Validation of Linear and Nonlinear Gait Variability Measures Derived From a Smartphone System Compared to a Gold-Standard Footswitch System During Overground Walking.

Smartphones, with embedded accelerometers, may be a viable method to monitor gait variability in the free-living environment. However, measurements estimated using smartphones must first be compared to known quantities to ensure validity. This study assessed the validity and reliability of smartphone-derived gait measures compared to a gold-standard footswitch system during overground walking. Seventeen adults completed three 8-minute overground walking trials during 3 separate visits. The stride time series was calculated as the time difference between consecutive right heel contact events within the footswitch and smartphone-accelerometry signals. Linear (average stride time, stride time standard deviation, and stride time coefficient of variation) and nonlinear (fractal scaling index, approximate entropy, and sample entropy) measures were calculated for each stride time series. Bland-Altman plots with 95% limits of agreement assessed agreement between systems. Intraclass correlation coefficients assessed reliability across visits. Bland-Altman plots revealed acceptable limits of agreement for all measures. Intraclass correlation coefficients revealed good-to-excellent reliability for both systems, except for fractal scaling index, which was moderate. The smartphone system is a valid method and performs similarly to gold-standard research equipment. These findings suggest the development and implementation of an inexpensive, easy-to-use, and ubiquitous telehealth instrument that may replace traditional laboratory equipment for use in the free-living environment.

Gait variability, fractal dynamics, and statistical regularity of treadmill and overground walking recorded with a smartphone.

BACKGROUND: The nonlinear variability present during steady-state gait may provide a signature of health and showcase one's walking adaptability. Although treadmills can capture vast amounts of walking data required for estimating variability within a small space, gait patterns may be misrepresented compared to an overground setting. Smartphones may provide a low-cost and user-friendly estimate of gait patterns among a variety of walking settings. However, no study has investigated differences in gait patterns derived from a smartphone between treadmill walking (TW) and overground walking (OW). RESEARCH QUESTION: This study implemented a smartphone accelerometer to compare differences in temporal gait variability and gait dynamics between TW and OW. METHODS: Sixteen healthy adults (8F; 24.7 ± 3.8 years) visited the laboratory on three separate days and completed three 8-minute OW and three TW trials, at their preferred speed, during each visit. The inter-stride interval was calculated as the time difference between right heel contact events located within the vertical accelerometery signals recorded from a smartphone while placed in participants front right pant pocket during walking trials. The inter-stride interval series was used to calculate stride time standard deviation (SD) and coefficient of variation (COV), statistical persistence (fractal scaling index), and statistical regularity (sample entropy). Two-way analysis of variance compared walking condition and laboratory visits for each measure. RESULTS: Compared to TW, OW displayed significantly (p < 0.01) greater stride time SD (0.014 s, 0.020 s), COV (1.26 %, 1.82 %), fractal scaling index (0.70, 0.79) and sample entropy (1.43, 1.63). No differences were found between visits for all measures. SIGNIFICANCE: Smartphone-based assessment of gait provides the ability to distinguish between OW and TW conditions, similar to previously established methodologies. Furthermore, smartphones may be a low-cost and user-friendly tool to estimate gait patterns outside the laboratory to improve ecological validity, with implications for free-living monitoring of gait among various populations.

Neuromuscular organization during balance-correcting responses induced with platform-translation and upper body cable-pull perturbation methods.

Balance-correcting responses are fast, accurate, and functionally- and directionally-specific. However, there remains a lack of clarity in the literature as to how balance-correcting responses are organized, perhaps due to use of various perturbation methods. This study investigated the differences in neuromuscular organization of balance-correcting responses induced with platform-translation (PLAT) and upper body cable-pull (PULL) methods. Healthy males (n = 15; age: 24.3 ± 3.0 years) underwent unexpected forward and backward PLAT and PULL perturbations of equivalent intensity. EMG of leg, thigh, and trunk anterior and posterior muscles was recorded bilaterally during forward-stepping trials. Muscle activation latencies were calculated with respect to perturbation initiation. Repeated measures ANOVAs tested for differences in muscle activation latencies between perturbation methods and body sides (anterior/posterior muscles, swing/stance limb sides); Holm-Bonferroni sequentially rejective procedure adjusted alpha during multiple comparisons. Anterior muscle activation latencies were similar between methods (∼210 ms). During PLAT trials, posterior muscles demonstrated symmetrical distal-proximal activation between 70 ms and 260 ms, bilaterally. During PULL trials, stance-limb side posterior muscles demonstrated proximal-distal activation 70-130 ms; the activation latencies (∼80 ms) were not different between the stance-limb side posterior muscles. Previous examinations of method comparisons have examined results across publications, and generally have not accounted for different stimulus characteristics. This study revealed markedly different neuromuscular organization of balance-correcting responses to two different perturbation methods that utilized, importantly, equivalent perturbation intensity. Interpretation of functional balance recovery responses requires clear understanding of the intensity and nature of the perturbation.

