Exploring the link between walking and lung cancer risk: a two-stage Mendelian randomization analysis

BACKGROUND

Previous observational research showed a potential link between physical activities such as walking and the risk of lung cancer. However, Mendelian randomization (MR) studies suggested there was no association between moderate to vigorous physical activity and lung cancer risk. We speculated that specific physical activities may be associated with lung cancer risk. Consequently, we conducted an MR study to examine the potential relationship between walking and the risk of lung cancer.

METHODS

We collected genetic summary data from UK Biobank. After excluding SNPs with F values less than 10 and those associated with confounding factors, we conducted a MR analysis to assess the causal effects between different types of walk and lung cancer. We also performed sensitivity analysis to validate the robustness of our findings. Finally, we analyzed the possible mediators.

RESULTS

MR analysis showed number of days/week walked for 10 + minutes was associated with a reduced risk of lung cancer risk (OR = 0.993, 95% CI = 0.987-0.998, P = 0.009). Additionally, usual walking pace was identified as a potentially significant factor in lowering the risk (OR = 0.989, 95% CI = 0.980-0.998, P = 0.015). However, duration of walks alone did not show a significant association with lung cancer risk (OR = 0.991, 95%CI = 0.977-1.005, P = 0.216). The sensitivity analysis confirmed the robustness of these findings. And number of days/week walked for 10 + minutes could affect fed-up feelings and then lung cancer risk. There was a bidirectional relationship between usual walking pace and sedentary behaviors (time spent watching TV).

CONCLUSION

The study unveiled a genetically predicted causal relationship between number of days/week walked for 10 + minutes, usual walking pace, and the risk of lung cancer. The exploration of potential mediators of walking phenotypes and their impact on lung cancer risk suggests that specific physical activities may reduce the risk of lung cancer.

Sedentary behaviour and related factors in people with multiple sclerosis

BACKGROUND

Sedentary behaviour is a major problem in persons with multiple sclerosis (pwMS). However, little is known about the related factors of sedentary behaviour in MS. Our study aimed to examine the association between sedentary behaviour and physical activity level, fear of falling, and fatigue.

METHOD

Demographic and clinical data have been recorded. Sedentary behaviour was assessed with the Marshall Sitting Questionnaire, physical activity level was evaluated with the Godin Leisure Time Exercise Questionnaire, fear of falling was evaluated with the Fall Efficacy Scale International, and fatigue was evaluated with the modified fatigue impact scale (MFIS). The Timed 25-Foot Walk, 6-Minute Walk Test, Timed Up and Go Test, and 12-Item Multiple Sclerosis Walking Scale were also used to assess walking and perceived walking disability.

RESULTS

We recruited 71 pwMS [49 were female (69 %), mean age:38.08 years, median EDSS:1.5]. The mean daily sitting time was 593.54 min (∼10 h). No significant correlation was found between sitting times and demographics, leisure time physical activity, fear of falling, walking, perceived walking disability, and neurological disability level (p > 0.05). Logistic regression analysis indicated that being male increased the risk of sedentary behaviour by 3.08 times, being employed increased the risk of sitting by 4.65 times, and each point increase in MFIS scores resulted in a 1.03-fold elevation in the odds of prolonged sitting.

CONCLUSION

The fact that pwMS, even with a mild disability spend almost 10 h sitting highlights the significance of sedentary behaviour in this population. Developing strategies to address modifiable factors, such as fatigue, may be effective in reducing sedentary behaviour.

Implementation of artificial intelligence for the detection of cutaneous melanoma within a primary care setting: prevalence and types of skin cancer in outdoor enthusiasts

Background

There is enthusiasm for implementing artificial intelligence (AI) to assist clinicians detect skin cancer. Performance metrics of AI from dermoscopic images have been promising, with studies documenting sensitivity and specificity values equal to or superior to specialists for the detection of malignant melanomas (MM). Early detection rates would particularly benefit Australia, which has the worlds highest incidence of MM per capita. The detection of skin cancer may be delayed due to late screening or the inherent difficulty in diagnosing early skin cancers which often have a paucity of clinical features and may blend into sun damaged skin. Individuals who participate in outdoor sports and recreation experience high levels of intermittent ultraviolet radiation (UVR), which is associated with the development of skin cancer, including MM. This research aimed to assess the prevalence of skin cancer in individuals who regularly participate in activities outdoors and to report the performance parameters of a commercially available AI-powered software to assess the predictive risk of MM development.

Methods

Cross-sectional study design incorporating a survey, total body skin cancer screening and AI-embedded software capable of predictive scoring of queried MM.

Results

A total of 423 participants consisting of surfers (n = 108), swimmers (n = 60) and walkers/runners (n = 255) participated. Point prevalence for MM was highest for surfers (6.48%), followed by walkers/runners (4.3%) and swimmers (3.33%) respectively. When compared to the general Australian population, surfers had the highest odds ratio (OR) for MM (OR 119.8), followed by walkers/runners (OR 79.74), and swimmers (OR 61.61) rounded out the populations. Surfers and swimmers reported comparatively lower lifetime hours of sun exposure (5,594 and 5,686, respectively) but more significant amounts of activity within peak ultraviolet index compared with walkers/runners (9,554 h). A total of 48 suspicious pigmented lesions made up of histopathology-confirmed MM (n = 15) and benign lesions (n = 33) were identified. The performance of the AI from this clinical population was found to have a sensitivity of 53.33%, specificity of 54.44% and accuracy of 54.17%.

Conclusions

Rates of both keratinocyte carcinomas and MM were notably higher in aquatic and land-based enthusiasts compared to the general Australian population. These findings further highlight the clinical importance of sun-safe protection measures and regular skin screening in individuals who spend significant time outdoors. The use of AI in the early identification of MM is promising. However, the lower-than-expected performance metrics of the AI software used in this study indicated reservations should be held before recommending this particular version of this AI software as a reliable adjunct for clinicians in skin imaging diagnostics in patients with potentially sun damaged skin.

Cumulated ambulation score as predictor of postoperative mobility in patients with proximal femur fractures

INTRODUCTION

The cumulated ambulation score (CAS) has been developed as an index for evaluating mobility in the early postoperative period. This study aimed to estimate the association between CAS and independent ambulation after surgery for proximal femur fractures.

MATERIALS AND METHODS

This retrospective cohort study included 223 elderly patients who underwent surgery for proximal femur fractures and had independent ambulation before the injury. Multivariable logistic regression analyses with cognitive impairment, pre-injury Barthel index, and CAS as the test variables were used to predict independent ambulation at 2 weeks (model 1) and 3 months (model 2) postoperatively. We established scoring systems based on the modeling results.

RESULTS

The number of patients with independent ambulation at 2 weeks and 3 months postoperatively was 115 and 169, respectively. Univariate analysis showed that the CAS was significantly associated with independent ambulation at 2 weeks and 3 months postoperatively. Multivariable analysis showed that models 1 and 2 had good predictive accuracies, with areas under the receiver-operating characteristic curve of 0.855 and 0.868, respectively. Among the explanatory variables, only the CAS in model 2 was not significantly associated with the postoperative ambulatory ability. Scoring systems for both models 1 and 2 also had good predictive accuracies, with cut-off scores of 3.5 for model 1 and 9.5 for model 2.

