Single-limb Stance Research Articles

Walking asymmetry and its relation to patient-reported and performance-based outcome measures in individuals with unilateral lower limb loss

ABSTRACT Gait asymmetry persists for most people after lower limb amputation and is associated with slower walking speeds. However, the relationship between gait asymmetry and patient-reported function remains unclear because they are not commonly assessed together. The purpose of this study was to determine relationships between gait asymmetries in people with lower limb loss and (1) patient-reported outcomes and (2) performance-based prosthetic functional measures. This cross-sectional analysis included nine people with unilateral limb loss aged 48.2 ± 13.1 years of mixed amputation etiology. Patient-reported outcomes included the Prosthetic Evaluation Questionnaire mobility subscale and Activities-specific Balance Confidence scale. Performance outcomes included the Berg Balance Scale and the 30-second sit-to-stand test. Walking performance measures included the 2-Minute Walk Test, during which APDM Opal sensors recorded spatiotemporal gait parameters, and daily step-counts from StepWatch4 activity monitors. The study found that the most asymmetric gait symmetry ratios (prosthetic-limb divided by intact-limb) could be attributed to prosthetic foot dorsiflexion-plantarflexion and rotation motion limitations: prosthetic-limb trailing double support (0.789 ± 0.052), toe-off (0.760 ± 0.068) and toe-out angle (0.653 ± 0.256). Single limb stance, and stance and swing phase durations were most strongly associated with balance and walking performance measures. Notably, no symmetry ratio was significantly associated with patient-reported prosthetic function (unadjusted Pearson correlation coefficients r < 0.50, P > 0.05). More gait symmetry was associated with better balance and walking performance but had no significant relationship with patient-reported function. Although achieving gait symmetry after lower limb loss is a common walking goal, symmetry was unrelated to the perception of functional mobility for people with lower limb loss.

Age-related differences in stepping stability following a sudden gait perturbation are associated with lower limb eccentric control of the perturbed limb.

Falls are a leading cause of severe injuries and a major threat to quality of life in older adults. Elderly fallers demonstrate insufficient eccentric quadriceps control during the weight acceptance phase of initial single limb stance. However, the functional role of eccentric control of the perturbed (leading) leg during walking balance recovery and its age-related differences have not yet been studied; thus we investigated age-related differences in eccentric control at the knee of the perturbed leg and its influence on the postural sway and stability of the trailing leg during balance recovery following unexpected surface drop perturbations. Ten younger and ten older healthy adults were compared during balance recovery following an 8cm unexpected surface drop perturbation at gait initiation. Outcomes related to perturbed leg included 1) eccentric knee extensor work; 2) electromyography (EMG) peak amplitude, peak latency, and eccentric EMG burst duration of the rectus femoris (RF); and 3) knee flexion angle during the single limb support. Outcomes related to stability of the trailing leg included 4) margin of stability (MoS) at first compensatory step touchdown after the perturbation. 5) Postural sway (standard deviation of center of mass acceleration) was measured in the anterior-posterior (A-P), medio-lateral (M-L), vertical directions during the single limb support. Compared to younger adults, older adults demonstrated lower eccentric knee extensor work (p=0.034), shorter RF EMG burst duration (p<0.01), delayed RF EMG peak latency (p=0.01), smaller knee flexion angle (p=0.01) and MoS (p=0.04), and higher postural sway (M-L (p=0.02), vertical (p<0.01)). There was a positive correlation between eccentric work and MoS (p=0.03) and a negative correlation between M-L postural sway and 1) RF eccentric EMG burst duration (p=0.04), and 2) eccentric work (p=0.01). Older adults demonstrated deficits in eccentric knee extensor control in the perturbed leg during single limb support, which contributed to reduced stability of the trailing leg compensatory step and greater postural sway during balance recovery. This finding provides insight into mechanisms of fall recovery from an unexpected unilateral postural perturbation and directions for lower limb strengthening exercises for aging populations.

Gait biomechanics after proximal femoral nailing of intertrochanteric fractures.

