Comfortable Self-selected Speed Research Articles

Pre-pubertal runners demonstrate greater variability in running kinematics than post-pubertal runners

BackgroundAdolescents undergo a period of motor incoordination during puberty characterized by high movement variability. It is unknown if differences in running kinematics variability exist among adolescent long-distance runners. Research questionIs kinematic variability different among male and female adolescent long-distance runners of different stages of physical maturation? MethodsWe enrolled 114 adolescent long-distance runners (ages 8–19, F = 55, M = 59) in this secondary analysis of a larger cross-sectional study. Participants completed a three-dimensional overground running analysis at a comfortable self-selected speed. Peak frontal, sagittal, and transverse plane hip, knee, and ankle/shoe joint angles from the right leg were identified during stance phase for at least five trials. Variability in running kinematics was quantified as the standard deviation of the peak joint angles among the running trials for each participant. Participants were stratified by sex and stage of physical maturation (pre-, mid-, post-pubertal) and two-way ANOVAs compared between-subjects variability among groups (p ≤ .05). ResultsSignificant sex by maturation interactions were observed for hip external rotation and ankle external rotation variability. Sex differences were observed for hip internal rotation, with males demonstrating greater variability, and ankle internal rotation, with females demonstrating greater variability. Pre-pubertal runners demonstrated significantly greater variability than mid-pubertal runners for hip flexion, and greater variability than post-pubertal runners for hip flexion, hip adduction, hip internal rotation, and knee flexion. SignificancePre-pubertal adolescent long-distance runners demonstrate greater stance phase variability in running kinematics than post-pubertal adolescent long-distance runners, while adolescent males and females demonstrate similar variability. Anthropometric and neuromuscular changes that occur during puberty likely influence running patterns and may contribute to more consistent kinematic patterns for post-pubertal runners.

Kinematics predictors of spatiotemporal parameters during gait differ by age in healthy individuals

Joint biomechanics and spatiotemporal gait parameters change with age or disease and are used in treatment decision-making. Research question: To investigate whether kinematic predictors of spatiotemporal parameters during gait differ by age in healthy individuals. Methods: We used an open dataset with the gait data of 114 young adults (M = 28.0 years, SD = 7.5) and 128 older adults (M = 67.5 years, SD = 3.8) walking at a comfortable self-selected speed. Linear regression models were developed to predict spatiotemporal parameters separately for each group using joint kinematics as independent variables. Results: In young adults, knee flexion loading response and hip flexion/extension were the common predictors of gait speed; hip flexion and hip extension contributed to explaining the stride length; hip flexion contributed to explaining the cadence and stride time. In older adults, ankle plantarflexion, knee flexion loading response, and pelvic rotation were the common predictors of the gait speed; ankle plantarflexion and knee flexion loading response contributed to explaining the stride length; ankle plantarflexion loading response and ankle plantarflexion contributed to explain the cadence, stride width and stride time. Significance: Our results suggest that the ability of joint kinematic variables to estimate spatiotemporal parameters during gait differs by age in healthy individuals. Particularly in older adults, ankle plantarflexion was the common predictor of the spatiotemporal parameters, suggesting the importance of the ankle for gait parameters in this age group. This provides insight for clinicians into the most effective evaluation and has been used by physical professionals in prescribing the most appropriate exercises to attenuate the effects produced by age-related neuromuscular changes.

Spre-Pubertal Runners Demonstrate Different Temporal-Spatial Parameters Than Mid- and Post-Pubertal Runners

