Walking In Place Research Articles

Pneumatic Interactive Gait Rehabilitation Orthosis: Design and Preliminary Testing

Motor rehabilitation techniques based on passive movement of the lower limbs have been developed over the past 15 years. Gait training automation is the latest innovation in these techniques. This paper describes the design and development of a pneumatic interactive gait rehabilitation orthosis (PIGRO), as well as the first experimental results obtained with healthy subjects. PIGRO consists of a modular and size-adaptable exoskeleton, pneumatic actuation systems for the six actuated degrees of freedom (DoF), and a control unit. The foot orthosis and ankle actuation can be removed and/or replaced with orthopaedic shoes so as to permit gait rehabilitation while advancing between parallel bars with ground contact and partial body weight support (i.e. not walking in place). Control logic provides closed-loop position control independently on each joint, with position feedback for each joint in real time. Imposed curves are physiological joint angles: it is also possible to choose between activating one or both legs and to modify curves to obtain different gait patterns if required. The paper concludes with a presentation of experimental results for the device's performance.

GUD WIP: Gait-Understanding-Driven Walking-In-Place.

Many Virtual Environments require walking interfaces to explore virtual worlds much larger than available real-world tracked space. We present a model for generating virtual locomotion speeds from Walking-In-Place (WIP) inputs based on walking biomechanics. By employing gait principles, our model - called Gait-Understanding-Driven Walking-In-Place (GUD WIP) - creates output speeds which better match those evident in Real Walking, and which better respond to variations in step frequency, including realistic starting and stopping. The speeds output by our implementation demonstrate considerably less within-step fluctuation than a good current WIP system - Low-Latency, Continuous-Motion (LLCM) WIP - while still remaining responsive to changes in user input. We compared resulting speeds from Real Walking, GUD WIP, and LLCM-WIP via user study: The average output speeds for Real Walking and GUD WIP respond consistently with changing step frequency - LLCM-WIP is far less consistent. GUD WIP produces output speeds that are more locally consistent (smooth) and step-frequency-to-walk-speed consistent than LLCM-WIP.

Human-Induced Particle Re-Suspension in a Room

A large-eddy simulation/immersed boundary method for particulate flows in an Eulerian framework is utilized to investigate short-term particle re-suspension due to human motion. The simulations involve a human walking through a room, stopping, and then walking in place, causing particles to be re-suspended from a carpet. The carpet layer is modeled as the porous medium and a classical adhesive force model is applied to model the resistance of the carpet-bound material to hydrodynamic forcing. The effects of parameters such as the foot penetration depth and adhesive force coefficient on mass re-suspended during the foot stamping events are examined. Simulations of particulate re-suspension experiments conducted in a room within a U.S. Environmental Protection Agency test house are also described. The simulations vary the type of human motion (stamping in place versus stamping in place with rotation). The results indicate that significant amounts of particulate material are re-suspended from the carpet layer due to the impingement of the feet during the motion event. The net mass re-suspended for human motion with rotation is two times greater than that for the motion without rotation, while the mass of re-suspended small particles is slightly greater than that of large particles. The re-suspension rates are estimated based on several time scales, and the predicted total particle number concentrations at several locations in the room show good agreement with experimental data. The present CFD model can be utilized to predict particle re-suspension rates as induced by human motion, but further work in modeling the fine-scale details of the re-suspension process is needed.

Embodied cognition and health persuasion: Facilitating intention–behavior consistency via motor manipulations

The present research examines health persuasion from an embodied cognition perspective by proposing that engaging the motor system during health persuasion will lead individuals to engage in healthier behavior and have greater consistency between their intentions and behavior. In two studies, participants watched a health video while either imaging themselves performing the behavior or imaging themselves performing the behavior while also engaging their motor systems with minimal, relevant behaviors. In Study 1, after watching a flossing video, females (but not males) flossed more times in the following week after touching a floss and in Study 2, all participants (males and females) exercised more in the week after watching an exercise video while walking in place. In both experiments, participants who engaged the motor system had stronger intention–behavior consistency than those who merely imagined themselves performing the health behavior. Implications of the findings are discussed for theories of embodied cognition, intention–behavior consistency, and health persuasion.