CONCLUSIONS

The CAS predicted independent ambulation at 2 weeks postoperatively; however, this relationship was limited at 3 months postoperatively. Therefore, the CAS may help estimate independent ambulation at discharge from an acute-care hospital.

Association between age-related hearing loss and gait disorders in older fallers

INTRODUCTION

Falls are associated with hearing loss, which might be explained by the onset of gait disorders. The objective of this study was to examine the association between Age-Related Hearing Loss (ARHL) and gait disorders assessed with GAITrite^® walkway in a population of fallers aged 75 and over while accounting for the vestibular function.

METHODS

We examined data from 53 older patients (mean 84.2 ± 5.1 years; 64% women) included after a GAITrite^® walkway assessment together with hearing and vestibular tests. People with high-frequency hearing loss, higher than 10% of the age and sex-matched population with the worst hearing, composed untimely ARHL group (n = 30), whereas all others had expected ARHL (n = 23). Presbyvestibulopathy was assessed accordingly to Barany Society criteria.

RESULTS

After adjustment for age, sex, body mass index, Mini-Mental State Examination score and presbyvestibulopathy, we found an increase in stride length mean in the untimely ARHL group (p = 0.046), but no between-group differences in stride length variability, cadence or velocity. Untimely ARHL was not associated with presbyvestibulopathy.

CONCLUSIONS

Untimely ARHL in older fallers was not associated with gait disorders in the studied population.

Angulation vs translation of transtibial prosthetic socket: their difference analyzed by socket reaction moments

BACKGROUND

Previous studies investigated the effects of alignment changes in transtibial prostheses on socket reaction moments. However, the effects of angular and translational alignment changes with equal displacement between the foot and the socket were not directly compared.

RESEARCH QUESTIONS

What are the different effects of angular and translational alignment changes in transtibial prostheses?

METHODS

Ten individuals with transtibial prostheses participated in the measurement of temporo-spatial parameters, socket reaction moments, and their timings under nine alignment conditions (3° flexion/extension, anterior/posterior translation, 6° adduction/abduction, medial/lateral translation, and baseline). The displacement of the prosthetic feet was set to be equal between the angular and translational changes.

RESULTS

No significant changes in walking speed were found. Similar effects were observed in the magnitudes, but not in timing, of the moments under angular and translational changes in the sagittal plane (p < 0.01 for the differences in peak extension moment among anterior translation, baseline, and extension conditions, and in peak flexion moment among anterior translation, baseline, and extension conditions). In the coronal plane, similar effects were found in the magnitudes of the moments in the early stance (p < 0.01 at 5 %, 20 %, and 75 % stance). A significant difference in magnitude was observed in the late stance (p < 0.01 between adduction and medial translation conditions).

SIGNIFICANCE

The timing of the socket reaction moment may be different in the sagittal plane, while the magnitudes of the socket reaction moment in the late stance may be different in the coronal plane between the angular and translational alignment changes.

Determining Objective Parameters to Assess Gait Quality in Franches-Montagnes Horses for Ground Coverage and Over-Tracking - Part 1: At Walk

Ground coverage and over-tracking are two gait quality traits describing the forward movement of the front respectively the hind limbs in relation to stride length and over-tracking distance. To investigate the complex interplay of different movement patterns in ground coverage and over-tracking, limb and body kinematics of 24 Franches-Montagnes (FM) stallions were measured with 3D optical motion capture (OMC) on a treadmill during an incremental speed test at the walk (1.4-2.0 m/s). The significance and amount of explained variance of kinematic parameters on stride length and over-tracking distance were estimated using linear mixed-effect models, with speed and horse as random effects. Two separate models were tested: a full model with all parameters measurable by OMC, and a reduced model with a subset of parameters also measurable with inertial measurement units (IMUs). The kinematic parameters were correlated to the subjective scores from six breeding experts to interpret their external validity. The parameter for ground coverage at the walk, explaining most of the variance in stride length, were the maximal forelimb retraction angle (11%) measured with OMC, and the range of pelvis pitch (10%) if measuring with IMUs. The latter was also the most relevant for quantifying over-tracking, explaining 24% to 33% of the variance in the over-tracking distance. The scores from most breeding experts were significantly correlated (r ≥ |0.41|) with the fore- and hind limb protraction angles, which reflect the textual definition of ground coverage and over-tracking. Both gait quality traits can be objectively quantified using either OMC or IMUs.

Individuals with fibromyalgia have a different gait pattern and a reduced walk functional capacity: a systematic review with meta-analysis

Background

The aim of the present study was to perform a systematic review and meta-analysis comparing walking test performance and gait pattern between individuals with and without fibromyalgia (FM).

Methodology

This systematic review was registered in PROSPERO with the following reference: CRD42018116200.The search for the scientific articles in this systematic review was carried out using the MEDLINE, SCOPUS, PEDRO, CINHAL and WEB OF SCIENCE databases. A combination of three conceptual groups of terms was used: (1) fibromyalgia; (2) walk (performance) tests; and (3) gait analysis. The included articles were analyzed for both functional and pattern of walking data of patients with FM. In order to provide a better estimate of the difference between individuals with and without FM on gait, a meta-analysis was performed on the 6MWT (6-minute walk test).

Results

Thirty-six studies were analyzed, with a total population of 4.078 participants (3.369 FM and 709 individuals without FM). From a functional point of view, the 6MWT distance covered by the group of individuals without FM was significantly greater than that of the individuals with FM in all the analyzed studies. In addition, when comparing the results obtained in the gait pattern analysis, it was observed that individuals with FM walked slower, with a shorter stride length and lower cadence compare to individuals without FM.

Conclusions

It is possible to affirm that individuals with FM perform walking tests differently than individuals without FM. It was observed that individuals with FM walk performing a cycle of shorter length and lower frequency, producing a slower gait, which results in a shorter distance traveled, in the same period of time, with respect to healthy subjects.

Experimental recommendations for estimating lower extremity loading based on joint and activity

Researchers often estimate joint loading using musculoskeletal models to solve the inverse dynamics problem. This approach is powerful because it can be done non-invasively, however, it relies on assumptions and physical measurements that are prone to measurement error. The purpose of this study was to determine the impact of these errors - specifically, segment mass and shear ground reaction force - have on analyzing joint loads during activities of daily living. We performed traditional marker-based motion capture analysis on 8 healthy adults while they completed a battery of exercises on 6 degree of freedom force plates. We then scaled the mass of each segment as well as the shear component of the ground reaction force in 5% increments between 0 and 200% and iteratively performed inverse dynamics calculations, resulting in 1681 mass-shear combinations per activity. We compared the peak joint moments of the ankle, knee, and hip at each mass-shear combination to the 100% mass and 100% shear combination to determine the percent error. We found that the ankle was most resistant to changes in both mass and shear and the knee was resistant to changes in mass while the hip was sensitive to changes in both mass and shear. These results can help guide researchers who are pursuing lower-cost or more convenient data collection setups.

