balance function in ambulatory people post-stroke is feasible; however, technical challenges were experienced. The test–retest reliability of virtual assessments of timed up and go test and sit-to-stand tasks for people with stroke, together with strong convergent validity of the measures compared to in-person assessments is promising.

This study investigates the reproducibility and concurrent validity of the Rate of Perceived Stability (RPS) Scale in people with stroke.On two separate days (2-10 days apart), participants provided their RPS ratings during clinical measures: 1)16 tasks from Community Balance and Mobility Scale (CBM), 2)6-minute walk test (6MWT), and 3)self-paced gait speed. Intraclass correlations (ICCs) assessed between day test-retest reliability of RPS ratings. Standard error of measurement (SEM) and smallest detectable change (SDC) addressed level of between day agreement. Spearman rank correlations (Thirty participants with stroke (50% female) participated. ICC ranged from 0.46 to 0.93 across tasks with 12/19 tasks showing ICCs above 0.75 (good test-retest reliability). SEM was 1-point for each task and SDC ranged from 2 to 4 across tasks. Concurrent validity between RPS and ratings of perceived challenge was good-to-excellent (RPS shows promise as a measure of balance intensity in people with stroke.IMPLICATIONS FOR REHABILITATIONThe RPS is a reliable and valid measure of balance intensity in ambulatory people with stroke.The RPS scale may be a useful clinical tool to address the gap in practice of measuring balance intensity during rehabilitation of walking balance post-stroke.

Background Encouraging upper limb use and increasing intensity of practice in rehabilitation are two important goals for optimizing upper limb recovery post stroke. Feedback from novel wearable sensors may influence practice behaviour to promote achieving these goals. A wearable sensor can potentially be used in conjunction with a virtually monitored home program for greater patient convenience, or due to restrictions that preclude in-person visits, such as COVID-19. This trial aims to (1) determine the efficacy of a virtual behaviour change program that relies on feedback from a custom wearable sensor to increase use and function of the upper limb post stroke; and (2) explore the experiences and perceptions of using a program coupled with wearable sensors to increase arm use from the perspective of people with stroke. Methods This mixed-methods study will utilize a prospective controlled trial with random allocation to immediate or 3-week delayed entry to determine the efficacy of a 3-week behaviour change program with a nested qualitative description study. The intervention, the Virtual Arm Boot Camp (V-ABC) features feedback from a wearable device, which is intended to increase upper limb use post stroke, as well as 6 virtual sessions with a therapist. Sixty-four adults within 1-year post stroke onset will be recruited from seven rehabilitation centres. All outcomes will be collected virtually. The primary outcome measure is upper limb use measured by grasp counts over 3 days from the wearable sensor (TENZR) after the 3-week intervention. Secondary outcomes include upper limb function (Arm Capacity and Movement Test) and self-reported function (Hand Function and Strength subscale from the Stroke Impact Scale). Outcome data will be collected at baseline, post-intervention and at 2 months retention. The qualitative component will explore the experiences and acceptability of using a home program with a wearable sensor for increasing arm use from the point of view of individuals with stroke. Semi-structured interviews will be conducted with participants after they have experienced the intervention. Qualitative data will be analysed using content analysis. Discussion This study will provide novel information regarding the efficacy and acceptability of virtually delivered programs to improve upper extremity recovery, and the use of wearable sensors to assist with behaviour change. Trial registration ClinicalTrials.govNCT04232163. January 18, 2020., Trials, 23, ISSN:1468-6694, ISSN:1745-6215, ISSN:1468-6708

Retraining stepping reactions in people post-stroke is vital. However, the relationship between the stimulus and resulting stepping performance in people post-stroke is unknown. We explored relationships between stepping stimulus and stepping reactions initiated by either paretic or non-paretic legs of people post-stroke and controls. Relationships were examined in the context of clinical measures of balance.Centre of mass dynamics were measured during self-initiated destabilizing leaning stimuli that required stepping reactions by paretic and non-paretic legs of people post-stroke (n = 10) and controls (n = 10) to recover balance. Step characteristics of the first two steps of stepping reactions were measured. Correlations were calculated between clinical measures of balance and mobility and the centre of mass and step characteristics.Steps were shorter and slower with decreased centre of mass fore-aft and downward displacement and velocity when initiated by paretic and non-paretic legs compared with controls. However, increase in centre of mass displacement and velocity in the fore-aft and downward direction tended to be associated with a greater increase in step length and speed when stepping reactions were initiated by the paretic and non-paretic legs compared with controls. Time to step initiation in response to onset of falling stimulus did not differ between groups. Strong positive correlations were found between clinical balance and mobility scores and centre of mass and step dynamics in fore-aft and vertical directions.These results support objective measurement of centre of mass to quantify the stimulus influencing step dynamics and stepping performance during retraining interventions following stroke.

