Gait

Anterior cruciate ligament (ACL) deficient and reconstructed knees display altered biomechanics during gait. Identifying significant gait changes is important for understanding normal and ACL function and is typically performed by statistical approaches. This paper focuses on the development of an explainable machine learning (ML) empowered methodology to: (i) identify important gait kinematic, kinetic parameters and quantify their contribution in the diagnosis of ACL injury and (ii) investigate the differences in sagittal plane kinematics and kinetics of the gait cycle between ACL deficient, ACL reconstructed and healthy individuals. For this aim, an extensive experimental setup was designed in which three-dimensional ground reaction forces and sagittal plane kinematic as well as kinetic parameters were collected from 151 subjects. The effectiveness of the proposed methodology was evaluated using a comparative analysis with eight well-known classifiers. Support Vector Machines were...

Plantar pressure assessment is a tool useful for study of the gait cycle. In this study, we present a means of assessing the gait cycle using a temporal analysis of plantar pressures and lower-leg muscle activities. Plantar pressures and surface electromyography (EMG) of the tibialis anterior (TA) and medial gastrocnemius (MG) muscles were recorded as 19 men walked on a treadmill at seven speeds between 0.45 and 1.79 m/s. A typical 'heel strike to toe off' gait pattern was observed. Speed had minimal effects on the shapes of the muscle EMG root-mean-square-and plantar pressure-time curves except for the pressure-time curves in the heel and midfoot. A linear relationship was found between speed and peak pressures in the heel, medial forefoot, and toes; pressures in these regions increased by 91-289% going from 0.45 to 1.79 m/s. The temporal pressure changes in the forefoot and toes were paralleled by changes in MG muscle activity (i.e., cross-correlations of 0.90); TA muscle activity was not cross-correlated with the temporal pressure patterns in any region. However, the peak values of TA muscle activity were found to be highly correlated across speeds with peak pressures in the heel and toes (i.e., r 0.98); similar high correlations were found between peak values of MG muscle activity and heel pressure. In summary, these data collected on able-bodied persons during motorized treadmill walking can be useful for comparison to those of patients undergoing treadmill evaluations for atypical gait cycle patterns and for tracking the progress of patients during gait rehabilitation.

Robotic technologies are being employed increasingly in the treatment of lower limb disabilities. Individuals suffering from stroke and other neurological disorders often experience inadequate dorsiflexion during swing phase of the gait cycle due to dorsiflexor muscle weakness. This type of pathological gait, mostly known as drop-foot gait, has two major complications, foot-slap during loading response and toe-drag during swing. Ankle foot orthotic (AFO) devices are mostly prescribed to resolve these complications. Existing AFOs are designed with or without articulated joint with various motion control elements like springs, dampers, four-bar mechanism, series elastic actuator, and so forth. This paper examines various AFO designs for drop-foot, discusses the mechanism, and identifies limitations and remaining design challenges. Along with two commercially available AFOs some designs possess promising prospective to be used as daily-wear device. However, the design and mechanism of ...

Background and Purpose This study examined the interrater and intrarater reliability, concurrent validity, and criterion validity of the Tinetti Mobility Test (TMT) as a fall risk screening tool in individuals with Parkinson disease (PD). Subjects Thirty individuals with PD voluntarily participated in the study, and data from a retrospective review of 126 patient records were included. Methods Physical therapists and physical therapist students rated live and videotaped performances of the TMT. Tinetti Mobility Test scores were correlated with Unified Parkinson's Disease Rating Scale (UPDRS) motor scores and comfortable gait speed. The ability of the TMT to accurately assess fall risk was determined. Results Interrater and intrarater reliability was good to excellent (intraclass correlation coefficient of >.80). Tinetti Mobility Test scores correlated with UPDRS motor scores (rs=−.45) and gait speed (rs=.53). The sensitivity and specificity of the TMT to identify fallers were...

Gait analysis has been an interesting area of research for several decades. In this paper, we propose imageflow-based methods to compute the motion and velocities of different body segments automatically, using a single inexpensive video camera. We then identify and extract different events of the gait cycle (double-support, mid-swing, toe-off and heel-strike) from video images. Experiments were conducted in which four walking subjects were captured from the sagittal plane. Automatic segmentation was performed to isolate the moving body from the background. The head excursion and the shank motion were then computed to identify the key frames corresponding to different events in the gait cycle. Our approach does not require calibrated cameras or special markers to capture movement. We have also compared our method with the Optotrak 3D motion capture system and found our results in good agreement with the Optotrak results. The development of our method has potential use in the markerless and unencumbered video capture of human locomotion. Monitoring gait in homes and communities provides a useful application for the aged and the disabled. Our method could potentially be used as an assessment tool to determine gait symmetry or to establish the normal gait pattern of an individual.