Gait in patients with axial spondyloarthritis: A systematic review of the literature

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease predominantly affecting the axial skeleton. axSpA includes radiographic (i.e., ankylosing spondylitis (AS)) and non-radiographic forms (nr-axSpA). Although recent studies have reported that patients with AS have impaired gait, axSpA's consequences on gait remain unknown. The present review's objectives were to identify: 1) how gait is assessed in patients with axSpA, and 2) what the gait characteristics are of patients with axSpA. This systematic review's protocol was registered in the Prospero database (CRD42020128509). Three databases were systematically searched using keywords related to axSpA and gait. Two independent reviewers selected the articles and extracted the data. The search revealed two hundred titles and abstracts, and two articles were finally included in this review, comprising a total of 132 patients with axSpA. One of the included studies used the 6 m maximum gait velocity test (axSpA: 2.2 ± 0.5 m/s), and the other used the six-minute walk test (axSpA: 414 ± 106 m). Neither study involved a control group to compare gait. Only two published studies assessed the gait performance of patients with axSpA using clinical tests. Furthermore, neither of them compared gait performance to healthy controls or differentiated gait between the AS and nr-axSpA forms of axSPA. The present literature review highlights the need for future research to learn more about how gait is impaired in different types of patients with axSpA.

Low-frequency STN-DBS provides acute gait improvements in Parkinson's disease: a double-blinded randomised cross-over feasibility trial

Background

Some people with Parkinson’s disease (PD) report poorer dynamic postural stability following high-frequency deep brain stimulation of the subthalamic nucleus (STN-DBS), which may contribute to an increased falls risk. However, some studies have shown low-frequency (60 Hz) STN-DBS improves clinical measures of postural stability, potentially providing support for this treatment. This double-blind randomised crossover study aimed to investigate the effects of low-frequency STN-DBS compared to high-frequency stimulation on objective measures of gait rhythmicity in people with PD.

Methods

During high- and low-frequency STN-DBS and while off-medication, participants completed assessments of symptom severity and walking (e.g., Timed Up-and-Go). During comfortable walking, the harmonic ratio, an objective measures of gait rhythmicity, was derived from head- and trunk-mounted accelerometers to provide insight in dynamic postural stability. Lower harmonic ratios represent less rhythmic walking and have discriminated people with PD who experience falls. Linear mixed model analyses were performed on fourteen participants.

Results

Low-frequency STN-DBS significantly improved medial–lateral and vertical trunk rhythmicity compared to high-frequency. Improvements were independent of electrode location and total electrical energy delivered. No differences were noted between stimulation conditions for temporal gait measures, clinical mobility measures, motor symptom severity or the presence of gait retropulsion.

Conclusions

This study provides evidence for the acute benefits of low-frequency stimulation for gait outcomes in STN-DBS PD patients, independent of electrode location. However, the perceived benefits of this therapy may be diminished for people who experienced significant tremor pre-operatively, as lower frequencies may cause these symptoms to re-emerge.

Trial registration: This study was prospectively registered with the Australian and New Zealand Clinical Trials Registry on 5 June 2018 (ACTRN12618000944235).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12984-021-00921-4.

Effect of robotic-assisted gait training on objective biomechanical measures of gait in persons post-stroke: a systematic review and meta-analysis

BACKGROUND

Robotic-Assisted Gait Training (RAGT) may enable high-intensive and task-specific gait training post-stroke. The effect of RAGT on gait movement patterns has however not been comprehensively reviewed. The purpose of this review was to summarize the evidence for potentially superior effects of RAGT on biomechanical measures of gait post-stroke when compared with non-robotic gait training alone.

METHODS

Nine databases were searched using database-specific search terms from their inception until January 2021. We included randomized controlled trials investigating the effects of RAGT (e.g., using exoskeletons or end-effectors) on spatiotemporal, kinematic and kinetic parameters among adults suffering from any stage of stroke. Screening, data extraction and judgement of risk of bias (using the Cochrane Risk of bias 2 tool) were performed by 2-3 independent reviewers. The Grading of Recommendations Assessment Development and Evaluation (GRADE) criteria were used to evaluate the certainty of evidence for the biomechanical gait measures of interest.

RESULTS

Thirteen studies including a total of 412 individuals (mean age: 52-69 years; 264 males) met eligibility criteria and were included. RAGT was employed either as monotherapy or in combination with other therapies in a subacute or chronic phase post-stroke. The included studies showed a high risk of bias (n = 6), some concerns (n = 6) or a low risk of bias (n = 1). Meta-analyses using a random-effects model for gait speed, cadence, step length (non-affected side) and spatial asymmetry revealed no significant differences between the RAGT and comparator groups, while stride length (mean difference [MD] 2.86 cm), step length (affected side; MD 2.67 cm) and temporal asymmetry calculated in ratio-values (MD 0.09) improved slightly more in the RAGT groups. There were serious weaknesses with almost all GRADE domains (risk of bias, consistency, directness, or precision of the findings) for the included outcome measures (spatiotemporal and kinematic gait parameters). Kinetic parameters were not reported at all.

CONCLUSION

There were few relevant studies and the review synthesis revealed a very low certainty in current evidence for employing RAGT to improve gait biomechanics post-stroke. Further high-quality, robust clinical trials on RAGT that complement clinical data with biomechanical data are thus warranted to disentangle the potential effects of such interventions on gait biomechanics post-stroke.

Effect of arm swaying from wearing a self-applied arm sling with a loop on walking and other mobility skills

[Purpose] This study aimed to investigate how wearing a self-applied arm sling with a loop during rising, standing up, and walking affects the magnitude of arm swaying and activities among elderly individuals compared with wearing a triangular bandage. [Participants and Methods] Fourteen elderly individuals participated in the study. The methods involved attaching a triaxial accelerometer to an arm wearing a triangular bandage or arm sling and conducting a 5-m walk test, sit-to-stand test five times, and rising up. We then calculated the time required for each action, and the acceleration, vibration intensity, and coefficient of variation of the affected arm; these were then compared between the two groups. [Results] All the participants were able to put on the arm sling with a loop. The step rate with a triangular bandage was higher than that without one. Swaying in the front/back direction in standing up was greater with the triangular bandage. [Conclusion] The self-applied arm sling with a loop was shown to have less front/back swaying during standing up. Wearing a triangular bandage may have narrowed the stride and increased the step rate due to discomfort. This result should be applied with caution, because it remains unclear whether arm slings with loops are advantageous.

Inertial motion capture validation of 3D knee kinematics at various gait speed on the treadmill with a double-pose calibration

BACKGROUND

Inertial motion capture (IMC) is rapidly gaining in popularity to evaluate gait in clinical settings. Previous examinations of IMC knee kinematics were often limited to the sagittal plane and IMC calibration has not been thoroughly investigated.

RESEARCH QUESTION

The objective was to validate IMC 3D knee kinematics calibrated with a double-pose during gait with reference to optical motion capture (OMC). The hypotheses are that IMC can estimate adequately knee kinematics and that both systems will detect similarly the changes with gait speed.

METHODS

Twenty-four healthy participants walked on the treadmill at gait speed of 0.6, 0.8, 1.0 and 1.2 m/s. Knee kinematics were obtained simultaneously with two magnetic and inertial measurement units and passive markers fixed on the KneeKG system. OMC was calibrated with a functional anatomical approach and the IMC with a double-pose.

RESULTS

Root mean square differences of the two systems yielded 3-6° for knee flexion, adduction and external rotation. Knee kinematics were more similar during the stance phase than the swing phase. Gait speed showed a significant progressive effect on the three knee angles that was similarly detected by the two systems.

SIGNIFICANCE

IMC 3D knee kinematics can be obtained independently with a simple calibration and only two magnetic and inertial measurement units at an acceptable level of error especially during stance.

