Spatiotemporal walking performance in different settings: effects of walking speed and sex.

Background: Understanding the factors that influence walking is important as quantitative walking assessments have potential to inform health risk assessments. Wearable technology innovation has enabled quantitative walking assessments to be conducted in different settings. Understanding how different settings influence quantitative walking performance is required to better utilize the health-related potential of quantitative walking assessments. Research question: How does spatiotemporal walking performance differ during walking in different settings at different speeds for young adults? Methods: Forty-two young adults [21 male (23 ± 4 years), 21 female (24 ± 5 years)] walked in two laboratory settings (overground, treadmill) and three non-laboratory settings (hallway, indoor open, outdoor pathway) at three self-selected speeds (slow, preferred, fast) following verbal instructions. Six walking trials of each condition (10 m in laboratory overground, 20 m in other settings) were completed. Participants wore 17 inertial sensors (Xsens Awinda, Movella, Henderson, NV) and spatiotemporal parameters were computed from sensor-derived kinematics. Setting × speed × sex repeated measures analysis of variance were used for statistical analysis. Results: Regardless of the speed condition, participants walked faster overground when compared to while on the treadmill and walked faster in the indoor open and outdoor pathway settings when compared to the laboratory overground setting. At slow speeds, participants also walked faster in the hallway when compared to the laboratory overground setting. Females had greater cadence when compared to males, independent of settings and speed conditions. Significance: Particularly at slow speeds, spatiotemporal walking performance was different between the settings, suggesting that setting characteristics such as walkway boundary definition may significantly influence spatiotemporal walking performance.

Precision Errors and Monitoring Time Interval in Pediatric Muscle Imaging and Neuromuscular Performance Assessment.

OBJECTIVES: To determine precision errors and monitoring time intervals in imaged muscle properties and neuromuscular performance, and to explore growth-related factors associated with precision errors in children. METHODS: We included 35 children (mean age 10.5yrs) in the precision study cohort and 40 children (10.7yrs) in the follow-up study cohort. We assessed forearm and lower leg muscle properties (area, density) with peripheral quantitative computed tomography. We measured neuromuscular performance via maximal pushup, grip force, countermovement and standing long jump force, power, and impulse along with long jump length. We calculated precision errors (root-mean-squared coefficient of variation) from the precision cohort and monitoring time intervals using annual changes from the follow-up cohort. We explored associations between precision errors (coefficient of variation) and maturity, time interval (between repeated measures), and anthropometric changes using Spearman's rank correlation (p<0.05). RESULTS: Muscle measures exhibited precision errors of 1.3-14%. Monitoring time intervals were 1-2.6yrs, except muscle density (>43yrs). We identified only one association between precision errors and maturity (maximal pushup force: rho=-0.349; p=0.046). CONCLUSIONS: Imaging muscle properties and neuromuscular performance measures had precision errors of 1-14% and appeared suitable for follow-up on ~2yr scales (except muscle density). Maximal pushup force appeared more repeatable in mature children.

The effect of acute equine temporomandibular joint inflammation on response to rein-tension and kinematics.

Background: Although the temporomandibular joint (TMJ) is the major contact point between the reins in the riders' hand, the bit in the mouth, and the rest of the horse under saddle, the role of inflammation of this joint on equine locomotion and rein tension is unknown. Objective: To determine the effect of acute TMJ inflammation on rein-tension and horse movement when horses were long-reined on a treadmill. Study design: A randomized, controlled, cross-over design. Methods: Five horses were trained by one clinician to walk and trot on a treadmill wearing long-reining equipment instrumented with a rein-tension device and reflective optical tracking markers. Subjective assessment of horse's dominant side, and movement, were determined without rein-tension (free walk and trot); and with rein-tension (long-reined walk and trot). Continuous rein-force data from both sides were collected over ~60s from each trial. Movement was recorded using a 12-camera optical motion capture system. One randomly assigned TMJ was subsequently injected with lipopolysaccharide and the treadmill tests repeated by investigators blinded to treatment side. A second, identical assessment was performed 10 days later with the opposite TMJ being the target of intervention. Results: All horses showed reduced rein-tension on the injected (inflamed) side. Increased rein-tension was required on the non-injected side at trot, to maintain them in the correct position on the treadmill post-injection. The only kinematic variable to show any significant change due to rein tension or TMJ inflammation during the walk or trot was an increase in forward head tilt in the presence of rein tension in the trot after injection. Main limitations: Low number of horses and investigation of response to acute inflammation only. Conclusion: TMJ inflammation changed, subjectively and objectively, the response to rein-input, but the horses did not become lame.

