Number Of Strides Research Articles

Physical assessment as a predictor of mortality in people with Parkinson's disease: A study over 7 years

The primary aim of this study was to ascertain whether a battery of physical function measures in a Parkinson's disease (PD) patient cohort predicted mortality status at 7-year follow-up. Secondary aims were establishing which specific tests were the most useful, and whether PD phenotype was a predictor. A retrospective correlation design was used in this study. A cohort of 109 PD patients underwent baseline physiotherapy assessment of gait, balance, posture, muscle strength, and ability to change postural set. We compared mortality status at 7-year follow-up and baseline physical assessment tests. Tinetti gait and balance scores, UPDRS score, 10-m walk test (time, velocity, and number of strides), posture in standing, lying to sitting, sitting to standing, getting up from floor assessments, and time to ascend and descend four steps were found to be statistically significant physical predictors of mortality at 7-year follow-up. In addition, age, sex, and mini-mental state examination were significant nonphysical predictors of mortality. Using Cox regression, a survival model was constructed with age, sex, and Tinetti gait score as independent predictors of mortality. The results of this study suggest that there is a link between reduced physical function and an increased mortality risk in PD populations.

Phenotypic Correlations of Stride Traits and Body Measurements in Lipizzaner Stallions and Mares

Besides being well known for their use in classical dressage, Lipizzaner horses are today becoming more and more popular for use in driving sport, with Croatia as the largest breeder in the world. To estimate their phenotypic predisposition for driving sport, this research analyzes the correlation between body measurements and traits of length and speed of walk and hand-led trot in 18 stallions (LS) and 53 mares (LM) by using a digital camera. Statistical analysis of the data concerning phenotypic correlations among the indicated traits has revealed the potential of documenting a large number of structural exterior body characteristics and quantitative measurements in Lipizzaner horses, and technical equipment has been found to be useful in research of stride traits. Higher withers height (WH) achieved through breeding was found to be negatively correlated with the number of strides per second during walk and trot, but positively correlated with walk stride length, especially in LS. Higher values for chest girth (CG) and cannon bone circumference (CBC) were found to be positively correlated with speed, as well as with stride length in LS, and negatively correlated with the number of strides per second during walk and trot in both LS and LM. Because for many years the goal of breeding Lipizzaners in Croatia has been to obtain a bigger body format and longer stride, leading to better results in a driving sport, these findings confirm breeding goals in selection work guided toward better stride length and extended stride as the most desirable traits for driving sport.

Energy Cost and Pole Forces during Nordic Walking under Different Surface Conditions

The purpose of the study was to identify the effect of three different surfaces on energy consumption and the forces acting on the walking poles during ground contact in Nordic walking (NW). Thirteen female NW instructors (age = 26 +/- 4 yr, weight = 58.5 +/- 4.2 kg, height = 168.1 +/- 4.6 cm) volunteered in the study. The subjects walked a distance of 1200 m at a controlled, constant speed of 2.2 m x s(-1) on each of a concrete surface (C), an artificial athletics track (A), and a naturally grown soccer lawn (G). They used NW poles with inbuilt strain gauge force transducers to measure ground reaction forces acting along the long axes of the poles. Oxygen uptake, capillary blood lactate (La), HR, and RPE were measured before and after the tests. Impact forces, maximum forces, force rates during ground contact identified from the registered force time histories, displayed significant differences related to the surface conditions. However, force time integrals did not show surface-related differences. Relative oxygen consumption showed significant differences between NW on C and on G whereas no surface-related differences could be identified between the surface conditions for the parameters La, HR, and RPE. Our data indicate that the impulse that is generated by the poles on the subjects is identical between the varying surfaces. Because there are differences for the oxygen uptake between C and G, the main regulator for the propulsion must be the musculature of the lower extremities. The work of the upper extremities seems to be a luxury effort for Nordic walkers with a proper technique.

