Assessing the role of ankle and hip joint proprioceptive information in balance recovery using vibratory stimulation

Background

Previous work suggests that proprioceptive information from ankle and hip are crucial in maintaining balance during upright standing; however, the contribution of these proprioceptive information during stepping balance recovery in not clear. The goal of the current study was to assess the role of ankle and hip proprioceptive information on balance recovery performance by manipulating type 1a afferent in muscle spindles using vibratory stimulation.

Methods

Twenty healthy young participants were recruited (age = 22.2 ± 2.7 years) and were randomly assigned to balance recovery sessions with either ankle or hip stimulation. Trip-like perturbations were imposed using a modified treadmill setup with a protecting harness. Vibratory stimulation was imposed bilaterally on ankle and hip muscles to expose participants to three condition of no-vibration, 40Hz vibration, and 80Hz vibration. Kinematics of the trunk and lower-extremities were measured using wearable sensors to characterize balance recovery performance. Outcomes were response time, recovery step length, trunk angle during toe-off and heel-strike of recovery stepping, and required time for full recovery.

Findings

Ankle vibratory stimulation elicited main effects on reaction time and recovery step length (p < 0.002); reaction time and recovery step length increased by 23.0% and 21.2%, respectively, on average across the conditions. Hip vibratory stimulation elicited significant increase in the full recovery time (p = 0.019), with 55.3% increase on average across the conditions.

Interpretation

Current findings provided evidence that vibratory stimulation can affect the balance recovery performance, causing a delayed recovery initiation and an impaired balance refinement after the recovery stepping when applied to ankle and hip muscles, respectively.

Does listening to audiobooks affect gait behavior?

BACKGROUND

The effect of listening to audiobooks, podcasts, and other audio files while walking on gait performance has not been well studied. Although the number of audio users is growing annually. Evidence suggests that a posture-first strategy contributes to gait stability in healthy individuals during dual-task conditions, but this effect may be diminished when the cognitive task is consciously prioritized.

OBJECTIVES

To study the effect of listening to an audiobook while walking, as a daily life-like dual-task, on spatiotemporal gait parameters.

METHODS

Forty young healthy (24.05 ± 3.66) subjects participated in the study. Spatiotemporal gait parameters were measured for 5 min on a treadmill once without (single-task) and once while listening to an audiobook through over-ear headphones (dual-task). Measured parameters included spatiotemporal parameters, gait phases, maximum pressure, and dual-task cost. Data were statistically analyzed using SPSS software.

RESULTS

There were no significant differences in any of the studied parameters between the single- and dual-task conditions, even though the subjective cognitive load of listening to audiobooks while walking was high. However, participants with different habits had significant differences in gait phases and maximum pressure. Rare listeners had a shorter stance phase, a longer swing phase, and a higher maximum pressure on the dominant heel. They also had significant differences in dual-task costs.

CONCLUSION

No differences in the spatiotemporal gait parameters for walking with and without listening to audiobooks, as a daily life-like dual-task, were observed. However, the difference between participants who listened rarely and participants who listened often may confirm the "posture first" strategy in young healthy people.

TRIAL REGISTRATION

DRKS00025837, retrospectively registered on 23.11.2021.

Bodyweight support alters the relationship between preferred walking speed and cost of transport

Humans tend to select a preferred walking speed (PWS) that minimizes the metabolic energy consumed per distance traveled, i.e. the Cost of Transport (CoT). The aims of this study were to: 1. compare PWS overground vs. on a treadmill at 100 and 50% of body weight, and 2. explore whether with body weight support, PWS corresponds to the speed that minimizes CoT. Fifteen healthy adults walked overground and on a lower body positive pressure treadmill with and without bodyweight support. Walking speeds (m^.s^-1) were recorded for each condition. Rate of energy expenditure (J^.kg^-1.min^-1) and CoT (J^.kg^-1.m^-1) were then determined from 5-min walking trials with 50% bodyweight support at PWS and ± 30% of the self-selected walking speed for that condition. PWS did not differ across conditions. With 50% body weight support, for each 30% increase in walking speed, rates of metabolic energy expenditure increased ∼15% while CoT decreased by ∼14%. Thus, with 50% body weight support, PWS did not correspond with the speed that minimized CoT. Bodyweight support decreases cost of maintaining an upright body but does not decrease the metabolic demand of limb advancement, contributing to the linear yet not proportional changes in rates of energy expenditure and CoT. We conclude that bodyweight support via an AlterG® treadmill disconnects the association between PWS and minimum CoT. These findings have implications for clinical populations (e.g., obese, elderly) who may benefit from walking on a bodyweight supporting treadmill but may select speeds incompatible with their physical activity goals.

The influence of wearing an ultrasound device on gait in children with cerebral palsy and typically developing children

BACKGROUND

Ultrasonography with motion analysis enables dynamic imaging of medial gastrocnemius (MG) muscles and tendons during gait. This revealed pathological muscle-tendon dynamics in children with spastic cerebral palsy (CP) compared to typically developing (TD) children. However, wearing an ultrasound probe on the lower leg could interfere with gait and bias muscle length changes observed with ultrasound.

RESEARCH QUESTION

Does wearing an ultrasound probe on the MG influence gait in children with CP and TD children?

METHODS

Eighteen children with spastic CP and 16 age-matched TD children walked at comfortable walking speed on an instrumented treadmill. One baseline gait condition (BASE) and two conditions with an ultrasound probe and custom-made probe holder were measured: on the mid-muscle fascicles (FAS) and on the muscle-tendon junction (MTJ). The effect of condition and group on spatiotemporal parameters, hip, knee and ankle kinematics, ankle moment, ankle power, and modeled MG muscle-tendon unit (MTU) length was assessed using two-way repeated measures ANOVA's. Statistical non-parametric mapping was applied for time-series. Post-hoc paired-samples t-tests were conducted, and the root mean square difference was calculated for significant parts.

RESULTS

Children took wider steps during FAS (CP, TD) and MTJ (TD) compared to BASE, and during FAS compared to MTJ (CP). Hip extension was lower (2.7°) during terminal stance for MTJ compared to FAS for TD only. There was less swing knee flexion (FAS 4.9°; MTJ 4.0°) and ankle plantarflexion around toe-off (FAS 3.0°; MTJ 2.4°) for both ultrasound placements, with no group effect. Power absorption during loading response was slightly increased for both ultrasound placements (0.12 W/kg), with no group effect. MTU shortened less in swing for both ultrasound placements (FAS 3.6 mm; MTJ 3.7 mm), with no group effect.

SIGNIFICANCE

Wearing an ultrasound probe causes minimal lower-limb gait alterations and MTU length changes that are mostly similar in CP and TD.

Comparing spatiotemporal gait parameters between overground walking and self-paced treadmill walking in persons after stroke

PURPOSE

Since self-paced treadmills enable more natural gait patterns compared to fixed-speed treadmills we examined the use of a self-paced treadmill as a alternative for overground gait analysis in persons after stroke.

MATERIAL AND METHODS

Twenty-five persons after stroke (10 males/15 females; 53 ± 12.05 years; 40.72 ± 42.94 months post-stroke) walked at self-selected speed overground (GAITRite, CIR Systems) and on a self-paced treadmill (GRAIL, Motek) in randomized order. Spatiotemporal parameters, variability and symmetry measures were compared using paired-sample t-tests or Wilcoxon Signed Rank tests. Concurrent validity was assessed using intraclass correlation coefficients and Bland-Altman plots. A regression model determined the contribution of the walking velocity to the changes in spatiotemporal parameters.

RESULTS

The velocity on the treadmill was significant lower compared to overground (p < 0.001). This difference predicted the significant changes in other spatiotemporal parameters to varying degrees (27.7%-83.8%). Bland-Altman plots showed large percentage of bias and limits of agreement. Variability and symmetry measures were similar between conditions.

CONCLUSIONS

When considering gait analysis in persons after stroke a self-paced treadmill may be a valuable alternative for overground analysis. Although a slower walking velocity, and accompanying changes in other spatiotemporal parameters, should be taken into account compared to overground walking.Implications for rehabilitationConsidering the advantages regarding space and time, instrumented treadmills provide opportunities for gait assessment and training in a stroke population.When using self-paced treadmills for clinical gait analysis in persons after stroke, the slower walking velocity and accompanying changes in other spatiotemporal parameters need to be taken into account.Stroke patients seem to preserve their walking pattern on a self-paced treadmill.