Evaluation of a smartphone accelerometer system for measuring nonlinear dynamics during treadmill walking: Concurrent validity and test-retest reliability.

The accelerometers embedded within smartphones may be a promising tool to capture gait patterns outside the laboratory and for extended periods of time. The current study evaluated the agreement and reliability of gait measures derived from a smartphone accelerometer system, compared to reference motion capture and footswitch systems during treadmill walking. Seventeen healthy young adults visited the laboratory on three separate days and completed three 8-minute treadmill walking trials, during each visit, at their preferred walking speed. The inter-stride interval series was calculated as the time difference between consecutive right heel contacts, located within the signals of the smartphone accelerometer, motion capture, and footswitch systems. The inter-stride interval series was used to estimate common linear gait measures and nonlinear measures, including fractal scaling index, approximate entropy, and sample entropy. Bland Altman plots with 95% limits of agreement and intraclass correlation coefficients assessed agreement and reliability, respectively. The smartphone system was found to be within the acceptable limits of agreement when compared to either reference system. The intraclass correlation coefficients values revealed moderate-to-excellent reliability for the smartphone system, with greater reliability found for linear compared to nonlinear measures and were similar to both reference systems, except for the fractal scaling index. These findings suggest the smartphone accelerometer system is a valid and reliable method for estimating linear and nonlinear gait measures during treadmill walking.

The Influence of the Relative Timing between Pole and Heel Strike on Lower Limb Loading among Young and Older Naïve Pole Walkers.

Current research is unclear with respect to whether pole walking (PW) reduces lower limb loading when compared to regular walking (RW). Contradictory findings in the literature may be related to the relative timing between pole and foot contact events, which were examined in the current study among naïve pole walkers. Fourteen young (4 F; 25.3 ± 5.4 years) and 8 older adults (4 F; 68.5 ± 3.2 years) performed PW and RW trials along a force plate embedded walkway at two different visits. The time difference between pole and foot contact during both the onset of ground contact and the peak force application was calculated. Several kinetic measures were calculated for the lower limbs and poles. A significant decrease during PW, compared to RW, was found for foot impulse (2.1%; p < 0.01), peak vertical ground reaction force (vGRF) (3.4%; p < 0.01), rate of loading (5.2%; p=0.02), and peak push-off vGRF (2.1%; p=0.01). No difference in pole loading was found between age groups and visits. No significant correlations were found between the relative timing and foot loading measures. Significant low-to-moderate negative correlations were found between peak foot and pole vGRFs (p=0.04), peak foot vGRF and pole strike impulse (p=0.01), peak foot vGRF and pole impulse (p=0.02), and peak foot push-off vGRF and pole impulse (p=0.01), suggesting that as pole loading increased, foot loading decreased. Findings suggest timing between pole and heel contact may not be related to unloading the lower limbs but may be related to other aspects of pole use since PW reduced lower limb loading.

Enhancing the odds of adopting e-learning or community-focused experiential learning as a teaching practice amongst university faculty.

Identifying the optimal approach for motivating faculty to adopt teaching innovation is important, given that broad-scale initiatives can utilize an inordinate amount of time and resources. Using a quantitative approach, we evaluate policy actions that are most strongly associated with the adoption of either e-learning or community-focused experiential learning, over a five-year period in a single institution. Comparisons between adopters and non-adopters affirm the relevance of previously documented facilitators and barriers. However, a logistic regression analysis demonstrates that actions that promote a supportive institutional culture (such as, an institutional plan, committee involvement, professional development and logistical support) as well as faculty perceptions and beliefs (i.e., "using new methods is not risky for student learning"; confidence and self-efficacy with respect to implementation), is strongly associated with the adoption of either e-learning (n = 118) or community-focused experiential learning (n = 97). In contrast, funding and professional dimensions (i.e., workload, historical precedence, and the institutional promotion of the innovation with respect to academic freedom) is weakly associated with adoption. The results not only provide a fine-grained analysis of current assumptions regarding the necessary conditions for implementing organizational change in the university context, but also suggest an approach that reinforces and sustains the adoption of teaching innovation over the long term. Theoretical and practical implications are discussed in reference to models of organizational change, faculty motivation and approaches to institutionalizing teaching innovation.