The exoskeleton expansion: improving walking and running economy

Since the early 2000s, researchers have been trying to develop lower-limb exoskeletons that augment human mobility by reducing the metabolic cost of walking and running versus without a device. In 2013, researchers finally broke this 'metabolic cost barrier'. We analyzed the literature through December 2019, and identified 23 studies that demonstrate exoskeleton designs that improved human walking and running economy beyond capable without a device. Here, we reviewed these studies and highlighted key innovations and techniques that enabled these devices to surpass the metabolic cost barrier and steadily improve user walking and running economy from 2013 to nearly 2020. These studies include, physiologically-informed targeting of lower-limb joints; use of off-board actuators to rapidly prototype exoskeleton controllers; mechatronic designs of both active and passive systems; and a renewed focus on human-exoskeleton interface design. Lastly, we highlight emerging trends that we anticipate will further augment wearable-device performance and pose the next grand challenges facing exoskeleton technology for augmenting human mobility.

The impact of shoe flexibility on gait, pressure and muscle activity of young children. A systematic review

Background

There is limited evidence of shoe impact in younger children, particularly in the context of immature gait patterns. It is unclear if the impact from shoes in younger children is similar to what has been seen in older children. This systematic review aims to identify any impact of shoe features on younger children’s gait, and if there are any differences between shoe sole flexibility compared to barefoot.

Methods

Study inclusion criteria included: typically developing children aged ≤6 years; comparison of barefoot and shod conditions (walking and/or running) with shoe features or style of shoe described; sample size > 1. Novelty types of footwear were excluded, as was any mention of in shoe support or modifications. Studies were located from six databases. Study methodology was assessed using the McMasters critical review form. Sample size weighted standardized mean differences (SMD) and 95% confidence intervals (CI) were calculated.

Results

Four studies were included. Participant age ranged from 15.2 to 78.7 months, with 262 participants across all studies. All studies had limited methodological bias based on their design type. Compared to barefoot walking, shoes increased velocity, step time and step length. Shod walking decreased cadence. Peak plantar pressure was generally lower in the stiff shoe design and there was a higher peak plantar pressure in the Ultraflex shoes. No studies were found investigating muscle activation.

Conclusions

Shoes affect younger children’s gait in spatiotemporal gait aspects, similar to those seen in older children. There is limited evidence on effects of particular shoe features such as sole hardness, on gait, and no evidence of any changes in muscle activation patterns. Further research is required to evaluate the impact of different types of shoe and shoe features in this population to provide clinical advice on the type of shoe that is appropriate in this age group.

Optimal shear cushion stiffness at different gait speeds

The present study quantified the effects of different shear cushion stiffness on the time to peak posterior shear force (TPPSF), peak posterior shear force (PPSF), average posterior loading rate (APLR), and maximum posterior loading rate (MPLR) at different locomotion speeds using a custom-made sliding platform, as well as to identify the optimal stiffness of shear cushion. Twelve male collegiate students (heel-strikers) performed walking at 1.5 m/s, jogging at 2.5 m/s, and running at 3.5 m/s. A custom-made sliding platform was used to provide the different shear cushion conditions. The shear cushion conditions were fixed (a fixed platform; control group), stiff (K = 2746 N/m), medium stiff (K = 2256 N/m), medium soft (K = 1667 N/m), and soft (K = 1079 N/m). The results showed that all cushion conditions produced sliding displacement and delayed the TPPSF during walking, jogging, and running compared with fixed condition. The APLR and MPLR were lowest under medium soft condition during walking, while the PPSF was similar between medium soft and soft conditions. For jogging and running, the PPSF as well as APLR and MPLR were the lowest under medium stiff condition except the maximum PLR was similar among stiff, medium stiff, and medium soft conditions during running. In conclusion, shear cushion produces appropriate sliding displacement and effectively delays the TPPSF to provide the musculoskeletal system additional time to absorb the impact and reduce loading. The present study demonstrates optimal stiffness of shear cushion at different traveling speeds and suggests that a shear cushion system can be applied in future designs of cushion structures.

A meta-analysis: Parkinson's disease and dual-task walking

A growing body of literature has reported the effects of dual tasks on gait performance in people with Parkinson's disease (PD). The purpose of this meta-analysis was to synthesize the existing literature and quantify the overall influence of dual tasks on gait performance in PD. A thorough literature search was conducted, and 19 studies met the stringent inclusion criteria. Two moderator variable analyses examined the dual-task effect by: (a) mean single-task gait speed for each study (≥1.1 m/s or < 1.1 m/s), and (b) the type of dual task (arithmetic, language, memory, and motor). Three main findings were revealed by a random effects model analysis. First, a strong negative effect of dual tasks on walking performance (SMD = -0.68) confirmed that gait performance is adversely affected by dual tasks in people with PD. Second, the significant negative effect of dual tasks is present regardless of the mean level of single-task gait speed in a study. Third, dual-task walking speed deteriorates regardless of the type of dual task. Together, these results confirm that dual tasks severely affect walking performances in people with PD.

The effects of alignment of an articulated ankle-foot orthosis on lower limb joint kinematics and kinetics during gait in individuals post-stroke

Mechanical tuning of an ankle-foot orthosis (AFO) is important in improving gait in individuals post-stroke. Alignment and resistance are two factors that are tunable in articulated AFOs. The aim of this study was to investigate the effects of changing AFO ankle alignment on lower limb joint kinematics and kinetics with constant dorsiflexion and plantarflexion resistance in individuals post-stroke. Gait analysis was performed on 10 individuals post-stroke under four distinct alignment conditions using an articulated AFO with an ankle joint whose alignment is adjustable in the sagittal plane. Kinematic and kinetic data of lower limb joints were recorded using a Vicon 3-dimensional motion capture system and Bertec split-belt instrumented treadmill. The incremental changes in the alignment of the articulated AFO toward dorsiflexion angles significantly affected ankle and knee joint angles and knee joint moments while walking in individuals post-stroke. No significant differences were found in the hip joint parameters. The alignment of the articulated AFO was suggested to play an important role in improving knee joint kinematics and kinetics in stance through improvement of ankle joint kinematics while walking in individuals post-stroke. Future studies should investigate long-term effects of AFO alignment on gait in the community in individuals post-stroke.

The effects of an articulated ankle-foot orthosis with resistance-adjustable joints on lower limb joint kinematics and kinetics during gait in individuals post-stroke

BACKGROUND

Resistance is a key mechanical property of an ankle-foot orthosis that affects gait in individuals post-stroke. Triple Action® joints allow independent adjustment of plantarflexion resistance and dorsiflexion resistance of an ankle-foot orthosis. Therefore, the aim of this study was to investigate the effects of incremental changes in dorsiflexion and plantarflexion resistance of an articulated ankle-foot orthosis with the Triple Action joints on lower limb joint kinematics and kinetics in individuals post-stroke during gait.

METHODS

Gait analysis was performed on 10 individuals who were post-stroke under eight resistance settings (four plantarflexion and four dorsiflexion resistances) using the articulated ankle-foot orthosis. Kinematic and kinetic data of the lower limb joints were recorded while walking using a three-dimensional Vicon motion capture system and a Bertec split-belt instrumented treadmill.