Proximal femur fractures in the elderly are associated with significant loss of independence, mobility, and quality of life. This prospective study aimed to: (1) investigate gait biomechanics in intertrochanteric fracture (ITF) patients (A1 and A2 AO/OTA) managed via femoral nailing at 6 weeks and 6 months postoperative and how these compared with similarly aged elderly controls; and (2) investigate whether femoral offset shortening (FOS) and lateral lag screw protrusion (LSP) were associated with changes in gait biomechanics at postoperative time points. Hip radiographs and gait data were collected for 34patients at 6 weeks and 6 months postoperatively. Gait data were also collected from similarly aged controls. FOS and LSP were measured from radiographs. Joint angles, external moments, and powers were calculated for the hip, knee, and ankle and compared between time points in ITF patients and healthy controls using statistical parametric mapping. The relationship between radiographic measures with gait speed, step length, peak hip abduction, and maximum hip abduction moment was assessed using a Pearson correlation. External hip adduction moments and hip power generation improved in the first 6 months postoperative, but differed significantly from healthy controls during single limb stance. LSP showed a moderate correlation with maximum hip abduction moment at 6 weeks postoperative (r = -0.469, p = 0.048).These results provide new detail on functional outcomes after ITF and potential mechanisms that functional deficiencies may stem from. Lag screw prominence may be an important factor in maintaining functional independence and minimizing the risk of secondary falls after ITF in the elderly.

Gait ability on center of pressure excursion using a pressure-sensitive mat in the elderly with ischemic stroke: a case–control study with propensity score matching

Background: Center of pressure (COP) is a useful measure for dynamic balance, which directly represents the ability of weight shift and control of the foot, however, there is no study analyzing COP during whole stance phase in the elderly with acute stroke.Methods: A total of 30 acute ischemic stroke patients (mean age±standard deviation [SD], 75.0±5.6 years; 11 females) and 30 propensity score matched controls (mean age±SD, 72.8±5.9 years; 17 females) using age, sex, and Korean version of Mini-Mental State Examination score were finally included. Participants performed barefoot walking trials on a pressure-sensitive mat until 20 footfalls in each limb were corrected. To evaluate gait function based on COP, mean and coefficient of variance as variability were calculated for 3 types of variables as followings: (1) durations of sub-phases in stance phase, (2) mean locations and displacement ranges of COP, and (3) velocities.Results: Significant difference was observed in many of both mean and variability variables. Especially, stroke patients had an increased duration, posterior location of COP, wide range of mediolateral and anteroposterior displacement range, and slow velocity in foot flat phase belonging to the double limb stance. In variability variables, stroke patients had significantly larger variabilities of COP velocities in all sub-phases except in foot flat phase and late propulsive phase were stood out.Conclusions: The elderly with acute ischemic stroke had inefficiency during double limb stance and reduced functional balance in single limb stance in both sides, implying impaired gait ability on COP excursion in these patients.

THE EFFECT OF A FREE COMMUNITY PEDIATRIC HEALTH INITIATIVE ON BMI, FITNESS MEASURES, AND QUALITY OF LIFE: A PILOT STUDY

Background: Pediatric obesity affects approximately 18% of children in the United States. Childhood obesity contributes to several health-related issues, including diabetes, hypertension, decreased quality of life (QOL), and adult morbidity. Risk factors for developing childhood obesity include socioeconomic factors, sedentary lifestyle, diet, and genetics. Programs tailored toward educating children and parents on healthy lifestyle choices, exercise, and nutrition have been shown to improve health-related outcomes for this population. Objective: The purpose of this study was to retrospectively investigate the effects of an 8-week community pediatric health program on body mass index (BMI), fitness measures, and QOL in overweight children. Methods: Subjects aged 8-16 years were recruited from a hospital-based weight management clinic to participate in an 8-week weight loss program. Subjects attended weekly one-hour sessions of health and wellness education, exercise instruction, home program development, and practical goal-setting. Seven children participated in the program and completed all outcome measures. Outcome measures included Body Mass Index (BMI), functional strength (jumping jacks, wall sits, push-ups, and sit-ups), balance (single-limb stance, SLS), flexibility (straight leg raise, SLR), endurance (6-minute walk test, 6MWT), and QOL assessment (Pediatric Quality of Life Inventory, PQOL). Outcomes were assessed at baseline and week eight. Results: Although the BMI did not show clinically significant improvement, three functional strength measures (wall sit p=0.026; push-ups p=0.010; sit-ups p=0.003), endurance (6MWT, p=0.026), and flexibility (left SLR, p=0.011, right SLR, p= 0.046) showed statistically significant improvement at week eight. Jumping jacks and the PQOL showed improvement without reaching statistical significance (p&gt;0.05). No improvement in SLS was noted (p&gt;0.05). Conclusion: The findings indicate a community-based pediatric health and wellness program significantly improved overweight children's fitness. Further research is needed to determine the long-term effects of this program.

