Biomechanical Balance Measures During Timed Up and Go Test Improve Prediction of Prospective Falls in Older Adults.

OBJECTIVE: To assess the feasibility of using biomechanical gait balance measures, the frontal and sagittal plane center of mass (COM)-Ankle angles, to prospectively predict recurrent falls in community-dwelling older adults. DESIGN: A cohort study with a 1-year longitudinal follow-up. Logistic regression was used to test the ability of the COM-Ankle angles to predict prospective falls. SETTING: General community. PARTICIPANTS: Sixty older adults over the age of 70 years were recruited using a volunteer sample. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE(S): Biomechanical balance parameters: the sagittal and frontal plane COM-Ankle angles during the sit-to-walk and turning phases of the timed Up and Go test. The COM-Ankle angles are the inclination angles of the line formed by the COM and lateral ankle (malleolus) marker of the stance foot in the sagittal and frontal planes. We also included the following clinical balance tests in the analysis: Activity-Specific Balance Confidence, Berg Balance Scale, Fullerton Advanced Balance scale, and timed Up and Go test. Their abilities to predict falls served as a reference for the biomechanical balance parameters. RESULTS: When the biomechanical gait balance measures were added to all the confounders, the explained variance was increased from 25.3% to 50.2%. Older adults who have a smaller sagittal plane COM-Ankle angle at seat-off, a greater frontal plane COM range of motion during STW and a smaller frontal plane angle during turning were more likely to become recurrent fallers. CONCLUSION(S): Our results indicated that dynamic biomechanical balance parameters could provide valuable information about a participant's future fall risks beyond what can be explained by demographics, cognition, depression, strength, and past fall history. Among all biomechanical parameters investigated, frontal plane COM motion measures during STW and turning appear to be the most significant predictors for future falls.

Study protocol: process and outcome evaluation of the Walk with Ease program for fall prevention.

BACKGROUND: Falls are the leading cause of injury related morbidity and mortality in older adults. Primary and secondary prevention strategies that address modifiable risk factors are critically important to reduce the number of falls and fall related injuries. A number of evidence-based fall prevention programs are available, but few offer potential for broad dissemination and public health impact due to implementation barriers, such as a need for trained program leaders and clinicians. METHODS: The study will use a randomized controlled trial design to evaluate incorporating physical therapy exercises (primary prevention strategy) within an existing intervention called Walk with Ease. While Walk with Ease has an established evidence-base related to the management of arthritis pain and symptoms, the present study will determine the potential to also reduce falls and fall risk in community-dwelling older adults. The integrated process and outcome evaluation will determine the relative effectiveness of individually-prescribed exercises (compared to standardized exercises) as well as the potential of 'habit training' resources (relative to generic behavior prompts) to improve compliance with exercises in this population. DISCUSSION: The study, conducted through a local clinical-community partnership will advance both the science and practice of community-based fall prevention programming, while also informing implementation strategies needed to promote broader dissemination. TRIAL REGISTRATION: ClinicalTrials.gov, NCT05693025, Registered January 20, 2023, Updated March 1, 2023.

Efficacy of exercise-based interventions in preventing falls among community-dwelling older persons with cognitive impairment: is there enough evidence? An updated systematic review and meta-analysis.

OBJECTIVE: Exercise prevents falls in the general older population, but evidence is inconclusive for older adults living with cognitive impairment. We performed an updated systematic review and meta-analysis to assess the potential effectiveness of interventions for reducing falls in older persons with cognitive impairment. METHODS: PubMed, EMBASE, CINAHL, Scopus, CENTRAL and PEDro were searched from inception to 10 November 2020. We included randomised controlled trials (RCTs) that evaluated the effects of physical training compared to a control condition (usual care, waitlist, education, placebo control) on reducing falls among community-dwelling older adults with cognitive impairment (i.e. any stage of Alzheimer's disease and related dementias, mild cognitive impairment). RESULTS: We identified and meta-analysed nine studies, published between 2013 and 2020, that included 12 comparisons (N = 1,411; mean age = 78 years; 56% women). Overall, in comparison to control, interventions produced a statistically significant reduction of approximately 30% in the rate of falls (incidence rate ratio = 0.70; 95% CI, 0.52-0.95). There was significant between-trial heterogeneity (I2 = 74%), with most trials (n = 6 studies [eight comparisons]) showing no reductions on fall rates. Subgroup analyses showed no differences in the fall rates by trial-level characteristics. Exercise-based interventions had no impact on reducing the number of fallers (relative risk = 1.01; 95% CI, 0.90-1.14). Concerns about risk of bias in these RCTs were noted, and the quality of evidence was rated as low. CONCLUSIONS: The positive statistical findings on reducing fall rate in this meta-analysis were driven by a few studies. Therefore, current evidence is insufficient to inform evidence-based recommendations or treatment decisions for clinical practice.PROSPERO Registration number: CRD42020202094.