Statistical precision and sensitivity of measures of dynamic gait stability

Recently, two methods for quantifying a system's dynamic stability have been applied to human locomotion: local stability (quantified by finite time maximum Lyapunov exponents, λS-stride and λL-stride) and orbital stability (quantified as maximum Floquet multipliers, MaxFm). Thus far, however, it has remained unclear how many data points are required to obtain precise estimates of these measures during walking, and to what extent these estimates are sensitive to changes in walking behaviour.To resolve these issues, we collected long data series of healthy subjects (n=9) walking on a treadmill in three conditions (normal walking at 0.83m/s (3km/h) and 1.38m/s (5km/h), and walking at 1.38m/s (5km/h) while performing a Stroop dual task). Data series from 0.83 and 1.38m/s trials were submitted to a bootstrap procedure and paired t-tests for samples of different data series lengths were performed between 0.83 and 1.38m/s and between 1.38m/s with and without Stroop task.Longer data series led to more precise estimates for λS-stride, λL-stride, and MaxFm. All variables showed an effect of data series length. Thus, when estimating and comparing these variables across conditions, data series covering an equal number of strides should be analysed. λS-stride, λL-stride, and MaxFm were sensitive to the change in walking speed while only λS-stride and MaxFm were sensitive enough to capture the modulations of walking induced by the Stroop task. Still, these modulations could only be detected when using a substantial number of strides (>150).

Comparison between a sensor (3D accelerometer) and ProReflex motion capture systems to measure stride frequency of horses on a treadmill

The most popular techniques used for studying equine kinematics are videographic recording combined with the analysis using a commercial software package or optoelectronic systems based on emission and detection of infrared or visible light. Such systems can be expensive, complicated to use and their use may be restricted to indoor use (in the case of infrared systems) or a limited number of strides when used outdoors. Recently, there has been considerable interest in monitoring motion using inertial measuring systems. The purpose of the present study was to determine the accuracy of the Pegasus system (European Technology for Business Ltd., Codicote, UK), which determines stride frequency directly when mounted on the withers. Eight horses of different breeds and sizes (447–588 kg) were studied at walk, trot and two speeds at canter on a treadmill. Simultaneous measurements of stride were made using the Pegasus and ProReflex motion capture systems. Mean stride frequencies (n = 8 horses) for the ProReflex and Pegasus systems at walk (0.86 ± 0.05 and 0.87 ± 0.05 strides per second, respectively), trot (1.36 ± 0.07 and 1.36 ± 0.07 strides per second, respectively) and canter (7 m s− 1: 1.92 ± 0.05 and 1.92 ± 0.05 strides per second, respectively; 8 m s− 1: 1.93 ± 0.05 and 1.94 ± 0.05 strides per second, respectively) were not significantly different (P>0.05). The mean difference between the two systems for all four speeds was − 0.002 strides per second (lower 95% CI: − 0.016; upper 95% CI: 0.011; P = 0.309). In conclusion, the differences between stride frequency measurements made with the Pegasus and ProReflex systems in horses exercising at walk, trot and slow canter on a treadmill are < 1% and not likely to be of physiological significance.

Association between daily ambulatory activity patterns and exercise performance in patients with intermittent claudication

To determine the association between daily ambulatory activity patterns and exercise performance in patients with intermittent claudication. One hundred thirty-three patients limited by intermittent claudication participated in this study. Patients were assessed on their ambulatory activity patterns for 1 week with a small, lightweight step activity monitor attached to the ankle using elastic velcro straps above the lateral malleolus of the right leg. The step activity monitor recorded the number of strides taken on a minute-to-minute basis and the time spent ambulating. Patients also were characterized on ankle-brachial index (ABI), ischemic window (IW) after a treadmill test, as well as initial claudication distance (ICD), and absolute claudication distance (ACD) during treadmill exercise. The patient characteristics (mean +/- SD) were as follows: ABI = 0.71 +/- 0.23, IW = 0.54 +/- 0.72 mm Hg.min.meter(-1), ICD = 236 +/- 198 meters, and ACD = 424 +/- 285 meters. The patients took 3366 +/- 1694 strides/day, and were active for 272 +/- 103 min/day. The cadence for the 30 highest, consecutive minutes of each day (15.1 +/- 7.2 strides/min) was correlated with ICD (r = 0.316, P < .001) and ACD (r = 0.471, P < 0.001), and the cadence for the 60 highest, consecutive minutes of each day (11.1 +/- 5.4 strides/min) was correlated with ICD (r = 0.290, P < .01) and ACD (r = 0.453, P < .001). Similarly, the cadences for the highest 1, 5, and 20 consecutive minutes, and the cadence for the 30 highest, nonconsecutive minutes all were correlated with ICD and ACD (P < .05). None of the ambulatory cadences were correlated with ABI (P > .05) or with ischemic window (P > .05). Daily ambulatory cadences are associated with severity of intermittent claudication, as measured by ACD and ICD, but not with peripheral hemodynamic measures.