Center of pressure characteristics differ during single leg stance throughout pregnancy and compared to nulligravida individuals

BackgroundFalls are common during pregnancy and present potential for injury to the pregnant individual and the baby. Research questionDo center of pressure characteristics during single leg stance differ between participants during and after pregnancy and nulligravida participants in the presence and absence of visual input? MethodsNineteen pregnant participants completed testing during the second trimester, the third trimester, and 4–6 months post-partum. Matched, nulligravida females completed testing once. All participants performed single leg stance on a force platform on each limb for up to 20 s with eyes open and with eyes closed. Center of pressure characteristics were compared between pregnant and nulligravida females using three separate 2 × 2 mixed way ANOVAs, one for each pregnancy time point (second trimester, third trimester, and post-partum) with Bonferroni correction. ResultsPregnant females demonstrated smaller single leg stance time with eyes closed during the third trimester. During the second and third trimester, pregnant participants demonstrated smaller sway and sway velocity across eyes open and eyes closed conditions. During the third trimester and post-partum, pregnant participants demonstrated greater median frequency of the center of pressure data. Pregnant participants also demonstrated smaller sample entropy in the anteroposterior direction during the second and third trimesters and in the mediolateral direction during the second trimester. SignificanceThe decreased total sway and sway velocity observed during pregnancy may reflect rigidity or a protective strategy during single limb stance. Additionally, center of pressure data were less smooth and more repetitive during pregnancy indicating robust differences in postural control strategies and potentially increased fall risk. Because single limb stance is a component of many activities of daily living, the single limb stance task may have clinical utility for testing or training balance in this population with a goal of decreasing falls.

EFFECTS OF NEUROMUSCULAR TRAINING ON SINGLE LIMB STABILITY IN YOUNG FEMALE ATHLETES

Background: Lower limb injuries in sports affect postural stability and balance. Muscular imbalance, postural malalignments, and altered biomechanics occurred in athletes due to injuries. Objective: To determine the effects of the 6-week neuromuscular training program on single-limb stability in young female athletes. Methodology: A single-subject study design was used in which n=20 female athletes aged between 18 to 25 years with previous lower limb injuries that lead to impaired balance and postural instability participated in this study included by the convenience sampling from the Faisalabad sports complex.. Athletes completed 6-week neuromuscular training program, with every session of 90 min and 3 times a week. Assessment of athletes was performed before and after the completion of the neuromuscular training program at 6 weeks, with a single-limb stance test, Stork balance stand test, and star excursion balance test. Results: The mean age of participants was 20.6±1.82 years. Single limb stance test score with eyes open pre 27.70±13.85 and post-test treatment 40.75±16.45 showed significant results with (p &lt;0.01). Stork balance test scores pre 28.40±17.25 and post-treatment 38.85±14.543 also showed significant results with (p &lt;0.01). Star excursion balance test right and left anterior, left medial, right and left lateral also showed significant results with (p &lt;0.01). Star excursion balance test right medial pre and post-treatment showed insignificant results with (p-value =0.234). Conclusion: Although 6-week neuromuscular training program showed a significant improvement on single-limb stability in young female athletes. But without control or comparative group we cannot establish its gender specific effectiveness. Keywords: Neuromuscular training, static and dynamic balance, single limb stance test, stork balance stand test, star excursion test.

Effectiveness of Wobble Board Exercises on Dynamic Balance among Undergraduate Students

BACKGROUND &amp; OBJECTIVE: Control of posture and balance is vital in mobility. Board exercise provides information about the motor strategies associated with muscle activation patterns that result when a person is standing on a wobble board surface that unexpectedly translates or tilts, which stimulates proprioception on the ankle.&#x0D; METHODOLOGY: This study recruited 37 Undergraduate medical students of Allied health sciences (including males and females) of age between 17 to 25 years, conducted at skill lab of Shalamar Institute of Health Sciences. It is a Pre-test, Post-test Quasi-Experimental study in which balance was assessed by performing SEBT while maintaining single-limb stance. After 2 weeks of training, a dynamic balance was reassessed using Star Excursion Balance Test (SEBT).&#x0D; RESULTS: A total of 37 patients are included in this study with the age of 22.0±1.65 years and BMI 20.9±3.02 are considered. The study includes 15 male and 22 female patients. This study shows significant differences in Pre-SEBT and Post-SEBT values of legs as p-value &lt;0.05.&#x0D; CONCLUSION: There were significant differences in Pre-exercising and Post-exercising SEBT. Study shows that wobble board-based rehabilitation training has a positive impact on improving balance of participants.