Aging is often associated with modifications of gait. Recent studies have revealed a strong relationship between gait and executive functions in healthy and pathological aging. We hypothesized that modification of gait due to aging may be related to changes in frontal lobe function.

This study proposes a simple estimate of hamstring length at initial contact (LEST) for use when musculoskeletal modelling is not available. The estimate is calculated by using the kinematic curves to measure the excessive flexion (above normal) at the hip and knee at initial contact. The excessive hip flexion is then multiplied by a scaling factor (k) and the excessive knee flexion subtracted from the result. Validation of this estimate was carried out using kinematic gait data from 25 children with cerebral palsy (50 limbs) by comparing the results of the estimate with an equivalent measure derived from musculoskeletal modelling (LTRUE). Very high agreement was found when LTRUE and LEST were compared for the three biarticular hamstring muscles, demonstrated by correlation coefficients of over 0.9. Different k values were tested with a value of 3 giving the best results overall. The estimate is acceptable as a simple ‘rule of thumb’ for use in clinical practice. It can provide useful additional information to complement the clinical examination and gait assessment results.

Spatial and temporal parameters of gait are of recognised clinical relevance in the assessment of motor pathologies, because they normally occur in established combinations which can be altered by pathologies. The data collected from 596 healthy subjects have been used to establish relationships among these parameters and a procedure to estimate deviation from normality based on the comparison between measured values and values estimated by exploiting these relationships. The applied multiple linear regression method (MLRM) was preliminarily validated by comparing its outputs with those of corresponding equations found in the literature, and by applying it to a control group of 12 healthy subjects.

Background: Quick procedures with proper psychometric properties that can capture the combined alignment of the foot-ankle complex in a position that may be more representative of the status of the lower limb during ground contact are essential for assessing a large group of athletes.

Individuals with incomplete spinal cord injury (iSCI) retain some control of the partially paralyzed muscles, necessitating careful integration of functional electrical stimulation (FES) with intact motor function. In this communication, the volitional surface electromyogram (sEMG) from partially paralyzed muscle was used to detect the intent to step in an iSCI volunteer. The classifier was able to trigger the FES-assisted swing phase with a false positive rate less than 1% and true positive rate of 82% for left foot-off (FO) and 83% for right FO over 110 steps taken during three testing sessions spread over a week.

In a randomised prospective controlled trial of 52 patients aged 16 to 65 we compared early non-weightbearing ankle mobilisation with ankle immobilisation following surgical treatment of bimalleolar ankle fractures. At 3 months there was no signi®cant dierence between the two groups in the range of ankle movements or pain. There was however a signi®cant dierence in the gait pattern with a higher proportion of cases in the early ankle mobilisation group having a symmetrical gait (P = 0.0001). #

Background/objectives: When performing activity associated with walking, the amount of walking a person does often will depend on their plans. This study was designed to evaluate the relationship between motor planning and ambulatory persistence in participants with Parkinson's disease (PD) and to see if ambulatory persistence was related to the ability to perform activities of daily living (ADL). Methods: 20 individuals with idiopathic PD were recruited to perform the Trail making Test (a test of motor planning) and to wear a step activity monitor for 48 h. The measurement of persistence of an ambulatory event consisted of the number of steps taken during an event and an ambulatory event was defined as continuous ambulation (taking step) without pausing for 3 or more seconds. The resumption of taking step (ambulation) after 3 or more seconds counted as a new ambulatory event. UPDRS-motor and ADL scale were also obtained. Analysis and results: The cumulative percentage of the total ambulatory events at each number of steps was plotted for each subject which when plotted could be described as a sigmoid curve. We found that this sigmoidal curve defined by the equation y = xn/(kn + xn), fit the data well, where k represents a constant specific to each subject, x represents the number of steps during each ambulatory event, and y represents the projected percentage of movement events containing x number of steps or less. (Root Mean Square Error (RMSE) = 0.02, R2 = 0.98). Trail making test part A was highly associated with the constant k (R = −0.74, p < 0.001). The constant k was also highly associated with the UPDRS ADL subscale (R = −0.81, p = 0.0001). A forward bivariate regression model including Part A of the Trail making test, and the UPDRS-ADL subscale predicted 66% of the variability of the constant k. The overall number of steps taken per day, and the UPDRS motor subscale did not contribute to the model. Conclusions: Defective motor planning in Parkinson's disease as measured by poor performance on a Trail making test is associated with a measurable alteration in ambulatory persistence, and altered ambulatory persistence, quantified by our proposed model parameter, correlates highly with the UPDRS ADL score. Thus, cognitive-motor planning defects might be a major source of disability in PD. We suggest that in future clinical practice gait tests can be used in order to quantify short-term planning ability in neurodegenerative diseases.