The Intersecting Influence of Age and Performance Stereotypes on Physical and Psychological Aspects of Stair Navigation in Older Adults.

Negative age-stereotypes can have widespread effects on older adult functionality; however, no research has explored psychophysical aspects of stair navigation after exposure to stereotype priming. The present study examined self-efficacy and biomechanics related to stair navigation in older adults (N = 90). Between-groups analyses revealed positively primed older adults ascended and descended the stairs significantly faster with greater velocity in the medio-lateral plane than older adults who received a negative prime or controls (p < .017). Moreover, negatively primed older adults rated their stair self-efficacy significantly lower compared with the control and positively primed groups (p < .017). These results suggest positively primed older adults can navigate stairs with more confidence, quickness, and efficiency. With implications for interventions aimed at maintaining older adult functionality, the present study highlights the potential benefits of positive age-stereotypes, especially related to challenging physical tasks.

A comparison of balance-correcting responses induced with platform-translation and shoulder-pull perturbation methods.

The understanding of reactive balance control mechanisms in humans emanates from studies utilizing a variety of perturbation methods, instructions, and sensory conditions. The use of different perturbation methods may produce method-specific balance-correcting responses. This study evaluated balance-correcting responses induced with platform-translation and shoulder-pull methods with equilibrated perturbation intensities, and whether the absence of vision affects balance-correcting responses differently between perturbation methods. Fifteen healthy young males participated. Unexpected forward and backward platform-translation and shoulder-pull perturbations were induced with eyes-open and eyes-closed. Participants were asked to behave naturally. Forward stepping trials were analyzed. Margin of stability (MOS) was calculated from the position data of reflective markers placed strategically around the body. MOS was reported at step onset and at foot contact. MOS was smaller at step onset (0.01 ± 0.01 m) and at foot contact (0.09 ± 0.01 m) during platform-translation trials and at both time points during shoulder-pull trials (0.04 ± 0.01 m and 0.17 ± 0.01 m, respectively). The absence of vision did not affect MOS at step onset. At foot contact during platform-translation with eyes-closed MOS was larger (0.11 ± 0.01 m) than with eyes-open (0.08 ± 0.01 m), but not different between eyes-open (0.17 ± 0.01 m) and eyes-closed (0.18 ± 0.01 m) during shoulder-pull. Participants required a second step to recover balance in 14% of the platform-translation and 3% of the shoulder-pull trials. During platform-translation trials participants demonstrated smaller MOS which placed them in a less favorable circumstance for balance recovery. Platform-translation appears to be more challenging than shoulder-pull perturbation in terms of balance recovery. This study underscores that caution is required when interpreting results of studies utilizing different perturbation paradigms.

Supporting sexual adjustment from the perspective of men living with spinal cord injury.

STUDY DESIGN: Descriptive phenomenological approach. OBJECTIVES: This study explored the lived experience of sexuality for men after spinal cord injury (SCI) and described the current state of tools and resources available to assist with sexual adjustment from the perspective of men living with SCI. SETTING: Men living in the community in Ontario, Canada. METHODS: Six men (age 24-49 years) with complete or incomplete SCI (C4-T12; <1-29 years post injury) participated in one individual, in-depth, standardized, open-ended interview (68-101 min). Analysis was conducted using Giorgi's method, and involved within case analysis followed by cross-case analysis. RESULTS: All participants reported that resources available to support sexual adjustment after SCI were inadequate, and the majority of men felt their healthcare providers lacked knowledge regarding, and comfort discussing sexuality after SCI. Men reported sexuality was not a priority of the rehabilitation centers and felt that healthcare providers did not understand the importance of addressing sexuality. Existing resources were described as too clinical and not necessarily relevant given changes in sensation and mobility post injury. Participants provided recommendations for the effective delivery of relevant sexual education information. CONCLUSIONS: To improve quality of life for men after SCI, suitable resources must be available to support sexual rehabilitation post injury. Future research should focus on developing strategies to facilitate discussions about sexuality between individuals with SCI and healthcare providers, and on developing resources that are effective and relevant for these men.