FINDINGS

Repeated measures analysis of variance revealed that adjustment of plantarflexion resistance had significant main effects on the ankle (P < 0.001) and knee (P < 0.05) angles at initial contact, while dorsiflexion resistance had significant (P < 0.01) main effects on the peak dorsiflexion angle in stance. Plantarflexion and dorsiflexion resistance adjustments appeared to affect the peak knee flexor moment in stance, but no significant main effects were revealed (P = 0.10). Adjustment of plantarflexion resistance also demonstrated significant (P < 0.05) main effects in the peak ankle positive power in stance.

INTERPRETATION

This study demonstrated that the adjustments of resistance in the ankle-foot orthosis with the Triple Action joints influenced ankle and knee kinematics in individuals post-stroke. Further work is necessary to investigate the long-term effects of the articulated ankle-foot orthoses on their gait.

peak power minimization

A simple model is developed to find vertical force profiles and stance durations that minimize either limb mechanical work or peak power demands during bipedal locomotion. The model predicts that work minimization is achieved with a symmetrical vertical force profile, consistent with previous models and observations of adult humans, and data for 487 participants (predominantly 11–18 years old) required to walk at a range of speeds at a Science Fair. Work minimization also predicts the discrete walk-run transition, familiar for adult humans. In contrast, modeled peak limb mechanical power demands are minimized with an early skew in vertical ground reaction force that increases with speed, and stance durations that decrease steadily with speed across the work minimizing walk-run transition speed. The peak power minimization model therefore predicts a continuous walk-run gait transition that is quantitatively consistent with measurements of younger children (1.1–4.7 years) required to locomote at a range of speeds but free to select their own gaits.

Modulation of joint and limb mechanical work in walk-to-run transition steps in humans

Surprisingly little information exists of the mechanics in the steps initializing the walk-to-run transition (WRT) in humans. Here, we assess how mechanical work of the limbs (vertical and horizontal) and the individual joints (ankle, knee and hip) are modulated as humans transition from a preferred constant walking velocity (v_walk) to a variety of running velocities (v_run; ranging from a sprint to a velocity slower than v_walk). WRTs to fast v_run values occur nearly exclusively through positive horizontal limb work, satisfying the goal of forward acceleration. Contrary to our hypothesis, however, positive mechanical work remains above that at v_walk even when decelerating. In these WRTs to slow running, positive mechanical work is remarkably high and is comprised nearly exclusively of vertical limb work. Vertical-to-horizontal work modulation may represent an optimization for achieving minimal and maximal v_run, respectively, while fulfilling an apparent necessity for energy input when initiating WRTs. Net work of the WRT steps was more evenly distributed across the ankle, knee and hip joints than expected. Absolute positive mechanical work exhibited a clearer modulation towards hip-based work at high accelerations (>3 m s^-2), corroborating previous suggestions that the most proximal joints are preferentially recruited for locomotor tasks requiring high power and work production. In WRTs to very slow v_run values, high positive work is nevertheless done at the knee, indicating that modulation of joint work is not only dependent on the amount of work required but also the locomotor context.

Long term consistency and location specificity of equine gluteus medius muscle activity during locomotion on the treadmill

Background

The equine m. gluteus medius (GM) is the largest muscle of the horse, its main movement function is the extension of the hip joint. The objective of the present study was to measure equine GM activity in three adjacent locations on GM during walk and trot on a treadmill, in order to document potential differences. Fourteen Haflinger mares were measured using surface electromyography and kinematic markers to identify the motion cycles on three occasions over 16 weeks. The electrodes were placed on left and right gluteus medius muscle over the middle of its widest part and 5 cm lateral and medial of it. For data processing, electrical activity was normalised to its maximum value and timing was normalised to the motion cycle. A Gaussian distribution approach was used to determine up to 10 modes of focussed activity, and results were analysed separately for stance and swing phase of the ipsilateral hindlimb.

Results

Fair reliability was found for mean mode values (Cronbach’s alpha = 0.66) and good reliability was found for mean mode locations (Cronbach’s alpha = 0.71) over the three data collection days. The magnitude of muscle activity identified as mean mode value was much larger at trot than at walk, and mean mode value was significantly different between stance phases of walk and trot for all electrode positions (p < 0.01). The pattern of muscle activity identified as mean mode location was significantly different for walk and trot at all electrode positions, both during stance and swing phases (p < 0.001). This indicates the different timing pattern between the gaits. Results of the three electrode positions on the same muscle during each gait were not significantly different when comparing the same measurement.

Conclusions

The middle of the equine GM does not show any indication of functional differentiation during walk and trot on a treadmill; this might be due to lack of segmentation as such, or due to lack of need for segmented use for these very basic main tasks of the muscle. The reliability of the sEMG measurements over several weeks was fair to good, an indication for the robustness of the methodology.

Bipedal gait model for precise gait recognition and optimal triggering in foot drop stimulator: a proof of concept

Electrical stimulators are often prescribed to correct foot drop walking. However, commercial foot drop stimulators trigger inappropriately under certain non-gait scenarios. Past researches addressed this limitation by defining stimulation control based on automaton of a gait cycle executed by foot drop of affected limb/foot only. Since gait is a collaborative activity of both feet, this research highlights the role of normal foot for robust gait detection and stimulation triggering. A novel bipedal gait model is proposed where gait cycle is realized as an automaton based on concurrent gait sub-phases (states) from each foot. The input for state transition is fused information from feet-worn pressure and inertial sensors. Thereafter, a bipedal gait model-based stimulation control algorithm is developed. As a feasibility study, bipedal gait model and stimulation control are evaluated in real-time simulation manner on normal and simulated foot drop gait measurements from 16 able-bodied participants with three speed variations, under inappropriate triggering scenarios and with foot drop rehabilitation exercises. Also, the stimulation control employed in commercial foot drop stimulators and single foot gait-based foot drop stimulators are compared alongside. Gait detection accuracy (98.9%) and precise triggering under all investigations prove bipedal gait model reliability. This infers that gait detection leveraging bipedal periodicity is a promising strategy to rectify prevalent stimulation triggering deficiencies in commercial foot drop stimulators. Graphical abstract Bipedal information-based gait recognition and stimulation triggering.

Genetic parameter estimation and implementation of the genetic evaluation for gaits in a breeding program for assisted-therapy in donkeys

Genetic analyses in donkeys are likely to face compromises in terms of sample size and population structure. This study aims at implementing a suitable model to estimate breeding values and genetic parameters for gaits in Andalusian donkeys. Empirical observation revealed that ambling donkeys (showing a slightly uneven, non-isochronous 1-2, 3-4 lateral sequence gait) did not walk (i.e. presented an isochronous, even 1-2-3-4 sequence gait) and vice versa. However, the two donkey groups could trot, equally. In this study, 2700 gait records were registered from 300 donkeys. The sample included 1350 gait records from 169 ambling/trotting donkeys and 1350 gait records from 131 walking/trotting donkeys. Fixed effects included year, season, sex, farm/owner, husbandry system, weather, ground type and appraisers. Weight and age were included as covariates. MTDFREML software was used to estimate (co)variance components, genetic parameters and predict breeding values and their accuracies in both sets, separately. Gaits' heritability ± SE estimates were 0.56 ± 0.155, 0.53 ± 0.317 and 0.67 ± 0.166 for amble, walk and trot, respectively. Genetic correlations were 0.31 ± 0.216, 0.42 ± 0.115 and 0.28 ± 0.178, for amble and walk, amble and trot and walk and trot, respectively. Not all gaits are suitable to treat every human sensomotor condition. We developed a locomotion selection index, assessing the relative loss/gain in index accuracy when each gait modality was excluded to develop different gait specific therapeutic lines to genetically select the best performing donkeys from each gait modality. Our results suggest that gait genetic lines could be developed and may be potential selection criteria to consider in assisted-therapy donkey breeding programs.