The conspicuity of first-responder safety garments

Introduction This study compared the conspicuity of three types of first-responder safety garments (NFPA 1971-2007 turnout gear coats, and ANSI/ISEA 107 and 207 safety vests). Method Participants drove instrumented vehicles on a closed track during both daytime and nighttime, indicating when they could first detect pedestrians in a simulated emergency response scene. Pedestrians wore one of the safety garments and stood on either side of the emergency scene, facing or perpendicular to oncoming traffic, and either stationary or walking in place. Results All three garment standards provided equal levels of conspicuity, in that the distances at which the pedestrians were detected were equivalent. Time of day was a significant factor, with longer mean detection distances being observed in daytime. Pedestrian orientation was significant, with mean detection distances being longest when facing traffic. Pedestrian motion did not result in significant differences in detection distance. Discussion The results suggest that all three garment types studied are equivalent in making first responders conspicuous as pedestrians when working an emergency response scene in close proximity to traffic. Impact on Industry Whether an NFPA or ANSI/ISEA compliant is worn, first responders are equally likely to be detected by passing motorists, and as such these garments should be considered to be equivalent.

3축 가속도 센서를 이용한 보행 횟수 검출 알고리즘과 활동 모니터링

최근 핸드폰, PDA 등에서 가속도센서를 이용한 연구가 많이 증가하고 있다. 본 논문에서는 3축 가속도센서를 이용해 사람이 보행 시 발생하는 데이터를 취득하여 사람의 걸음 수를 계산해 내는 알고리즘과 활동량을 실시간으로 모니터링 할 수 있는 UI 시스템을 개발하였다. 걷기, 제자리 걷기, 뛰기, 천천히 걷기 등의 각 상황별 걸음 수를 정밀하게 측정하기 위해 적응적인 임계값을 사용하는 보행 횟수 검출 알고리즘을 제안하였다. 또 이러한 알고리즘에 의해 얻은 보행 횟수를 이용해서 활동량으로 환산하고 UI화면에 실시간으로 보임으로써 정량화된 활동량으로 실시간 모니터링이 가능하도록 하였다. 실험결과 제안한 보행 횟수 검출 알고리즘이 에너지 기반의 기존의 고정 임계값을 이용하는 알고리즘 보다 <TEX>$5{\sim}10%$</TEX> 정확도가 높은 결과 값을 얻을 수 있었으며 특히, 천천히 걷기에서 정확도가 높아진 것을 확인하였다. The research for a 3-axial accelerometer sensor has increased dramatically in the fields of cellular phone, PDA, etc. In this paper, we develop a human walking detection algorithm using 3-axial accelerometer sensor and a user interface system to show the activity expenditure in real-time. To measure a walking number more correctly in a variety of walking activities including walking, walking in place, running, slow walking, we propose a new walking number detection algorithm using adaptive threshold value. In addition, we calculate the activity expenditure base on counted walking number and display calculated activity expenditure on UI in real-time. From the experimental results, we could obtain that the detection rate of proposal algorithm is higher than that of existing algorithm using a fixed threshold value about <TEX>$5{\sim}10%$</TEX>. Especially, it could be found out high detection rate in walking in place.

Static and dynamic postural control adaptations induced by playing ice hockey

In ice hockey, players produce high velocities by skating and game actions are typically characterized by sudden accelerations and brisk decelerations. Thus, the vestibular system is particularly stressed. The aims of this study were to evaluate sensorial organization and head stabilization control of ice hockey players in order to investigate if this kind of activity induces specific sensorimotor adaptation. We studied 8 elite hockey players, 8 amateur players and 10 healthy controls. Three tests were performed: (1) sensory organization test (SOT) to evaluate sensorial organization in maintaining steady stance in quiet standing; (2) head stabilization stance test (H-STAN) to evaluate head-to-trunk stabilization during quiet steady stance; and (3) stepping test (STEP) to evaluate skills in maintaining the head stable with respect to the trunk during walking in place. In SOT, elite players had a greather visual component and reduced vestibular component. In H-STAN test, elites, when standing on foam, presented head less stable than trunk. In STEP test, with respect to normal subjects and amateurs the head of elites was less stable in the sagittal plane with eyes open and more stable in the frontal plane with eyes closed.