Background:Temporal-spatial parameters (TSPs; e.g., cadence, step length) have been associated with running-related injuries in adult long-distance runners. However, it is unknown if TSPs are different among adolescent runners of different physical maturation stages. During sprinting, pre-pubertal runners demonstrated lower cadence and shorter step length than mid- and post-pubertal runners, but TSPs have not been investigated for adolescents of different physical maturation stages when running at submaximal speeds.Hypothesis/Purpose:The purpose of this study was to compare TSPs among adolescent long-distance runners of different physical maturation stages. It was expected that pre-pubertal runners would demonstrate a lower cadence and shorter step length than mid- and post-pubertal runners but there would be no differences in TSPs between mid- and post-pubertal runners.Methods:The study was a cross-sectional design with 93 adolescent long-distance runners (F=48, M=45). Participants were categorized into pre- (n=15, age=10.3±1.6 y), mid- (n=35, age=13.0±1.1 y), and post-pubertal (n=43, age=16.4±1.2 y) physical maturation groups. Participants underwent a three-dimensional running analysis at a comfortable self-selected speed. TSPs (cadence [steps/min], step length [m]) were compared among physical maturation groups using one-way ANCOVA (covariate=running speed) with Sidak pairwise comparisons when a main effect was found (P<.05).Results:The average running speeds for pre-, mid-, and post-pubertal runners were 3.36±0.51 m/s, 3.49±0.71 m/s, and 3.79±0.69 m/s, respectively. ANCOVA analysis showed significant differences in cadence (P<.001) and stride length (P<.001) among physical maturation groups when controlling for running speed (Table 1.1). Pre-pubertal runners had a greater cadence (178±13 steps/min) than mid- (169±12 steps/min, P=.01) and post-pubertal runners (168±11 steps/min, P<.001). Pre-pubertal runners also had a shorter step length (1.13±0.20 m) than mid- (1.24±0.20 m, P=.01) and post-pubertal runners (1.36±0.21 m, P<.001). There were no significant differences between mid- and post-pubertal runners (P>.22).Conclusion:When controlling for running speed, pre-pubertal runners demonstrated a greater cadence and shorter step length than both mid- and post-pubertal runners. Lower cadence and longer stride lengths have been associated with running-related injuries in adults. If TSPs have the same association with injury in adolescents as adults, then our study suggest mid- and post-pubertal runners may be at a higher risk of sustaining a running-related injury than pre-pubertal runners due to their lower cadence and longer step lengths. However, prospective research is necessary to better understand the importance of TSPs and running-related injuries in adolescent long-distance runners.Table 1.Temporal-spatial parameters comparison among adolescent long-distance runners of different physical maturation stages.

Influence of hamstring flexibility on running kinematics in adolescent long-distance runners

BackgroundStudies have found no or minimal differences in running kinematics between flexible and inflexible adult runners. The interaction between hamstring flexibility and running kinematics has not been reported in adolescent long-distance runners. Research questionDoes hamstring flexibility influence running kinematics in adolescent long-distance runners? MethodsAdolescent long-distance runners (n = 140, ages 9–19) were enrolled in our cross-sectional study. Hamstring flexibility was assessed with the forward bending Beighton task. Runners were categorized if they tested positive or negative on the forward bending task. Participants ran at a comfortable self-selected speed on a treadmill. Runners who tested positive on the forward bending task (n = 17) were matched with runners who tested negative on the task (n = 17) according to sex, physical maturation, and running speed. Statistical parametric mapping compared trunk, pelvis, hip, and knee kinematic waveforms throughout the gait cycle and independent sample t tests compared temporal-spatial parameters between the groups. ResultsRunners who tested positive on the forward bending task demonstrated significantly greater anterior pelvic tilt during stance (average difference = 4.8° ± 0.4°, p < .001) and swing (average difference = 4.3° ± 0.2°, p < .01) compared to runners who tested negative on the forward bending task. No significant differences were found between groups for the remaining kinematic waveforms or for any temporal-spatial parameters (p > .05). SignificanceThis is the first study to report the interaction between hamstring flexibility and running kinematics in adolescent long-distance runners. The greater anterior pelvic tilt demonstrated by runners with greater hamstring flexibility may place more eccentric demands on the hamstring musculature. However, as there were no other differences in joint kinematics or temporal-spatial parameters between groups, greater hamstring flexibility does not appear to have a significant interaction with running kinematics when running at sub-maximal speeds. Our results suggest hamstring flexibility does not predispose adolescent long-distance runners to sub-optimal segment positions associated with running-related injuries.