The Associations Among Self-Compassion, Self-Esteem, Self-Criticism, and Concern Over Mistakes in Response to Biomechanical Feedback in Athletes.

Athletes regularly face the possibility of failing to meet expectations in training and competition, and it is essential that they are equipped with strategies to facilitate coping after receiving performance feedback. Self-compassion is a potential resource to help athletes manage the various setbacks that arise in sport over and above other psychological resources. The primary purpose of this research was to explore how athletes respond to objective biomechanical feedback given after a performance. Specifically, we investigated if levels of self-compassion, self-esteem, self-criticism, and concern over mistakes were related to one another before and after a series of sprint tests interspersed with biomechanical feedback, and whether self-compassionate athletes achieved a better sprint performance after receiving and implementing biomechanical feedback. Forty-eight athletes (20 female: M age = 19.8 years, SD = 3.1; 28 male: M age = 23.6 years, SD = 7.8) completed online measures of self-compassion, self-esteem, self-criticism and concern over mistakes before performing four sets of 40-m sprints. Participants received personalized biomechanical feedback after each sprint that compared their performance to gold standard results. Following all sprints, they then completed measures of self-criticism, and reported emotions, thoughts, and reactions. Self-compassion was positively correlated with self-esteem (r = 0.57, p < 0.01) and negatively related to both self-criticism (r = -0.52, p < 0.01) and concern over mistakes (r = -0.69, p < 0.01). We also found that athletes with higher levels of self-compassion prior to sprint performance experienced less self-critical thoughts following biomechanical feedback and subsequent sprint trials (r = -0.38, p < 0.01). Although the results of this study provide some support for the effectiveness of self-compassion in promoting healthy emotions, thoughts, and reactions in response to sprint performance-based biomechanical feedback, a moderated regression analysis between the first and fourth sprint time variables revealed that self-compassion was not a moderator for change in sprint performance (R 2 = 0.64, ΔR 2 = 0.10, p > 0.05). These findings suggest that there are likely longer-term benefits of athletes using self-compassion to cope with biomechanical feedback, but that any benefits might be limited in a short series of sprint trials.

Age differences in upper extremity joint moments and strength during a laboratory-based tether-release forward fall arrest in older women.

Age-related declines in upper extremity muscle strength may affect an older adult's ability to land and control a simulated forward fall impact. The role of individual upper extremity joints during a forward fall impact has not been examined. The purpose was to evaluate the age differences in upper extremity joint moment contributions during a simulated forward fall and upper extremity muscle strength in older women. A convenience sample of 68 older women (70 (8) yrs) performed three trials of a simulated forward fall. Percentage joint moments of the upper extremity were recorded. Upper extremity muscle strength was collected via handgrip, hand-held dynamometry of the shoulder and elbow and a custom multi-joint concentric and eccentric strength isokinetic dynamometer protocol. Percentage joint moment contributions differed between women in their sixties and seventies with significantly greater relative shoulder joint involvement (P =.008), coupled with lower elbow joint contributions (P =.004) in comparison to 80 year olds. An increase in each year of age was associated with a 4% increase in elbow contribution (Beta = -0.421, r2 = 17.9, P = 0.0001) and a 3.7% decrease in shoulder contribution (Beta = 0.373, r2 = 14.6, P = 0.002). Older women exhibit different landing strategies as they age. Fall injury prevention research should consider interventions focused on these differences taking into account the contributions of upper extremity strength.

Don't get tripped up: Haptic modalities alter gait characteristics during obstacle crossing.