The impact of added mass placement on metabolic and temporal-spatial characteristics of transfemoral prosthetic gait

BACKGROUND

Despite prosthetic technology advancements, individuals with transfemoral amputation have compromised temporal-spatial gait parameters and high metabolic requirements for ambulation. It is unclear how adding mass at different locations on a transfemoral prosthesis might affect these outcomes. Research question Does walking with mass added at different locations on a transfemoral prosthesis affect temporal-spatial gait parameters and metabolic requirements compared to walking with no additional mass?

METHODS

Fourteen participants with unilateral transfemoral amputations took part. A 1.8 kg mass was added to their prostheses in three locations: Knee, just proximal to the prosthetic knee; Shank, mid-shank on the prosthesis; or Ankle, just proximal to the prosthetic foot. Temporal-spatial gait parameters were collected as participants walked over a GAITRite® walkway and metabolic data were collected during treadmill walking for each of these conditions and with no mass added, the None condition. Separate linear mixed effects models were created and post-hoc tests to compare with the control condition of None were performed with a significance level of 0.05.

RESULTS

Overground self-selected walking speed for Ankle was significantly slower than for None (p < 0.05) (None: 1.16 ± 0.24; Knee: 1.15 ± 0.19; Shank: 1.14 ± 0.24; Ankle 0.99 ± 0.20 m/s). Compared to None, Ankle showed significantly increased oxygen consumption during treadmill walking (p < 0.05) (None: 13.82 ± 2.98; Knee: 13.83 ± 2.82; Shank: 14.30 ± 2.89; Ankle 14.56 ± 2.99 ml O₂/kg/min). Other metabolic outcomes (power, cost of transport, oxygen cost) showed similar trends. Knee and Shank did not have significant negative effects on any metabolic or temporal-spatial parameters, as compared to None (p > 0.05). Significance Results suggest that additional mass located mid-shank or further proximal on a transfemoral prosthesis may not have negative temporal-spatial or metabolic consequences. Clinicians, researchers, and designers may be able to utilize heavier components, as long as the center of mass is not further distal than mid-shank, without adversely affecting gait parameters or metabolic requirements.

Biomechanical differences between self-paced and fixed-speed treadmill walking in persons after stroke

BACKGROUND

Using self-paced treadmills for gait analysis requires less space compared to overground gait labs while a more natural walking pattern could be preserved compared to fixed-speed treadmill walking. Although self-paced treadmills have been used in stroke related intervention studies, studies comparing self-paced to fixed-speed treadmill walking in this population are scarce.

METHODS

Twenty-five persons after stroke (10 males/15 females; 53 ± 12.05 years; 40.72 ± 42.94 months post stroke) walked on a treadmill in a virtual environment (GRAIL, Motek) in two conditions (self-paced and fixed-speed). After familiarization, all participants completed two trials (3 min) at comfortable walking velocity in randomized order. A paired-sample t-test or Wilcoxon Signed Rank test was used to calculate differences between both conditions for spatiotemporal parameters. Statistical Parametric mapping was conducted using the t-tests (SPM(t)), to statistically compare the kinematic and kinetic curves.

RESULTS

The self-selected walking velocity on the treadmill was higher in the self-paced condition compared to the fixed-speed condition (p < 0.001). However, most variability and symmetry measures were similar in both conditions. Only the standard deviation of the step length at the paretic side was significant higher (p = 0.007) and step length symmetry was significantly better (p = 0.032) in the self-paced condition. Detected kinematic and kinetic differences were small (< 3°, < 0.1 Nm/kg) and stride to stride variability was comparable in both conditions.

CONCLUSION

Based on the results of the current study, self-paced walking can be used as an equivalent to fixed-speed treadmill walking in persons after stroke. Accordingly, this justifies the use of this more functional mode in clinical gait assessment and rehabilitation trials.

Effects of anteriorly-loaded treadmill walking on dynamic gait stability in young adults

BACKGROUND

Anteriorly-loaded walking is common in many occupations and may increase fall risk. Dynamic gait stability, defined by the Feasible Stability Region (FSR) theory, quantifies the kinematic relationship between the body's center of mass (COM) and base of support (BOS). FSR-based dynamic gait stability has been used to evaluate the fall risk.

RESEARCH QUESTION

How does front load carriage affect dynamic gait stability, step length, and trunk angle among young adults during treadmill walking?

METHODS

In this between-subject design study, 30 healthy young adults were evenly randomized into three load groups (0%, 10%, or 20% of body weight). Participants carried their assigned load while walking on a treadmill at a speed of 1.2 m/s. Body kinematics were collected during treadmill walking. Dynamic gait stability (the primary variable) was calculated for two gait events: touchdown and liftoff. Step length and trunk angle were measured as secondary variables. One-way analysis of variance was conducted to detect any group-related differences for all variables. Post-hoc analysis with Bonferroni correction was performed when main group differences were found.

RESULTS

No significant differences but medium to large effect sizes were found between groups for dynamic gait stability at touchdown (p = 0.194, η² = 0.114) and liftoff (p = 0.122, η² = 0.139). Trunk angle significantly increased (indicating backward lean) with the front load at touchdown (p < 0.001, η² = 0.648) and liftoff (p < 0.001, η² = 0.543). No significant between-group difference was found related to the step length (p = 0.344, η² = 0.076).

SIGNIFICANCE

Carrying a front load during walking significantly alters the trunk orientation and may change the COM-BOS kinematic relationship and, therefore, fall risk. The findings could inform the design of future studies focusing on the impact of anterior load carriage on fall risk during different locomotion.

The effect of a frontal plane gait perturbation bout on knee biomechanics and muscle activation in older adults and individuals with knee osteoarthritis

BACKGROUND

Walking can be a challenging task for individuals with knee osteoarthritis and many older adults. The purpose was to determine the immediate effect of a frontal plane perturbation bout during walking on knee biomechanics and muscle activation patterns in these groups.

METHODS

44 asymptomatic older adults and 32 individuals with knee osteoarthritis were recruited. Sagittal and frontal plane knee biomechanics and muscle activation levels were calculated and recorded during treadmill walking. After a baseline collection at 6-min, a random series of unexpected medial/lateral walkway surface perturbations were delivered over approximately 24 min. Data was collected immediately after the perturbations. Discrete measures extracted from biomechanical waveforms, and principal component analysis to analyze muscle activation were utilized to determine time effects and interactions using analysis of variance models (alpha = 0.05).

FINDINGS

After the perturbation bout, sagittal plane range of motion was significantly increased in the osteoarthritis group (Effect Size = 0.24) and in both groups peak knee adduction moment (Effect Size = 0.10) and difference between peak flexion and extension moments (Effect Size = 0.16) were significantly increased. Muscle amplitudes in both groups were significantly reduced (PP1-scores) after perturbation bout, whereas significant time-based gait cycle activation pattern alterations identified by PP2- and PP3-scores were related to group and muscle assignment.

INTERPRETATION

Perturbations were tolerated by all participants, resulting in significant alterations to biomechanical outcomes and muscle activation levels and patterns. Demand on the knee joint was not increased after perturbations. Gait perturbation training in these groups may be feasible using a frontal plane perturbation bout.

Real-time kinematic-based detection of foot-strike during walking

Detection of foot-strike events is an integral part of gait analysis, as it allows the temporal registration of gait cycles. At the same time, it is necessary to register gait phases in real-time for applications such as wearable assistive devices and gait biofeedback that work synchronously with the human gait. Although many algorithms have been proposed for detecting foot-strikes with either wearable (e.g. Inertial Measurement Units (IMUs)) or non-wearable (e.g. force plates) sensors, there is a great need for real-time algorithms that rely only on recording the kinematics of the leg motion. This work proposes a novel and efficient kinematic algorithm, called the Foot VErtical & Sagittal Position Algorithm (F-VESPA), which has several advantages over existing methods. First, it accurately estimates foot-strike events using kinematic data without requiring access to future data points, hence achieving reduced latency during real-time implementation. Moreover, it does not require tuning of the utilized parameters, rendering it robust to different subjects and treadmill speeds. The algorithm is tested in a large set of subjects across various treadmill speeds, and it is shown to outperform even offline implementations of existing prominent kinematic algorithms. Using a 150 Hz data collection system, the F-VESPA achieved a median of 33 ms for the total true errors in detecting foot-strike. The F-VESPA is a highly responsive kinematic algorithm that can detect foot-strike events in real-time, with high accuracy, robustness and reduced latency, enabling real-time temporal registration of gait cycles.

Effects of camera viewing angles on tracking kinematic gait patterns using Azure Kinect, Kinect v2 and Orbbec Astra Pro v2

BACKGROUND

Depth sensors could be a portable, affordable, marker-less alternative to three-dimension motion capture systems for gait analysis, but the effects of camera viewing angles on their joint angle tracking performance have not been fully investigated.