Saccade and Fixation Eye Movements During Walking in People With Mild Traumatic Brain Injury.

Background: Clinical and laboratory assessment of people with mild traumatic brain injury (mTBI) indicate impairments in eye movements. These tests are typically done in a static, seated position. Recently, the use of mobile eye-tracking systems has been proposed to quantify subtle deficits in eye movements and visual sampling during different tasks. However, the impact of mTBI on eye movements during functional tasks such as walking remains unknown. Objective: Evaluate differences in eye-tracking measures collected during gait between healthy controls (HC) and patients in the sub-acute stages of mTBI recovery and to determine if there are associations between eye-tracking measures and gait speed. Methods: Thirty-seven HC participants and 67individuals with mTBI were instructed to walk back and forth over 10-m, at a comfortable self-selected speed. A single 1-min trial was performed. Eye-tracking measures were recorded using a mobile eye-tracking system (head-mounted infra-red Tobbii Pro Glasses 2, 100 Hz, Tobii Technology Inc. VA, United States). Eye-tracking measures included saccadic (frequency, mean and peak velocity, duration and distance) and fixation measurements (frequency and duration). Gait was assessed using six inertial sensors (both feet, sternum, right wrist, lumbar vertebrae and the forehead) and gait velocity was selected as the primary outcome. General linear model was used to compare the groups and association between gait and eye-tracking outcomes were explored using partial correlations. Results: Individuals with mTBI showed significantly reduced saccade frequency (p = 0.016), duration (p = 0.028) and peak velocity (p = 0.032) compared to the HC group. No significant differences between groups were observed for the saccade distance, fixation measures and gait velocity (p > 0.05). A positive correlation was observed between saccade duration and gait velocity only for participants with mTBI (p = 0.025). Conclusion: Findings suggest impaired saccadic eye movement, but not fixations, during walking in individuals with mTBI. These findings have implications in real-world function including return to sport for athletes and return to duty for military service members. Future research should investigate whether or not saccade outcomes are influenced by the time after the trauma and rehabilitation.

Comparison the effect of kinetic parameters of innovative storing-restoring hybrid passive (comfort gait) ankle-foot orthosis (AFO) with posterior leaf spring AFO in drop-foot patients: a prospective cohort study

Background: Drop-foot syndrome is a disorder in which the dorsiflexor muscles are weakened or completely paralyzed, leading to foot slapping after the initial contact and foot-dragging during the swing phase. Passive and hybrid passive ankle-foot orthoses (AFOs) are often prescribed as an intervention for this disorder; however, the effects of these AFOs on kinetic parameters during the gait of drop-foot patients seem unclear. This study aimed to compare the affected lower limb joints of ankle, knee, and hip kinetics parameters (moments and powers) during walking in drop-foot patients using an innovative AFO storing-restoring hybrid passive AFO, named “Comfort Gait” and posterior leaf spring (PLS) AFO. Methods: Ten drop-foot patients were recruited in the current study to walk at a comfortable self-selected speed while wearing two different AFO selections. Kinetic parameters with a motion capture system were obtained for these patients. Results: The results of this study revealed a significant increase in the peak values of kinetic parameters of the lower limb of the affected side (ankle, knee, and hip moments and powers) with the innovative designed AFO when compared to PLS AFO (P&lt;0.05). Conclusions: The significant increase of kinetic parameters in drop foot with use of the Comfort Gait as compared to the PLS AFO might suggest the effectiveness of this innovative AFO in improving the gait of foot drop patients more than the use of PLS AFO. Level of Evidence: Level II

The influence of foot hyperpronation on pelvic biomechanics during stance phase of the gait: A biomechanical simulation study.