Objective Successful stepping reactions, led by either the paretic or nonparetic leg, in response to a loss of balance are critical to safe mobility poststroke. The purpose of this study was to measure sagittal plane hip, knee, ankle, and trunk kinematics during 2-step stepping reactions initiated by paretic and nonparetic legs of people who had stroke and members of a control group. Methods Principal component analysis (PCA) was used to reduce the data into movement patterns explaining interlimb coordination of the stepping and stance legs. Correlations among principal components loading scores and clinical measures of balance ability (as measured on the Community Balance and Mobility scale), motor impairment (as measured on the foot and leg sections of the Chedoke-McMaster Stroke Assessment), and step characteristics (length and velocity) were used to examine the effect of stroke on stepping reaction movement patterns. Results The first 5 principal components explained 95.9% of the movement pattern of stepping reactions and differentiated between stepping reactions initiated by paretic legs, nonparetic legs, or the legs of controls. Moderate-strong associations (ρ/r > 0.50) between specific principal component loading scores and clinical measures and step characteristics were dependent on the initiating leg. Lower levels of motor impairment, higher levels of balance ability, and faster and longer steps were associated with stepping reactions initiated by the paretic leg that comprised paretic leg flexion and nonparetic leg extension. Step initiation with the nonparetic leg showed associations between higher scores on clinical measures and movement patterns of flexion in both paretic and nonparetic legs. Conclusions Movement patterns of stepping reactions poststroke were influenced by the initiating leg. After stroke, specific movement patterns showed associations with clinical measures depending on the initiating leg, suggesting that these movement patterns are important to retraining of stepping reactions. Specifically, use of flexion patterning and assessment of between-leg pattern differentiation may be important aspects to consider during retraining of stepping reactions poststroke. Impact Evidence-based interventions targeting balance reactions are still in their infancy. This investigation of stepping reactions poststroke addresses a major gap in research.

Purpose: This study examined the validity of the Fitbit Flex activity monitor for step count and distance walked among post–cardiac surgery patients. Method: Participants (n=20) from a major urban cardiac surgery centre were recruited 1–2 days before hospital discharge. The Fitbit Flex step count and distance walked outputs and video recording of each participant performing the 6-minute walk test were collected. Fitbit Flex output was compared with criterion measures of manual step count obtained from the video recording and manual measurement of distance walked. Statistical analysis compared the output and criterion measures using paired sample t-tests, Pearson correlation coefficients, Lin's concordance correlations, and Bland–Altman plots. Sub-analysis compared slower walking (

This study examined the task dependence of sensory inputs on motoneuron excitability by comparing the inhibitory postsynaptic potential (IPSP) evoked by stimulation of the sural nerve between a standing postural task (Free Standing) and a comparable voluntary isometric contraction performed in a supine position (Lying Supine). We hypothesized that there would be a smaller IPSP in standing than in the supine position, based on the task dependence of the ankle plantarflexor activity on the standing task. Ten healthy participants participated in a total of 15 experiments. Single motor unit (MU) firings were recorded with both intramuscular fine-wire electrodes and high-density surface electromyography. Participants maintained the MU discharge at 6–8 Hz in Free Standing or Lying Supine while the right sural nerve was stimulated at random intervals between 1 and 3 s. To evaluate the reflex response, the firing times of the discriminated MUs were used to construct peristimulus time histograms and peristimulus frequencygrams. The sural nerve stimulation resulted in weaker inhibition in Free Standing than in Lying Supine. This finding is discussed in relation to the putative activation of persistent inward currents in standing posture and the task-dependent advantages of overriding inhibitory synaptic inputs to the plantarflexors to maintain the standing posture. NEW & NOTEWORTHY The task-dependent modulation of sensory inputs on motoneuron excitability in standing is not well understood. Evoking an inhibitory postsynaptic potential (IPSP) resulted in a smaller IPSP in gastrocnemius motoneurons in standing than in the supine position. Mildly painful sensory inputs produced weaker motoneuron inhibition in standing, suggesting an imperative to maintain ankle plantarflexion activity for the task of upright stance.

Background: Ankle plantarflexor muscle impairment contributes to asymmetrical postural control poststroke. Objective: This study examines the relationship of plantarflexor electromyography (EMG) wi...