The effects of single versus multiple training sessions on the motor learning of two Krav Maga strike techniques, in women.

BACKGROUND: Experts of the Krav Maga (KM) self-defense system propose that KM techniques are based on simple body movements which are suggested to be learned rapidly and retained. This study investigated the acquisition, retention, and further improvement with additional training of two KM strike techniques among novice female practitioners: straight punch and defensive kick. METHODS: Sixteen healthy females (age: 23 ± 3.7 years) without any previous martial arts/self-defense experience volunteered to participate. All participants received an initial 30-min instruction session (AQ), taught by a certified KM instructor, where each technique was deconstructed into three checkpoints (defined as a component of the entire movement) for learning. Participants were divided into two groups, one of which received additional training. Several kinematic and kinetic measures were recorded at four timepoints: immediately before AQ, immediately after AQ, 5 days after AQ, and 12 days after AQ. RESULTS: Results suggest that both techniques were learned rapidly, as checkpoint performance was significantly improved after AQ. Kick velocity and impact force also increased significantly after AQ; however, these measures did not change after AQ for the punch technique. Additional training did not improve either punch or kick performance beyond that learned during AQ. CONCLUSION: The findings from this study suggest that a single training session may be sufficient to learn and retain KM strike techniques relatively permanently; and the acquisition of the kick technique may lead to concomitant improvements in kick velocity and impact force.

Evaluation of the Effects of Prescribing Gait Complexity Using Several Fluctuating Timing Imperatives.

Variability in the temporal structure of gait patterns, measured by "Fractal Index" (FI), is thought to represent abundancy of movement patterns facilitating adaptive control of walking. However we do not know how FI changes according to different walking rhythms or if this is repeatable, as needed to exploit the paradigm for rehabilitation. Fourteen healthy young adults synchronised heel contact to an auditory metronome twice each in four conditions (uncued, white noise, pink noise, and red noise) and three sessions. FI differed based on the walking condition while no effect of session was revealed. The results of this study suggest gait fractality changes systematically with different stimuli and can be consistently prescribed in a desired direction within a group of healthy young individuals.

Stepping threshold with platform-translation and shoulder-pull postural perturbation methods.

The type of balance recovery, feet-in-place or stepping, is predicated on the perturbation intensity, often defined by the combination of applied force and displacement. Few studies examined the relationship between characteristics required to produce a stepping response with one of the postural perturbation methods. The purpose of this study was to investigate the relationship between perturbation characteristics (applied force and displacement) required to elicit a forward stepping response with platform-translation and shoulder-pull methods, and to establish whether a common set of perturbation characteristics existed across both perturbation methods. Fourteen young healthy males participated. Temporally unexpected platform translations and shoulder pulls were induced by release of free weights, which fell a controlled height exerting a pull on the platform or on the participant via a shoulder harness. Participants responded with either feet-in-place or stepping responses. The force and displacement were varied to investigate the range of force-displacement combinations required to elicit stepping responses. Force-displacement combinations that elicited stepping responses were recorded and normalized to the participant's body weight (BW) and the base of support (BOS; participant's foot length). The lowest force and associated displacement that elicited stepping responses showed an inverse linear relationship during both platform-translation and shoulder-pull trials. The lowest force-displacement combination common to both perturbation methods was found to be 8.75%BW and 105%BOS, which, in the future work, could enable a direct comparison of the neuromuscular and biomechanical responses to different perturbation methods in a manner that attempts to equilibrate the perturbation stimulus across the methods.

Curling for Confidence: Psychophysical Benefits of Curling for Older Adults.