Assessing Pain in Persons with Dementia: Relationships Among the Non-communicative Patient’s Pain Assessment Instrument, Self-report, and Behavioral Observations

Pain is a common problem for many older adults, with up to 50% of community-dwelling and 70% to 80% of nursing home residents experiencing pain regularly. Effective pain management requires thorough assessment, appropriate intervention, and systematic reassessment. Pain assessment, however, is complicated by dementia, which impairs memory, reasoning, recognition, and communication, and affects elders’ ability to verbally report pain. As such, observational measures are needed to assess pain in this vulnerable population. The Non-communicative Patient’s Pain Assessment Instrument (NOPPAIN) was developed for this purpose, but more validation of this measure is needed. Thus, the purpose of this study was to (1) evaluate reliability of the NOPPAIN tool when used by nurses and to (2) compare NOPPAIN ratings with self-report and other well-established behavioral rating procedures. Forty participants (20 cognitively intact and 20 impaired) were randomly selected for this study from a larger sample. In the parent study, participants were asked to perform everyday activities (i.e., sit, stand, walk in place, transfer in and out of bed) while being videotaped. The tapes, all previously scored using microanalytic observational coding, were rated again by naïve raters using the NOPPAIN measure. Results indicated (1) high inter- and intrarater reliability of the NOPPAIN and (2) significant correlations of the NOPPAIN with self-reported pain and detailed behavioral coding. Findings support the reliability and validity of the NOPPAIN measurement tool and suggest this easy-to-use tool may be adequate for measuring pain indicators in older adults.

Verification of Individual Identification Method Using Bioelectric Potential of Plant during Human Walking

In this study, we monitored electromagnetic waves generated by human activity and investigated a method for individual identification by looking at the bioelectric potential of a rubber tree. Four subjects were asked to walk in place at a distance of 60 cm from a rubber tree while we measured variations in the bioelectric potential of the tree as produced by the stepping. The results confirmed that electromagnetic waves generated by a human subject walking in place produce a measurable response in the bioelectric potential of a plant. It was also found that this variation in bioelectric potential varies in synchrony with each subject's walking pace. The spectral envelope of the observed signal was approximated using a straight line and the distribution of the coefficients of this line was plotted. Even for a simple straight-line approximation, we demonstrated that this coefficient distribution varies considerably among individual subjects.

The Use of a Handheld Calorimetry Unit to Estimate Energy Expenditure During Different Physiological Conditions

Accurately determining rates of energy expenditure (EE) under free-living conditions is important in understanding the mechanisms involved in the development and prevention of obesity. Metabolic carts are not portable enough for most free-living situations. The purpose of this study was to compare a portable, handheld indirect calorimetry device (HealtheTech Incorporated, Golden, CO) to a metabolic cart (Physio-Dyne Instrument Corporation, Quogue, NY) during 3 different physiologic states. EE was measured by both the handheld calorimeter (5-10 minutes) and the metabolic cart (15-20 minutes) in 20 healthy subjects (18-35 years of age). Measurements were made during 3 physiologic states: (1) postabsorptive rest (REE), (2) postprandial rest (fed energy expenditure, FEE), and (3) while walking in place (activity energy expenditure, AEE). There were no significant differences between the means of the cart vs the hand-held device for REE (mean +/- SE; kcal/d; 1552 +/- 64 vs 1551 +/- 63), FEE (1875 +/- 99 vs 1825 +/- 86), and AEE (3333 +/- 218 vs 3489 +/- 152). The range over which the techniques were tested was 1300-5000 kcal/d. The agreement between the 2 methods was excellent for REE (0.80, p < .0001), FEE (0.89, p < .0001), and AEE (0.75, p < .0002). Compared with the metabolic cart, the handheld device provided similar estimates of energy expenditure during resting, postprandial, and physically active states. This suggests that portable indirect calorimetry devices can provide reliable and valuable information in free-living research situations for which maximal energy expenditure is <5000 kcal/d.