Single-session reliability of discrete gait parameters in ambulatory children with cerebral palsy based on GMFCS level

The single-session reliability of 28 discrete spatiotemporal and kinematic variables was evaluated from computerized gait analysis (CGA) in 33 ambulatory children with cerebral palsy (CP), subcategorized according to Gross Motor Function Classification System (GMFCS) Levels I ( n = 11), II ( n = 12) and III ( n = 10). Nineteen boys and 14 girls participated, mean age = 8 years 1 month (S.D. = 3 years 0 month). Intraclass correlation coefficients (ICCs) estimated reliability, and the number of strides required to obtain an ICC of at least 0.90 was determined. The reliability of discrete gait parameters was dependent upon GMFCS level, with children in GMFCS Level I exhibiting the highest reliability (ICC range = 0.70–0.96). GMFCS Levels II and III had lower levels of reliability with ICC values varying from 0.54 to 0.95 and 0.45 to 0.98, respectively. With the exclusion of pelvis range of motion (ROM), an average of four strides provided a reliability estimate of at least 0.90 for GMFCS Level I, while six strides were needed for children in Levels II and III. On the basis of the intrasession reliability results from the present study, further work is recommended to examine the test–retest reliability of these gait parameters in children with CP.

Detection of tripping gait patterns in the elderly using autoregressive features and support vector machines

Elderly tripping falls cost billions annually in medical funds and result in high mortality rates often perpetrated by pulmonary embolism (internal bleeding) and infected fractures that do not heal well. In this paper, we propose an intelligent gait detection system (AR–SVM) for screening elderly individuals at risk of suffering tripping falls. The motivation of this system is to provide early detection of elderly gait reminiscent of tripping characteristics so that preventive measures could be administered. Our system is composed of two stages, a predictor model estimated by an autoregressive (AR) process and a support vector machine (SVM) classifier. The system input is a digital signal constructed from consecutive measurements of minimum toe clearance (MTC) representative of steady-state walking. The AR–SVM system was tested on 23 individuals (13 healthy and 10 having suffered at least one tripping fall in the past year) who each completed a minimum of 10min of walking on a treadmill at a self-selected pace. In the first stage, a fourth order AR model required at least 64 MTC values to correctly detect all fallers and non-fallers. Detection was further improved to less than 1min of walking when the model coefficients were used as input features to the SVM classifier. The system achieved a detection accuracy of 95.65% with the leave one out method using only 16 MTC samples, but was reduced to 69.57% when eight MTC samples were used. These results demonstrate a fast and efficient system requiring a small number of strides and only MTC measurements for accurate detection of tripping gait characteristics.

Patterns of ambulatory activity in subjects with and without intermittent claudication

This study compared the patterns of ambulatory activity in subjects with and without intermittent claudication. The study participants were 98 subjects limited by intermittent claudication and 129 controls who were matched for age, gender, and race. Subjects were assessed on their ambulatory activity patterns for 1 week with a small, lightweight step activity monitor attached to the ankle using elastic Velcro (Velcro Industries BV, Manchester, NH) straps above the lateral malleolus of the right leg. The step activity monitor recorded the number of strides taken on a minute-to-minute basis, the time spent ambulating, and the time and number of strides measured at low (<15 strides/min), medium (15 to 30 strides/min), and high (>30 strides/min) cadences. Subjects with intermittent claudication took fewer total strides each day than the controls (3149 +/- 1557 strides/d vs 4230 +/- 1708 strides/d; P < .001) and fewer strides at medium (1228 +/- 660 strides/day vs 1638 +/- 724 strides/day; P = .001) and high (766 +/- 753 strides/day vs 1285 +/- 1029 strides/day; P < .001) cadences. Subjects with intermittent claudication also had a lower daily average cadence than the controls (11.8 +/- 2.9 strides/min vs 13.5 +/- 3.1 strides/min; P < .001) and spent less total time ambulating each day (264 +/- 109 min/day vs 312 +/- 96 min/day; P = .034), primarily at medium (58 +/- 30 min/day vs 75 +/- 32 min/day; P < .001) and at high (19 +/- 17 min/day vs 30 +/- 22 min/day; P = .001) cadences. Intermittent claudication is associated with lower total daily ambulatory activity owing both to less time ambulating and to fewer strides taken while ambulating, particularly at moderate and high cadences.