Ankle foot mthoses (AFOs) are currently being prescribed for children with cerebral palsy (CP) to assist with their walking. Used appropriately, some of the apparent benefits CP children receive &om wearing AFOs are the control ofundesirable motions, stabilization ofweakmucles, and reduction ofabnormal muscle tone (Condi e and Meadaws, 1993). Despite much discussion i n the literature of orthotic devices and their effects, there is still a lack of qmntitative evi dence on how wearing an AFO affects the walking of a CP child (Knutson and Clark, 1991). The goal of this study is to use gait analysis to provide an objective measure of how walking with the ai d of either an AFO or an SMO (supramalleolat orthosis: sometimes referred to as a dynamic AFO) diffeers Eiom warking with no or&tic aid. Also, comparisons bewesn AFOs and SMOs can be made. Methodology Gait analysis, which has proven val uabl e i n studying children with CP (Gage, 1991), was performed on 11 children with spastic diplegia, ages 4 to 11. A four-camera system was used with the Hel en Hayes reflective marker placement to obtain kinematic data, while two conceal ed force plates provi ded the kinetic data. Three of the patients had had previous surgery (Achilles tendon lengthening), and all were previous brace users. Each child made Four different visits to the gait lab, titb visits spaced one month apart. The fust visit was a basel i ne of walking with shoes but no ortbosis, and the patient wore no bracing for one month prior to this visit. The second month the child wore an AFO (or SMO as randomIy assiwed) and then returned for a study at the end al the month. 'Itx third month served as a second baseline, while during the fourth month the patient wore an SMO (or AFO, whichever was not worn i n the second month) before reporting to the l ab for a fmai gait study. Shoes were worn the entire time and throughout the gait studies. For each condition studied, at least three walking trials were recorded, and ensemble averages of the data obtained. A repeated measmes ANOVA was performed, with a statistical significance level set at p < 0.05. The parameters on which we have Focused are the s&al pl ane ranges of motion (excursions) and sagittal pl ane moments at the hip, knee, and ankle. Also examined were temporal-distance factors and powers generated or absorbed at the hip, knee, and an!& joints.

Background: Forefoot ulcers (FU) are one of the most disabling and relevant chronic complications of diabetes mellitus (DM). In recent years there is emerging awareness that a better understanding of the biomechanical factors underlying the diabetic ulcer could lead to improve the management of the disease, with significant socioeconomic impacts. Our purpose was to try to detect early biomechanical factors associated with disease progression. Methods: Thirty subjects (M/F: 22/8; mean age ± SD: 61,84 ± 10 years) with diagnosis of type II DM were included. The participants were divided into 3 groups (10 subjects per group) according to the stage of evolution of the disease: Group 1, subjects with newly diagnosed type II DM, without clinical or instrumental diabetic peripheral neuropathy (DPN) nor FU (group called "DM"); Group 2, with DPN but without FU (group called "DPN"); Group 3, with DPN and FU (group called "DNU"). All subjects underwent 3-D Gait Analysis during walking at self-selected speed, measuring spatio-temporal, kinematic and kinetic parameters and focusing on ankle and foot joints. The comparative analysis of values between groups was performed using 1-way ANOVA. We also investigated group to group differences with Tukey HSD test. The results taken into consideration were those with a significance of P < 0,05. 95 % confidence interval was also calculated. Results: A progressive and significant trend of reduction of ROM in flexion-extension of the metatarso-phalangeal joint (P = 0.0038) and increasing of step width (P = 0.0265) with the advance of the disease was evident, with a statistically significant difference comparing subjects with recently diagnosed diabetes mellitus and subjects with diabetic neuropathy and foot ulcer (P = 0.0048 for ROM and P = 0.0248 for step width at Tukey's test). Conclusions: The results provide evidence that foot segmental kinematics, along with step width, can be proposed as simple and clear indicators of disease progression. This can be the starting point for planning more targeted strategies to prevent the occurrence and the recurrence of a FU in diabetic subjects.