Competing Models of Work in Quadrupedal Walking: Center of Mass Work is Insufficient to Explain Stereotypical Gait.

The walking gaits of cursorial quadrupedal mammals tend to be highly stereotyped as a four-beat pattern with interspersed periods of double and triple stance, often with double-hump ground reaction force profiles. This pattern has long been associated with high energetic economy, due to low apparent work. However, there are differing ways of approximating the work performed during walking and, consequently, different interpretations of the primary mechanism leading to high economy. A focus on Net Center of Mass (COM) Work led to the claim that quadrupedal walking is efficient because it effectively trades potential and kinetic energy of the COM. Individual Limbs COM Work instead focuses on the ability of the limbs to manage the trajectory of the COM to limit energetic losses to the ground (“collisions”). By focusing on the COM, both these metrics effectively dismiss the importance of rotation of the elongate quadrupedal body. Limb Extension Work considers work required to extend and contract each limb like a strut, and accounts for the work of body pitching. We tested the prescriptive ability of these approximations of work by optimizing them within a quadrupedal model with two approximations of the body as a point-mass or a rigid distributed mass. Perfect potential-kinetic energy exchange of the COM was possible when optimizing Net COM Work, resulting in highly compliant gaits with duty factors close to one, far different than observed mammalian gaits. Optimizing Individual Limbs COM Work resulted in alternating periods of single limb stance. Only the distributed mass model, with Limb Extension Work as the cost, resulted in a solution similar to the stereotypical mammalian gait. These results suggest that maintaining a near-constant limb length, with distributed contacts, are more important mechanisms of economy than either transduction of potential-kinetic energy or COM collision mitigation for quadrupedal walking.

The Relationship Between Measures of Postural Control in Concussion Assessment.

To determine the relationship between postural sway performance during commonly utilized postural control assessments following a concussion, including the modified Balance Error Scoring System (mBESS), concussion balance test (COBALT), and sensory organization test (SOT) in healthy young adults. Twenty participants completed all balance testing. The mBESS conditions included double limb stance, single limb stance, and tandem stance. The COBALT was comprised of yaw plane head shake (HS) and vestibular ocular reflex cancellation conditions performed on firm and foam surfaces. Subjects performed 6 conditions of the SOT (C1-C6), which systematically perturbed sensory inputs. Postural sway performance was measured using a single force plate and quantified as a sway score for the mBESS and COBALT, and an equilibrium score for the SOT. Spearman rank correlations were used to examine the relationship between postural sway performance for each test. There was a moderate positive correlation between mBESS-tandem stance and the HS on foam COBALT condition (r = .643, P = .002). There was a moderate negative correlation between mBESS-double limb stance and SOT-C6 (r = -.512, P = .021), and between mBESS-single limb stance and SOT-C6 (r = -.523, P = .018). The COBALT and SOT demonstrated numerous moderate to good negative correlations (r = -.448 to -.708, P ≤ .05), including a good negative correlation between HS on foam and SOT-C1 (r = -.725, P = .0003). Performance on the mBESS had minimal relationship to performance on the COBALT and SOT, suggesting that the clinical standard may not challenge sensory integration at the same capacity as other tests. All COBALT conditions had fair to good associations to at least 2 SOT conditions, suggesting both assessments are representative of sensory integration. Further investigation of the current clinical approach is warranted as the COBALT may be a clinically feasible test of sensory integration.

Improvement in Postural Control Following Concussion in Adolescent Athletes: From Clinical Presentation to Initiation of Return to Play