Introduction Balance confidence and perception of task challenge is an important construct to measure in rehabilitation of people with lower-limb amputation (LLA). Measurement of electrodermal activity (EDA) captures physiological arousal responses reflecting an individual’s perceived challenge in a task. This study explores the feasibility of the use of EDA during outdoor walking tasks to capture task-specific physiological arousal changes associated with perception of challenge in people with amputation. Objective To develop and demonstrate feasibility of a portable EDA/GPS system mapping physiological arousal while challenging walking balance outdoors in individuals with LLA and controls. Methods Sixteen people (eight with LLA and eight age-/sex-matched controls) completed an outdoor walking course in the community (3 laps). A battery-powered portable device was developed containing EDA/GPS sensors with data logged on a microcontroller. Phasic EDA response was extracted from EDA signal to explore the physiological arousal response to walking tasks. Results Physiological arousal demonstrated task-specific modulation with ascending stairs without a handrail showing higher levels of phasic EDA than walking on a paved incline (p = 0.01) or a gravel decline (p = 0.01) in people with LLA. While evidence of habituation over repeated trials was shown in controls with lap 1 of walking down a gravel decline showing higher levels of phasic EDA than lap 3 (p = 0.01). Phasic EDA maps, representative of arousal levels throughout the walking course, showed individual-specific response. Conclusion Mapping of EDA during outdoor walking is feasible. Modulation of physiological arousal between outdoor walking tasks and over repeated trials is suggestive of clinical utility. Further research is warranted to explore how EDA may be incorporated into assessment of response to outdoor walking amongst individuals following LLA.

There is limited investigation of the interaction between motor unit recruitment and rate coding for modulating force during standing or responding to external perturbations. Fifty-seven motor units were recorded from the medial gastrocnemius muscle with intramuscular electrodes in response to external perturbations in standing. Anteriorly directed perturbations were generated by applying loads in 0.45-kg increments at the pelvis every 25–40 s until 2.25 kg was maintained. Motor unit firing rate was calculated for the initial recruitment load and all subsequent loads during two epochs: 1) dynamic response to perturbation directly following each load drop and 2) maintenance of steady state between perturbations. Joint kinematics and surface electromyography (EMG) from lower extremities and force platform measurements were assessed. Application of the external loads resulted in a significant forward progression of the anterior-posterior center of pressure (AP COP) that was accompanied by modest changes in joint angles (

In order to quantify the effects of physical activity such as walking on chronic disease, accurate measurement of physical activity is needed. The objective of this study was to determine the validity and reliability of a new activity monitor, the Fitbit One, in a population of healthy adults.Cross-sectional study.Thirty healthy adults ambulated at 5 different speeds (0.90, 1.12, 1.33, 1.54, 1.78 m/s) on a treadmill while wearing three Fitbit One activity monitors (two on the hips and one in the pocket). The order of each speed condition was randomized. Fitbit One step count output was compared to observer counts and distance output was compared to the calibrated treadmill output. Two-way repeated measures ANOVA, concordance correlation coefficients, and Bland and Altman plots were used to assess validity and intra-class correlation coefficients (ICC) were used to assess reliability.No significant differences were noted between Fitbit One step count outputs and observer counts, and concordance was substantial (0.97-1.00). Inter-device reliability of the step count was high for all walking speeds (ICC ≥ 0.95). Percent relative error was less than 1.3%. The distance output of the Fitbit One activity monitors was significantly different from the criterion values for each monitor at all speeds (P0.001) and exhibited poor concordance (0.0-0.05). Inter-device reliability was excellent for all treadmill speeds (ICC ≥ 0.90). Percent relative error was high (up to 39.6%).The Fitbit One activity monitors are valid and reliable devices for measuring step counts in healthy young adults. The distance output of the monitors is inaccurate and should be noted with caution.

Objective Our aim was to investigate any changes in the estimated time-course of the afterhyperpolarisation (AHP) in motoneurones innervating the tibialis anterior following stroke, with a secondary objective to compare the results from two different AHP estimation techniques. Methods Motor units from tibialis anterior on the paretic and non-paretic sides of 15 subjects with chronic stroke were recorded using intramuscular electrodes during voluntary isometric contraction. Participants varied the motor unit firing rate from its lowest rate to approximately 10Hz. The AHP duration was estimated using the interval death rate (IDR) and transition point methods. Results The AHP decay time-constant was significantly different between sides (paretic: 41.7±8.5ms, non-paretic: 36.2±6.4ms). Additionally, the paretic AHP time-constant was significantly longer in participants with low motor recovery (45.9±9.1ms) than with high motor recovery (39.3±10.0ms) as measured by CMSA score. The AHP estimates from the two techniques were correlated ( r =0.78). Conclusions The AHP time-course prolongation on the paretic side of people with chronic stroke is more pronounced in people with low motor recovery. Significance Changes in the motoneurone AHP time course post-stroke were related to muscle function and may play a role in the commonly-observed reduction of motor unit discharge rate during voluntary contractions following stroke.