Determinants of pedestrian and bicyclist crash severity by party at fault in San Francisco, CA

Pedestrian and bicyclist safety is of growing concern, especially given the increasing numbers of urban residents choosing to walk and bike. Sharing the roads with automobiles, these road users are particularly vulnerable. An intuitive conceptual model is proposed of the determinants of injury severity in crashes between vehicles and nonmotorized road users. Using 10 years of crash data from San Francisco, CA, we estimate logistic regression models to illuminate key determinants of crash severity for both pedestrian and bicyclist collisions. The analyses are separated by party at fault to test the novel hypothesis that environmental factors affecting driver speed and reaction time may be especially important when the driver is not at fault. Pedestrian results are broadly consistent with prior research, and offer considerable support for this hypothesis. The strongest predictors of injury severity include pedestrian advanced age, driver sobriety, vehicle type, and a set of variables that help determine driver speed and reaction time. Bicyclist results were weaker overall, and the distinction by party at fault was less important.

Understanding the context for pet cat and dog feeding and exercising behaviour among pet owners in Ireland: a qualitative study

Background

Pet cat and dog obesity contributes to increased risk of several diseases, including cancer and diabetes mellitus as well as a worsening of orthopaedic problems, and a reduction in survival rate. This study aims to develop a better understanding of cat and dog owners’ self-reported beliefs and factors that influence owner behaviour around feeding and exercising their pet cat or dog, as there is a lack of in-depth understanding in this area. Seven focus group discussions, with 43 pet owners in total, were conducted.

Results

Pet owners often reported a perceived a low level of control over feeding; often undermined by other people feeding of their pet, their pets begging for food, and their pets attitude towards food. Treats were used in the absence of owner control over pet begging and emotional attachment, and to influence pet behaviour. The majority of participants had positive attitudes to pet exercise, which could be related to pet specific requirements, especially differences in cats and dogs. There were some negative experiences of stress associated with dog walking and fears over aggressive confrontations with other dogs.

Conclusion

Feeding one’s pet is influenced by beliefs about pet specific needs, pet food and pet health, pet owners’ perceived control over feeding, and the implications for the pet owner. Pet exercise is influenced by beliefs about pet specific exercise needs, and the implications of exercising one’s pet for the pet owner. Understanding owner behaviours on feeding and exercise allows for a more targeted approach to preventing and treating pet obesity.

Center of mass with the use of smartphone during walking in healthy individuals

[Purpose] The purpose of this study was to measure the center of mass using a smartphone application during walking in healthy. [Subjects and Methods] Forty eight healthy participants volunteered for this study. Measurements of center of mass were obtained by gait analysis application using smartphone while subjects performed 6 meter walking test. The measured data were automatically calculated by the application, subjects performed three trial walks to get a more accurate data analysis. [Results] There were no significant differences among subjects or between genders during the three trials in the vertical and lateral displacement of COM, and the results of the Kolmogorov-Simirnov test showed no differences in vertical and lateral displacement of COM in all subjects or between genders. However, the vertical displacement of COM significantly varied in male subjects than in female subjects, but the lateral displacement of COM did not significantly differ between the male and female subjects. [Conclusion] We can use the Smartphone application to measure the COM for walking; however more studies comparing advanced technological instruments with the smartphone application are needed.

Inertial measurement systems for segments and joints kinematics assessment: towards an understanding of the variations in sensors accuracy

BACKGROUND

Joints kinematics assessment based on inertial measurement systems, which include attitude and heading reference system (AHRS), are quickly gaining in popularity for research and clinical applications. The variety of the tasks and contexts they are used in require a deep understanding of the AHRS accuracy for optimal data interpretation. However, published accuracy studies on AHRS are mostly limited to a single task measured on a limited number of segments and participants. This study assessed AHRS sensors kinematics accuracy at multiple segments and joints through a variety of tasks not only to characterize the system's accuracy in these specific conditions, but also to extrapolate the accuracy results to a broader range of conditions using the characteristics of the movements (i.e. velocity and type of motion). Twenty asymptomatic adults ([Formula: see text] = 49.9) performed multiple 5 m timed up and go. Participants' head, upper trunk, pelvis, thigh, shank and foot were simultaneously tracked using AHRS and an optical motion capture system (gold standard). Each trial was segmented into basic tasks (sit-to-stand, walk, turn).

RESULTS

At segment level, results revealed a mean root-mean-squared-difference [Formula: see text] varying between 1.1° and 5.5° according to the segment tracked and the task performed, with a good to excellent agreement between the systems. Relative sensor kinematics accuracy (i.e. joint) varied between 1.6° and 13.6° over the same tasks. On a global scheme, analysis of the effect of velocity on sensor kinematics accuracy showed that AHRS are better adapted to motions performed between 50°/s and 75°/s (roughly thigh and shank while walking).

CONCLUSION

Results confirmed that pairing of modules to obtain joint kinematics affects the accuracy compared to segment kinematics. Overall, AHRS are a suitable solution for clinical evaluation of biomechanics under the multi-segment tasks performed although the variation in accuracy should be taken into consideration when judging the clinical meaningfulness of the observed changes.

An articulated ankle-foot orthosis with adjustable plantarflexion resistance, dorsiflexion resistance and alignment: A pilot study on mechanical properties and effects on stroke hemiparetic gait

Mechanical properties of an articulated ankle-foot orthosis (AFO) are closely related to gait performance in individuals post-stroke. This paper presents a pilot study on the mechanical properties of a novel articulated AFO with adjustable plantarflexion resistance, dorsiflexion resistance and alignment, and its effect on ankle and knee joint kinematics and kinetics in an individual post-stroke during gait. The mechanical properties of the AFO were quantified. Gait analysis was performed using a 3D motion capture system with a split-belt instrumented treadmill under 12 different settings of the mechanical properties of the AFO [i.e. 4 plantarflexion resistances (P1<P4), 4 dorsiflexion resistances (D1<D4), 4 initial alignments (A1<A4)]. The AFO demonstrated systematic changes in moment-angle relationship in response to changes in AFO joint settings. The gait analysis demonstrated that the ankle and knee angle and moment were responsive to changes in the AFO joint settings. Mean ankle angle at initial contact changed from -0.86° (P1) to 0.91° (P4) and from -1.48° (A1) to 4.45° (A4), while mean peak dorsiflexion angle changed from 12.01° (D1) to 6.40° (D4) at mid-stance. The novel articulated AFO appeared effective in influencing lower-limb joint kinematics and kinetics of gait in the individual post-stroke.

Comparison of air pollution exposures in active vs. passive travel modes in European cities: A quantitative review

BACKGROUND

Transport microenvironments tend to have higher air pollutant concentrations than other settings most people encounter in their daily lives. The choice of travel modes may affect significantly individuals' exposures; however such considerations are typically not accounted for in exposure assessment used in environmental health studies. In particular, with increasing interest in the promotion of active travel, health impact studies that attempt to estimate potential adverse consequences of potential increased pollutant inhalation during walking or cycling have emerged. Such studies require a quantification of relative exposures in travel modes.