Background:Impairments in balance or postural control are common following sport-related concussion (SRC). The Balance Error Scoring System (BESS) is widely utilized to assess static postural stability, but laboratory-based balance measures have been shown to more accurately detect changes in postural control.Hypothesis/Purpose:To determine whether postural control improved between presentation to the sports medicine clinic and return-to-sport (RTS) initiation, and whether this trend mirrored symptom scores and cognitive performance. A secondary aim was to assess whether changes in postural control were more accurately captured with center of pressure (COP) based measures compared to BESS.Methods:Patients diagnosed with a SRC were tested within 10 days of presentation (V0) and when cleared by a physician to begin a RTS protocol (V1). Clinical measures included Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) and the King-Devick (K-D) test. The BESS was performed with eyes closed while standing barefoot on a force platform for 6 conditions: double-limb stance, single-limb stance, and tandem stance on both firm and foam surfaces. BESS scores and total balance time were recorded for each condition, and COP-based measures were computed for both double-limb stance conditions (Table 1). Sample entropy was computed to quantify COP regularity over time with increased values indicating improvement in postural control. Wilcoxon signed-rank tests were performed to determine significance between visits (α<0.05).Results:Forty patients (17 males, 13.8±2.0 years) were included for analysis. ImPACT verbal and visual memory scores improved by 10% and 12%, respectively, total symptom score decreased (V0 18.03±13.85, V1 0.97±2.08; p<0.01), and visual motor speed and reaction time were both 11% faster on the K-D test. For postural control, the BESS indicated significant improvement given the reduction in errors on both surfaces (Firm Total: V0 3.23±2.09, V1 2.25±2.11, p=0.01; Foam Total: V0 7.38±2.05, V1 6.08±1.76, p<0.01; Table 1). Similarly, COP-based measures exhibited better overall balance between visits (Figure 1), primarily in the medial-lateral direction on the firm and the anterior-posterior direction on the foam. Lastly, sample entropy improved between visits, indicating more effective postural control.Conclusion:Significant improvement in postural control was observed during the recovery period which mirrored improvement in symptom scores and cognitive performance. Additionally, while COP-based measures showed similar trends to the BESS, they provided more detailed information in regards to balance recovery. Specifically, findings from the double stance condition highlight the utility of a more advanced assessment of postural control for determining RTS readiness following a SRC.Table 1.COP-based measures of balance performance at diagnosis (V0) and clearance (V1) visitsFigure 1.Representative stabilograms of double stance balance on firm and foam surfaces at diagnosis (V0) and clearance visits (V1)

Walking Gait Mechanics among Individuals with Chronic Ankle Instability Who Do and Do Not Experience Unresolved Ankle Pain: A Cross-sectional Pilot Study.

The purpose of this pilot study was to compare temporal walking gait parameters between patients with chronic ankle instability (CAI) who experience ongoing ankle pain and those who do not. Secondly, examine the relationship between pain intensity and vertical ground reaction forces (vGRF) among patients with CAI who experience ankle pain. Twenty-two CAI participants (18-35 years) who did (n=9) or did not (n=13) experience ongoing ankle pain were enrolled in this cross-sectional study. Participants performed 5 walking trials across a GAITRite® instrumented walkway and force platform embedded into the laboratory floor. Temporal variables (swing, single- and double-limb support) were extracted from the instrumented walkway for the involved limb and normalized to percent of gait cycle (%GC). All vGRF data collected through the force platform were normalized to each participant's body weight and used to calculate the peak vGRF, time-to-peak vGRF, and the average loading rate. All data were averaged across the 5 walking trials for statistical analysis. Pain intensity levels were assessed using the Pain Subscale of the Foot and Ankle Disability Index, where lower scores represent greater pain intensity levels. Significance was set a priori at P<0.05. Preliminary results suggests that CAI participants with ankle pain might spend less time in single-limb stance (Pain: 38.1 %GC vs. No Pain: 39.2 %GC; p=0.08), but more time in double-limb stance (Pain 23.8 %GC vs. No Pain: 22.1 %GC; p=0.07) than those without pain. Additionally, a strong negative correlation (p < 0.001; r = -0.956) between ankle pain intensity levels and average vGRF loading rate was observed among those with ankle pain. The preliminary data suggests patients with CAI who experience ongoing ankle pain might modify their walking gait pattern, which might occur because of the close relationship between higher average loading rates and increased pain intensity levels.

Effects of a Medial Unloader Brace on Gait Mechanics in Patients with Osteochondritis Dissecans