Concussed athletes walk slower than non-concussed athletes during cognitive-motor dual-task assessments but not during single-task assessments 2 months after sports concussion: a systematic review and meta-analysis using individual participant data.

OBJECTIVES: To determine whether individuals who sustained a sports concussion would exhibit persistent impairments in gait and quiet standing compared to non-injured controls during a dual-task assessment . DESIGN: Systematic review and meta-analysis using individual participant data (IPD). DATA SOURCES: The search strategy was applied across seven electronic bibliographic and grey literature databases: MEDLINE, EMBASE, CINAHL, SportDISCUS, PsycINFO, PsycARTICLES and Web of Science, from database inception until June 2017. ELIGIBILITY CRITERIA FOR STUDY SELECTION: Studies were included if; individuals with a sports concussion and non-injured controls were included as participants; a steady-state walking or static postural balance task was used as the primary motor task; dual-task performance was assessed with the addition of a secondary cognitive task; spatiotemporal, kinematic or kinetic outcome variables were reported, and; included studies comprised an observational study design with case-control matching. DATA EXTRACTION AND SYNTHESIS: Our review is reported in line with the Preferred Reporting Items for Systematic review and Meta-Analyses-IPD Statement. We implemented the Risk of Bias Assessment tool for Non-randomised Studies to undertake an outcome-level risk of bias assessment using a domain-based tool. Study-level data were synthesised in one of three tiers depending on the availability and quality of data: (1) homogeneous IPD; (2) heterogeneous IPD and (3) aggregate data for inclusion in a descriptive synthesis. IPD were aggregated using a 'one-stage', random-effects model. RESULTS: 26 studies were included. IPD were available for 20 included studies. Consistently high and unclear risk of bias was identified for selection, detection, attrition, and reporting biases across studies. Individuals with a recent sports concussion walked with slower average walking speed (χ2=51.7; df=4; p<0.001; mean difference=0.06 m/s; 95% CI: 0.004 to 0.11) and greater frontal plane centre of mass displacement (χ2=10.3; df=4; p=0.036; mean difference -0.0039 m; 95% CI: -0.0075 to -0.0004) than controls when evaluated using a dual-task assessment up to 2 months following concussion. SUMMARY/CONCLUSIONS: Our IPD evidence synthesis identifies that, when evaluated using a dual-task assessment, individuals who had incurred a sports concussion exhibited impairments in gait that persisted beyond reported standard clinical recovery timelines of 7-10 days. Dual-task assessment (with motion capture) may be a useful clinical assessment to evaluate recovery after sports concussion. PROTOCOL PRE-REGISTRATION: This systematic review was prospectively registered in PROSPERO CRD42017064861.

Effects of transcranial direct current stimulation over right posterior parietal cortex on attention function in healthy young adults.

Attention involves three distinct networks for alerting, orienting, and executive control. Interventions targeting the specific attentional networks remain lacking. Transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability, which potentially serves as an interventional tool to treat individuals with attention impairment. The purpose of this study was to examine the effects of applying tDCS over the right posterior parietal cortex (PPC) on the performance of the three attentional networks. Twenty-six healthy young adults performed the Attention Network Test before and after anodal or sham tDCS stimulation over the right PPC. The alerting, orienting, and executive effects were assessed before and after the stimulation. The results demonstrated that the orienting effect was significantly improved after real tDCS relative to sham, whereas the alerting and executive control effects remained unaffected. Consistent with previous clinical and functional imaging studies, this suggests that the right PPC is actively engaged with the spatial orienting of attention.

Detection of Acute and Long-Term Effects of Concussion: Dual-Task Gait Balance Control Versus Computerized Neurocognitive Test.