METHODS

The literature on air pollution exposures in travel microenvironments in Europe was reviewed. Studies which measured various travel modes including at least walking or cycling in a simultaneous or quasi-simultaneous design were selected. Data from these studies were harmonized to allow for a quantitative synthesis of the estimates. Ranges of ratios and 95% confidence interval (CI) of air pollution exposure between modes and between background and transportation modes were estimated.

RESULTS

Ten studies measuring fine particulate matter (PM_2.5), black carbon (BC), ultrafine particles (UFP), and/or carbon monoxide (CO) in the walk, bicycle, car and/or bus modes were included in the analysis. Only three reported on CO and BC and results should be interpreted with caution. Pedestrians were shown to be the most consistently least exposed of all across studies, with the bus, bicycle and car modes on average 1.3 to 1.5 times higher for PM_2.5; 1.1 to 1.7 times higher for UFP; and 1.3 to 2.9 times higher for CO; however the 95% CI included 1 for the UFP walk to bus ratio. Only for BC were pedestrians more exposed than bus users on average (bus to walk ratio 0.8), but remained less exposed than those on bicycles or in cars. Car users tended to be the most exposed (from 2.9 times higher than pedestrians for BC down to similar exposures to cyclists for UFP on average). Bus exposures tended to be similar to that of cyclists (95% CI including 1 for PM_2.5, CO and BC), except for UFP where they were lower (ratio 0.7).

CONCLUSION

A quantitative method that synthesizes the literature on air pollution exposure in travel microenvironments for use in health impact assessments or potentially for epidemiology was conducted. Results relevant for the European context are presented, showing generally greatest exposures in car riders and lowest exposure in pedestrians.

Impact of a walking program of 10,000 steps per day and dietary counseling on health-related quality of life, energy expenditure and anthropometric parameters in obese subjects

PURPOSE

The aim of this pilot study was to assess the impact of a physical activity program of walking 10,000 steps per day along with monthly dietary counseling on the body composition, biological parameters, resting energy expenditure (REE) and health-related quality of life (HRQoL) of obese individuals.

METHODS

Thirty-five obese adults (26 women; age: 39.2 ± 13.4 years, body mass, BM: 104.1 ± 18.7 kg and body mass index, BMI: 38.3 ± 6.6 kg m^-2) followed a walking program (instructions were provided so that the participants increase their walking distance by 1000 steps each week, until to perform at least 10,000 steps per day) and received qualitative dietary advice (cookbook presenting numerous recipes with low calories and dietary advices was provided) for 6 months. Before and after the intervention, anthropometric (BM, BMI, waist and hip circumferences, fat mass: FM and lean body mass: LBM) and biological data (total cholesterol, high-density lipoprotein, low-density lipoprotein, triglyceride and glucose concentrations), REE and HRQoL (including eight dimensions and two summaries) were assessed.

RESULTS

After the intervention, BM (difference: 3.8 kg or 3.7 %), BMI (difference: 1.4 kg m^-2 or 3.7 %), hip circumference (difference: 4.6 cm or 4.3 %), FM in kg (difference: 4.0 kg or 8.9 %) and FM in percentage of BM (difference: 1.6 kg or 6.1 %) were significantly decreased, whereas number of steps (difference: 7579 steps or 135 %), LBM in percentage of BM (difference: 2.6 kg or 4.5 %) and REE (difference: 78 kcal d^-1 or 4.8 %) were significantly increased (p < 0.05). Moreover, two HRQoL subdimension scores (physical functioning and physical component summary; increase by 15.3 and 4.6, respectively, p < 0.05) and anxiety (reduction by 1.2, p < 0.05) were also significantly improved. Conversely, the biological data showed no significant change (p > 0.05).

CONCLUSION

Walking 10,000 steps per day in association with dietary counseling improved anthropometric data, REE, the physical domains of HRQoL and anxiety in obese adults.

Children and adults minimise activated muscle volume by selecting gait parameters that balance gross mechanical power and work demands

Terrestrial locomotion on legs is energetically expensive. Compared with cycling, or with locomotion in swimming or flying animals, walking and running are highly uneconomical. Legged gaits that minimise mechanical work have previously been identified and broadly match walking and running at appropriate speeds. Furthermore, the ‘cost of muscle force’ approaches are effective in relating locomotion kinetics to metabolic cost. However, few accounts have been made for why animals deviate from either work-minimising or muscle-force-minimising strategies. Also, there is no current mechanistic account for the scaling of locomotion kinetics with animal size and speed. Here, we report measurements of ground reaction forces in walking children and adult humans, and their stance durations during running. We find that many aspects of gait kinetics and kinematics scale with speed and size in a manner that is consistent with minimising muscle activation required for the more demanding between mechanical work and power: spreading the duration of muscle action reduces activation requirements for power, at the cost of greater work demands. Mechanical work is relatively more demanding for larger bipeds – adult humans – accounting for their symmetrical M-shaped vertical force traces in walking, and relatively brief stance durations in running compared with smaller bipeds – children. The gaits of small children, and the greater deviation of their mechanics from work-minimising strategies, may be understood as appropriate for their scale, not merely as immature, incompletely developed and energetically sub-optimal versions of adult gaits.

Highlighted Article: The gross mechanics of walking and running children and adults support a new model for the costs dominating level terrestrial locomotion – muscle activation for mechanical work or power.

Accuracy and reliability of the RGB-D camera for measuring walking speed on a treadmill

AIM

RGB-D cameras (Red Green Blue+Depth) are widely employed in exergames designed to physically stimulate elderly people. Nevertheless, the intensity of the physical activity reached with the existing solutions is rarely sufficient to obtain a real impact on the physical fitness and thus on the health status of this population. In this context, a Point Cloud Based System (PCBS) has been developed to interface ordinary motorized treadmills with exergames through a simple RGB-D camera, to induce players to perform physical activities at higher intensities. The goal of this study was to assess the accuracy and reliability of PCBS to measure the walking speed of a subject on a standard motorized treadmill based on the image streams of an RGB-D camera.

METHODS

36 participants performed three 10min walking exercises, divided in 5 blocks of 2min at the following constant ordered speeds: 0.42, 0.69, 0.97, 1.25 and 1.53ms(-1). The measured walking speeds are compared to those obtained through a Marker Based Control System (MBCS).

RESULTS

Results showed a high system accuracy (bias: 0.013±0.015ms(-1)), a good reliability (ICC=0.63-0.91) and a low variability (SEM=1-5%; MD=2.7-14%).

DISCUSSION

Accuracy and reliability of PCBS are consistent with those obtained in similar existing systems measuring gait parameters.

CONCLUSION

Within the context of the development of exergames, PCBS may be combined with exergames to perform physical activities at sufficiently high intensities in the elderly population, in order to improve their physical health and possibly prevent/delay cognitive impairment.