Differences in stride between healthy ostriches (Struthio camelus) and those affected by tibiotarsal rotation : research note

Twenty healthy ostriches (ten cocks and ten hens), and twenty birds with tibiotarsal rotation (nine cocks and 11 hens) (14 months old) were isolated, hooded and weighed. A run (50 m x 2.5 m) was divided into sections marked 5 m, 10 m, 15 m and 20 m. Time taken for each bird to pass these points was recorded and speed computed. The degree of tibiotarsal rotation in the right foot was mean +/- SEM, 156 +/- 2.69 degrees. Comparisons between left and right foot length in healthy birds showed no significant differences. Foot length was significantly lower in tibiotarsal rotation (P = 0.03). The right foot in tibiotarsal rotation was significantly shorter than the left foot. The number of strides per each 5 m division were significantly (P < 0.05) greater in tibiotarsal rotation by comparison with healthy birds. At 20 m, healthy cocks had more strides than hens. The stride length in hens was significantly (P < 0.05) greater than cocks at 5, 10 and 15 m, respectively, but lower throughout in tibiotarsal rotation (P = 0.001). The speed of hens was significantly (P < 0.05) greater than cocks. Tibiotarsal rotation resulted in significantly (P < 0.05) reduced speeds. Hens may be able to escape danger faster than cocks. The occurrence of tibiotarsal rotation necessitates consideration of genetics, management, sex, nutrition and growth rates.

Forced to crowd or choosing to cluster? Spatial distribution indicates social attraction in broiler chickens

We investigated the response of commercially farmed broiler (meat) chickens to their social environment at five stocking densities, using spatial distribution and behaviour. We used a computer model in which a ‘social aversion/attraction’ parameter was set at different values to give simulations in which the chickens were averse, indifferent or positively attracted to each other. We examined the spatial distribution of real chickens that were neither feeding nor drinking, using video records taken within commercial houses, to see which setting of the model best fitted the observed data. At all stocking densities, chickens were more clustered than indifferent (randomly distributed) chickens, and their distribution best fitted a social attraction model in which simulated birds rejected a potential position if their distance from other birds was too great. The parameter setting that best fitted the observed data was a model in which simulated chickens had a high probability of rejecting a position if the nearest chicken was more than an estimated 75 cm away: they were socially attracted rather than socially averse. This result suggests that, even at high commercial stocking densities, real broiler chickens may find the close proximity of other birds more attractive than aversive. Except for jostling and number of strides per walking bout, behaviour did not change across the stocking densities studied, nor, except for gait, did the most obvious measures of bird health (mortality, culls, leg health).

Effects of Roughness and Compressibility of Flooring on Cow Locomotion

We examined the effects of roughness and degree of compressibility of flooring on the locomotion of dairy cows. We observed 16 cows walking down specially constructed walkways with materials that differed in surface roughness and degree of compressibility. Use of a commercially available soft rubber flooring material decreased slipping, number of strides, and time to traverse the corridor. These effects were most apparent at difficult sections of the corridor, such as at the start, at a right-angle turn, and across a gutter. Covering the walkway with a thin layer of slurry increased frequency of slipping, number of strides, and time taken to traverse the walkway. Effects of adding slurry were not overcome by increasing surface roughness or compressibility. Placing more compressible materials under a slip-resistant material reduced the time and number of steps needed to traverse the corridor but did not reduce slips, and the effects on cow locomotion varied nonlinearly with the degree of compressibility of the floor. Use of commercially available rubber floors improved cow locomotion compared with concrete floors. However, standard engineering measures of the floor properties may not predict effects of the floor on cow behavior well. Increasing compressibility of the flooring on which cows walk, independently of the roughness of the surface, can improve cow locomotion.