While physical activity is increasingly promoted for older adults, there is a paucity of sport promotion, which has distinct benefits from exercise and remains stereotypically associated with younger age. Curling is a moderately intense and safe sport that continues to gain popularity; however, no research has investigated psychophysical benefits of curling for older adults. The present study compares high-experience (20+ years; n = 63) and low-experience (<20 years; n = 53) curlers (aged 60+ years) with older adult noncurlers (n = 44) on measures of daily functionality, balance confidence, and perceptions of the aging process. While no significant differences were found between high- and low-experience curlers, any level of experience reported significantly better functionality, physical confidence, and aging attitudes compared to noncurlers (p ≤ .05). Although further research is necessary, the results suggest that any level of curling experience can enhance older adult psychophysical well-being, and warrants consideration for physical activity promotion and falls prevention programs.

Impact of Spasticity on Balance Control during Quiet Standing in Persons after Stroke.

BACKGROUND: Balance impairments, falls, and spasticity are common after stroke, but the effect of spasticity on balance control after stroke is not well understood. METHODS: In this cross-sectional study, twenty-seven participants with stroke were divided into two groups, based on ankle plantar flexor spasticity level. Fifteen individuals with high spasticity (Modified Ashworth Scale (MAS) score of ≥2) and 12 individuals with low spasticity (MAS score <2) completed quiet standing trials with eyes open and closed conditions. Balance control measures included centre of pressure (COP) root mean square (RMS), COP velocity, and COP mean power frequency (MPF) in anterior-posterior and mediolateral (ML) directions. Trunk sway was estimated using a wearable inertial measurement unit to measure trunk angle, trunk velocity, and trunk velocity frequency amplitude in pitch and roll directions. RESULTS: The high spasticity group demonstrated greater ML COP velocity, trunk roll velocity, trunk roll velocity frequency amplitude at 3.7 Hz, and trunk roll velocity frequency amplitude at 4.9 Hz, particularly in the eyes closed condition (spasticity by vision interaction). ML COP MPF was greater in the high spasticity group. CONCLUSION: Individuals with high spasticity after stroke demonstrated greater impairment of balance control in the frontal plane, which was exacerbated when vision was removed.

The analysis of knee joint loading during drop landing from different heights and under different instruction sets in healthy males.

BACKGROUND: Mechanical loading during exercise has been shown to promote tissue remodeling. Safe and accessible exercise may be beneficial to populations at risk of diminished bone and joint health. We examined the effect of drop height and instruction on knee loading during a drop-landing task and proposed a task that makes use of drop heights that may be appropriate for rehabilitation purposes and functional in daily life to examine transient knee joint loads. METHODS: Twenty males (22.0 ± 2.8 years) performed drop landings from 22 cm (low) and 44 cm (high) heights, each under three instructions: "land naturally" (natural), "softly" (soft), and "stiffly" (stiff). Knee compression force and external flexion moment were estimated using three-dimensional inverse dynamics and normalized to body mass. RESULTS: Peak knee compression force was larger (p < 0.001) for high (17.8 ± 0.63 N/kg) than low (14.8 ± 0.61 N/kg) heights. There was an increase (p < 0.001) in the knee compression force across soft (11.8 ± 0.40 N/kg), natural (17.0 ± 0.62 N/kg), and stiff (20.2 ± 0.67 N/kg) instructions. Peak knee flexion moment in high-natural (2.12 ± 0.08 Nm/kg) was larger (p < 0.001) than in high-soft (1.88 ± 0.08 Nm/kg), but lower than in high-stiff (2.23 ± 0.08 Nm/kg). No differences in peak knee flexion moment were observed across instructions for the low height. CONCLUSIONS: We propose a drop-landing task that creates a scalable increase in knee compression loading. The absence of increased knee flexion moment with drop from the low height, compared to high, suggests that individuals could perform the task without incremental risk of knee injury. This task could be used in future studies to examine the effect of acute bouts of mechanical loading on bone and cartilage metabolism.

Sagittal plane lumbar loading when navigating an obstacle and carrying a load.

The current study quantified lumbar loading while carrying an anterior load mass and navigating an obstacle. Eight healthy male participants walked down a walkway and crossed an obstacle under three randomised LOAD conditions; empty-box (2 KG), five kilogram (5 KG) and ten kilogram (10 KG). Each walk was assessed at two events: left foot mid-stance (LMS) and right toe-crossing (TC) to characterise any changes from approach to crossing. Measures of interest included: trunk pitch, L4/L5 joint moment, compression, joint anterior-posterior shear and erector spinae activation. Findings demonstrate that obstacle crossing extended posture by 50, 41, 44%, respectively for each carried load magnitude. Further, these results indicate that shear rather than compressive loading may be an important consideration during crossing due to increase by 8, 9, 22% from LMS to TC for each load magnitude tested. These results provide insight into sagittal lumbar loading when navigating an obstacle while carrying a load. Practitioner Summary: The risk of carrying while navigating obstacles on the lumbar spine is not completely understood. The forces at the lumbar spine while simultaneously carrying and obstacle crossing were analysed. Data indicate that carrying and obstacle crossing influence lumbar shear loads, thereby moderately increasing the relative risk at lumbar spine.