Background:Non-operative treatment for osteochondritis dissecans (OCD) of the knee traditionally includes casting, bracing, and activity restrictions. An unloader brace is an option that may result in improved compliance due to the ability of the patient to continue daily activities while maintaining brace wear, and it may have biomechanical advantages for lesion healing. However, the biomechanical efficacy of a medial unloader brace has not been confirmed in a pediatric population.Hypothesis/Purpose:To determine whether the use of a medial unloader brace alters gait mechanics in patients with medial femoral condyle OCD. We hypothesized that while knee alignment in the coronal plane will remain unaltered, the valgus moment will decrease due to the applied tension of the adjusted unloader brace.Methods:Fifteen medial femoral condylar OCD patients (14 male, 12.7±2.6 years, 156.9±14.8 cm, and 52.0±16.2 kg) were tested utilizing a medial Ossur Unloader One knee brace. All patients performed over-ground walking at a self-selected speed under three brace conditions: no brace (NB), unadjusted (U), and adjusted (A; prescribed tension applied). Pelvis and lower extremity kinematic and kinetic data were computed in the sagittal, coronal, and transverse planes during single-limb stance phase (SLS). Wilcoxon signed-rank tests were performed to identify statistical differences between brace conditions (α=0.05), and clinical significance was only determined when statistically significant joint angle and moment differences were greater than 3° and 0.1Nm/kg, respectively.Results:Between braced conditions, mean knee valgus was not statistically significant, however, peak internal knee valgus moment consistently decreased with each brace condition (NB-A: 0.06 Nm/kg, p=0.017). Similarly, hip abduction moment at the second peak of SLS decreased while wearing the brace (NB-U: p=0.061, NB-A: 0.07 Nm/kg, p=0.009).Conclusion:Peak knee valgus moment was decreased during walking with an adjusted medial unloader brace. These results highlight potential biomechanical advantages of a medial unloader brace for medial femoral condylar OCD. Future work will measure compliance of brace wear and compare additional brace designs.Table 1.Coronal plane hip and knee kinematics and kinetics (Mean ± SD) for each brace condition.Figure 1.Average coronal knee angle and moment throughout gait cycle

Sexual Dimorphism Impact on the Ground Reaction Force Acting on the Mediolateral Direction During Level Walking: Hip Abductor Muscle Biomechanics and Its Correlation to GRF Moment Arm.

The female pelvis morphology represents an evolved compensation between two opposing needs: a broad pelvis enough to deliver a sizeable brained offspring while remaining narrow enough to allow for effective bipedal gait. The precise expectation of hip abductor force generation is critical in anthropological studies and experimental practice of human stride mechanics. Hip implants and surgical procedures for hip anatomy reconstruction are based on the static single-leg stance paradigm. The current work investigated the impact of sexual dimorphism on the ground reaction force (GRF) acting on the mediolateral direction during level walking, emphasizing the difference in hip abductor muscle biomechanics and its correlation to ground reaction force moment arm, R. The ground reaction force in the mediolateral direction, hip abduction and adduction moments during the gait cycle and ground reaction force moment arm, R were measured. The current study concludes that the male individuals exhibit significantly higher mass-specific mediolateral ground reaction force during level walking. In contrast, hip abductor moments/kg body weight, medialization of the trochanter, R, and hip coronal were more significant in female individuals. We conclude that increased abductor moment and medialization of the greater trochanter will increase R, hip coronal and decrease abductor moment arm, r, in female individuals, affecting the effective mechanical advantage (EMA) of hip abductors in single-limb stance during level walking.

Optical flow balance perturbations alter gait kinematics and variability in chronic ankle instability patients

BackgroundIndividuals with chronic ankle instability (CAI) have known balance impairments thought to be the result of an inability to reweight sensory information. CAI patients place greater emphasis on visual information during single-limb stance than healthy controls but this evidence is based on removing visual information during static conditions. Research questionDoes perturbed optical flow effect step kinematics and variability in those with CAI differently than healthy controls? What is the relationship among ankle laxity, plantar cutaneous sensation, and susceptibility to perturbed optical flow in those with CAI? Methods17 CAI patients and 17 healthy individuals participated in a crossover experimental study. Participants walked on a treadmill at 1.25 m/s while watching a speed-matched virtual hallway with and without continuous mediolateral (ML) optical flow perturbations. Three-dimensional pelvic and foot kinematics were recorded at 100 Hz for at least 300 consecutive steps in each condition. Step width (SW) and step length (SL) values were calculated from consecutive heel positions. Gait variability was characterized as the standard deviation of step width (SWV), step length (SLV), and ML sacrum motion (SMV) across all steps performed in each condition. ResultsThe CAI group exhibited a greater change in SWV (p = 0.037), SLV (p = 0.040), and ML SMV (p = 0.047) from the perturbed to unperturbed conditions relative to the healthy controls. A condition main effect was also noted for SW (p < 0.001) and SL (p < 0.001) as ML optical flow perturbations resulted in significant changes in SW and SL relative to the normal walking condition. SignificanceWalking with ML optical flow perturbations induced greater variability changes in those with CAI relative to controls. When combined with the existing literature, this finding suggests that CAI individuals have a greater reliance on visual information in both static and dynamic (i.e. walking gait) conditions relative to healthy individuals.