RESEARCH QUESTIONS

This study evaluated the accuracies of three depth sensors [Azure Kinect (AK); Kinect v2 (K2); Orbbec Astra (OA)] for tracking kinematic gait patterns during treadmill walking at five camera viewing angles (0°/22.5°/45°/67.5°/90°).

METHODS

Ten healthy subjects performed fifteen treadmill walking trials (3 speeds × 5 viewing angles) using the three depth sensors to measure joint angles in sagittal hip, frontal hip, sagittal knee, and sagittal ankle. Ten walking steps were recorded and averaged for each walking trial. Range of motion in terms of maximum and minimum joint angles measured by the depth sensors were compared with the Vicon motion capture system as the gold standard. Depth sensors tracking accuracies were compared against the Vicon reference using root-mean-square error (RMSE) on the joint angle time series. Effects of different walking speeds, viewing angles, and depth sensors on the tracking accuracy were observed using three-way repeated-measure analysis of variance (ANOVA).

RESULTS

ANOVA results on RMSE showed significant interaction effects between viewing angles and depth sensors for sagittal hip [F(8,72) = 4.404, p = 0.005] and for sagittal knee [F(8,72)=13.211, p < 0.001] joint angles. AK had better tracking performance when subjects walked at non-frontal camera viewing angles (22.5°/45°/67.5°/90°); while K2 performed better at frontal viewing angle (0°). The superior tracking performance of AK compared with K2/OA might be attributed to the improved depth sensor resolution and body tracking algorithm.

SIGNIFICANCE

Researchers should be cautious about camera viewing angle when using depth sensors for kinematic gait measurements. Our results demonstrated Azure Kinect had good tracking performance of sagittal hip and sagittal knee joint angles during treadmill walking tests at non-frontal camera viewing angles.

No difference in knee muscle activation and kinematics during treadmill walking between adolescent girls with and without asymptomatic Generalised Joint Hypermobility

Background

Altered knee muscle activity in children with asymptomatic Generalized Joint Hypermobility (GJH) is reported during isometric contraction, static and dynamic balance tasks and jumping, but has not been studied during gait. Therefore, the aim was to investigate group differences in knee muscle activity simultaneously with knee joint kinematics during treadmill walking between children with and without GJH.

Methods

Girls 14–15 years of age with GJH (inclusion criteria: Beighton score ≥6 of 9 and positive hyperextension ≥10° (one/both knees)) and a matched control group without GJH (inclusion criteria: Beighton score ≤5 and no knee hyperextension ≥10° ) were recruited. In total 16 participants with GJH and 10 non-GJH participants were included in the study.

Surface electromyography (sEMG) was measured from the quadriceps, hamstrings and gastrocnemius muscles of the dominant leg during treadmill walking. Maximal voluntary isometric contractions while sitting were used for normalisation of sEMG to % of Maximum Voluntary EMG (%MVE). Knee joint angles during treadmill walking were measured by electrogoniometer. Furthermore, co-contraction index (CCI) was calculated, and presented for muscle groups of hamstrings-quadriceps (HQ) and gastrocnemius-quadriceps (GQ). CCI of medial and lateral sides of the knee, including ratio of the medial and lateral CCI for HQ and GQ were calculated.

Results

No group differences were found in demographics, muscle activation level, nor CCI and CCI ratios. However, participants with GJH displayed significantly decreased knee joint angle, mean (153º vs. 156º; p =0.03) and minimum (105º vs. 111º; p=0.01), during treadmill walking compared with controls.

Conclusion

Muscle activity during gait was not different between participants with GJH and non-GJH participants. However, participants with GJH displayed minor but statistically significant increased knee flexion during gait. Since the clinical consequences of increased knee joint flexion during gait are unknown, future studies should follow a larger cohort longitudinally during overground walking for development of clinical complications in this group.

Uncontrolled manifold analysis of the effects of a perturbation-based training on the organization of leg joint variance in cerebellar ataxia

Walking patterns of persons affected by cerebellar ataxia (CA) are characterized by wide stride-to-stride variability ascribable to: the background pathology-related sensory-motor noise; the motor redundancy, i.e., an excess of elemental degrees of freedom that overcomes the number of variables underlying a specific task performance. In this study, we first tested the hypothesis that healthy and, especially, CA subjects can effectively exploit solutions in the domain of segmental angles to stabilize the position of either the foot or the pelvis (task performance) across heel strikes, in accordance with the uncontrolled manifold (UCM) theory. Next, we verified whether a specific perturbation-based training allows CA subjects to further take advantage of this coordination mechanism to better cope with their inherent pathology-related variability. Results always rejected the hypothesis of pelvis stabilization whereas supported the idea that the foot position is stabilized across heel strikes by a synergic covariation of elevation and azimuth angles of lower limb segments in CA subjects only. In addition, it was observed that the perturbation-based training involves a decreasing trend in the variance component orthogonal to the UCM in both groups, reflecting an improved accuracy of the foot control. Concluding, CA subjects can effectively structure the wide amount of pathology-related sensory-motor noise to stabilize specific task performance, such as the foot position across heel strikes. Moreover, the promising effects of the proposed perturbation-based training paradigm are expected to improve the coordinative strategy underlying the stabilization of the foot position across strides, thus ameliorating balance control during treadmill locomotion.

On the application of entropic half-life and statistical persistence decay for quantification of time dependency in human gait

Entropic half-life (ENT½) and statistical persistence decay (SPD) was recently introduced as measures of time dependency in stride time intervals during walking. The present study investigated the effect of data length on ENT½ and SPD and additionally applied these measures to stride length and stride speed intervals. First, stride times were collected from subjects during one hour of treadmill walking. ENT½ and SPD were calculated from a range of stride numbers between 250 and 2500. Secondly, stride times, stride lengths and stride speeds were collected from subjects during 16 min of treadmill walking. ENT½ and SPD were calculated from the stride times, stride lengths and stride speeds. The ENT½ values reached a plateau between 1000 and 2500 strides whereas the SPD increased linearly with the number of included strides. This suggests that ENT½ can be compared if 1000 strides or more are included, but only SPD obtained from same number of strides should be compared. The ENT½ and SPD of the stride times were significantly longer compared to that of the stride lengths and stride speeds. This indicates that the time dependency is greater in the motor control of stride time compared to that of stride lengths and stride speeds.

Age effects on step adaptation during treadmill walking with continuous step length biofeedback

BACKGROUND

The inability to adjust step length can lead to falls in older people when navigating everyday terrain. Precisely targeted forward placement of the leading foot, constituting step length adjustment, is required for adaptive gait control, but this ability may reduce with ageing. The objective of this study was to investigate ageing effects on step length adaptation using real-time biofeedback.

RESEARCH QUESTION

Does ageing affect the ability to adapt step length to match a target using real-time biofeedback?

METHODS

Fifteen older adults (67 ± 3 years; 8 females) and 27 young adults (24 ± 4 years; 13 females) completed a step length adaptation test while walking at preferred speed on a treadmill. The test involved walking while viewing a monitor at the front of the treadmill that showed a real-time signal of absolute left-right foot displacement. The task was to match the local maxima of the signal (i.e. step length) to two target conditions, at 10 % longer or 10 % shorter than mean baseline step length. When the target was displayed, it remained unchanged for a set of 10 consecutive step attempts. Three sets of 10 attempts for each target condition were allocated in random order, for a total of 30 step attempts per target. Average absolute error and average error (bias) of step length accuracy was computed for each target condition and compared between groups.

RESULTS

The step adaptation test identified that older adults had greater mean absolute error for both short and long step targets and showed a step length-dependent bias significantly different to the young.

SIGNIFICANCE

Real-time foot position feedback could be a useful tool to train and evaluate step adaptation in older people.

Plantar pressure distribution and spatiotemporal gait parameters after the radial shock wave therapy in patients with chronic plantar fasciitis

Radial shock wave therapy (RSWT) has been recommended as an appropriate, safe and effective method in the treatment of chronic plantar fasciitis (PF). The main purpose of this study was to examine how RSWT affects gait parameters. This study included 23 patients with unilateral, chronic PF. RSWT were administered in 5 interventions, during a consecutive 3-week period. Objective kinetic (force distribution under the forefoot, midfoot, rearfoot) and spatiotemporal parameters (cadence, step length, stance phase duration) during treadmill walking at, preferred" speed were evaluated on. 4 sessions: before therapy, immediately after (primary endpoint), 3 and 6 weeks after therapy. The mean reduction in the reported pain when taking first steps in the morning from baseline to the primary endpoint, 3- and 6-weeks post procedure was 42.7%, 50.1% and 66.9% respectively. Similar reduction was seen in the reported pain during walking. After the therapy during gait at the preferred speed patients had a significantly higher force beneath the rearfoot and forefoot of both limbs. Force beneath the midfoot was not significantly affected by treatment. The step length in both limbs increased by 3.3-3.6 cm after RSWT. After the therapy stance phase duration in symptomatic foot was longer by 7% and it slightly decreased until POST-6wk. Similar changes were seen in an asymptomatic limb. The spatiotemporal and kinetic results indicate that RSWT therapy induces changes in patient's gait structure and alter regional loading in the affected foot.