OBJECTIVE: To examine the acute (within 72h of injury) and long-term (2mo postinjury) independent associations between objective dual-task gait balance and neurocognitive measurements among adolescents and young adults with a concussion and matched controls. DESIGN: Longitudinal case-control. SETTING: Motion analysis laboratory. PARTICIPANTS: A total of 95 participants completed the study: 51 who sustained a concussion (mean age, 17.5±3.3y; 71% men) and 44 controls (mean age, 17.7±2.9y; 72% men). Participants who sustained a concussion underwent a dual-task gait analysis and computerized neurocognitive testing within 72 hours of injury and again 2 months later. Uninjured controls also completed the same test protocol in similar time increments. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: We compared dual-task gait balance control and computerized neurocognitive test performance between groups using independent samples t tests. Multivariable binary logistic regression models were then constructed for each testing time to determine the association between group membership (concussion vs control), dual-task gait balance control, and neurocognitive function. RESULTS: Medial-lateral center-of-mass displacement during dual-task gait was independently associated with group membership at the initial test (adjusted odds ratio [aOR], 2.432; 95% confidence interval [CI], 1.269-4.661) and 2-month follow-up test (aOR, 1.817; 95% CI, 1.014-3.256) tests. Visual memory composite scores were significantly associated with group membership at the initial hour postinjury time point (aOR, .953; 95% CI, .833-.998). However, the combination of computerized neurocognitive test variables did not predict dual-task gait balance control for participants with concussion, and no single neurocognitive variable was associated with dual-task gait balance control at either testing time. CONCLUSIONS: Dual-task assessments concurrently evaluating gait and cognitive performance may allow for the detection of persistent deficits beyond those detected by computerized neurocognitive deficits alone.

Sex-Specific Relationships Between Hip Strength and Hip, Pelvis, and Trunk Kinematics in Healthy Runners.

Weak hip muscle strength and excessive hip motion during running have been suggested as potential risk factors for developing patellofemoral pain syndrome (PFPS) in females, but not males. There is conflicting evidence on the relationship between hip strength and hip kinematics, which may be partly due to sex differences in the relationship between these parameters. Hip, pelvis, and trunk kinematics were collected while 60 healthy, habitual runners (23 females, 37 males) ran overground, and isometric hip abduction and external rotation strengths were measured bilaterally. Pearson correlation coefficients quantified sex-specific correlations between hip strength and kinematics, and unpaired t tests assessed sex differences in hip strength and kinematics. Hip abduction strength was moderately and inversely correlated to hip adduction excursion in females, and pelvic internal rotation excursion in males. Hip external rotation strength was moderately and inversely correlated to trunk flexion excursion in females. Finally, females displayed less hip external rotation strength and greater excursion at the hip and trunk during running compared to males. Despite the significant correlations, the relatively low r2 values suggest that additional factors outside of strength contribute to a substantial portion of the variance in trunk, pelvis, and hip kinematics.

Effects of Muscle Strength and Balance Control on Sit-to-Walk and Turn Durations in the Timed Up and Go Test.

OBJECTIVE: To examine the association of muscle strength and balance control with the amount of time taken to perform sit-to-walk (STW) or turning components of the Timed Up and Go (TUG) test in older adults. DESIGN: Correlations; multiple regression models. SETTING: General community. PARTICIPANTS: Older adults (N=60) age >70 years recruited from the community. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Muscle strength, balance control, and TUG test performance time. Muscle strength was quantified by peak joint moments during the isometric maximal voluntary contraction test for bilateral hip abductors, knee extensors, and ankle plantar flexors. Balance control was assessed with the Berg Balance Scale, Fullerton Advanced Balance Scale, and center of mass and ankle inclination angle derived during the TUG test performance. RESULTS: We found that balance control measures were significantly associated with both STW and turning durations even after controlling for muscle strength and other confounders (STW duration: P<.001, turning duration: P=.001). Adding strength to the regression model was found to significantly improve its prediction of STW duration (F change =5.945, P=.018), but not turning duration (F change =1.03, P=.14). CONCLUSIONS: Our findings suggest that poor balance control is an important factor that contributes to longer STW and turning durations on the TUG test. Furthermore, strength has a higher association with STW than turning duration.