Despite the theoretical link between foot hyperpronation and biomechanical dysfunction of the pelvis, the literature lacks evidence that confirms this assumption in truly hyperpronated feet subjects during gait. Changes in the kinematic pattern of the pelvic segment were assessed in 15 persons with hyperpronated feet and compared to a control group of 15 persons with normally aligned feet during the stance phase of gait based on biomechanical musculoskeletal simulation. Kinematic and kinetic data were collected while participants walked at a comfortable self-selected speed. A generic OpenSim musculoskeletal model with 23 degrees of freedom and 92 muscles was scaled for each participant. OpenSim inverse kinematic analysis was applied to calculate segment angles in the sagittal, frontal and horizontal planes. Principal component analysis was employed as a data reduction technique, as well as a computational tool to obtain principal component scores. Independent-sample t-test was used to detect group differences. The difference between groups in scores for the first principal component in the sagittal plane was statistically significant (p = 0.01; effect size = 1.06), but differences between principal component scores in the frontal and horizontal planes were not significant. The hyperpronation group had greater anterior pelvic tilt during 20%-80% of the stance phase. In conclusion, in persons with hyperpronation we studied the role of the pelvic segment was mainly to maintain postural balance in the sagittal plane by increasing anterior pelvic inclination. Since anterior pelvic tilt may be associated with low back symptoms, the evaluation of foot posture should be considered in assessing the patients with low back and pelvic dysfunction.

The use of gait analysis in the assessment of patients afflicted with spinal disorders.

Use gait analysis to establish and detail the clinically relevant components of normal human gait, analyze the gait characteristics for those afflicted with spinal pathology, and identify those aspects of human gait that correlate with pre- and postoperative patient function and outcomes. Twenty patients with adult degenerative scoliosis (ADS), 20 patients with cervical spondylotic myelopathy (CSM), and 15 healthy volunteers performed over-ground gait trials with a comfortable self-selected speed using video cameras to measure patient motion, surface electromyography (EMG) to record muscle activity, and force plates to record ground reaction force (GRF). Gait distance and temporal parameters, ankle, knee, hip, pelvic, and trunk range of motion (ROM), duration of lower extremity EMG activity and peak vertical GRF were measured. Patients with ADS and CSM exhibited a significantly slower gait speed, decrease in step length, cadence, longer stride time, stance time, double support time, and an increase in step width compared to those in the control group. These patients also exhibited a significantly different ankle, knee, pelvic, and trunk ROM. Moreover, spinal disorder patients exhibited a significantly longer duration of rectus femoris, semitendinosus, tibialis anterior and medial gastrocnemius muscle activity along with an altered vertical GRF pattern. Gait analysis provides an objective measure of functional gait in healthy controls as well as those with ADS and CSM. This study established and detailed some of the important kinematic and kinetic variables of gait in patients with spinal disorders. We recommend that spine care providers use gait analysis as part of their clinical evaluation to provide an objective measure of function. These slides can be retrieved under Electronic Supplementary Material.

Short-term Impact of Anterior Cruciate Ligament Reconstruction in an Adolescent Population on 3D Knee Kinematics