Mode-dependent control of human walking and running as revealed by split-belt locomotor adaptation

Here, we investigate the association of neural control between walking and running, and in particular, how these two gait modes at different velocities are controlled by the central nervous system. The subjects were fully adapted by acquiring modified motor patterns to either walk or run on a split-belt treadmill driven in split mode (asymmetry in the velocities of two belts at 1.0 and 2.0 m s(-1)). Subsequently, we tested how the adaptation affected walking and running at three different velocities in the tied mode (equal belt velocities). At 0.75 m s(-1), we found a preference to walk, at 1.50 m s(-1), there was a preference to both walk and run, and at a velocity of 2.25 m s(-1) there was a preference to run. Both walking and running on the split belt resulted in the emergence of a significant aftereffect (asymmetrical movement) at all of the velocities tested when walking after adapting to walk and running after adapting to run. However, for contrasting modes (i.e. running after adapting to walk and walking after adapting to run), such aftereffects were far less evident at all velocities; thus showing only limited transfer across gait modes. The results demonstrate a clear mode dependency in the neural control of human walking and running. In addition, only for walking, was there a degree of velocity dependency.

The effect of ankle-foot orthosis plantarflexion stiffness on ankle and knee joint kinematics and kinetics during first and second rockers of gait in individuals with stroke

BACKGROUND

Stiffness of an ankle-foot orthosis plays an important role in improving gait in patients with a history of stroke. To address this, the aim of this case series study was to determine the effect of increasing plantarflexion stiffness of an ankle-foot orthosis on the sagittal ankle and knee joint angle and moment during the first and second rockers of gait.

METHODS

Gait data were collected in 5 subjects with stroke at a self-selected walking speed under two plantarflexion stiffness conditions (0.4Nm/° and 1.3Nm/°) using a stiffness-adjustable experimental ankle-foot orthosis on a Bertec split-belt fully instrumented treadmill in a 3-dimensional motion analysis laboratory.

FINDINGS

By increasing the plantarflexion stiffness of the ankle-foot orthosis, peak plantarflexion angle of the ankle was reduced and peak dorsiflexion moment was generally increased in the first rocker as hypothesized. Two subjects demonstrated increases in both peak knee flexion angle and peak knee extension moment in the second rocker as hypothesized. The two subjects exhibited minimum contractility during active plantarflexion, while the other three subjects could actively plantarflex their ankle joint.

INTERPRETATION

It was suggested that those with the decreased ability to actively plantarflex their ankle could not overcome excessive plantarflexion stiffness at initial contact of gait, and as a result exhibited compensation strategies at the knee joint. Providing excessively stiff ankle-foot orthoses might put added stress on the extensor muscles of the knee joint, potentially creating fatigue and future pathologies in some patients with stroke.

[Possible changes in energy-minimizer mechanisms of locomotion due to chronic low back pain - a literature review]

One goal of the locomotion is to move the body in the space at the most economical way possible. However, little is known about the mechanical and energetic aspects of locomotion that are affected by low back pain. And in case of occurring some damage, little is known about how the mechanical and energetic characteristics of the locomotion are manifested in functional activities, especially with respect to the energy-minimizer mechanisms during locomotion. This study aimed: a) to describe the main energy-minimizer mechanisms of locomotion; b) to check if there are signs of damage on the mechanical and energetic characteristics of the locomotion due to chronic low back pain (CLBP) which may endanger the energy-minimizer mechanisms. This study is characterized as a narrative literature review. The main theory that explains the minimization of energy expenditure during the locomotion is the inverted pendulum mechanism, by which the energy-minimizer mechanism converts kinetic energy into potential energy of the center of mass and vice-versa during the step. This mechanism is strongly influenced by spatio-temporal gait (locomotion) parameters such as step length and preferred walking speed, which, in turn, may be severely altered in patients with chronic low back pain. However, much remains to be understood about the effects of chronic low back pain on the individual's ability to practice an economic locomotion, because functional impairment may compromise the mechanical and energetic characteristics of this type of gait, making it more costly. Thus, there are indications that such changes may compromise the functional energy-minimizer mechanisms.

Joint-level mechanics of the walk-to-run transition in humans

Two commonly proposed mechanical explanations for the walk-to-run transition (WRT) include the prevention of muscular over-exertion (effort) and the minimization of peak musculoskeletal loads and thus injury risk. The purpose of this study was to address these hypotheses at a joint level by analysing the effect of speed on discrete lower-limb joint kinetic parameters in humans across a wide range of walking and running speeds including walking above and running below the WRT speed. Joint work, peak instantaneous joint power, and peak joint moments in the sagittal and frontal plane of the ankle, knee and hip from eight participants were collected for 10 walking speeds (30-120% of their WRT) and 10 running speeds (80-170% of their WRT) on a force plate instrumented treadmill. Of the parameters analysed, three satisfied our statistical criteria of the 'effort-load' hypothesis of the WRT. Mechanical parameters that provide an acute signal (peak moment and peak power) were more strongly associated with the gait transition than parameters that reflect the mechanical function across a portion of the stride. We found that both the ankle (peak instantaneous joint power during swing) and hip mechanics (peak instantaneous joint power and peak joint moments in stance) can influence the transition from walking to running in human locomotion and may represent a cascade of mechanical events beginning at the ankle and leading to an unfavourable compensation at the hip. Both the ankle and hip mechanisms may contribute to gait transition by lowering the muscular effort of running compared with walking at the WRT speed. Although few of the examined joint variables satisfied our hypothesis of the WRT, most showed a general marked increase when switching from walking to running across all speeds where both walking and running are possible, highlighting the fundamental differences in the mechanics of walking and running. While not eliciting the WRT per se, these variables may initiate the transition between stable walking and running patterns. Those variables that were invariant of gait were predominantly found in the swing phase.

Domestic cat walking parallels human constrained optimization: optimization strategies and the comparison of normal and sensory deficient individuals

To evaluate how fundamental gait parameters used in walking (stride length, frequency, speed) are selected by cats we compared stride characteristics selected when walking on a solid surface to those selected when they were constrained to specific stride lengths using a pedestal walkway. Humans spontaneously select substantially different stride length-stride frequency-speed relationships in walking when each of these parameters is constrained, as in walking to a metronome beat (frequency constrained), evenly spaced floor markers (stride length constrained) or on a treadmill (speed constrained). In humans such adjustments largely provide energetic economy under the prescribed walking conditions. Cats show a similar shift in gait parameter selection between conditions as observed in humans. This suggests that cats (and by extension, quadrupedal mammals) also select gait parameters to optimize walking cost-effectiveness. Cats with a profound peripheral sensory deficit (from pyridoxine overdose) appeared to parallel the optimization seen in healthy cats, but without the same level of precision. Recent studies in humans suggest that gait optimization may proceed in two stages - a fast perception-based stage that provides the initial gait selection strategy which is then fine-tuned by feedback. The sensory deficit cats appeared unable to accomplish the feedback-dependent aspect of this process.

The effects of clothes on independent walking in toddlers

The spatiotemporal features of walking in toddlers are known to be related to the level of maturation of the central nervous system. However, previous studies did not assess whether there could be an effect of clothes on the acquisition of walking. In this study, it was hypothesized that clothes modify the toddlers' walking. To test this hypothesis, 22 healthy toddlers divided into 3 groups of walking experience were assessed in four clothing conditions (Diaper+Trousers; Diaper+Pants of tracksuit; Diaper; Underwear). Results revealed significant effects of clothing on velocity and step length of toddlers from 6 to 18 months of walking experience. These results suggested that biomechanical constraints induced by the textile features alter the walking of toddlers. Therefore, in studies of toddler's gait, the clothing worn should be carefully mentioned and controlled.