A previous study indicated that peripheral visual information strongly affects the judgment of egocentric distances for users of immersive virtual environments. The experiment described in this document aimed to investigate if these effects could be explained in terms of changes in gait caused by visual information in the extreme periphery. Three conditions with varying degrees of peripheral occlusion were tested and participants&#x27; walking characteristics measured. The results indicate that the improvements in distance ...

The purpose of this study was to assess the reliability of 24 kinetic and kinematic variables from three synchronized systems used to represent normal running gait. Five male runners (mean 23.4 years, mass 80.2 kg) ran down a runway at a constant velocity (3.5-4.0 m/s). This was repeated until 10 acceptable trials had been performed which was then repeated 7 days later. The mean of the 10 trials was used for kinetic analysis and the mean of 5 trials for the kinematics. All of the kinematic variables achieved a reliability greater than 0.93. The 6 variables that were able to demonstrate a high reliability (\ 0.94) from a single trial came from all systems. This suggests that variables and systems used to collect and analyse gait should be assessed for their reliability using the population to be studied before actual data collection.

Functional electrical stimulation (FES) is an accepted treatment method for paresis or paralysis after spinal cord and head injury as well as stroke and other neurological upper motor neuron disorders. At the beginning, FES worked like an electrophysiological brace for the correction of drop foot of patients after a stroke. When analyzing early accomplishments, it becomes evident that FES was influenced rather by technological and biomedical engineering development than by contemporary knowledge on neurocontrol of movement in individuals with upper motor neuron paralysis. Nevertheless, with better understanding of pathophysiology of spasticity and neurocontrol of impaired movement, FES advanced from an electrophysiological brace to a treatment modality for the improvement of muscle control, neuroaugmentation of residual movements, and supportive procedure for "spontaneous recovery" of motor control. In the present article we shall illustrate barriers which delayed FES to be applied in clinical practice of neuron rehabilitation from "Yesterday" to "Today." We shall discuss the importance to apply FES early after the onset of neurological conditions to prevent disuse of noninjured portions of the CNS. Moreover, FES can play a significant role in the supporting processes of neuroplasticity in the subacute phase of upper motor neuron dysfunction. Therefore, the electrophysiological brace of "Yesterday" provides "Today" a correction of missing neuromuscular function. At the same time, it is an active external device for the correction of motor deficits interacting with the somatosensory-motor integration. Thus, "Yesterday" and "Today" of the same technological approach can be very different, thanks to a different understanding and assessment of "external" and "internal" components of human motor control.

This study examined how young healthy adults learn stilt walking. Ten healthy male university students attended
two sessions of testing held on two consecutive days. In each session participants performed three blocks of 10 stiltwalking
trials. Angular movements of head and trunk and the spatial and temporal gait parameters were recorded.
When walking on stilts young adults improved their gait velocity through modifications of step parameters while
maintaining trunk movements close to that observed during normal over-ground walking. Participants improved
their performance by increasing their step frequency and step length and reducing the double support percentage
of the gait cycle. Stilts are often used for drywall installation, painting over-the-head areas and raising workers
above the ground without the burden of erecting scaffolding. This research examines the locomotor adaptation
as young healthy adults learn the complex motor task of stilt walking; a task that is frequently used in the
construction industry.

Dual-task methodology has been increasingly used to assess cognitive motor interference while walking. However, whether the observed dual-task-related gait changes are systematically related to methodological variations remains unclear and researchers still lack knowledge of what cognitive task to use in different groups for clinical purposes or for research. We systematically reviewed experimental studies that measured gait performance with and without performing concurrent cognitive task. Our results suggest that cognitive tasks that involve internal interfering factors seem to disturb gait performance more than those involving external interfering factors. Meta-analysis results show that the overall effect of different cognitive tasks was prominent in gait speed. In healthy participants, meta-regression analysis suggests strong associations between age and speed reduction under dual-task conditions and between the level of cognitive state and speed reduction under dual-task conditions. Standardizing research methodologies, as well as improving their ecological validity, enables better understanding of dualtask-related gait changes in different populations and improves, in turn, our understanding of neural mechanisms and gait control in general in content.