Return to Physical Activity Timing and Dual-Task Gait Stability Are Associated 2 Months Following Concussion.

OBJECTIVE: The effect of physical activity resumption on functional recovery following concussion is poorly understood. We sought to examine the relationship between physical activity resumption timing and gait stability 2 months following concussion. SETTING: Motion analysis laboratory. PARTICIPANTS: Twenty-nine individuals who sustained a concussion and were subsequently allowed to return to preinjury levels of physical activity within 2 months postinjury. DESIGN: Prospective cohort study. MAIN MEASURES: The return-to-activity day (RTA-day) was identified as the first day postinjury that each participant was medically cleared to resume regular physical activity. Whole-body center-of-mass (COM) motion during single-task and dual-task walking was assessed 2 months postinjury. Correlation coefficients were calculated between the RTA-day and single/dual-task gait stability as well as symptom severity measurements 2 months postinjury. RESULTS: Dual-task medial-lateral COM displacement (r = -0.52, P = .004) and peak medial-lateral COM velocity (r = -0.37, P = .048) were significantly correlated with RTA-day. Dual-task peak forward velocity and single-task gait stability measures were not significantly correlated with RTA-day. CONCLUSIONS: The time of RTA-day clearance, within a 2 months postinjury period, is significantly correlated with dual-task medial-lateral gait stability measured at the end of that period, suggesting that frontal plane gait stability recovery is sensitive to the timing of RTA-day.

Distracting visuospatial attention while approaching an obstacle reduces the toe-obstacle clearance.

Obstacle crossing during walking requires visuospatial attention to identify the obstacle, so that individuals can integrate visual and somatosensory information for raising the foot with appropriate height and timing without being tripped. However, the interaction between control of foot trajectory and orientation of visuospatial attention during obstacle crossing is complicated and remains unclear. This study probed where attention is directed when approaching and stepping over an obstacle during gait and examined how the presence of the obstacle affects the distribution of attention during walking. Eleven young healthy adults performed a visuospatial attention task while standing (Stand), crossing over an obstacle placed either before (ObsBefore) or after (ObsAfter) the visual target, or crossing without the visual target (ObsOnly). Toe-obstacle clearance was reduced for the trailing leg in the ObsAfter condition but remained the same for the ObsBefore and ObsOnly conditions. In addition, the accuracy rate of the visuospatial attention task tended to be higher at the locations closer to the obstacle. Taken together, these results demonstrate that visuospatial attention and the processes underlying obstacle crossing during locomotion interact in both a spatially and temporally dependent manner.

A randomized controlled trial of patient-reported outcomes with tai chi exercise in Parkinson's disease.

A previous randomized, controlled trial of tai chi showed improvements in objectively measured balance and other motor-related outcomes in patients with Parkinson's disease. This study evaluated whether patient-reported outcomes could be improved through exercise interventions and whether improvements were associated with clinical outcomes and exercise adherence. In a secondary analysis of the tai chi trial, patient-reported and clinical outcomes and exercise adherence measures were compared between tai chi and resistance training and between tai chi and stretching exercise. Patient-reported outcome measures were perceptions of health-related benefits resulting from participation, assessed by the Parkinson's Disease Questionnaire (PDQ-8) and Vitality Plus Scale (VPS). Clinical outcome measures included motor symptoms, assessed by a modified Unified Parkinson's Disease Rating Scale-Motor Examination (UPDRS-ME) and a 50-foot speed walk. Information on continuing exercise after the structured interventions were terminated was obtained at a 3-month postintervention follow-up. Tai chi participants reported significantly better improvement in the PDQ-8 (-5.77 points, P = 0.014) than did resistance training participants and in PDQ-8 (-9.56 points, P < 0.001) and VPS (2.80 points, P = 0.003) than did stretching participants. For tai chi, patient-reported improvement in the PDQ-8 and VPS was significantly correlated with their clinical outcomes of UPDRS-ME and a 50-foot walk, but these correlations were not statistically different from those shown for resistance training or stretching. However, patient-reported outcomes from tai chi training were associated with greater probability of continued exercise behavior than were either clinical outcomes or patient-reported outcomes from resistance training or stretching. Tai chi improved patient-reported perceptions of health-related benefits, which were found to be associated with a greater probability of exercise adherence. The findings indicate the potential of patient perceptions to drive exercise behavior after structured exercise programs are completed and the value of strengthening such perceptions in any behavioral intervention.