Viewpoint oscillation improves the perception of distance travelled in static observers but not during treadmill walking

Optic flow has been found to be a significant cue for static observers’ perception of distance travelled. In previous research conducted in a large-scale immersive display (CAVE), adding viewpoint oscillations to a radial optic flow simulating forward self-motion was found to modulate this perception. In the present two experiments, we investigated (1) whether the improved distance travelled perceptions observed with an oscillating viewpoint in a CAVE were also obtained when the subjects were wearing a head mounted display (HMD, an Oculus Rift) and (2) whether the absence of viewpoint oscillations during treadmill walking was liable to affect the subjects’ perception of self-motion. In Experiment 1, static observers performed a distance travelled estimation task while facing either a purely linear visual simulation of self-motion (in depth) or the same flow in addition to viewpoint oscillations based on the subjects’ own head oscillations previously recorded during treadmill walking. Results show that the benefits of viewpoint oscillations observed in a CAVE persisted when the participants were wearing an HMD. In Experiment 2, participants had to carry out the same task while walking on a treadmill under two different visual conditions simulating self-motion in depth: the one with and the other without the visual consequences of their head translations. Results showed that viewpoint oscillations did not improve the accuracy of subjects’ distance travelled estimations. A comparison between the two experiments showed that adding internal dynamic information about actual self-motion to visual information did not allow participants better estimates.

Cognitive performance during gait is worsened by overground but enhanced by treadmill walking

PURPOSE

Walking is an attention-demanding task that affects and is affected by cognitive performance. Since treadmill walking (TW) assists gait automaticity, we have hypothesized that TW affects cognitive performance to a smaller extent than overground walking (OW).

METHODS

Thirty young adults were recruited. Each subject walked overground over a 20-meter straight hallway at three different speeds (slow, normal and fast). Each task was repeated 3 times under Single Task (OW-ST) and Dual Task (OW-DT) condition, in a randomized sequence. DT was a serial subtraction by 7 starting from a different number (> 100) in each trial. Afterwards, each subject walked on the treadmill at the same three speeds as during OW-ST, while performing the dual task (TW-DT). The correct cognitive response (CCR), calculated from the number of correct responses and mistakes, was compared between rest, OW-DT and TW-DT. Dual-task cost (DTC) was calculated for speed and for CCR.

RESULTS

Backward counting diminished normal and fast OW-DT speed by about 15 %. Slow OW-DT speed was not significantly reduced. In turn, OW affected the cognitive performance. DTC for speed during OW-DT increased during normal and fast speed. CCR significantly decreased, more at slower OW-DT speed. Conversely, CCR was not worsened by TW-DT. CCR did not decline at slow TW-DT speed and improved significantly from slow and normal to fast speeds. DTC for CCR resulted smaller in TW-DT than OW-DT.

CONCLUSIONS

Decline in the cognitive performance during OW-DT is more prominent at slow speed, in keeping with higher demand of attentional resources for this unusual locomotor behaviour. Conversely, motorized TW improves the cognitive performance likely because it reduces the attentional cost of walking. Gait training by TW might improve automaticity in patients with movement disorders.

Minimal effects of age and prolonged physical and mental exercise on healthy adults' gait

BACKGROUND

Gait adaptability in old age can be examined by responses to various perturbations. Fatigability due to mental or muscle exercises can perturb internal cognitive and muscle resources, necessitating adaptations in gait.

RESEARCH QUESTION

What are the effects of age and mental and muscle fatigability on stride outcomes and gait variability?

METHODS

Twelve older (66-75yrs) and twelve young (20-25 yrs) adults walked at 1.2 m/s before and after two fatigue conditions in two separate sessions. Fatigue conditions were induced by repetitive sit-to-stand task (RSTS) and by 30-min of mental tasks and randomized between days (about a week apart). We calculated the average and coefficient of variation of stride length, width, single support, swing time and cadence, and the detrended fluctuations analysis (DFA) based on 120 strides time intervals. We also calculated multi-scale sample entropy (MSE) and the maximal Lyapunov exponent (λmax) of mediolateral (ML) and anteroposterior (AP) of the Center of Pressure (CoP) trajectories.

RESULTS

In both age groups, RSTS modestly affected stride length, single support time, cadence, and CV of stride length (p ≤ 0.05), while the mental task did not affect gait. After fatigability, λmax - ML increased (p ≤ 0.05), independent of fatigue condition. All observed effects were small (η²: 0.001 to 0.02).

SIGNIFICANCE

Muscle and mental fatigability had minimal effects on gait in young and healthy older adults possibly because treadmill walking makes gait uniform. It is still possible that age-dependent muscle activation underlies the uniform gait on the treadmill. Age- and fatigability effects might be more overt during real life compared with treadmill walking, creating a more effective model for examining gait and age adaptability to fatigability perturbations.

Variability of spatiotemporal gait parameters in children with and without Down syndrome during treadmill walking

BACKGROUND

Increasing walking speed and including bilateral external ankle load have been shown to improve aspects of the gait pattern of children with Down syndrome (DS). However, it is unknown if speed and ankle load improves the cycle-to-cycle variability in a similar way.

RESEARCH QUESTION

How do changes of walking speed and external ankle load impact spatiotemporal variability during treadmill walking in children with and without DS?

METHODS

Thirteen children with DS (aged 7-10 years) and thirteen age- and sex-matched typically developing (TD) children participated in this study. Subjects completed two bouts of 60-second treadmill walking at two different speeds (slow and fast) and two load conditions (no load and ankle load equaling to 2% bodyweight at each side). Kinematic data was captured using a Vicon motion capture system. Mean and coefficient of variance of spatiotemporal gait variables were calculated and compared between children with and without DS.

RESULTS AND SIGNIFICANCE

Across all conditions, the DS group took shorter and wider steps than the TD group, but walked with a similar swing percentage, double support percentage, and foot rotation angle. Further, the DS group demonstrated greater variability of all spatiotemporal parameters, except for step width and foot rotation angle. Our results indicated that children with DS can modulate their spatiotemporal gait pattern accordingly like their TD peers when walking faster on a treadmill and/or with an external ankle load. Smaller step width variability in the DS group suggests that mediolateral stability may be prioritized during treadmill walking to safely navigate the treadmill and complete walking tasks. Similar temporal parameters but distinct spatial parameters in the DS group suggest that they may have developed similar rhythmic control but are confined by their spatial movement limitations.

Dose-response relationship between ambulatory load magnitude and load-induced changes in COMP in young healthy adults

OBJECTIVE

To determine the dose-response relationship between ambulatory load magnitude during a walking stress test and load-induced changes in serum concentration of cartilage oligomeric matrix protein (sCOMP) in healthy subjects.

DESIGN

sCOMP was assessed before and after a 30-min walking stress test performed on three test days by 24 healthy volunteers. In each walking stress test, one of three ambulatory loads was applied in a block randomized crossover design: normal body weight (BW) (100%BW = normal load); reduced BW (80%BW = reduced load); increased BW (120%BW = increased load). Knee kinematics and ground reaction force (GRF) were measured using an inertial sensor gait analysis system and a pressure plate embedded in the treadmill.

RESULTS

Load-induced increases in sCOMP rose with increasing ambulatory load magnitude. Mean sCOMP levels increased immediately after the walking stress test by 26.8 ± 12.8%, 28.0 ± 13.3% and 37.3 ± 18.3% for the reduced, normal or increased load condition, respectively. Lower extremity kinematics did not differ between conditions.

CONCLUSIONS

The results of this study provide important evidence of a dose-response relationship between ambulatory load magnitude and load-induced changes in sCOMP. Our data suggests that in normal weight persons sCOMP levels are more sensitive to increased than to reduced load. The experimental framework presented here may form the basis for studying the relevance of the dose-response relationship between ambulatory load magnitude and load-induced changes in biomarkers involved in metabolism of healthy articular cartilage and after injury.