Force plate targeting has no effect on spatiotemporal gait measures and their variability in young and healthy population.

Force plate targeting has been referenced as a confounding factor in gait research, but the literature is sparse. Asking participants to target force plates is a convenient strategy to increase the number of acceptable trials, but may inadvertently alter the motor control of gait and limit external validity. This study aimed to investigate the effect of visual targeting on spatiotemporal, kinematic, and kinetic measures of gait and their variability. Young healthy participants were asked to traverse a walkway with three embedded hidden force plates. Starting from a participant-specific initial position and leading with the same foot each time, participants performed series of natural walking trials (no targeting and unaware of the hidden force plates), followed by targeting walking trials. For the targeting trials, participants were asked to step completely within the bounds of a tape outline (∼50cm×45cm), which coincided with the position of the last hidden force plate. The results demonstrated evidence of targeting during targeting trials; compared to natural walking trials, mean heel-target distance variability for targeting trials decreased progressively for the steps approaching the targeting step, reaching significance (p<0.05) for the target (41%), and post-target steps (39%). Despite visual targeting, no significant differences between targeting and natural trials were detected in spatiotemporal, kinematic, and kinetic gait measures, or the variability of the measures. When the experimental set-up was tailored to the individual participant's gait variables (step/stride length), visual targeting of the force plates appeared to have no effect on the magnitude or variability of any gait measures.

Development of a video-based technique for ambulatory monitoring of foot placement with an instrumented rollator.

OBJECTIVE: To develop a video-based system, mounted on a rollator to quantify the step width values of rollator users in the community. SUBJECTS: A total of 5 able-bodied young adults, age range 24-28 years. METHODS: A digital video camera system was mounted on the rollator frame to capture the position of the participant's feet during overground walking. A method of estimating step width from the video data was developed and evaluated against the output from a concurrently recording Vicon MX motion capture system. RESULTS: Mean step widths of the rollator and motion capture systems were 14.40 cm (standard deviation (SD) 4.64) and 14.37 cm (SD 4.34), respectively, revealing a strong level of agreement; intra-class correlation coefficient 0.999 (95% confidence interval (95% CI) 0.987-1.000; and root-mean-square difference 0.70 cm. CONCLUSION: The video-based system mounted on a rollator to collect foot placement data enabled accurate measurement of step width during rollator use. The ability to record foot placement measurements outside the laboratory setting, characterizing foot placement patterns occurring in the community, will enable research into how these assistive devices influence mobility during everyday use.

Upper limb contributions to frontal plane balance control in rollator-assisted walking.

While assisting with balance is a primary reason for rollator use, few studies have examined how the upper limbs are used for balance. This study examines upper limb contributions to balance control during rollator-assisted walking. We hypothesized that there would be an increased upper limb contribution, measured by mean vertical loading (Fz) and variation in frontal plane center-of-pressure (COPhigh), when walking balance is challenged/impaired. Experiment 1 compared straight-line and beam-walking in young adults (n = 11). As hypothesized, Fz and COPhighincreased in beam-walking compared to baseline (mean Fz: 13.7 vs. 9.1% body weight (BW), p < 0.001, RMS COPhigh: 1.35 vs. 1.07 cm, p < 0.001). Experiment 2 compared older adults who regularly use rollators (RU, n = 10) to older adult controls (CTL, n = 10). The predicted higher upper limb contribution in the RU group was not supported. However, when individuals were grouped by balance impairment, those with the lowest Berg Balance scores (< 45) demonstrated greater speed-adjusted COPhigh than those with higher scores (p = 0.013). Furthermore, greater COPhigh and Fz were correlated to greater reduction in step width, supporting the role of upper limb contributions to frontal plane balance. This work will guide studies assessing reliance on rollators by providing a basis for measurement of upper limb balance contributions.