The effect of cognitive task complexity on gait stability in adolescents following concussion.

Concussion has been reported to result in disturbances to motor and cognitive functions. One way to examine these disturbances is through a dual-task assessment. Many secondary cognitive tasks have been proposed as appropriate tools during concussion assessment; however, task complexity has not been compared within a dual-task investigation. The purpose of this study was to prospectively examine how gait balance control was affected by three secondary cognitive tasks of varying complexity following concussion. Forty-six adolescents completed a dual-task walking protocol which included walking without any cognitive task (WALK), walking while completing a single auditory Stroop (SAS), multiple auditory Stroop (MAS), and a question and answer task (Q&A). Those who sustained a concussion (n = 23, mean age 15.4 ± 1.3 years) reported to the laboratory within 72 h of injury and in the following time increments: 1 week, 2 weeks, 1 month, and 2 months post-injury. Twenty-three healthy control subjects (mean age 15.4 ± 1.3 years), individually matched to each concussion subject, completed the same protocol in similar time increments. The concussion group demonstrated greater total center of mass (COM) medial/lateral displacement in the MAS and Q&A conditions compared with the control group. The concussion group also displayed the greatest peak COM anterior velocity in the least complex condition (WALK), and a significant decrease was observed as task complexity increased (SAS > MAS > Q&A). These findings indicate that gait balance control may be affected by task complexity following concussion and represent a way to identify motor recovery following concussion.

Acute and longitudinal changes in motor cortex function following mild traumatic brain injury.

PRIMARY OBJECTIVE: To evaluate excitability and inhibition of the motor cortex acutely and longitudinally following mild traumatic brain injury (mTBI). RESEARCH DESIGN: A longitudinal paired case-control design was used to examine cortical excitability and inhibition in 15 adults who had sustained an mTBI (mean age = 20.8 ± 1.2 years) and 15 matched control participants (mean age = 21.1 ± 1.3 years). METHODS AND PROCEDURES: Participants visited the lab within 72 hours of injury and again at 1, 2, 4 and 8 weeks post-injury. During each visit, transcranial magnetic stimulation was used to examine resting motor threshold (RMT), motor evoked potential peak-to-peak amplitude (MEPamp) and cortical silent period (CSP) duration of the first dorsal interosseous muscle. MAIN OUTCOMES AND RESULTS: There were no differences between groups in RMT (p = 0.10) or MEPamp (p = 0.22) at 72 hours post-injury or across the 2-month testing period (p ≥ 0.68), indicating similar cortical excitability. However, the CSP duration was higher in individuals with mTBI, indicating greater intra-cortical inhibition compared with the control group at 72 hours post-injury (p = 0.03) and throughout the 2 months of recovery (p = 0.009). CONCLUSIONS: mTBI appeared to have little effect on cortical excitability, but an acute and long-lasting effect on intra-cortical inhibition.

Concurrent validity of inertial measurement units in range of motion measurements of upper extremity: A systematic review and meta-analysis.

Inertial measurement units (IMUs) have proven to be valuable tools in measuring the range of motion (RoM) of human upper limb joints. Although several studies have reported on the validity of IMUs compared to the gold standard (optical motion capture system, OMC), a quantitative summary of the accuracy of IMUs in measuring RoM of upper limb joints is still lacking. Thus, the primary objective of this systematic review and meta-analysis was to determine the concurrent validity of IMUs for measuring RoM of the upper extremity in adults. Fifty-one articles were included in the systematic review, and data from 16 were pooled for meta-analysis. Concurrent validity is excellent for shoulder flexion-extension (Pearson's r = 0.969 [0.935, 0.986], ICC = 0.935 [0.749, 0.984], mean difference = -3.19 (p = 0.55)), elbow flexion-extension (Pearson's r = 0.954 [0.929, 0.970], ICC = 0.929 [0.814, 0.974], mean difference = 10.61 (p = 0.36)), wrist flexion-extension (Pearson's r = 0.974 [0.945, 0.988], mean difference = -4.20 (p = 0.58)), good to excellent for shoulder abduction-adduction (Pearson's r = 0.919 [0.848, 0.957], ICC = 0.840 [0.430, 0.963], mean difference = -7.10 (p = 0.50)), and elbow pronation-supination (Pearson's r = 0.966 [0.939, 0.981], ICC = 0.821 [0.696, 0.900]). There are some inconsistent results for shoulder internal-external rotation (Pearson's r = 0.939 [0.894, 0.965], mean difference = -9.13 (p < 0.0001)). In conclusion, the results support IMU as a viable instrument for measuring RoM of upper extremity, but for some specific joint movements, such as shoulder rotation and wrist ulnar-radial deviation, IMU measurements need to be used with caution.