Co-activation is not altered in the contra-lateral limb of individuals with moderate knee osteoarthritis compared to healthy controls

BACKGROUND

Contra-lateral knee joint function in individuals with moderate knee osteoarthritis is not well understood, despite the functional burden of bilateral osteoarthritis on end stage clinical management. The purpose of this study was to determine whether co-activation and joint biomechanics are altered in the contra-lateral limb compared to age-matched controls.

METHODS

20 Individuals with moderate knee osteoarthritis and 20 asymptomatic individuals walked on an instrumented dual belt treadmill at a self-selected speed. Surface electromyography of the knee joint musculature, including quadriceps, hamstrings and gastrocnemius muscles, normalized to maximum voluntary isometric contractions, as well as sagittal plane motion and sagittal and frontal plane moments were collected. Co-contraction indices were calculated and discrete variables from motion and moment data were extracted. Two-sample t-tests and 2-sample mixed model ANOVAs were performed with alpha <0.05.

FINDINGS

Contra-lateral knee muscle co-activation differences were not found between groups (p > 0.65). Peak knee adduction moment (0.41 Nm/kg vs. 0.32 Nm/kg) and knee adduction moment impulse (0.14 Nm s/kg vs. 0.10 Nm s/kg) were higher in the contra-lateral limb compared to the asymptomatic group respectively, whereas the sagittal motion (9.8° vs. 14.4°) and moment ranges (0.66 Nm/kg vs. 0.86 Nm/kg) during stance were less dynamic (p < 0.03).

INTERPRETATION

The contra-lateral limb was functioning differently biomechanically despite no changes present in muscle co-activation. Findings suggest biomechanical changes are occurring without greater demand on the neuromuscular system to preserve contra-lateral joint function in moderate knee osteoarthritis gait. A greater focus should be made to address biomechanical abnormalities in both knees of individuals with moderate unilateral symptomatic knee osteoarthritis.

Local dynamic stability during treadmill walking can detect children with developmental coordination disorder

OBJECTIVE

Developmental coordination disorder (DCD) is an innate impairment of motor coordination that affects basic locomotion and balance. This study investigated local dynamic stability of trunk accelerations during treadmill walking as an objective evaluation of gait stability and the sensitivity and specificity of this measure to discriminate children with DCD from typically developing children.

METHOD

Eight children with DCD and ten age- and gender-matched typically developing children (TD) walked four minutes on a treadmill. Trunk accelerations in vertical, medio-lateral and anterior-posterior directions were recorded with a sternum mounted accelerometer at 256Hz. Short term local dynamic stability (λs), root mean square (RMS) and relative root mean square (RMSR) were calculated from measures of orthogonal trunk accelerations. Receiver operating characteristic curve (ROC) analysis was performed to discriminate between groups based on short term local dynamic stability.

RESULTS

λs was significantly greater in children with DCD in the main movement direction (AP) (DCD: 1.69±0.17 λs; TD:1.41±0.17 λs; p=0.005), indicating reduced local dynamic stability. RMS and RMSR accelerations showed no difference between children with DCD and TD children in any direction. The ROC analysis of λs in separate directions and in two dimensions showed an excellent accuracy of discriminating between children with DCD and TD children. Anterior-posterior direction in combination with medio-lateral or vertical showed best performance with an area under the curve (AUC) of 0.91.

CONCLUSION

We have shown that children with developmental coordination disorder have general reduced local dynamic stability and that the short term Lyapunov exponent has good power of discrimination between DCD and TD.

Study of the association between gait variability and physical activity

BACKGROUND

Gait variability can be considered an indirect measure of gait stability, in particular regarding temporal or spatial variability assessment. Physical activity, such as walking, is advised for the elderly and can be improved by gait stability. The aim of this study was to investigate the associations between gait stability and physical activity in women of different age ranges.

METHODS

Forty-two healthy women of different age ranges (18-40 yrs. and 65-75 yrs.) were recruited in the study. To assess physical activity, the subjects wore a multi-sensor activity monitor for a whole week, inferring the time spent in moderate to vigorous physical activity (MVPA). MVPA were analysed in bouts of at least 10 subsequent minutes (MVPAbouts) and in overall minutes (MVPAtot). A kinematic analysis was performed with an optoelectronic system to calculate gait variability - expressed as standard deviation (SD) and coefficient of variability (CV) of step width, stride length, stance and swing time (during treadmill walking at different speeds).

RESULTS

Elderly women, with high walking speed (5 km/h), and moderate step width variability (CV = 8-27%), met the recommended levels of physical activity (MVPAtot and MVPAbouts). Furthermore, gait variability, adjusted for age and number of falls, was significantly and negatively associated with MVPAtot only at 3.5 km/h, and with MVPAbouts only at 4 km/h.

CONCLUSIONS

In a population of healthy elderly women, gait variability was significantly and negatively associated with the level of physical activity. Healthy elderly women, with moderate gait variability (step width variability), and high preferred walking speed, seem to be able to meet the recommended levels of physical activity.

Walking modality, but not task difficulty, influences the control of dual-task walking

During dual-task gait, changes in the stride-to-stride variability of stride time (STV) are suggested to represent the allocation of cognitive control to walking [1]. However, contrasting effects have been reported for overground and treadmill walking, which may be due to differences in the relative difficulty of the dual task. Here we compared the effect of overground and treadmill dual-task walking on STV in 18 healthy adults. Participants walked overground and on a treadmill for 120s during single-task (walking only) and dual-task (walking whilst performing serial subtractions in sevens) conditions. Dual-task effects on STV, cognitive task (serial subtraction) performance and perceived task difficulty were compared between walking modalities. STV was increased during overground dual-task walking, but was unchanged during treadmill dual-task walking. There were no differences in cognitive task performance or perceived task difficulty. These results show that gait is controlled differently during overground and treadmill dual-task walking. However, these differences are not solely due to differences in task difficulty, and may instead represent modality dependent control strategies.

30 min of treadmill walking at self-selected speed does not increase gait variability in independent elderly

Walking is one of the preferred exercises among elderly, but could a prolonged walking increase gait variability, a risk factor for a fall in the elderly? Here we determine whether 30 min of treadmill walking increases coefficient of variation of gait in elderly. Because gait responses to exercise depend on fitness level, we included 15 sedentary and 15 active elderly. Sedentary participants preferred a lower gait speed and made smaller steps than the actives. Step length coefficient of variation decreased ~16.9% by the end of the exercise in both the groups. Stride length coefficient of variation decreased ~9% after 10 minutes of walking, and sedentary elderly showed a slightly larger step width coefficient of variation (~2%) at 10 min than active elderly. Active elderly showed higher walk ratio (step length/cadence) than sedentary in all times of walking, but the times did not differ in both the groups. In conclusion, treadmill gait kinematics differ between sedentary and active elderly, but changes over time are similar in sedentary and active elderly. As a practical implication, 30 min of walking might be a good strategy of exercise for elderly, independently of the fitness level, because it did not increase variability in step and stride kinematics, which is considered a risk of fall in this population.

The interacting effects of treadmill walking and different types of visuospatial cognitive task: Discriminating dual task and age effects

OBJECTIVE

The objective of this study is to examine the influence that visuospatial cognitive tasks have on gait function during DT treadmill walking, and as a function of age. Conversely, to examine the influence that walking has on executive functions involving visuospatial processing.

METHODS

Twenty-five young (26±6.1years) and 25 older adults (76±3.9) performed different types of computerized visuomotor (VM) tracking and visuospatial cognitive tasks (VCG) while standing and treadmill walking. Spatiotemporal gait variables, average values and co-efficient of variation (COV) were obtained from 40 consecutive steps during single- and dual-task walk trials. Performance-based measures of the VM and VCG task were obtained during standing and walking.

RESULTS

VM dual-task walking had a significant effect on gait measures in the young age group (YG), but no DT effect was observed in the old age group (OG). Visuomotor tracking performance, however, was significantly reduced in the OG as compared to the YG when tested in both standing and walking. The opposite was true for VCG; a significant DT effect on gait performance was observed in the OG, but no DT effect was observed in the YG. Success rate of the VCG task decreased during walking, but only for OG.

CONCLUSION

Controlling gait speed and objective evaluation of the visuospatial cognitive tasks helps to determine the level of engagement in the DT tasks. This is important in order to determine the strategies used during the DT test protocols, i.e. cross-domain interference.

Dual-belt treadmill familiarization: Implications for knee function in moderate knee osteoarthritis compared to asymptomatic controls

BACKGROUND

Effect of treadmill familiarization on knee function in osteoarthritis is not clear. Purpose was to determine whether spatiotemporal characteristics, knee joint biomechanics and muscle activation patterns change as individuals with and without medial compartment knee osteoarthritis familiarize to dual-belt treadmill walking over 6min.