Objectives:Gait analysis is a proven method for assessing knee biomechanical adaptations in anterior cruciate ligament deficient (ACLD) patients and to quantify the impact of the reconstructive surgery (ACLR). In an adult population, ACLR has shown partial kinematic correction, as they remain in internal tibial rotation, putting them at risk of rotational instability and develop osteoartitis. ACLD adolescents likely adopt similar gait changes to reduce knee instability, but may show quicker or more return to the normal compared to adults. The purpose of this study is to compare the tridimensional (3D) knee kinematics before and after ACLR in adolescents.Methods:25 ACLD patients aged between 13 and 19 years old on a waiting list for ACLR were recruited. Bilateral knee 3D kinematic data was gathered during treadmill walking at comfortable self-selected speed using the KneeKGTM System before and 6-9 months after ACLR. Each participant underwent the same surgical protocol (2-strand hamstring tendon graft, hamstring harvest proximally and kept distally, transphyseal tibial tunnel and transepiphyseal femoral tunnel) by the same experienced surgeon. Three analyses were done: ACLD knee pre vs. post-surgery, contralateral healthy knee pre vs. post-surgery, and ACLR knee vs. healthy contralateral knee.Results:In the sagittal and transverse planes, kinematic patterns remained similar to the pre-op; maintaining the characteristic knee flexion gait pattern during single support phase which is well documented in adult ACLD (hamstring facilitation strategy). The ACLR knee exhibited a more valgus dynamic alignment compared to pre-surgery throughout the gait cycle. The healthy contralateral knee kinematics displayed no significant changes in the frontal and sagittal planes after surgery compared to the pre-op pattern. In the transverse plane, post-op gait analysis showed significantly more external rotation at heel-strike and through weight acceptance. While looking at the gait symmetry post-surgery, ACLR knee revealed significantly more valgus while remaining in greater flexion during single limb support. In the transverse plane, an external rotation tendency is observed in the ACLR knee throughout the gait cycle, except during weight acceptance.Conclusion:This study shows that kinematic adaptations found in ACLD adolescents are likely to endure short term after surgery. For example, the greater knee flexion gait pattern used before surgery is still used after ACLR. Interestingly, adolescents used an external tibial rotation adaptation to limit internal tibial instability before the surgery and this pattern was still present post-surgery. Even if theses protection strategies are efficient, the increased dynamical valgus movement seen could place the graft under pressure while increasing patellofemoral stresses, a common complaint after ACLR. Lastly, post-surgery, the contralateral knee seems to mimic the external tibial rotation gait pattern strategy seen in ACL-knee. This study demonstrates that gait protective strategies are still present short term after the surgery. Biomechanical assessment helps ID these adaptations to optimize post-op rehabilitation and prevent secondary injuries.

Data set of healthy old people assessed for three walking conditions using accelerometric and opto-electronic methods.

Gait patterns of healthy aging are needed to allow a comparison with pathological situations. However, little data is available. To present gait pattern of healthy older specially selected to be "healthy walkers". Fifty-seven older people benefited from a geriatric assessment including clinical and functional evaluations to include only those without gait disorders. Gait data were simultaneously recorded using a tri-axial accelerometer placed on the waist and four 3D position markers placed on the feet at the level of the heel and the toe. Volunteers walked at comfortable self-selected speed (CW), fast self-selected speed (FW), and finally in dual task walking condition (DTW). The extracted gait parameters were: gait speed, stride length, stride frequency, regularity and symmetry, swing, stance and double support time and ratio and minimum toe clearance. Gait speed and stride length were normalized to the right leg length. Fifty-seven older people with a mean age of 69.7 ± 4.2 years old (range from 65 to 82 years) were included. Data were analyzed according to the gender and according to the age (<70 or ≥70 years old). After normalization to leg length, the main significant differences were shown for stride length and minimum toe clearance in CW, FW and in DTW that were shorter in women. The regularity in FW was significantly lower among older volunteers. This work provides a data set considering 14 gait parameters obtained from 57 healthy old people strictly selected and assessed for three walking conditions and shows that GS, SL and MTC have to be related to the gender. The age-related impact on gait performances appears reduced in this cohort.

Glucose uptake heterogeneity of the leg muscles is similar between patients with multiple sclerosis and healthy controls during walking

BackgroundDifficulties in ambulation are one of the main problems reported by patients with multiple sclerosis. A previous study by our research group showed increased recruitment of muscle groups during walking, but the influence of skeletal muscle properties, such as muscle fiber activity, has not been fully elucidated. The purpose of this investigation was to use the novel method of calculating glucose uptake heterogeneity in the leg muscles of patients with multiple sclerosis and compare these results to healthy controls. MethodsEight patients with multiple sclerosis (4 men) and 8 healthy controls (4 men) performed 15min of treadmill walking at a comfortable self-selected speed following muscle strength tests. Participants were injected with≈8mCi of [18F]-fluorodeoxyglucose during walking after which positron emission tomography/computed tomography imaging was performed. FindingsNo differences in muscle strength were detected between multiple sclerosis and control groups (P>0.27). Within the multiple sclerosis, group differences in muscle volume existed between the stronger and weaker legs in the vastus lateralis, semitendinosus, and semimembranosus (P<0.03). Glucose uptake heterogeneity between the groups was not different for any muscle group or individual muscle of the legs (P>0.16, P≥0.05). InterpretationsPatients with multiple sclerosis and healthy controls showed similar muscle fiber activity during walking. Interpretations of these results, with respect to our previous study, suggest that walking difficulties in patients with multiple sclerosis may be more associated with altered central nervous system motor patterns rather than alterations in skeletal muscle properties.