Objective The purpose of this study was to examine simultaneously the level of physiological arousal and the postural response to external perturbations in people post-stroke compared to age-matched controls to build a more comprehensive understanding of the effect of stroke on postural control and balance self-efficacy. Methods Participants stood with each foot on separate force platforms. Ten applications of loads of 2% body weight at the hips perturbed the participant anteriorly under two conditions: investigator-triggered or self-triggered (total 20). Electrodermal activity (EDA; measurement of physiological arousal), electromyography (EMG) of the ankle plantarflexor muscles and anterior-posterior center of pressure measurements were taken pre-perturbation (anticipatory) and post-perturbation (response) and compared between the initial (first two) and final (last two) perturbations. Results Participants post-stroke demonstrated significantly higher levels of anticipatory EDA and anticipatory paretic plantarflexor EMG during both self- and investigator-triggered conditions compared to controls. Anticipatory EDA levels were higher in the final perturbations in participants post-stroke in both conditions, but not in controls. Habituation of the EDA responses post-perturbation was exhibited in the self-triggered perturbations in controls, but not in participants post-stroke. Conclusions Physiological arousal and postural control strategies of controls revealed habituation in response to self-triggered perturbations, whereas this was not seen in participants post-stroke. Significance Understanding the physiological arousal response to challenges to standing balance post-stroke furthers our understanding of postural control mechanisms post-stroke.

BackgroundThe Community Balance and Mobility Scale (CB&M) is increasingly used to evaluate walking balance following stroke.ObjectiveThis study applied Rasch analysis to evaluate and refine the CB&M for use in ambulatory community-dwelling adults following stroke.MethodsThe CB&M content was linked to task demands and motor skill classifications. Rasch analysis was used to evaluate internal construct validity (structural validity) and refine the CB&M for use with ambulatory community-dwelling adults following stroke. The CB&M data were collected at 3 time points: at discharge from inpatient rehabilitation and at 6 and 12 months postdischarge (N=238). Rasch analysis evaluated scale dimensionality, item and person fit, item response bias, scoring hierarchy, and targeting. Disordered scoring hierarchy was resolved by collapsing scoring categories. Highly correlated and “misfitting” items were removed. Sensitivity to change was evaluated with standardized response means (SRMs) and one-way repeated-measures analysis of variance.ResultsThe CB&M was primarily linked to closed body transport task demands. Significant item-trait interaction, disordered scoring hierarchies, and multidimensionality were found. Scoring categories were collapsed in 15/19 items, and 5 misfitting items were removed. The resulting stroke-specific 14-item unidimensional CB&M (CB&MStroke) fit Rasch model expectations, with no item response bias, acceptable targeting (13% floor effects and 0% ceiling effects), and moderate-to-strong sensitivity to change at 6 months postdischarge (SRM=0.63; 95% confidence interval=−1.523, −0.142) and 12 months postdischarge (SRM=0.73; 95% confidence interval=−2.318, −0.760).LimitationsFindings are limited to a modest-sized sample of individuals with mild-to-moderate balance impairment following stroke.ConclusionsThe CB&MStroke shows promise as a clinical scale for measuring change in walking balance in ambulatory community-dwelling adults poststroke. Future studies are recommended in a larger sample to validate and further refine the scale for use in this clinical population.

Adaptive rowing is rowing or sculling for rowers with a physical disability. It debuted at the Paralympic Games in 2008. In order to ensure an equitable playing field, rowers with similar levels of physical function and disability are classified into different sport classes for competition. Rowers with an inability to use a sliding seat and impaired trunk function resulting in an inability to perform trunk forward and backward lean via hip flexion/extension are assigned to the Arms and Shoulders (AS) class. AS rowers have to use a chest strap set immediately below the chest in order to localize any trunk movement in AS class. Conditions created by adaptations of rowing equipment and technique within the AS class create unique stresses on the upper thoracic region. The following case report demonstrates how etiology and management of a rib stress fracture in an AS rower differs in comparison to able-body rowers. Of significant importance were the limitations imposed on the rower's ability to maintain rowing-specific fitness, due to the nature of the rib stress fracture and requirement to decrease force transmission through the ribs for several weeks. The rower's gradual return to full training was further impacted by obligatory use of the chest strap, which directly applied pressure over the injured area. Protective orthosis for the chest was designed and applied in order to dissipate pressure of the chest strap over the thorax during rowing (most importantly at the catch position) both on the ergometer and in the boat.