METHODS

20 individuals with knee osteoarthritis and 20 asymptomatic controls walked at a self-selected speed. Spatiotemporal characteristics, sagittal plane joint motions, sagittal and frontal plane moments and knee joint muscle activation patterns, amplitude normalized to maximum isometric contractions were analyzed. Discrete measures were extracted from each biomechanical waveform and principal component analysis was used to determine knee joint muscle activation patterns. Statistical significance was determined using Analysis of Variance models (alpha=0.05).

FINDINGS

Spatiotemporal gait characteristics, knee motion and moment differences were found between groups however no group by time interactions existed and no changes in these variables were found over 6min of walking. Group differences in muscle activation patterns were found in all muscle activations. Muscle activation amplitude and patterns at minute 5 and 6 were generally lower, less prolonged and more dynamic when compared to minute 1 and 3.

INTERPRETATION

Individuals with and without medial compartment knee osteoarthritis familiarized to treadmill walking in a similar manner. Minimal changes to knee biomechanics were found during treadmill familiarization. Five to six minutes of familiarization should be considered for surface electromyography in these populations.

The effect of treadmill-based and track-based walking training on physical fitness in ankle-sprain experienced young people

The purpose of this study was to evaluate the effects of 12-week treadmill-based (MT) and track-based (TT) walking program on maximal oxygen consumption (VO_2max), muscular endurance, muscle strength, and ankle range of motion (ROM) in ankle sprain experienced young people. Twenty subjects (12 males, 8 females) volunteered to participate in this study and divided into two groups (MT and TT). All subjects completed MT and TT 4 times per week with each session of 60 min with 65% from maximum heart rate. Incremental test on treadmill and 20-m shuttle run test for endurance capacity (VO_2max), 2-km walking test for muscular endurance, vertical jump for strength, and ankle ROM for flexibility were analyzed before and after the training intervention. We found significant increase in incremental, 2-km walking and 20-m shuttle run after both MT and TT. Just after TT were significant increased vertical jump and ankle ROM. In conclusion, TT seems to induce a more positive effect on muscle strength in lower extremity and ankle ROM than treadmill-based walking training in ankle sprain experienced young people.

Comparison of body's center of mass motion relative to center of pressure between treadmill and over-ground walking

Treadmills have been used in rehabilitation settings to provide convenient protocols and continuous monitoring of movement over multiple cycles at well-controlled speeds for gait and balance training. However, the potential differences in the movement control may affect the translation of the training outcomes to real life over-ground walking (OW). The similarities and differences in the balance control between treadmill walking (TW) and OW have largely been unexplored. The current study bridged the gap by comparing the motions of the body's center of mass (COM) relative to the center of pressure (COP) between TW and OW, in terms of the COM-COP inclination angle (IA) and its rate of change (RCIA). The movement of the COM and COP separately were quite different between OW and TW, but when describing the COM motion relative to the COP, the COM motions became similar qualitatively with similar butterfly patterns. However, significantly increased peak values in themediolateral RCIA and greater ranges of mediolateral IA were found during TW (p<0.004). In the sagittal plane, the posterior velocity of the belt led to an anterior RCIA (posterior RCIA in OW) with increasing anterior IA during early double-limb support phase, and reduced posterior RCIA (p<0.009) with an increased anterior IA (p<0.001) during the remainder of the phase. These differences between TW and OW may have to be taken into account in future designs of strategies to optimize the translation of treadmill gait training outcomes into real life over-ground walking.

Effects of belt speed on the body's center of mass motion relative to the center of pressure during treadmill walking

Treadmills are often used in clinical settings to improve walking balance control in patients with gait impairments. However, knowledge of the effects of belt speed on balance control remains incomplete. The current study determined such effects in terms of inclination angles (IA) and the rate of change (RCIA) of the center of mass (COM) motion relative to the center of pressure (COP) in twelve healthy adults at five belt speeds, including the subjects' preferred walking speed (PWS), as measured using a motion capture system and an instrumented treadmill. The values of IAs and RCIAs at key gait events and their average values over single-limb support (DLS) and double-limb support (DLS) were compared between speeds using one-way repeated measures analysis of variances. While the COM-COP controls were different between SLS and DLS, they were inter-related to form an integrated whole. Among the belt speeds, the range of frontal IA during SLS was smallest at the PWS (p<0.05). With increasing speed, most variables of the sagittal IAs and RCIAs, and of the frontal RCIAs during DLS showed a linearly increasing trend (p<0.001). A linearly decreasing trend was found in the frontal IA at toe-off and in the average frontal RCIA during SLS (p<0.05). The PWS appeared to be the best compromise between frontal stability during SLS and smooth weight-transfer during DLS. The current results provide useful baseline data for selecting speeds according to training needs, and may be helpful for developing protocols for gait retraining for patients with gait impairment.

Effect of rain boot shaft length on lower extremity muscle activity during treadmill walking

[Purpose] This study aimed to determine the extent of lower extremity muscle activity before and after walking based on rain boot shaft length. [Subjects and Methods] The subjects, 12 young and healthy females, were divided into three groups based on rain boot shaft length (long, middle, and short). They walked on a treadmill for 30 minutes. Activity of the rectus femoris, vastus lateralis, semitendinosus, tibialis anterior, peroneus longus, and gastrocnemius was measured using electromyography before and after walking. Two-way repeated measures analysis of variance was performed to compare the muscle activities of each group. [Results] There were no significant differences in terms of the interactive effects between group and time for all muscles, the main effects of group, or the main effects of time. [Conclusion] The results of this study may indicate that movement of the lower extremities was not significantly limited by friction force based on the characteristics of the boot material or the circumference of the boot shaft. Thus, it may be helpful instead to consider the material of the sole or the weight of the boots when choosing which rain boots to wear.

Changes in cortico-spinal excitability following uphill versus downhill treadmill exercise

An acute bout of aerobic exercise induces neuroplasticity in the motor cortex. Moreover, paired associative stimulation (PAS) is known to induce neuroplasticity in M1. However, the possible influence of the type of exercise on the neuroplastic changes remains unknown. The present study investigated the effects of two different modes of muscle contraction produced during locomotor exercise on changes in corticospinal (CS) excitability. Subjects performed two 30-min treadmill exercises at an intensity corresponding to 60% of their maximal heart rate with either a +10% (uphill) or -10% (downhill) slope. These exercises were followed or not by paired associative stimulation method (PAS₂₅) which consisted of 200 paired stimuli (0.25Hz, 15min) of median nerve electrical stimulation followed by transcranial magnetic stimulation of the hand M1 area (ISI 25ms). Motor evoked potentials (MEP), assessed through abductor pollicis brevis (APB) activity were obtained before exercise, at 5min, 15min and 30min after exercise. A significant (P<0.05) increase of the MEP amplitude was observed 30min after both exercises but was not different between the two modes of locomotion. On the contrary, MEP amplitude with PAS₂₅ increased only 30min after downhill exercise. We conclude that sub-maximal treadmill exercise increases CS excitability within a period of 30min. However, the predominant mode of muscle contraction during uphill versus downhill locomotion does not influence CS excitability when assessed using a non-exercised muscle. However, results from PAS₂₅ suggest that specific neuroplastic changes occur likely due to homeostatic mechanisms induced by exercise plus a PAS protocol.

Treadmill walking is not equivalent to overground walking for the study of walking smoothness and rhythmicity in older adults

Treadmills are appealing for gait studies, but some gait mechanics are disrupted during treadmill walking. The purpose of this study was to examine the effects of speed and treadmill walking on walking smoothness and rhythmicity of 40 men and women between the ages of 70-96 years. Gait smoothness was examined during overground (OG) and treadmill (TM) walking by calculating the harmonic ratio from linear accelerations measured at the level of the lumbar spine. Rhythmicity was quantified as the stride time standard deviation. TM walking was performed at two speeds: a speed matching the natural OG walk speed (TM-OG), and a preferred TM speed (PTM). A dual-task OG condition (OG-DT) was evaluated to determine if TM walking posed a similar cognitive challenge. Statistical analysis included a one-way Analysis of Variance with Bonferroni corrected post hoc comparisons and the Wilcoxon signed rank test for non-normally distributed variables. Average PTM speed was slower than OG. Compared to OG, those who could reach the TM-OG speed (74.3% of sample) exhibited improved ML smoothness and rhythmicity, and the slower PTM caused worsened vertical and AP smoothness, but did not affect rhythmicity. PTM disrupted smoothness and rhythmicity differently than the OG-DT condition, likely due to reduced speed. The use of treadmills for gait smoothness and rhythmicity studies in older adults is problematic; some participants will not achieve OG speed during TM walking, walking at the TM-OG speed artificially improves rhythmicity and ML smoothness, and walking at the slower PTM speed worsens vertical and AP gait smoothness.