Muscle synergies for the control of single-limb stance with and without visual information in young individuals

PurposeSingle-limb stance is a demanding postural task featuring a high number of daily living and sporting activities. Thus, it is widely used for training and rehabilitation, as well as for balance assessment. Muscle activations around single joints have been previously described, however, it is not known which are the muscle synergies used to control posture and how they change between conditions of normal and lack of visual information.MethodsTwenty-two healthy young participants were asked to perform a 30 s single-limb stance task in open-eyes and closed-eyes condition while standing on a force platform with the dominant limb. Muscle synergies were extracted from the electromyographical recordings of 13 muscles of the lower limb, hip, and back. The optimal number of synergies, together with the average recruitment level and balance control strategies were analyzed and compared between the open- and the closed-eyes condition.ResultsFour major muscle synergies, two ankle-dominant synergies, one knee-dominant synergy, and one hip/back-dominant synergy were found. No differences between open- and closed-eyes conditions were found for the recruitment level, except for the hip/back synergy, which significantly decreased (p = 0.02) in the closed-eyes compared to the open-eyes condition. A significant increase (p = 0.03) of the ankle balance strategy was found in the closed-eyes compared to the open-eyes condition.ConclusionIn healthy young individuals, single-limb stance is featured by four major synergies, both in open- and closed-eyes condition. Future studies should investigate muscle synergies in participants with other age groups, as well as pathological conditions.

Recovery of balance and gait after stroke is deteriorated by confluent white matter hyperintensities: Cohort study

BackgroundWhite matter hyperintensities (WMHs) are well known to affect post-stroke disability, mainly by cognitive impairment. Their impact on post-stroke balance and gait disorders is unclear. ObjectivesWe aimed to test the hypothesis that WMHs would independently deteriorate post-stroke balance and gait recovery. MethodsThis study was performed in 210 individuals of the cohort Determinants of Balance Recovery After Stroke (DOBRAS), consecutively enrolled after a first-ever hemisphere stroke. Clinical data were systematically collected on day 30±3 (D30) post-stroke and at discharge from the rehabilitation ward. WMHs were searched on MRI, graded with the Fazekas scale, and dichotomized as no/mild (absence/sparse) or moderate/severe (confluent). The primary endpoint was the recovery of the single limb stance, assessed with the Postural Assessment Scale for Stroke (PASS). The secondary endpoint was the recovery of independent gait, assessed with the modified Fugl–Meyer Gait Assessment (mFMA). The adjusted hazard ratios (aHRs) of achievements of these endpoints by level of WMHs were estimated by using Cox models, accounting for other relevant clinical and imaging factors. ResultsIndividuals with moderate/severe WMHs (n=86, 41%) had greater balance and gait disorders and were more often fallers than others (n=124, 59%). Overall, they had worse and slower recovery of single limb stance and independent gait (P<0.001). Moderate/severe WMHs was the most detrimental factor for recovery of balance (aHR 0.46, 95% confidence interval [CI] 0.32–0.68, P<0.001) and gait (0.51, 0.35–0.74, P<0.001), along with age, stroke severity, lesion volume and disrupted corticospinal tract. With cerebral infarct, endovascular treatments had an independent positive effect, both on the recovery of balance (aHR 1.65, 95% CI 1.13–2.4, P=0.009) and gait (1.78, 1.24–2.55, P=0.002). ConclusionsWMHs magnify balance and gait disorders after stroke and worsen their recovery. They should be better accounted for in post-stroke rehabilitation, especially to help establish a prognosis of mobility. ClinicalTrials.gov registrationNCT03203109.