The difficulties confronted by amputees during overground walking are rarely investigated. In this study, we evaluated, in real-world situations, the influence of ground surface on walking in young, active amputees by measuring temporal and spatial gait parameters (free walking speed [FWS], step length [SL], step rate), energy expenditure (EE) (e.g., oxygen uptake, oxygen cost [O 2 C]), and Rating of Perceived Exertion (RPE). Ten active transtibial amputees and ten nondisabled control subjects walked at self-selected speeds on three types of ground surface (asphalt, mown lawn, and high grass). No significant differences were observed between the two groups on asphalt and mown lawn. Differences between nondisabled subjects and amputees occurred for FWS (p = 0.03) and O 2 C (p = 0.04) on asphalt and mown lawn and for all variables in high grass. When amputees (even though very active) were exposed to a particularly difficult environment, their FWS decreased (p = 0.008) and their EE and RPE increased (p = 0.005) compared with nondisabled subjects. In high grass, both groups reduced their self-selected speeds (-15% for control subjects and -16% for amputees). Control subjects reduced their velocity by reducing both SL (-8.7%) and cadence (-7.1%), whereas amputees reduced their velocity by reducing SL (-17%) only.

The aims of this case report are to describe the application of an early and intensive task-oriented physical therapy program for gait relearning following stroke and to report the patients&#39; ability to comply with the program. Ten patients, 60 to 75 years of age (mean = 69.8, SD = 7.3), with a middle cerebral artery infarct (confirmed by computerized tomography) were assigned to this special physical therapy program. Patients were treated twice a day, 5 days a week, from the eighth day after stroke for 5 consecutive weeks. To promote gait relearning, a program of early standing (using a tilt table when necessary), combined with weight-shifting exercises and feedback via a limb-load monitor as well as locomotor activities including exercises on a Kinetron and treadmill walking, was adapted for each patient&#39;s level of motor recovery. Walking on the treadmill (with a safety harness) was initiated as early as the second week after stroke in 4 patients, and all patients had start...

We read the article by Klute et al1 with interest; however, we
identified a number of issues with the article. The authors
compared the socket fit, activity level, and limb volume of 2
different prosthetic suspension systems, namely a vacuumassisted
suspension system (VASS) and a pin suspension.1
Because limited literature is available on the effect of vacuumassisted
suspension as a means of controlling residual limb
volume and pistoning,2 the article would have been more
clinically helpful if some ambiguities were clarified.
https://www.ncbi.nlm.nih.gov/pubmed/22541316

Hamstring injection of Botulinum toxin A (BtA) may have a role in the conservative management of flexed knee gait in cerebral palsy or in simulating the effect of surgery. Ten children who were likely to require future hamstring lengthening were injected. Short term outcome was assessed by clinical examination and 3-D gait analysis. Mean popliteal angle decreased by 16°and maximum knee extension in stance increased by 8°, the latter relapsing by 12 weeks. Mean pelvic tilt tended to increase suggesting that isolated hamstring weakening be approached with caution. Energy cost of walking was not significantly changed in six of the ten patients. A small increase in knee extension in stance was often associated with patient satisfaction. There are theoretical grounds for expecting an associated increased longitudinal muscle growth after BtA injection.

This paper focuses on studies on reconfigurable multi acquire findings on how multi-legs robot can walk, climb vertical pipe and walk along the horizontal pipe after climbing. Three degrees of freedom (3DOF) multi pipeline or to check on vertical and horizontal pipes. The robot system is tested to climb the vertical pipe and then move along horizontal pipe for inspection or other purposes. This can reduce the cost and percentage of human risk exposure during inspection on outer pipe. This multi speed, wheeled robot possesses greater advantages. Therefore, this system design has combination of both wheel and multiple legs ensure that the to system has higher stability, more gait movement, and higher speed manoeuvrability. The gaits analysis for the system movement includes a operation, either walking, climbing or hanging. The target result is the system able to climb 500 mm height with 85 mm radius pipe. The potential applications for the system are: Be equipped with ultrasonic senso...

A significant amount of new bone was formed by 6 months postoperatively in each group. The mean change in bone height in the rhBMP-2/ACS subjects was 7.83 ± 3.52 mm versus 9.46 ± 4.11 mm for the bone graft subjects. At 6 months after dental restoration, the induced ...