Effects of temperature on maximum acceleration, deceleration and power output during vertical running in geckos

We studied performance and kinematics of the diurnal gekkonid lizard Phelsuma dubia while running vertically on a smooth surface at different temperatures. Trials were conducted at 5 degrees C intervals from 15 degrees C to 35 degrees C. High-speed video recordings and digitization were used to obtain measures of instantaneous velocity, acceleration, deceleration and mass-specific power output and maximal values for each were taken as performance measures. Kinematic variables were also obtained from high-speed video recordings and included stride length and duration, step (stance phase) length and duration, and duty factor. Maximal instantaneous velocity, acceleration and deceleration increased by a factor of approximately 1.7 between 15 degrees C and 25 degrees C, and less so (approximately 1.2x) between 25 degrees C and 35 degrees C. Mass-specific power output was more temperature-sensitive, increasing 2.5x up to 25 degrees C and a further 1.4x above that temperature. Stride length increased 1.5x over the entire temperature interval studied, while stride duration decreased by a factor of 1.9, suggesting that velocity is modulated by changes in both stride length and duration in P. dubia. Duty factor was not significantly influenced by temperature. Stride length was the only kinematic measure to be influenced by stride number, with second steps from a standstill being longer than first steps. We discuss the significance of velocity and acceleration being affected in a similar manner by temperature, and that speed is modulated by both changes in stride length and duration.

Visual guidance during competition performance and run‐through training in long jumping

To ensure precise foot placement on the take-off board, long jumpers visually regulate their stride pattern during their run-up. A relationship between how much visual guidance they use and the horizontal distance they jump has not, however, been quantified. Run-up precision is often practiced using run-throughs, which exclude the take-off and, therefore, the high physical stress of the complete long jump. The validity with which this common training method simulates the long jump approach remains, however, to be verified. Four state-standard long jumpers and two heptathletes completed two sessions, each comprising six runthroughs and six competition long jumps. A 50 Hz video camera was manually panned from an elevated platform to film each trial, to enable subsequent gait characteristic evaluations. Linear regression analyses identified that a longer visual regulation phase, measured in time, distance or number of strides, was a key predictor of long jump distance. The number of strides that were visually regulated during the long jump approach was, accordingly, positively correlated with long jump distance (r = 0.67, p = 0.001). The amount of visual regulation used during run-throughs was, however, less than half (p = 0.001) of that observed during long jump approaches. Our results should compel long jump coaches to supplement run-through training with additional visual guidance exercises, to encourage their athletes to visually regulate more of their long jump approach.

Evaluation of physical therapy in parkinsonian patients with freezing of gait: a pilot study

Objective: Freezing of gait is a frequently disabling symptom in Parkinson's disease, poorly responding to dopaminergic treatment. We investigated the short-term effectiveness of a rehabilitation protocol in parkinsonian patients with freezing of gait. Design: Prospective, uncontrolled pilot study with open label design. Setting: Outpatient service for rehabilitation of neurological disorders. Subjects: Twelve patients (8 male, 4 female; aged 59-78 years; Hoehn-Yahr stage: 2-3; mean disease duration: 14.29±SD 4.1 years). Interventions: Patients attended three (45 min) sessions every week, over a six-week period, of physical therapy focused to improve balance, postural control and walking, and to learn new strategies for overcoming freezing of gait. Main outcome measures: Patients were evaluated before (T0), at the end (T1), and one month after (T2) rehabilitation by means of clinical rating scales (Unified Parkinson Disease Rating Scale-Motor Section; Freezing of Gait Questionnaire; Parkinson Disease Quality of Life Score) and gait parameters (number of strides, stride length and velocity) during a standardized walking test. Results: The scores of Freezing of Gait Questionnaire and of Parkinson Disease Quality of Life Questionnaire (but not of the Unified Parkinson Disease Rating Scale-Motor Section) were significantly improved after treatment (T1). Gait parameters were significantly improved at T1 and T2. Conclusions: We showed the potential short-term efficacy of a rehabilitative approach to freezing of gait in Parkinson's disease. The positive outcome was documented by clinical rating scales and objective gait evaluation. The rapid reversibility of the clinical benefit suggests that further studies are needed to better define the optimal frequency and duration of treatment.

Effect of incremental exercise on initiation and movement times in a choice response, whole body psychomotor task

Objectives: To examine how exercise at moderate and maximal intensities affects performance on a choice response time, whole body psychomotor task. Methods: Subjects (n = 12) were tested on a...