보행경로 너비에 따른 노인의 시 · 공간적 보행 분석

본 연구의 목적은 노인과 정상 성인의 보행경로 너비에 따른 보행 시, 시 공간적 보행 변수의 변화를 알아보기 위함이다. 연구의 대상자는 낙상의 경험이 없는 건강한 노인 20명과 20대 성인 18명으로 하였으며, 3가지 다른 너비의 보행경로(평상시 보행(usual walking), 좁은 너비 보행(narrow base walking), 한줄 보행(centerline-guided walking)에서 보행을 실시하였다. 평상시 보행은 보행경로에 제한을 두지 않았고, 좁은 너비 보행은 각 대상자의 양측 ASIS 사이의 거리를 1/2로 나눈 너비를 보행경로로 설정하였으며, 한줄 보행은 보행경로 중앙에 한 줄을 표시하여 보행을 실시하였다. 보행을 실시하는 동안, GAITRite system을 이용하여 시 공간적 보행 변수의 변화를 비교 분석하였다. 보행경로 너비에 따른 시 공간적 보행 변수 비교에서 20대 성인은 모든 변수에서 유의한 차이를 나타내지 않았으나, 노인의 경우 보행속도, 분속수, 양 뒤꿈치 사이 기저면, 기능적 보행지수가 통계적으로 유의하게 감소하였다(p<.05). 본 연구의 결과를 통해 노인은 20대 성인에 비해 보행경로의 너비가 좁아질수록 낙상에 대한 두려움으로 인해 보행변수에 영향을 미친다는 것을 확인할 수 있었으며, 이를 통해 노인의 낙상 예방 훈련을 위한 적절한 보행너비에 대한 이론적 근거를 제시할 수 있을 것으로 생각된다. The purpose of this study was to investigate the changes in temporospatial variables in healthy elderly and healthy adults during usual walking, narrow base walking and centerline-guided walking. Twenty healthy elderly and nineteen healthy adults were participated in this study. In each conditions, the subjects were walked on a 6m walkway at comfortable self-selected speeds under three conditions : (1) usual walking, (2) walking within a 50% of the distance between the subject's ASIS (3) walking along a centerline. GAITRite system was used for kinematic analysis to assess the temporospatial variables. There were no significant changes in healthy adults(p>.05), but walking speed, cadence, H-H base support, functional ambulation performance were significantly decreased progressively as pathway narrowed in elderly adults(p<.05). The results show that elderly people had more difficulty with walking on narrow pathway for fear of falling. This study provides data for use in basic research into safe walking and preventing falling for elderly.

Frontal joint dynamics when initiating stair ascent from a walk versus a stand

Ascending stairs is a challenging activity of daily living for many populations. Frontal plane joint dynamics are critical to understand the mechanisms involved in stair ascension as they contribute to both propulsion and medio-lateral stability. However, previous research is limited to understanding these dynamics while initiating stair ascent from a stand. We investigated if initiating stair ascent from a walk with a comfortable self-selected speed could affect the frontal plane lower-extremity joint moments and powers as compared to initiating stair ascent from a stand and if this difference would exist at consecutive ipsilateral steps on the stairs. Kinematics data using a 3-D motion capture system and kinetics data using two force platforms on the first and third stair treads were recorded simultaneously as ten healthy young adults ascended a custom-built staircase. Data were collected from two starting conditions of stair ascent, from a walk (speed: 1.42±0.21m/s) and from a stand. Results showed that subjects generated greater peak knee abductor moment and greater peak hip abductor moment when initiating stair ascent from a walk. Greater peak joint moments and powers at all joints were also seen while ascending the second ipsilateral step. Particularly, greater peak hip abductor moment was needed to avoid contact of the contralateral limb with the intermediate step by counteracting the pelvic drop on the contralateral side. This could be important for therapists using stair climbing as a testing/training tool to evaluate hip strength in individuals with documented frontal plane abnormalities (i.e. knee and hip osteoarthritis, ACL injury).