Bone turnover increases during supervised treadmill walking in Thai postmenopausal women

Introduction

Treadmill walking is a cheap and attainable form of exercise, which carries a low injury risk and confers other health benefit. The aim of this study is to investigate the effects of 3-month treadmill walking on biochemical bone markers in Thai postmenopausal women.

Material and methods

Thai postmenopausal women participated in a 3-month supervised treadmill walking program. The program consisted of treadmill walking, the intensity of which was 55-70% of maximal heart rate, with duration of 30 min per day, at a frequency of 3 days a week. Crosslinked C-terminal telopeptides of type I collagen (CTX-I) and N-terminal propeptides of type I procollagen (PINP) level were measured at baseline and at 1 week after 3-month training.

Results

Eighteen women completed the training program. The average age of patients was 59.39 ± 4.18 years. The average period after menopause was 9.28 ± 6.52 years. CTX-I and PINP levels at baseline were 0.43 ± 0.14 and 52.15 ± 13.43 ng/ml. CTX-I and PINP levels after 3-month training were 0.80 ± 0.26 and 66.77 ± 22.82 ng/ml. Bone resorption and formation markers were significantly increased after treadmill walking (p < 0.01).

Conclusion

Bone turnover increases after 3-month supervised treadmill walking in Thai postmenopausal women.

Biomechanical and perceived differences between overground and treadmill walking in children with cerebral palsy

The treadmill is widely used as an instrument for gait training and analysis. The primary purpose of this study was to compare biomechanical variables between overground and treadmill walking in children with cerebral palsy (CP). Perceived differences between the two walking modes were also investigated by comparing self-selected walking speeds. Twenty children with CP performed both overground and treadmill walking at a matched speed for biomechanical comparison using a 3-D motion analysis system. In addition, they were asked to select comfortable and fastest walking speeds under each walking condition to compare perceived differences. Significant differences in spatiotemporal variables were found including higher cadence and shorter stride length during treadmill walking at a matched speed (for all, P<.003). The comparison of joint kinematics demonstrated significant differences between overground and treadmill walking, which showed increases in peak angles of ankle dorsi-flexion, knee flexion/extension, and hip flexion (for all, P<.001), increases in ankle and hip excursions and a decrease in pelvic rotation excursion while walking on treadmill (for all, P<.002). Comparison of perceived difference revealed that children with CP chose significantly slower speeds when asked to select their comfortable and fastest walking speeds on the treadmill as compared to overground (for both, P<.001). Our results suggest that these biomechanical and perceived differences should be considered when using a treadmill for gait intervention or assessment.

The effects of the length of rain boots on balance during treadmill walking

[Purpose] Effects of muscle fatigue on lower-extremity balance were evaluated in 12 healthy young women in their 20s while they walked on a treadmill wearing rain boots of different lengths. [Methods] The rain boots were divided into three groups based on the shaft length (Long, Middle, Short). Romberg's test was applied and limits of stability were measured before and after treadmill walking. [Results] Romberg's test showed a significant main effect for time. There were significant differences between the center of gravity area, length, and velocity when the eyes were open and the center of gravity length, velocity, and length/cm(2) when the eyes were closed. Changes in the limits of stability also showed a significant main effect of time. There were significant differences in pre-test and post-test values in the left, right, forward, and total directions. [Conclusion] It was found that muscle fatigue in the lower extremities generated by walking in rain boots affected the joints and the adjuster muscles, depending on shaft lengths. Compensation due to visual feedback and the length of the boot shaft affected movement of the distal joints, resulting in a reduced ability to balance.

Stumbling reactions during perturbed walking: Neuromuscular reflex activity and 3-D kinematics of the trunk - A pilot study

Reflex activity of the lower leg muscles involved when compensating for falls has already been thoroughly investigated. However, the trunk׳s role in this compensation strategy remains unclear. The purpose of this study, therefore, was to analyze the kinematics and muscle activity of the trunk during perturbed walking. Ten subjects (29 ± 3 yr;79 ± 11 cm;74 ± 14 kg) walked (1m/s) on a split-belt treadmill, while 5 randomly timed, right-sided perturbations (treadmill belt deceleration: 40 m/s(2)) were applied. Trunk muscle activity was assessed with a 12-lead-EMG. Trunk kinematics were measured with a 3D-motion analysis system (12 markers framing 3 segments: upper thoracic area (UTA), lower thoracic area (LTA), lumbar area (LA)). The EMG-RMS [%] (0-200 ms after perturbation) was analyzed and then normalized to the RMS of normal walking. The total range of motion (ROM;[°]) for the extension/flexion, lateral flexion and rotation of each segment were calculated. Individual kinematic differences between walking and stumbling [%; ROM] were also computed. Data analysis was conducted descriptively, followed by one- and two-way ANOVAs (α=0.05). Stumbling led to an increase in ROM, compared to unperturbed gait, in all segments and planes. These increases ranged between 107 ± 26% (UTA/rotation) and 262 ± 132% (UTS/lateral flexion), significant only in lateral flexion. EMG activity of the trunk was increased during stumbling (abdominal: 665 ± 283%; back: 501 ± 215%), without significant differences between muscles. Provoked stumbling leads to a measurable effect on the trunk, quantifiable by an increase in ROM and EMG activity, compared to normal walking. Greater abdominal muscle activity and ROM of lateral flexion may indicate a specific compensation pattern occurring during stumbling.

Influence of contextual task constraints on preferred stride parameters and their variabilities during human walking

Walking is not always a free and unencumbered task. Everyday activities such as walking in pairs, in groups, or on structured walkways can limit the acceptable gait patterns, leading to motor behavior that differs from that observed in more self-selected gait. Such different contexts may lead to gait performance different than observed in typical laboratory experiments, for example, during treadmill walking. We sought to systematically measure the impact of such task constraints by comparing gait parameters and their variability during walking in different conditions over-ground, and on a treadmill. We reconstructed foot motion from foot-mounted inertial sensors, and characterized forward, lateral and angular foot placement while subjects walked over-ground in a straight hallway and on a treadmill. Over-ground walking was performed in three variations: with no constraints (self-selected, SS); while deliberately varying walking speed (self-varied, SV); and while following a toy pace car programmed to vary speed (externally-varied, EV). We expected that these conditions would exhibit a statistically similar relationship between stride length and speed, and between stride length and stride period. We also expected treadmill walking (TM) would differ in two ways: first, that variability in stride length and stride period would conform to a constant-speed constraint opposite in slope from the normal relationship; and second, that stride length would decrease, leading to combinations of stride length and speed not observed in over-ground conditions. Results showed that all over-ground conditions used similar stride length-speed relationships, and that variability in treadmill walking conformed to a constant-speed constraint line, as expected. Decreased stride length was observed in both TM and EV conditions, suggesting adaptations due to heightened awareness or to prepare for unexpected changes or problems. We also evaluated stride variability in constrained and unconstrained tasks. We observed that in treadmill walking, lateral variability decreased while forward variability increased, and the normally-observed correlation between wider foot placement and external foot rotation was eliminated. Preferred stride parameters and their variability appear significantly influenced by the context and constraints of the walking task.

Gait attentional load at different walking speeds

Gait is an attention-demanding task even in healthy young adults. However, scant evidence exists about the attentional load required at various walking speeds. The aim of this study was to investigate motor-cognitive interference while walking at spontaneous, slow and very slow speed on a treadmill while carrying out a backward counting task, in a group (n = 22) of healthy young participants. Cognitive performance was also assessed while sitting. Higher DT cost on the cognitive task was found at spontaneous and very slow walking speed, while at slow walking speed the cognitive task was prioritized with higher DT cost on the motor task. The attentional allocation during DT depends on walking speed with gait prioritization at spontaneous and very slow speed that likely represent more challenging motor conditions.

The Effects of Diverse Warm-up Exercises on Balance

[Purpose] To examine how stretching, plyometric, and treadmill exercises influence the dynamic balance necessary for sports activities. [Subjects and Methods] Twenty-two healthy subjects participated in this study. The subjects conducted stretching, plyometric exercises, and treadmill walking for set times over a period of three days. The subjects’ dynamic balance was then measured. The measurements were taken prior to the intervention, immediately after the intervention, and 20 minutes after the intervention. All the intervention times were set at 16 minutes, excluding resting times. The data were analyzed with using the two-way ANOVA. [Results] There was no interaction between exercises and time. There were no statistical differences among the exercises and no statistical differences in changes over time. [Conclusion] This study found that warm-up exercises such as plyometric exercises, stretching, and treadmill walking have no effect on the dynamic of balance in healthy subjects.