Cardiorespiratory responses to basic aquatic exercise – A pilot study

This study aimed to examine cardiorespiratory responses to six basic aquatic exercises and to compare the impact of the exercises between healthy females (H group, n=10) and females with diagnosed cardiopulmonary diseases (C group, n=10). The average age of the participants was 52.6(±5.9) years. Each exercise was performed for 3 min. During the exercises, heart rate (HR), oxygen consumption (VO2), blood lactate concentration (BLA), and rate of perceived exertion (RPE) were measured. In each pair of exercises, the latter part was more strenuous than the first. Walking in place was least and cross-country skiing the most strenuous mode of exercise. Energy expenditure (EE) ranged between 2.5±0.8 MET in the C group and 6.0±1.6 MET in the H group. RPE ranged between 11.0±2.5 in the C group and 13.6±2.4 in the H group. The C group had significantly lower HR in cross-country skiing and running forward, as well as lower VO2 in running in place, cross-country skiing and running forward, as compared to the H group....

Static walking in place as an alternative to pharmacological stress testing in obese patients for evaluation of coronary artery disease

Static walking in place as an alternative to pharmacological stress testing in obese patients for evaluation of coronary artery disease

Virtual Locomotion: Walking in Place through Virtual Environments

This paper presents both an analysis of requirements for user control over simulated locomotion and a new control technique designed to meet these requirements. The goal is to allow the user to move through virtual environments in as similar a manner as possible to walking through the real world. We approach this problem by examining the interrelationships between motion control and the other actions people use to act, sense, and react to their environment. If the interactions between control actions and sensory feedback can be made comparable to those of actions in the real world, then there is hope for constructing an effective new technique. Candidate solutions are reviewed once the analysis is developed. This analysis leads to a promising new design for a sensor-based virtual locomotion called Gaiter. The new control allows users to direct their movement through virtual environments by stepping in place. The movement of a person's legs is sensed, and in-place walking is treated as a gesture indicating the user intends to take a virtual step. More specifically, the movement of the user's legs determines the direction, extent, and timing of their movement through virtual environments. Tying virtual locomotion to leg motion allows a person to step in any direction and control the stride length and cadence of his virtual steps. The user can walk straight, turn in place, and turn while advancing. Motion is expressed in a body-centric coordinate system similar to that of actual stepping. The system can discriminate between gestural and actual steps, so both types of steps can be intermixed.

ENERGY COST OF WALKING/JOGGING IN A LAMINAR FLOW POOL: GENDER DIFFERENCES

654 Metabolic responses to walking/jogging in a laminar flow resistance pool were determined for 10 females and 18 males who were comfortable in a water environment. Each subject completed three, 6 minute submaximal workloads while in water at the level of xiphoid process under the following conditions: walking against no current (i.e., walking in place); walking/jogging against a 30 m·min−1 (1.08 mph); and, 54 m·min−1 (1.94 mph) current in a laminar flow resistance pool (Swim-Ex) made available by Bronston Chiropractic clinic, LaCrosse, WI. The frontal flow resistance for stage two approximated 30 m·min−1 (1.08 mph) and 54 m·min−1 (1.94 mph) for the third stage. Overall the VO2 (l·min−1) significantly (p < 0.01) increased as the resistance increased with the VO2 approximately 9% higher between no current and 30 m·min−1 walking and 42% higher for walking/jogging at 54 m·min−1 compared to the 30 m·min−1 resistance. The men's absolute VO2 (l·min−1) was significantly (p < 0.01) higher than the women's at all stages, however, when expressed relative to body weight (ml·kg−1·min−1) the only significant (p < 0.05) gender difference was found at the highest workload (54 m·min−1). There were no significant (p > 0.05) differences in heart rate responses between genders. According to the ACSM (1995) calculations the estimated MET cost for walking at 53.7 m·min−1 is 2.5 compared to the 7.1 METS measured in response to the third workload of 54 m·min−1. These results suggest that walking against a laminar flow current requires approximately 2.8 times the energy of land walking at comparable speeds with less musculo-skeletal stress.