Objective: To identify walking balance measures which have been established for use with ambulatory people post stroke and reflect the balance requirements of community walking. Data sources: MEDLINE, Embase, AMED. Review methods: Measures reflecting walking balance, with tasks that include a stepping action in standing, used with people post stroke were reviewed. Measures with clinical utility were evaluated for psychometric properties, including reliability, validity and clinical interpretation. Results: Nine measures (24 papers) were identified that met the requirement of measuring walking balance in people post stroke with demonstrated clinical utility. Outcome measures with multiple tasks (Brunel Balance Assessment, Modified Emory Functional Ambulation Profile, Dynamic Gait Index, Community Balance and Mobility Scale, and mini-Balance Evaluation Systems Test) as opposed to single task measures (Step Test, Side Step Test and Four Square Step Test, Timed Up and Go), reflect a broader range of walking balance required to accommodate the variable challenges which may be expected at the community level of walking. Most tools report excellent reliability when used by physiotherapists. Validity remains far more challenging to establish. Evaluation of clinical interpretation is limited for all measures. Conclusion: The multiple-task outcome measures reviewed reflected walking balance activities often undertaken during community mobility. Single-task measures may be useful as screening measures, identifying walking balance deficits associated with basic/lower levels of walking balance. Construct validity and clinical interpretability of each measure in ambulatory people post stroke requires further research to identify the level of community mobility represented by each measure of walking balance.

One male with unilateral osteoarthritis (OA) of the knee underwent testing of corticospinal (CS) excitability (as quantified from motor-evoked potentials (MEPs) in the rectus femoris (RF) using transcranial magnetic stimulation) and quadriceps muscle strength. Baseline data indicated reduced MEP amplitudes in the RF of the affected limb compared to the unaffected limb. Increases in RF MEP amplitudes from both limbs were observed immediately following a 30-minute exercise session focusing on muscle strengthening. Following an 8-week muscle strengthening intervention, the participant exhibited increased MEP amplitudes and muscle strength in the affected limb. These findings suggest that alterations in peripheral muscle function found in patients with knee OA may have an origin centrally within the motor cortex and that interlimb differences may be evident in those with unilateral disease. These findings also suggest that CS excitability may be improved following a muscle strengthening intervention.

Achieving excellence in rowing requires optimization of technique to maximize efficiency and force production. Investigation of the kinematics of the trunk, upper and lower extremity, together with muscle activity of the trunk, provides an insight into the motor control strategies utilized over a typical race. Nine elite female rowers performed a 2000 m race simulation. Kinematic data of the trunk and extremities, together with electromyography (EMG) activity of spinal and pelvic extensor and flexor muscles, were compared at 250 and 1500 m. At 1500 m, there was greater dissociation in the timing of leg extension and arm flexion and delayed trunk extension. Also at 1500 m, the spine demonstrated a delayed peak extension angular velocity of the T4-T7 and L3-S1 spinal segments in the early drive along with delayed and increased peak extension angular velocity of T10-L1 and L1-L3 spinal segments during the late drive. Trunk muscle fatigue was not evident; however, the abdominals demonstrated larger EMG burst areas at 1500 m. Alterations in trunk kinematics suggest that the trunk acts as a less stiff lever on which to transfer the forces of the legs to the arms and handle. Increased abdominal activity may reflect increased demand to control the trunk, given the altered coordination between the legs, trunk and arms.

Purpose: The purpose of this study was to characterize the EMG of trunk muscles together with kinematics of the pelvis and the spine of elite female rowers during the rowing stroke. Methods: Nine Rowing Canada national team candidates performed a 2000-m race simulation. EMG activity of spinal and pelvic extensor and flexor muscles and kinematic data of the pelvis and the spine were collected and analyzed during the period of peak force production. Results: During this period, pelvic and spinal extensor muscles demonstrated similarities in the timing of muscle activity with minimal coactivation of flexors and extensors. Minimal excursion of spinal segments occurred during the stroke with most of the extension occurring at the pelvis. Flexor activity occurred toward late drive, suggesting that trunk extension is slowed by increasing activity of the flexor muscles. Conclusions: This study provides data of trunk kinematics and muscle recruitment patterns in elite female rowers. During the period of peak force production, there is minimal coactivation of trunk flexor and extensor muscles and, of the spinal segments, L3-S1 shows the most movement, which may make it more susceptible to soft tissue injury.