Influence of Ethnic Origin on Predictive Parameters of Performance in Sprint Running in Prepubertal Boys

Afro-American and Caribbean athletes have long dominated sprint running, although the reasons for their disproportionate success remain unclear. The studies of sprinting ability in blacks versus whites have shown contradictory results. This study compared the anthropometric measurements and the physical test results (vertical jump and sprint) of Caucasian and Afro-Caribbean prepubertal boys. Seventeen healthy untrained prepubertal boys, 8 Caucasians and 9 Afro-Caribbeans (11.49 +/- 0.74 years) performed vertical jump tests (a countermovement jump according to the Sargent method, using Abalakov material) and short sprints (30 m). Age, height, weight, and fat mass percentage were also recorded. The sprints were filmed to determine the number of strides over the 30 m. No significant difference was noted for sprint performance between the Caucasians and Afro-Caribbeans (respectively, 5.59 seconds +/- 0.44 vs. 5.51 s +/- 0.50). The predictors of sprint performance differed between the two groups: the vertical jump test was the main predictor for the Caucasian group, whereas the stride number/height ratio was the main predictor for the Afro-Caribbean group. This last group had better ratio (0.14 +/- 0.15 vs. 0.16 +/- 0.02, p < 0.05) and better jump test results (36.77 cm +/- 2.90 vs. 31.12 cm +/- 4.76, p < 005). The prepubertal Afro-Caribbeans seemed to be endowed to run faster but they did not. We hypothesize that they were unable to use their greater leg strength to develop an optimal stride. Further study is needed to investigate what occurs at other maturational stages.

Validity of the prosthetic activity monitor to assess the duration and spatio-temporal characteristics of prosthetic walking

The prosthetic activity monitor (PAM) is an instrument to assess over the long-term the duration and spatio-temporal characteristics of walking of amputees, during normal daily life. In this study, the validity of PAM-derived measurements was investigated. Twelve transtibial amputees performed an activity protocol, consisting of stationary and walking activities, and activities associated with nonlocomotor movements. The protocol also included potential sources of error and activities assumed to be prone to misdetection. Measurements consisted of the PAM and video recordings. Agreement between video analysis and PAM output was the main outcome measure. The PAM generally correctly classified stationary activities (100% inactive, 0% active, 0% locomotion), nonlocomotor activities (45% inactive, 55% active, 0% locomotion) and walking activities (0% inactive, 1.8% active, 98.2% locomotion). When walking, the number of strides taken was slightly underestimated (-1.0%). The underestimation of distance travelled (-6.2%) and walking speed (-5.8%) was greater. The agreement with video output decreased when the PAM was misaligned, when persons walked at a speed below the defined minimum speed, and when persons walked with crutches. The PAM provides valid data on activity classes and number of strides. Although the majority of the distance data was satisfactory, in some cases considerable differences were found between the PAM and the video data. The impact of alignment, walking speed, and use of assistive devices on the PAM's operation should be considered.

Use of an 'on board' datalogger to determine lizard activity patterns, body temperature and microhabitat use for extended periods in the field

We describe a technique developed to provide continuous long-term records of movement by individual lizards in the field. Using a small, lightweight and robust activity logger we are able to record over short intervals the number of strides taken, the body temperature and the incident light intensity on the dorsal surface of an animal. Using these data, activity patterns, behaviour and microhabitat choice can be determined in the absence of an observer, thus reducing biases due to observer presence. In our study the logger stored recordings every 2 min for 15 days.

High-precision satellite positioning system as a new tool to study the biomechanics of human locomotion

New Global Positioning System (GPS) receivers allow now to measure a location on earth at high frequency (5 Hz) with a centimetric precision using phase differential positioning method. We studied whether such technique was accurate enough to retrieve basic parameters of human locomotion. Eight subjects walked on an athletics track at four different imposed step frequencies (70–130 steps/min) plus a run at free pace. Differential carrier phase localization between a fixed base station and the mobile antenna mounted on the walking person was calculated. In parallel, a triaxial accelerometer, attached to the low back, recorded body accelerations. The different parameters were averaged for 150 consecutive steps of each run for each subject (total of 6000 steps analyzed). We observed a perfect correlation between average step duration measured by accelerometer and by GPS ( r=0.9998, N=40). Two important parameters for the calculation of the external work of walking were also analyzed, namely the vertical lift of the trunk and the velocity variation per step. For an average walking speed of 4.0 km/h, average vertical lift and velocity variation were, respectively, 4.8 cm and 0.60 km/h. The average intra-individual step-to-step variability at a constant speed, which includes GPS errors and the biological gait style variation, were found to be 24.5% (coefficient of variation) for vertical lift and 44.5% for velocity variation. It is concluded that GPS technique can provide useful biomechanical parameters for the analysis of an unlimited number of strides in an unconstrained free-living environment.