The attentional capacity required of haptic modalities while obstacle crossing may limit their effectiveness. Therefore, this study examined the attentional demands of haptic modalities during obstacle crossing. Nineteen healthy young adults walked across a 10 m laboratory floor within two modality blocks using either: 1) light touch on a railing, or 2) pulling haptic anchors. Randomly dispersed within these blocks were trials without added haptic input and verbal reaction time (VRT) tasks. VRT was compared across the three walking conditions. Gait characteristics, obstacle crossing stability, and obstacle toe clearance were compared across the three walking conditions (normal walking, light touch walking, anchored walking) and 2 VRT conditions (absence vs. presence). VRTs did not differ according to walking conditions (p > .05). Step length variability for the normal walking condition was significantly greater than for both the light touch and anchored walking conditions (p = .026). Toe clearance for the trail leg was less during light touch than normal walking (p = .020). The presence of the VRT resulted in greater toe clearance for both lead (p = .018) and trail limbs (F(2,34) = 8.053, p = .011). Neither haptic modality required significantly increased attentional demand; however, light touch walking results in less obstacle toe clearance. Haptic modalities likely provide greater benefit than risk to users during obstacle crossing.

Does functional performance and upper body strength predict upper extremity reaction and movement time in older women?

BACKGROUND: Reaction time to initiate upper limb movement and movement time to place hands on the landing surface may be important factors in forward fall landing and impact, contributing to injury reduction. The aim was to investigate the relationship of physical function and upper body strength to upper limb reaction and movement time in older female participants. METHODS: 75 female participants (72 ± 8 yrs) performed 5 arm response trials. Reaction time (signal to initiation of movement), and movement time (initial movement to contact), were collected using 3D motion capture. Additional variables were: handgrip; sit-to-stand; shoulder flexion and elbow extension strength measured by hand-held dynamometry; one-legged balance; fall risk; and physical activity scores. Prediction variables for reaction and movement time were determined in separate backward selection multiple regression analyses. Significance was set at P < 0.05. FINDINGS: Significant regression equations for RT (r2 = 0.08, P = 0.013) found a relationship between stronger handgrip (Beta = -0.002) and faster reaction time, accounting for 8% variance. For movement time (r2 = 0.06, P = 0.036) greater shoulder flexion strength (Beta = -0.04) was related to faster movement time, explaining 6% variance. Stronger SF strength was related to a decrease in MT by 4%. DISCUSSION: A relationship between arm strength measures and faster upper body reaction and movement time was shown, with 10-20% higher strength associated with a 5% faster response time. Even though this was a relatively weak relationship, given that strength is a modifiable component this provides a potential avenue for future intervention efforts. This in turn could have an impact on forward fall landing and potential reduction of injury risk.

Investigating proactive balance control in individuals with incomplete spinal cord injury while walking on a known slippery surface.

BACKGROUND: Up to 83 % of individuals with incomplete spinal cord injury (iSCI) experience ≥ 1 fall/year. Individuals with iSCI employ more cautious walking strategies than able-bodied (AB) individuals during normal walking. Whether individuals with iSCI can use proactive balance strategies to adapt to expected slip perturbations/reduce slip severity while walking has not been previously assessed. METHODS: 19 individuals with iSCI (AIS D; 14 males; 61 ± 18 years) and 17 AB individuals (13 males; 61 ± 18 years) completed 3 walking conditions: normal walking trials, an unexpected slip trial, and expected slip trials. Steel rollers induced a slip in the antero-posterior (AP) direction. Outcome variables included step length, center of mass velocity, foot-floor angle, AP margin of stability, and maximum post-slip velocity (PSV). RESULTS: The iSCI group used a greater magnitude of cautious strategies (i.e. walking slower with shorter, flatter steps) than AB individuals in all conditions. However, the lack of significant interaction effects indicate that the proactive adaptations compared to normal walking (i.e. walking slower with shorter, flatter steps, and a more anterior xCOM-position) were similar between the two groups (AB & iSCI). Both groups showed a similar rate of adaptation (after just 1 slip) and these feedforward changes were maintained throughout the remaining slip trials which was effective at reducing maximum PSV. CONCLUSIONS: Individuals with iSCI use proactive balance strategies to adapt to a known slippery surface in a similar manner to AB individuals both in terms of the proportion and timing of adaptation.

Haptic input and balance control: An exploratory study examining normative messaging.

This study examined the effect of descriptive norm messaging information on the relationship between haptic input and balance control. Participants were randomly assigned to either a message group where they balanced with haptic input after receiving a descriptive norm message about the positive effect of haptic input or a control group. Findings from an analysis of covariance revealed a significant difference between the two groups. Those in the descriptive norm message group had better balance control than those in the control group. These findings suggest that efforts designed to improve balance control through haptic input may be enhanced through normative messaging.