The reliability of triceps surae electromyographic responses to standing perturbations in people after stroke and healthy controls is unknown. High-Density surface Electromyography (HDsEMG) is a technique that records electromyographic signals from different locations over a muscle, overcoming limitations of traditional surface EMG such as between-day differences in electrode placement. In this study, HDsEMG was used to measure responses from soleus (SOL, 18 channels) and medial and lateral gastrocnemius (MG and LG, 16 channels each) in 10 people after stroke and 10 controls. Timing and amplitude of the response were estimated for each channel of the grids. Intraclass Correlation Coefficient (ICC) and normalized Standard Error of Measurement (SEM%) were calculated for each channel individually (single-channel configuration) and on the median of each grid (all-channels configuration). Both timing (single-channel: ICC=0.75-0.96, SEM%=5.0-9.1; all-channels: ICC=0.85-0.97; SEM%=3.5-6.2%) and amplitude (single-channel: ICC=0.60-0.91, SEM%=25.1-46.6; ICC=0.73-0.95, SEM%=19.3-42.1) showed good-to-excellent reliability. HDsEMG provides reliable estimates of EMG responses to perturbations both in individuals after stroke and in healthy controls; reliability was marginally better for the all-channels compared to the single-channel configuration.

This study compared self-induced stepping reactions of seventeen participants after stroke and seventeen controls. Surface electromyographic (EMG) signals were recorded bilaterally from the soleus (SOL), tibialis anterior (TA), biceps femoris (BF) and rectus femoris (RF) muscles. Principal component analysis (PCA) was used to reduce the data into muscle activation patterns and examine group differences (paretic, non-paretic, control leg). The first principal component (PC1) explained 46.7% of the EMG signal of the stepping leg. Two PCs revealed distinct activation features for the stepping paretic leg: earlier TA onset at step initiation and earlier BF and SOL onset at mid-step. For the stance leg, PC1 explained 44.4% of the EMG signal and significant differences were found in the non-paretic leg compared to paretic (p < 0.001) and control (p < 0.001). In PC1, at step onset the BF and SOL EMG and the RF and TA EMG were increased over the latter half of the step. No PC loadings were distinct for the paretic leg during stance, however differences were found in the non-paretic leg: earlier TA burst and increased BF and SOL EMG at step initiation. The results suggest impairments in the paretic leg when stepping and compensatory strategies in the non-paretic stance leg.

There is considerable evidence on the impairments that a cerebral stroke will have down-stream of the stroke, i.e., in the spinal motoneuron and the muscle. Motor impairment following stroke has been documented as force production that is slow, weak, and lacking in precision (Garland et al., 2009) and is associated with difficulty in fully activating the muscle (Klein et al., 2013). Furthermore, in functional tasks such as standing balance and gait, there is evidence of deficits in intra-limb coordination of muscles even on the non-paretic side (Marigold and Eng, 2006; Raja et al., 2012). In this opinion paper, we will first briefly review the changes observed at the level of the motor unit (MU) after stroke and second reflect upon whether some changes in the intrinsic properties of motoneurons, typically considered to be maladaptive, might also reflect a positive adaptation that could assist in force production. Lastly, this paper will explore the control of MUs between limbs during standing balance and suggest that, while some impairment may exist, there remains the possibility of a preservation of fundamental motor control strategies after stroke that might be a target for rehabilitation.

Background: Following stroke, many people have difficulty activating their paretic muscles quickly and with sufficient power to regain their balance by taking quick and effective steps. Reduced dynamic balance and mobility following stroke, or ‘walking balance’, is associated with reduced self-efficacy and restrictions in daily living activities, community integration, and quality of life. Targeted training of movement speeds required to effectively regain balance has been largely overlooked in post-stroke rehabilitation. The Fast muscle Activation and Stepping Training (FAST) program incorporates fast functional movements known to produce bursts of muscle activation essential for stepping and regaining standing balance effectively. The purpose of this study is to: 1) compare the effectiveness of an outpatient FAST program to an active control outpatient physiotherapy intervention in improving walking balance following stroke, and 2) explore potential mechanisms associated with improvements in walking balance. Methods/Design: This will be an assessor-blinded, parallel group randomized controlled trial design. Sixty participants (30 per group) who have sustained a stroke within the previous six months will be randomly assigned with stratification for lower limb motor recovery to receive twelve 45-minute 1:1 physiotherapy intervention sessions over 6 – 10 weeks in an outpatient setting of either: 1) FAST intervention - systematic and progressive practice of fast squatting and stepping exercises, or 2) active control - conventional physiotherapy directed at improving balance and mobility that includes no targeted fast movement training. The same blinded research physiotherapist will assess outcomes at three time points: 1) baseline (prior to intervention), 2) follow up (within one week post-intervention); and 3) retention (one month post-intervention). The primary outcome is dynamic balance assessed using the Community Balance and Mobility Scale. We will also assess fast and self-selected walking speed, balance self-efficacy, and the ability to respond to internal and external perturbations to balance and associated changes in postural muscle activation. Discussion: The targeted training of fast functional movements in the FAST program is expected to improve walking balance following stroke compared to the active control intervention. Unique to this study is the investigation of potential mechanisms associated with improvements in walking balance. Trial registration: NCT01573585