청소년 비만정도와 보행 지면반력의 관계 연구

Overweight or obese adolescents are at a high risk of injury due to the load applied to their body joints while walking. Therefore, the purpose of this study was to define a difference in GRF(Ground Reaction Force) according to the gait cycle of normal, overweight, and obese groups in adolescence, and to identify the gait characteristics of overweight(obese) adolescents.<BR> Healthy adolescents were recruited and classified into normal, overweight, and obesity according to the degree of obesity(BMI). In addition, events were set as E1(LR: Loading Response), E2(MSLS: Mid Single Limb Stance), and E3(PS: Pre-Swing). For each event, the GRF of both feet was calculated along x(ML: MedioLateral), y(AP: AnteroPosterior), and z(Vertical) axes. The calculated GRF was normalized to the weight of each subject, so %BW was computed. Mean and standard deviation were calculated, multivariate analysis of variance(MANOVA) and Correlation analysis(Pearson, both side) were practiced. The statistical significance level was set to .05.<BR> Vertical GRF of LR in left foot from normal group was greater than obese group, and left and right feet ML GRF of MSLS from both overweight and obese groups showed smaller than normal group(p＜.05). Overweight and obese groups had greater right feet ML GRF of PS than normal group, and overweight group showed higher values than normal group in left foot Vertical GRF of PS, too(p＜.05). In addition, in PS of normal group, BMI and AP GRF in both feet of showed a negative correlation, and in MSLS of obese group, AP GRF in left foot showed a negative correlation(p＜.05).<BR> In the gait of overweight and obese group, they have a gait characteristic that reducing Vertical GRF to decrease the amount of impulse from the load response. Since this gait strategy may cause more joint fatigue, intervention to correct a gait posture along with reduction of body fat will be demended.

Effects of assistive devices on postural control following a balance disturbance along the anterior-posterior direction.

Assistive devices provide balance and stability to those who require a greater base of support, especially during ambulation or in tasks essential to functional daily living. In ambulatory assistive device use, center of pressure (COP) movement as one of the measurements of postural control is a factor when assessing fall risk, with an overall goal of maintaining postural equilibrium. There is a lack of research on assistive devices, such as walkers, regarding measurable outcome variables related to fall risk. The purpose of this study was to determine how much the postural control in single limb stance during a balance perturbance is affected by utilizing three different walker types designed to promote stability: the standard walker, the front-wheeled walker with straight wheels and the front-wheeled walker with caster wheels. Is postural sway control in single limb stance during a balance perturbance affected by walker type? Twenty-three healthy adults participated and gave consent. The NeuroCom® SMART EquiTest® system was utilized to simulate forward falls. Subjects stood on the system's force plate, which was tipped backwards quickly, forcing subjects to attempt to maintain balance. Each participant experienced 18 simulated perturbations, during which they were asked to maintain balance while using one of three walkers in single-limb stance. Each trial was completed using random assignment of three different walker types. Leg dominance of the stance leg was also randomized for each trial. The type of walker and the leg dominance in the standing limb significantly affected postural control in a balance perturbance in the A-P direction. The walker type significantly affected the COP maximum displacement in anterior-posterior (AP) direction. However, the leg dominance significantly affected COP maximum displacement in AP and medio-lateral (ML) directions and COP velocity in AP direction. The findings suggest that when fully grounded, a standard walker is more stable than the front-wheeled walker. However, this does not indicate that the standard walker is more stable than other types of walkers when it is being picked up and moved forward during normal use.

Muscle activations during functional tasks in individuals with chronic ankle instability: a systematic review of electromyographical studies.

It has been reported that individuals with chronic ankle instability (CAI) show motor control abnormalities. The study of muscle activations by means of surface electromyography (sEMG) plays a key role in understanding some of the features of movement abnormalities. Do common sEMG activation abnormalities and strategies exists across different functional movements? Literature review was conducted on PubMed, Web-of-Science and Cochrane databases. Studies published between 2000 and 2020 that assessed muscle activations by means of sEMG during any type of functional task in individuals with CAI, and used healthy individuals as controls, were included. Methodological quality was assessed using the modified Downs&Black checklist. Since the methodologies of different studies were heterogeneous, no meta-analysis was conducted. A total of 63 articles investigating muscle activations during gait, running, responses to perturbations, landing and hopping, cutting and turning; single-limb stance, star excursion balance task, forward lunges, ball-kicking, y-balance test and single-limb squatting were considered. Individuals with CAI showed a delayed activation of the peroneus longus in response to sudden inversion perturbations, in transitions between double- and single-limb stance, and in landing on unstable surfaces. Apparently, while walking on ground there are no differences between CAI and controls, walking on a treadmill increases the variability of muscles activations, probably as a "safety strategy" to avoid ankle inversion. An abnormal activation of the tibialis anterior was observed during a number of tasks. Finally, hip/spine muscles were activated before ankle muscles in CAI compared to controls. Though the methodology of the studies herein considered is heterogeneous, this review shows that the peroneal and tibialis anterior muscles have an abnormal activation in CAI individuals. These individuals also show a proximal muscle activation strategy during the performance of balance challenging tasks. Future studies should investigate whole-body muscle activation abnormalities in CAI individuals.