The effects of light touch on gait and dynamic balance during normal and tandem walking in individuals with an incomplete spinal cord injury.

STUDY DESIGN: Prospective cross-sectional study OBJECTIVES: To investigate the effect of adding haptic input during walking in individuals with incomplete spinal cord injury (iSCI). SETTING: Research laboratory. METHODS: Participants with iSCI and age- and sex-matched able-bodied (AB) individuals walked normally (SCI n = 18, AB n = 17) and in tandem (SCI n = 12, AB n = 17). Haptic input was added through light touch on a railing. Step parameters, and mediolateral and anterior-posterior margins of stability (means and standard deviations) were calculated. Surface electromyography data were collected bilaterally from the tibialis anterior (TA), soleus (SOL), and gluteus medius (GMED) and integrated over a stride. Repeated measures ANOVAs examined within- and between-group differences (α = 0.05). Cutaneous and proprioceptive sensation of individuals with iSCI were correlated to changes in outcome measures that were affected by haptic input. RESULTS: When walking normally, adding haptic input decreased stride velocity, step width, stride length, MOSML, MOSML_SD, MOSAP, and MOSAP_SD, and increased GMED activity on the limb opposite the railing. During tandem walking, haptic input had no effect; however, individuals with iSCI had a larger step width SD and MOSML_SD compared with the AB group. Sensory abilities of individuals with iSCI were not correlated to any of the outcome measures that significantly changed with added haptic input. CONCLUSIONS: Added haptic input improved balance control during normal but not in tandem walking. Sensory abilities did not impact the use of added haptic input during walking.

Reactive balance responses to an unexpected slip perturbation in individuals with incomplete spinal cord injury.

BACKGROUND: Frequent falls while walking among individuals with incomplete spinal cord injury may suggest impairments in reactive balance control; however, reactive balance control during walking has not been studied in this population. The objective was to compare reactive balance control with respect to changes in margin of stability, onset of arm and heel responses, and onset and magnitude of muscle activity following an unexpected slip perturbation in individuals with incomplete spinal cord injury and able-bodied individuals. METHODS: Kinematic and electromyography data were obtained during normal walking and one unexpected slip. Changes in margin of stability following a compensatory or aborted step, onset of arms and trail heel responses, and onset and magnitude of activation of the tibialis anterior, soleus and gluteus medius were calculated. Multivariate analyses compared responses between incomplete spinal cord injury and able-bodied groups. FINDINGS: Data from 16 participants with incomplete spinal cord injury (all American Spinal Injury Association Impairment Scale Grade D, 8 with tetraplegia) and 13 age-and-sex matched able-bodied individuals were included. Individuals with incomplete spinal cord injury demonstrated limited ability to increase margin of stability in the lateral direction during a compensatory or aborted step, and a smaller magnitude of soleus activity compared to able-bodied individuals. INTERPRETATION: There are limitations in reactive balance control of individuals with incomplete spinal cord injury, which may be a reason for the high frequency of falls in this population. Reactive balance assessment should be included as a component of routine balance assessment and fall avoidance strategies in this population.

Adding Light Touch While Walking in Older Adults: Biomechanical and Neuromotor Effects.

Adding haptic input may improve balance control and help prevent falls in older adults. This study examined the effects of added haptic input via light touch on a railing while walking. Participants (N = 53, 75.9 ± 7.9 years) walked normally or in tandem (heel to toe) with and without haptic input. During normal walking, adding haptic input resulted in a more cautious and variable gait pattern, reduced variability of center of mass acceleration and margin of stability, and increased muscle activity. During tandem walking, haptic input had minimal effect on step parameters, decreased lower limb muscle activity, and increased cocontraction at the ankle closest to the railing. Age was correlated with step width variability, stride length variability, stride velocity, variability of medial-lateral center of mass acceleration, and margin of stability for tandem walking. This complex picture of sensorimotor integration in older adults warrants further exploration into added haptic input during walking.

Comparing the effect of haptic modalities on walking balance control: Is using one or two arms better?