To the Editor: Boykin et al. [2] presented a review of 18 rowers (21 hips) with MRI-confirmed labral tears in the anterior half of the acetabulum treated from 2003 to 2010. The most common presentations were groin pain (15 of 21 hips) and positive anterior femoroacetabular impingement (FAI) sign (17 of 21 hips). Fifteen of 21 hips had radiographic FAI (10 pure cam lesions and five mixed cam/pincer). Mechanism of labral injury was proposed to be repeated hip hyperflexion. It was stated that rowers’ hips go from extreme flexion to extension during the stroke. Among the hips that were treated with arthroscopic surgery (18 of 21), femoral head/neck osteochondroplasty was performed in six cases. Among these 18 patients, 10 returned to rowing, six did not, and two had missing data at a mean of 8 months (range, 3 to 25 months) after surgery. The unfavorable return to sport in this series was contrasted with an epidemiologic study showing a low percentage of rowing injuries resulted in an inability to train for more than 1 month [9]. Regarding mechanism of injury, rowers’ hips do not enter anatomical extension during rowing (approximately 20° of hip flexion remains in the finish position) [3, 8]. Hyperflexion implies joint flexion beyond normal limits [5]. Normal passive ROM at the hip joint is 135° flexion and 30° extension [4]. Kinematic analysis reveals that the ROM of the hip falls within normal ROM during rowing, and is not hyperflexed [3]. Therefore, it is likely that the high incidence of FAI in this series precipitated the tears and symptoms among majority of the rowers. Importantly, femoral alpha angle measurement of Magnetic Resonance Arthrography shows considerable variability, and clinical impingement tests remain the most reliable predictor of the presence of FAI [6]. With regards to the main goal of the paper — determining “the likelihood that a rower with labral injury, treated arthroscopically, will return to sport,” — is it possible that the low postoperative return rate was a consequence of performing femoral head/neck osteochondroplasty in only six of 15 hips with cam lesions, therefore, not directly addressing the joint impairment? Additionally, the three patients with bilateral hip pathology were only surgically treated unilaterally. How did the three untreated hips impact return to rowing? Furthermore, it is known that symptom duration longer than 3 years is associated with poor outcome after hip arthroscopy [1], however, no preoperative symptom duration was presented [2]. Finally, as return to rowing was assessed as early as 3 months postoperatively, what was the rehabilitation protocol? Return to sport after hip arthroscopy should be advanced slowly to prevent continued irritation or reinjury [7]. In the cited retrospective study regarding musculoskeletal injury present in elite-level rowers competing at the Junior World Rowing Championships, [9] the authors emphasized that study design may have resulted in under-reporting of severe rowing injury, as severely injured rowers may not have recovered to compete at the World Rowing Championships. Additionally, without presenting return to sport data in context of number of rowers who wanted to return to rowing but could not due to reoccurring symptoms, this aspect of analysis by Boykin et al. is limited in its utility [2].

Background and PurposeStepping reactions are important for walking balance and community-level mobility. Stepping reactions of people with stroke are characterized by slow reaction times, poor coordination of motor responses, and low amplitude of movements, which may contribute to their decreased ability to recover their balance when challenged. An important aspect of rehabilitation of mobility after stroke is optimizing the motor learning associated with retraining effective stepping reactions. The Challenge Point Framework (CPF) is a model that can be used to promote motor learning through manipulation of conditions of practice to modify task difficulty, that is, the interaction of the skill of the learner and the difficulty of the task to be learned. This case series illustrates how the retraining of multidirectional stepping reactions may be informed by the CPF to improve balance function in people with stroke.Case DescriptionFour people (53–68 years of age) with chronic stroke (>1 year) and mild to moderate motor recovery received 4 weeks of multidirectional stepping reaction retraining. Important tenets of motor learning were optimized for each person during retraining in accordance with the CPF.OutcomesParticipants demonstrated improved community-level walking balance, as determined with the Community Balance and Mobility Scale. These improvements were evident 1 year later. Aspects of balance-related self-efficacy and movement kinematics also showed improvements during the course of the intervention.DiscussionThe application of CPF motor learning principles in the retraining of stepping reactions to improve community-level walking balance in people with chronic stroke appears to be promising. The CPF provides a plausible theoretical framework for the progression of functional task training in neurorehabilitation.