Frontal plane margin of stability is increased during texting while walking

Injurious falls associated with cell phone use during ambulation are increasingly common. Studies examining texting while walking suggest this task alters the attentional component of walking to the extent that safety may be compromised. Here, we quantified the extent to which frontal plane dynamic stability while walking was affected by the cognitive and physical demands of texting. Twenty experienced texters performed four, 10-min treadmill walking tasks at a self-selected velocity in random order: (1) normal walk (control), (2) walking while verbally performing mathematical calculations (cognitive demand), (3) walking while bimanually holding and looking directly at a phone (physical demand), and (4) walking while texting continuous mathematical calculations (cognitive and physical). We quantified the frontal plane minimum margin of stability (MOSmin), a measure that considers the position and normalized velocity of the center of mass with respect to the lateral border of the base of support was calculated over each 10-min walking period. Compared to the normal walking condition, the texting and phone holding conditions resulted in a small but significant (6%) increase in MOSmin (p=0.005 and 0.026, respectively). Compared to normal walking, the effect of performing mathematical calculations on MOSmin was not significant (p=0.80). These results suggest that frontal plane stability of experienced texters during controlled treadmill walking conditions can be affected by the physical, but not the cognitive demand of texting. This may represent a compensatory mechanism by the CNS to ensure stability in the event of an unexpected disturbance.

Effects of exercise training on indicators of adipose tissue angiogenesis and hypoxia in obese rats

OBJECTIVE

To investigate the effects of obesity and exercise training on regional adipose tissue angiogenesis and hypoxia markers in rats.

METHODS

Lean (Fa/Fa) and obese (fa/fa) male Zucker rats at 2 months of age were randomly assigned to a sedentary or an exercise training group (lean sedentary: n=7, lean exercise: n=8, obese sedentary: n=7, obese exercise: n=8). The exercise group walked on a rat treadmill 5 times per week for 8 weeks. Inguinal and epididymal adipose tissue vascular endothelial growth factor A (VEGF-A) and lactate levels were determined.

RESULTS

There were significant effects of obesity in increasing inguinal (P<0.001) and epididymal (P<0.05) adipose tissue VEGF-A, and a significant effect of exercise training in increasing epididymal adipose tissue VEGF-A (P<0.05). There was a significant effect of obesity in increasing inguinal adipose tissue lactate levels (P<0.001). Compared to lean sedentary animals, obese sedentary animals had significantly higher epididymal adipose tissue lactate levels (P<0.001); compared to obese sedentary animals, obese exercise rats had significantly lower epididymal adipose tissue lactate levels (P<0.05).

CONCLUSIONS

Exercise training increased adipose tissue VEGF-A, an important factor of tissue angiogenesis, and lowered adipose tissue lactate, an indicator of adipose tissue hypoxia in obese rats. However, these effects are depot-specific and only observed in intra-abdominal adipose tissue.

The interacting effect of cognitive and motor task demands on performance of gait, balance and cognition in young adults

Mobility limitations and cognitive impairments, each common with aging, reduce levels of physical and mental activity, are prognostic of future adverse health events, and are associated with an increased fall risk. The purpose of this study was to examine whether divided attention during walking at a constant speed would decrease locomotor rhythm, stability, and cognitive performance. Young healthy participants (n=20) performed a visuo-spatial cognitive task in sitting and while treadmill walking at 2 speeds (0.7 and 1.0 m/s).Treadmill speed had a significant effect on temporal gait variables and ML-COP excursion. Cognitive load did not have a significant effect on average temporal gait variables or COP excursion, but variation of gait variables increased during dual-task walking. ML and AP trunk motion was found to decrease during dual-task walking. There was a significant decrease in cognitive performance (success rate, response time and movement time) while walking, but no effect due to treadmill speed. In conclusion walking speed is an important variable to be controlled in studies that are designed to examine effects of concurrent cognitive tasks on locomotor rhythm, pacing and stability. Divided attention during walking at a constant speed did result in decreased performance of a visuo-spatial cognitive task and an increased variability in locomotor rhythm.

Stride length asymmetry in split-belt locomotion

The number of studies utilizing a split-belt treadmill is rapidly increasing in recent years. This has led to some confusion regarding the definitions of reported gait parameters. The purpose of this paper is to clearly present the definitions of the gait parameters that are commonly used in split-belt treadmill studies. We argue that the modified version of stride length for split-belt gait, which is different from the standard definition of stride length and actually is a measure of limb excursion, should be referred to as 'limb excursion' in future studies. Furthermore, the symmetry of stride length and stride time is specifically addressed.

Different motor tasks impact differently on cognitive performance of older persons during dual task tests

BACKGROUND

Dual task paradigm states that the introduction of a second task during a cognitive or motor performance results in a decreased performance in either task. Treadmill walk, often used in clinical applications of dual task testing, has never been compared to overground walk, to ascertain its susceptibility to interference from a second task. We compared the effects of overground and treadmill gait on dual task performance.

METHODS

Gait kinematic parameters and cognitive performance were obtained in 29 healthy older adults (mean age 75 years, 14 females) when they were walking freely on a sensorized carpet or during treadmill walking with an optoelectronic system, in single task or dual task conditions, using alternate repetition of letters as a cognitive verbal task.

FINDINGS

During overground walking, speed, cadence, step length stride length, and double support time (all with P value<0.001) and cognitive performance (number of correct words, P<0.001) decreased substantially from single to dual task testing. When subjects walked at a fixed speed on the treadmill, cadence decreased significantly (P=0.005), whereas cognitive performance remained unaffected.

INTERPRETATION

Both motor and cognitive performances decline during dual task testing with overground walking. Conversely, cognitive performance remains unaffected in dual task testing on the treadmill. In the light of current dual task paradigm, these findings may have relevant implication for our understanding of motor control, as they suggest that treadmill walk does not involve brain areas susceptible to interference from the introduction of a cognitive task.

Estimating fall risk with inertial sensors using gait stability measures that do not require step detection

Falls have major consequences both at societal (health-care and economy) and individual (physical and psychological) levels. Questionnaires to assess fall risk are commonly used in the clinic, but their predictive value is limited. Objective methods, suitable for clinical application, are hence needed to obtain a quantitative assessment of individual fall risk. Falls in older adults often occur during walking and trunk position is known to play a critical role in balance control. Therefore, analysis of trunk kinematics during gait could present a viable approach to the development of such methods. In this study, nonlinear measures such as harmonic ratio (HR), index of harmonicity (IH), multiscale entropy (MSE) and recurrence quantification analysis (RQA) of trunk accelerations were calculated. These measures are not dependent on step detection, a potentially critical source of error. The aim of the present study was to investigate the association between the aforementioned measures and fall history in a large sample of subjects (42 fallers and 89 non - fallers) aged 50 or older. Univariate associations with fall history were found for MSE and RQA parameters in the AP direction; the best classification results were obtained for MSE with scale factor τ = 2 and for maximum length of diagonals in RQA (72.5% and 71% correct classifications, respectively). MSE and RQA were found to be positively associated with fall history and could hence represent useful tools in the identification of subjects for fall prevention programs.

Gait adaptability and brain activity during unaccustomed treadmill walking in healthy elderly females

This study evaluated brain activity during unaccustomed treadmill walking using positron emission tomography (PET) and [(18)F]fluorodeoxyglucose. Twenty-four healthy elderly females (75-82 years) participated in this study. Two PET scans were performed after 25 min of rest and after walking for 25 min at 2.0 km/h on a treadmill. Participants were divided into low and high step-length variability groups according to the median coefficient of variation in step length during treadmill walking. We compared the regional changes in brain glucose metabolism between the two groups. The most prominent relative activations during treadmill walking compared to rest in both groups were found in the primary sensorimotor areas, occipital lobe, and anterior and posterior lobe of the cerebellum. The high step-length variability group showed significant relative deactivations in the frontal lobe and the inferior temporal gyrus during treadmill walking. There was a significant relative activation of the primary sensorimotor area in the low step-length variability group compared to the high step-length variability group (P = 0.022). Compared to the low step-length variability group, the high step-length variability group exhibited a greater relative deactivation in the white matter of the middle and superior temporal gyrus (P = 0.032) and hippocampus (P = 0.034) during treadmill walking compared to resting. These results suggest that activation of the primary sensorimotor area, prefrontal area, and temporal lobe, especially the hippocampus, is associated with gait adaptability during unaccustomed treadmill walking.