BACKGROUND: Adding haptic input by lightly touching a railing or using haptic anchors may improve walking balance control. Typical use of the railing(s) and haptic anchors requires the use of one and two arms in an extended position, respectively. It is unclear whether it is arm configuration and/or the number of arms used or the addition of sensory input that affects walking balance control. RESEARCH QUESTION: This study examined whether using one arm or two arms to add haptic input through light touch on a railing or using the haptic anchors affects walking balance control. METHODS: In this study, young adults (n = 24) walked while using (actual use) or pretending to use (pretend use) the railing(s) and haptic anchors with one or two arms. Inertial-based sensors (Mobility Lab, APDM) were used to measure stride velocity, relative time spent in double support (%DS), and peak normalized medio-lateral trunk velocity (pnMLTV). RESULTS: Using two arms lead to a decrease in pnMLTV compared to using one arm and pnMLTV was lower in the actual use trials compared to the pretend use trials for the anchors only. Stride velocity and %DS did not change between trials when one or two arms were used or when participants actually or pretended to use the haptic tools. Participants walked slower when using the railing compared to the anchors. SIGNIFICANCE: The importance of considering the number of arms is highlighted in the improved balance control when using two arms with either tool. The augmented sensory input adds to the stabilizing effect of arm configuration for the anchors but not the railings. These results have implications for future research and rehabilitation efforts emphasizing sensorimotor integration to improve walking balance control.

Are there attentional demands associated with haptic modalities while walking in young, healthy adults?

STUDY DESIGN: A prospective, observational study. OBJECTIVES: To assess the attentional demands of using haptic modalities during walking using a multi-task paradigm in young, healthy adults. SETTING: Biomechanics of Balance and Movement (BBAM) Lab, University of Saskatchewan. METHODS: Twenty-two (12 male) young, healthy adults performed walking trials with and without a verbal reaction time (VRT) task, as well as with and without the use of haptic anchors and light touch on a railing. Walking performance was evaluated using normalized stride velocity and step width, and dynamic stability was evaluated using step width variability and medial-lateral margin of stability (ML MOS) and its variability. RESULTS: There were no significant differences in VRT when walking with and without added haptic input and no interactions between the added VRT task and added haptic input. Step width increased and variability of the ML MOS increased during trials with the VRT task compared to trials without the VRT task. The ML MOS decreased when using both haptic tools with a greater decrease when using light touch on the railing compared to when using the haptic anchors. Normalized stride velocity and step width decreased when using light touch on the railing only. CONCLUSION: Both haptic tools affected stability during walking. Using the railing to add haptic input had a greater effect on walking stability and was the only haptic tool to affect walking performance. Attentional demands should be considered in future research and applications of adding haptic input during walking.

A single-spring model predicts the majority of variance in impact force during a fall onto the outstretched hand.

The objective of this study was to validate a single-spring model in predicting measured impact forces during an outstretched arm falling scenario. Using an integrated force plate, impact forces were assessed from 10 young adults (5 males; 5 females), falling from planted knees onto outstretched arms, from a random order of drop heights: 3, 5, 7, 10, 15, 20, and 25 cm. A single-spring model incorporating body mass, drop height plus the estimated linear stiffness of the upper extremity (hand, wrist and arm) was used to predict impact force on the hand. We used an analysis of variance linearity test to test the validity of using a linear stiffness coefficient in the model. We used linear regression to assess variance (R2) in experimental impact force predicted by the single-spring model. We derived optimum linear stiffness coefficients for male, female and sex-combined. Our results indicated that the association between experimental and predicted impact forces was linear (P < 0.05). Explain variance in experimental impact force was R2 = 0.82 for sex-combined, R2 = 0.88 for males and R2 = 0.84 for females. Optimum stiffness coefficients were 7436 N/m for sex-combined, 8989 N/m for males and 4527 N/m for females. In conclusion, a linear spring coefficient used in the single-spring model proved valid for predicting impact forces from fall heights up to 25 cm. Results also suggest the use of sex-specific spring coefficients when estimating impact force using the single-spring model. This model may improve impact force to bone strength ratios (factor-of-risk) and prediction of forearm and wrist fracture.

Walking Stability During Normal Walking and Its Association with Slip Intensity Among Individuals with Incomplete Spinal Cord Injury.