Center of mass motion and plantar pressure distribution during walking in overweight individuals.

BACKGROUND: Gait imbalance has been reported in overweight individuals and could further impair their mobility and quality of life. As the feet are the most distal part of the body and sensitively interface with external surroundings, evaluating the plantar pressure distribution can provide critical insights into their roles in regulating gait balance control. Therefore, the purpose of this study was to evaluate the effect of body weight and different gait speeds on the plantar pressure distribution and whole-body center of mass (COM) motion during walking. METHODS: Eleven overweight individuals (OB) and 13 non-overweight individuals (NB) walked on a 10-meter walkway at three speed conditions (preferred, 80% and 120% of preferred speed). Gait balance was quantified by the mediolateral COM sway. Plantar pressure data were obtained using wireless pressure-sensing insoles that were inserted into a pair of running shoes. Analysis of variance models were used to examine the effect of body size, gait speeds, or their interactions on peak mediolateral COM and peak plantar pressure during walking. RESULTS: Significant group effects of peak plantar pressure under the lateral forefoot (P = 0.03), lateral midfoot (P = 0.02), and medial heel (P = 0.02) were observed. However, the mediolateral COM motion and spatiotemporal gait parameters only revealed significant speed effects. SIGNIFICANCE: Findings from this study indicated that overweight individuals exhibited increased plantar pressure under the lateral aspect of the foot, particularly during the late stance phase of walking, in an effort to maintain a comparable mediolateral COM motion to that of non-overweight individuals. Such elevated pressure in overweight individuals may potentially increase the risk of musculoskeletal pathology in the long term. The identified patterns are noteworthy as they have practical implications for designing targeted interventions and improving the overall health of individuals with a high BMI.

Dual-task effect on gait balance control in adolescents with concussion.

OBJECTIVE: To prospectively and longitudinally examine how concussion affects gait balance control in adolescents during single- and dual-task walking. DESIGN: Cohort, prospective, repeated-measures design. SETTING: Motion analysis laboratory. PARTICIPANTS: Adolescents (N=20) identified as suffering a concussion were matched with healthy control subjects (N=20) and tested 5 times across a 2-month period after injury. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Gait temporal-distance parameters included average walking speed, step length, and step width; whole body center of mass (COM) parameters included medial/lateral displacement and peak COM medial/lateral and anterior velocities; dual-task cost, which was defined as percent change from single- to dual-task conditions; and Stroop test accuracy. RESULTS: No between-group differences were observed for step length and step width. The dual-task cost for average walking speed for subjects with concussion was greater than control subjects across the 2-month testing period (main effect of group P=.019), as was the dual-task costs for peak anterior COM velocity (main effect of group P=.017) and total COM medial/lateral displacement (main effect of group P=.013). The total COM medial/lateral displacement (group × task interaction P=.006) and peak COM medial/lateral velocity (main effect of group P=.027; main effect of task P=.01) were significantly greater in subjects with concussion compared with control subjects during dual-task walking. Subjects with concussion were significantly less accurate than controls on the Stroop test (main effect of group P=.004). CONCLUSIONS: The findings suggest that concussion affects the ability of adolescents to control body posture during gait up to 2 months after injury. Furthermore, dual-task paradigms may provide additional useful information in the clinical assessment and recovery of concussion.

Contribution of lower extremity muscles to center of mass acceleration during walking: Effect of body weight.