Do lower-extremity joint dynamics change when stair negotiation is initiated with a self-selected comfortable gait speed?

Previous research on the biomechanics of stair negotiation has ignored the effect of the approaching speed. We examined if initiating stair ascent with a comfortable self-selected speed can affect the lower-extremity joint moments and powers as compared to initiating stair ascent directly in front of the stairs. Healthy young adults ascended a custom-built staircase instrumented with force platforms. Kinematics and kinetics data were collected simultaneously for two conditions: starting from farther away and starting in front of the stairs and analyzed at the first and second ipsilateral steps. Results showed that for the first step, participants produced greater peak knee extensor moment, peak hip extensor and flexor moments and peak hip positive power while starting from farther away. Also, for both the conditions combined, participants generated lesser peak ankle plantiflexor, greater peak knee flexor moment, lesser peak ankle negative power and greater peak hip negative power while encountering the first step. These results identify the importance of the starting position in experiments dealing with biomechanics of stair negotiation. Further, these findings have important implications for studying stair ascent characteristics of other populations such as older adults.

Effect of centerline-guided walking on gait characteristics in healthy subjects

One of the challenges in collecting ground reaction force (GRF) and moment data for gait analysis is to obtain “good hits” when the subject walks past the forceplates. We examined whether centerline-guided walking would significantly increase the chance of good hits and alter gait characteristics. Thirty-five healthy individuals (age: 37±13 yrs) walked on a walkway with five embedded forceplates at comfortable self-selected speeds under two conditions: (1) free walking and (2) walking along a centerline and avoiding stepping on it. Gait kinematics and GRF were collected using an 8-camera optoelectronic system and five forceplates, respectively. Surface electromyographic (EMG) activity of the rectus femoris, hamstring, gastrocnemius (GAS), and tibialis anterior (TA) were monitored bilaterally. The probability of good hits significantly increased with the centerline-guided walking ( p=0.008). Repeated measures MANOVA and follow-up univariate tests revealed no significant differences between the two conditions in any of the spatiotemporal parameters except for a significant increase in step width with centerline walking ( p<0.001). Centerline guiding significantly increased peak mediolateral GRF ( p<0.001) and hip adduction/abduction and ankle internal/external rotation ranges of motion ( p<0.01). In addition, the average EMG activity in GAS and TA during the stance phase significantly increased with the centerline walking ( p<0.001). In general, the centerline walking tended to impact women more than men. Centerline-guided walking increases the chance of good hits but biomechanical characteristics of gait in the frontal and transverse planes and EMG activity should be interpreted with caution, especially in women.

Motion of the whole body's center of mass when stepping over obstacles of different heights.

Tripping over obstacles and imbalance during gait were reported as two of the most common causes of falls in the elderly. Imbalance of the whole body during obstacle crossing may cause inappropriate movement of the lower extremities and result in foot-obstacle contact. Thus, this study was performed to investigate the effect of obstacle height on the motion of the whole body's center of mass (COM) and its interaction with the center of pressure (COP) of the stance foot while negotiating obstacles. Six healthy young adults were instructed to perform unobstructed level walking and to step over obstacles of heights corresponding to 2.5, 5, 10, and 15% of the subject's height, all at a comfortable self-selected speed while walking barefoot. A 13-link biomechanical model of the human body was used to compute the kinematics of the whole body's COM. Stepping over the higher obstacles resulted in significantly greater ranges of motion of the COM in the anterior-posterior and vertical directions, a greater velocity of the COM in the vertical direction, and a greater anterior-posterior distance between the COM and COP. In contrast, the motion of the COM in the medial-lateral direction was less likely to be affected when negotiating obstacles of different heights.