BACKGROUND: Ambulatory individuals with incomplete spinal cord injury (iSCI) experience frequent falls suggesting impairments in their balance control. Individuals with iSCI are more stable during normal walking as compared to able-bodied (AB) individuals; however, it is not known whether this increased stability helps prevent hazardous slips. OBJECTIVE: To compare walking stability during normal walking between iSCI and AB individuals, and to study the association between stability during normal walking and the intensity of an unexpected slip perturbation. DESIGN: Cross-sectional. SETTING: Biomechanics of Balance and Movement lab, University of Saskatchewan, Saskatoon. PARTICIPANTS: Twenty iSCI (15 men; age: M = 60.05, SD = 17.77 years) and 16 (12 men; age: M = 58.92, SD = 17.10 years) AB individuals. METHODS: Stability measures during unperturbed walking at a self-selected speed were collected from all the participants. Additionally, stability measures were also collected from 10 of the AB participants walking at a slower speed. An unexpected slip perturbation was recorded in all participants during a self-selected speed trial and peak-slip heel velocity post slip was recorded. MAIN OUTCOME MEASUREMENTS: Measures of stability: ankle co-contraction, required coefficient of friction, walking velocity, foot angle, anteroposterior margin of stability, percentage double support, step length, and step width were compared between iSCI, AB-self selected, and AB-slow walking groups. Associations between slip intensity, indicated by peak post-slip heel velocity, and stability measures were also examined through correlation analysis. RESULTS: Individuals with iSCI walked slower, took shorter steps, and spent a greater percentage of time in double support compared with AB individuals walking at a self-selected pace (P < .01). Slower walking velocity was correlated with slower post-slip velocity in participants with iSCI (P = .01) only. CONCLUSIONS: Individuals with iSCI walk with greater stability than AB individuals during unperturbed walking because of a lower self-selected speed, which appears to reduce the intensity of an unexpected slip perturbation. LEVEL OF EVIDENCE: III.

Physical Therapists' Use of Evaluation Measures to Inform the Prescription of Ankle-Foot Orthoses for Children with Cerebral Palsy.

Aims: To examine how physical therapists (PTs) use evaluation measures to guide prescription and re-assessment of ankle-foot orthoses (AFOs) for children with CP. Methods: PTs in Canada who work with children with CP were invited to complete an online survey. Survey questions examined PT evaluation and interpretation of findings at initial AFO prescription and re-assessment. Closed-ended responses were analyzed using descriptive statistics, and a conventional content analysis examined responses to open-ended questions. Results: Sixty responses from ten provinces were analyzed. Three themes emerged from the open-ended responses, which were supported by closed-ended responses. (1) Focus on impairment-level measures. Although evaluation primarily involved observational, non-standardized measures of impairments and gait pattern, most respondents also considered participation-level constructs. (2) Lack of confidence/knowledge. Respondents reported a moderate level of confidence concerning decision-making about AFO type and characteristics. 3) Inconsistent practices between therapists, possibly reflecting the paucity of available evidence or individualization of the prescription. Conclusions: Non-standardized, observational assessment methods, and impairment-level constructs appear to guide AFO prescription decisions. Integrating current knowledge into practice, developing best practice guidelines, and developing standardized tools to assess the effects of AFOs on participation may promote confidence, consistency, and improved outcomes.

Biomechanical and physiological age differences in a simulated forward fall on outstretched hands in women.

BACKGROUND: Falling on the outstretched hands, a protective mechanism to arrest the body and avoid injury, requires upper limb and trunk motor control for effective body descent. Older women are particularly susceptible to injury from a forward fall, but the biomechanical and physiological (e.g., muscle strength) factors related to this increased risk are poorly understood. Determining age differences in the modifiable neuromuscular factors related to a forward fall landing and descent could help to inform injury prevention strategies. The purpose was to investigate age related differences in upper extremity strength and fall arrest strategy differences during a simulated fall and to evaluate the relationships between muscle strength and biomechanical variables. METHODS: Nineteen younger (mean age 23.0 yrs., SD 3.8) and 16 older (mean age 68.2 yrs., SD 5.3) women performed five trials of simulated falls. Biomechanical measures and electromyographic muscle activity were recorded during the descents. Concentric, isometric and eccentric strength of the non-dominant upper limb was measured via a dynamometer using a customized protocol. FINDINGS: Older women demonstrated lower concentric elbow extension strength compared to younger women (p = 0.002). Landing strategies differed where younger women had significantly greater elbow joint angle (p = 0.006) and velocity (p = 0.02) at impact. Older women demonstrated diminished capacity to absorb energy and control descent on outstretched hands compared to younger women (p = 0.001). INTERPRETATION: The landing strategy used by older women along with decreased energy absorption may increase risk of fall-related injury and increase the likelihood of trunk or head impact with the ground.