Objective. To evaluate the sensitivity and specificity of the Gait, Arms, Legs, and Spine (GALS) examination to screen for signs and symptoms of rheumatoid arthritis (RA) when used by family physicians and nurse practitioners. Methods. Participating health care professionals (2 rheumatologists, 3 family physicians, and 3 nurse practitioners) were trained to perform the GALS examination by viewing an instructional DVD and attending a training workshop. One week after training, the health care professionals performed the GALS examination on 20 individuals with RA and 21 individuals without RA. All participants were recruited through 2 rheumatology practices, and each participant was assessed by 4 health care professionals. The health care professionals were asked to record whether observed signs and symptoms were potentially consistent with a diagnosis of RA. The health care professionals understood the study objective to be their agreement on GALS findings among one another and were unaware that one-half of the participants had RA. Sensitivity and specificity were calculated to determine the ability of the GALS examination to screen for RA using the rheumatologist as the standard for comparison. Results. Sensitivity and specificity values varied from 60-100% and 70-82%, respectively, for the 3 family physicians, and 60-90% and 73-100%, respectively, for the 3 nurse practitioners. Conclusion. Following a very short training period, family physicians and nurse practitioners appeared to be able to use the GALS examination as a screening tool for RA signs and symptoms, particularly for identifying an individual with positive results who will benefit from further investigation or rheumatology referral.

Running performance, energy requirements and musculoskeletal stresses are directly related to the action-reaction forces between the limb and the ground. For human runners, the force-time patterns from individual footfalls can vary considerably across speed, footstrike and footwear conditions. Here, we used four human footfalls with distinctly different vertical force-time waveform patterns to evaluate whether a basic mechanical model might explain all of them. Our model partitions the body's total mass (1.0M b ) into two invariant mass fractions (lower limb=0.08, remaining body mass=0.92) and allows the instantaneous collisional velocities of the former to vary. The best fits achieved (R 2 range=0.95-0.98, mean=0.97±0.01) indicate that the model is capable of accounting for nearly all of the variability observed in the four waveform types tested: barefoot jog, rear-foot strike run, fore-foot strike run and fore-foot strike sprint. We conclude that different running ground reaction force-time patterns may have the same mechanical basis.

Brain activity during observation and imagery of gait was investigated. Sixteen subjects were scanned with a 3-Tesla MRI scanner while viewing six types of video clips: observation of gait movement (GO) from the third-person perspective, observation of stepping movement, observation of standing posture, "virtual walking" (VW) that was observation of visual scenes mimicking the visual afferent during walking, and the scrambled version of the GO and VW stimuli. In the VW condition, moving scenes provided a virtual visual environment in which subjects easily imagined as if they were actually walking from the first-person perspective. A behavioral experiment revealed a correlation of cadence during actual walking with that during imaginary walking under the influence of the VW stimuli, indicating that a gait planning mechanism was shared by actual walking and gait imagery. The VW condition activated the dorsal premotor cortex (PMd), supplementary motor area/cingulate motor area (SMA/CMA), parahippocampal gyrus, and subcortical nuclei. The GO stimuli yielded activation of the SMA, PMd, inferior frontal gyrus, and inferior parietal lobule. Moreover, the conjunction null test of GO and VW revealed common activity in the SMA/CMA and PMd, which were reportedly active during actual gait movement, in addition to visual areas. Detailed analyses of activity during stepping or standing observation supported the specificity of the SMA and PMd to GO. These findings suggest that motor planning centers of gait, including the SMA and PMd, are activated during both imagination (first-person perspective) and observation (third-person perspective) of gait behaviors.

In a variety of applications, inertial sensors are used to estimate spatial parameters by double integrating over time their coordinate acceleration components. In human movement applications, the drift inherent to the accelerometer signals is often reduced by exploiting the cyclical nature of gait and under the hypothesis that the velocity of the sensor is zero at some point in stance. In this study, the validity of the latter hypothesis was investigated by determining the minimum velocity of progression of selected points of the foot and shank during the stance phase of the gait cycle while walking at three different speeds on level ground. The errors affecting the accuracy of the stride length estimation resulting from assuming a zero velocity at the beginning of the integration interval were evaluated on twenty healthy subjects. Results showed that the minimum velocity of the selected points on the foot and shank increased as gait speed increased. Whereas the average minimum velocity of the foot locations was lower than 0.011 m/s, the velocity of the shank locations were up to 0.049 m/s corresponding to a percent error of the stride length equal to 3.3%. The preferable foot locations for an inertial sensor resulted to be the calcaneus and the lateral aspect of the rearfoot. In estimating the stride length, the hypothesis that the velocity of the sensor can be set to zero sometimes during stance is acceptable only if the sensor is attached to the foot.