Context: Lateral trunk-flexion strength is an important determinant of overall trunk stability and function, but the reliability in measuring this outcome clinically in athletic individuals is not known. Objective: To determine the interrater and intrarater reliability of lateral trunk-flexion strength measurement in athletic individuals using handheld dynamometry. Design: Reliability study. Setting: Research laboratory. Participants: 12 healthy, athletic individuals. Intervention: Lateral trunk-flexion strength was measured using handheld dynamometry across 2 different trunk placements (lateral aspect of the axilla and laterally at the level of the midtrunk) and 2 testing occasions by 2 therapists. Three maximum-effort trials during a "make test" at each placement were completed for each therapist on both occasions. Main Outcome Measures: Maximum force output was identified and converted to a torque. Intraclass correlation coefficients (ICC2,1) were calculated for each dynamometer placement, therapist, and test occasion to determine intrarater and interrater reliability. Results: Intrarater reliability was moderate to good (ICC2,1 = .53-.77), while interrater reliability was good to very good (ICC2,1 = .79-81) at the axilla position. For the midtrunk position, intrarater reliability was good to very good (ICC2,1 = .80-.86), while interrater reliability was good on both days (ICC2,1 = .87-.88). Finally, the standard errors of measurement were low for the axilla position (0.20 Nm/kg; 95% CI .15, .28) and midtrunk position (0.09 Nm/kg; 95% CI .07, .12). Conclusions: Maximum lateral trunk-flexion strength can be reliably measured in athletic individuals with greater overall strength. Based on the 2 positions used in this study, measurement with a dynamometer placement at the midtrunk may be more reliable than that obtained at the axilla.

Background: Little is known about the relationships of circulating levels of biomarkers of cartilage degradation with biomechanical outcomes relevant to knee osteoarthritis (OA) or biomarker changes following non-pharmacological interventions. The objectives of this exploratory, pilot study were to: 1) examine relationships between biomarkers of articular cartilage degradation and synthesis with measures of knee joint load during walking, and 2) examine changes in these biomarkers following 10 weeks of strengthening exercises. Methods Seventeen (8 male, 9 female; 66.1 +/- 11.3 years of age) individuals with radiographically-confirmed medial tibiofemoral OA participated. All participants underwent a baseline testing session where serum and urine samples were collected, followed by a three-dimensional motion analysis. Motion analysis was used to calculate the external knee adduction moment (KAM) peak value and impulse. Following baseline testing, participants were randomized to either 10 weeks of: 1) physiotherapist-supervised lower limb muscle strengthening exercises, or 2) no exercises (control). Identical follow-up testing was conducted 11 weeks after baseline. Biomarkers included: urinary C-telopeptide of type II collagen (uCTX-II) and type II collagen cleavage neoepitope (uC2C), serum cartilage oligomeric matrix protein (sCOMP), serum hyaluronic acid (sHA) and serum C-propeptide of type II procollagen (sCPII). Linear regression analysis was used to examine relationships between measures of the KAM and biomarker concentrations as baseline, as well as between-group differences following the intervention. Results KAM impulse predicted significant variation in uCTX-II levels at baseline (p = 0.04), though not when controlling for disease severity and walking speed (p = 0.33). KAM impulse explained significant variation in the ratio uCTX-II;sCPII even when controlling for additional variables (p = 0.04). Following the intervention, changes in sCOMP were significantly greater in the exercise group compared to controls (p = 0.04). On average those in the control group experienced a slight increase in sCOMP and uCTX-II, while those in the exercise group experienced a reduction. No other significant findings were observed. Conclusions This research provides initial evidence of a potential relationship between uCTX-II and knee joint load measures in patients with medial tibiofemoral knee OA. However, this relationship became non-significant after controlling for disease severity and walking speed, suggesting further research is necessary. It also appears that sCOMP is amenable to change following a strengthening intervention, suggesting a potential beneficial role of exercise on cartilage structure. Trial registration Clinicaltrials.gov NCT01241812