Unilateral strength training leads to muscle-specific sparing effects during opposite homologous limb immobilization.

Cross education (CE) occurs after unilateral training whereby performance of the untrained contralateral limb is enhanced. A few studies have shown that CE can preserve or "spare" strength and size of an opposite immobilized limb, but the specificity (i.e., trained homologous muscle and contraction type) of these effects is unknown. The purpose was to investigate specificity of CE "sparing" effects with immobilization. The nondominant forearm of 16 participants was immobilized with a cast, and participants were randomly assigned to a resistance training (eccentric wrist flexion, 3 times/week) or control group for 4 weeks. Pre- and posttesting involved wrist flexors and extensors eccentric, concentric and isometric maximal voluntary contractions (via dynamometer), muscle thickness (via ultrasound), and forearm muscle cross-sectional area (MCSA; via peripheral quantitative computed tomography). Only the training group showed strength preservation across all contractions in the wrist flexors of the immobilized limb (training: -2.4% vs. control: -21.6%; P = 0.04), and increased wrist flexors strength of the nonimmobilized limb (training: 30.8% vs. control: -7.4%; P = 0.04). Immobilized arm MCSA was preserved for the training group only (training: 1.3% vs. control: -2.3%; P = 0.01). Muscle thickness differed between groups for the immobilized (training: 2.8% vs. control: -3.2%; P = 0.01) and nonimmobilized wrist flexors (training: 7.1% vs. control: -3.7%; P = 0.02). Strength preservation was nonspecific to contraction type ( P = 0.69, [Formula: see text] = 0.03) yet specific to the trained flexors muscle. These findings suggest that eccentric training of the nonimmobilized limb can preserve size of the immobilized contralateral homologous muscle and strength across multiple contraction types. NEW & NOTEWORTHY Unilateral strength training preserves strength, muscle thickness, and muscle cross-sectional area in an opposite immobilized limb. The preservation of size and strength was confined to the trained homologous muscle group. However, strength was preserved across multiple contraction types.

Measuring balance confidence after spinal cord injury: the reliability and validity of the Activities-specific Balance Confidence Scale.

CONTEXT/OBJECTIVE: The study objectives were to evaluate the test-retest reliability, convergent validity, and discriminative validity of the Activities-specific Balance Confidence (ABC) scale in individuals with incomplete spinal cord injury (iSCI). DESIGN: Prospective, cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Twenty-six community-dwelling individuals with chronic iSCI (20 males, 59.7 + 18.9 years old) and 26 age- and sex-matched able-bodied (AB) individuals participated. INTERVENTIONS: None. OUTCOME MEASURES: Measures of balance and gait were collected over two days. Clinical measures included the ABC scale, Mini-Balance Evaluation System's Test, 10-meter Walk Test, SCI Functional Ambulation Profile, manual muscle testing of lower extremity muscles, and measures of lower extremity proprioception and cutaneous pressure sensitivity. Biomechanical measures included the velocity and sway area of centre of pressure (COP) movement during quiet standing. RESULTS: The ABC scale demonstrated high test-retest reliability (intraclass correlation coefficient = 0.93) among participants with iSCI. The minimal detectable change was 14.87%. ABC scale scores correlated with performance on all clinical measures (ρ=0.60-0.80, P<0.01), with the exception of proprioception and cutaneous pressure sensitivity (P=0.20-0.70), demonstrating convergent validity. ABC scale scores also correlated with overall COP velocity (ρ=-0.69, P<0.001) and COP velocity in the anterior-posterior direction (ρ=-0.71, P<0.001). Participants with iSCI scored significantly lower on the ABC scale than the AB participants (P<0.001), and the area under the receiver operating characteristic curve was 0.95, demonstrating discriminative validity. CONCLUSION: The ABC scale is a reliable and valid measure of balance confidence in community-dwelling, ambulatory individuals with chronic iSCI.