Overweight or obesity is known to be associated with altered activations of lower extremity muscles. Such changes in muscular function may lead to the development of mobility impairments or joint diseases. However, little is known about how individual lower extremity muscles contribute to the whole-body center of mass (COM) control during walking and the effect of body weight. This study examined the contribution of individual lower extremity muscle force to the COM accelerations during walking in overweight and non-overweight individuals. Musculoskeletal simulations were performed for the stance phase of walking with data collected from 11 overweight and 13 non-overweight adults to estimate lower extremity muscle forces and their contributions to the COM acceleration. Mean time-series data from each parameter were compared between body size groups using Statistical Parametric Mapping. Compared to the non-overweight group, the overweight group revealed a greater gastrocnemius contribution to the mediolateral (p = 0.006) and vertical (p < 0.001) COM accelerations during mid-stance, and had a lower vastus contribution to the anteroposterior COM acceleration (p < 0.001) during pre-swing. Increased contributions from the large posterior calf muscles to the mediolateral COM acceleration may be related to efforts to alleviate COM sway in overweight individuals.

Dual task cost in adults with persistent concussion symptoms.

BACKGROUND: Persistent concussion symptoms (PCS) negatively affects common activities of daily living including deficits in both single and dual-task (DT) gait. DT gait deficits are present post-concussion; however, task prioritization and the effects of differing cognitive challenge remain unexplored in the PCS population. RESEARCH QUESTION: The purpose of this study was to investigate single and dual-task gait performance in individuals with persistent concussion symptoms and to identify task priorization strategies during DT trials. METHODS: Fifteen adults with PCS (age: 43.9+11.7 y.o.) and 23 healthy control participants (age: 42.1+10.3 y.o.) completed five trials of single task gait followed by fifteen trials of dual task gait along a 10-m walkway. The cognitive challenges consisted of five trials each of visual stroop, verbal fluency, and working memory cognitive challenges. Groups were compared on DT cost stepping characteristics with independent samples t-test or Mann-Whitney U tests. RESULTS: There were significant overall gait Dual Task Cost (DTC)difference between groups for gait speed (p = 0.009, d=0.92) and step length (p = 0.023, d=0.76). Specific to each DT challenge, PCS participants were slower during Verbal Fluency (0.98 + 0.15 m/s and 1.12 + 0.12 m/s, p = 0.008; d=1.03), Visual Stroop (1.06 + 0.19 m/s and 1.20 + 0.12 m/s, p = 0.012, d=0.88), and Working Memory (1.02 + 0.15 m/s and 1.16 + 0.14 m/s, p = 0.006, d=0.96). There were significant cognitive DTC differences between groups for WM accuracy (p = 0.008, d=0.96), but not for VS accuracy (p = 0.841, d=0.061) or VF total words (p = 0.112, d=0.56). SIGNIFICANCE: The PCS participants displayed a posture-second strategy whereby gait performance generally decreased in the absence of cognitive changes. However, during the Working Memory DT, PCS participants had a mutual interference response whereby both motor and cognitive performance decreased suggesting the cognitive task plays a key role in the DT gait performance of PCS patients.

Inter-joint coordination variability during a sit-to-stand fatiguing protocol.

A repetitive sit-to-stand (STS) task is often used as a fatiguing protocol. Although post-fatigue reductions in muscle strength have been frequently used to indicate fatigue, little is known about changes in body movement during the fatiguing process. This study examined changes in variability of hip-knee and knee-ankle coordination during the STS fatiguing course in 15 young (age: 26.7 ± 5.8 years; 9 females, 6 males) and 15 older adults (age: 69.3 ± 5.7 years; 9 females, 6 males). Participants were asked to perform repetitive STS movements until exhaustion or for 30 min at a self-selected pace. Motion data from 3 consecutive STS cycles were extracted from every minute during the entire fatiguing course and time normalized to STS duration and dummy coded as five stages: 0-20, 20-40, 40-60, 60-80, and 80-100% of the course. Outcome variables were hip-knee and knee-ankle inter-joint coordination variabilities. A 2*5 mixed-effect ANOVA was used to examine changes in variability during different stages of the course in young and older adults. No Age × Time interactions were found in either hip-knee or knee-ankle coordination variability. The hip-knee coordinative variability significantly increased along the STS fatiguing course regardless of age, and the knee-ankle variability from standing to sitting was also higher at the ending, when compared to the beginning, of the fatiguing protocol. The impact of fatigue during repetitive STS protocol is not only limited to a force production decline but also manifested as increased coordinative variability, which could be considered as a fatigue indicator.