Vision and vestibular adaptation

This article summarizes six recent degree-of-freedom studies of visual-vestibular interaction during natural activities and relates the findings to canal-otolith interactions evaluated during eccentric axis rotations. Magnetic search coils were used to measure angular eye and head movements of young and elderly subjects. A flux gate magnetometer was used to measure three-dimensional head translation. Three activities were studied: standing quietly, walking in place, and running in place. Each activity was evaluated with three viewing conditions: a visible target viewed normally, a remembered target in darkness, and a visible target viewed with ×2 binocular telescopic spectacles. Canal-otolith interaction was assessed with passive, whole-body, transient, and steady-state rotations in pitch and yaw at multiple frequencies about axes that were either oculocentric or eccentric to the eyes. For each rotational axis, subjects regarded visible and remembered targets located at various distances. Horizontal and vertical angular vestibulo-ocular reflexes were demonstrable in all subjects during standing, walking, and running. When only angular gains were considered, gains in both darkness and during normal vision were less than 1.0 and were generally lower in elderly than in young subjects. Magnified vision with ×2 telescopic spectacles produced only small gain increases as compared with normal vision. During walking and running all subjects exhibited significant mediolateral and dorsoventral head translations that were antiphase locked to yaw and pitch head movements, respectively. These head translations and rotations have mutually compensating effects on gaze in a target plane for typical viewing distances and allow angular vestibulo-ocular reflex gains of less than 1.0 to be optimal for gaze stabilization during natural activities. During passive, whole-body eccentric pitch and yaw head rotations, vestibulo-ocular reflex gain was modulated as appropriate to stabilize gaze on targets at the distances used. This modulation was evident within the first 80 msec of onset of head movement, too early to be caused by immediate visual tracking. Modeling suggests a linear interaction between canal signals and otolith signals scaled by the inverse of target distance. Vestibulo-ocular reflex performance appears to be adapted to stabilize gaze during translational and rotational perturbations that occur during natural activities, as is appropriate for relevant target distances. Although immediate visual tracking contributes little to gaze stabilization during natural activities, visual requirements determine the performance of vestibulo-ocular reflexes arising from both canals and otoliths. (Otolaryngol Head Neck Surg 1998;119:78-88.)

3D Analysis of Human Locomotion Before and After Caloric Stimulation

Human locomotion was analysed in the sagittal and coronal planes using a position detector system composed of 2 infrared video cameras and a data processor. Normal healthy volunteers with 8 marker points on the body were asked to walk in place (WIP) and on a treadmill (WOT). Vertical and medial/lateral (M/L) translational movements were measured. Head angular movements in the sagittal (pitch) and coronal (roll) planes were also analysed. Pitch movements counteracted the vertical head movements. Head movement was remarkably attenuated in the vertical axis compared with that of the trunk. However, head M/L movement showed no difference with that of the lower part of the body. Ice water caloric stimulation was introduced to cause acute unilateral vestibular deficit. The stride length and step cycle became small after caloric stimulation in WOT, but not in WIP. The characteristic change in locomotive pattern was a large lateral sway of the hip joint occurring to the side away from calorization (right) during one foot standing (right foot) (t-test, p = 0.057). Measurement of M/L sway amplitude showed an increase only at the hip joint. As the changes in head and neck movements were not significant after caloric stimulation, it appears that the vestibulo-spinal reflex contributes little to maintaining the dynamic balance of the upper body. The importance of the hip joint for locomotion (hip strategy) was confirmed from the present data.

Visual-Vestibular Interaction During Standing, Walking, and Running

In artificial laboratory situations where subjects undergo repetitive self-generated or externally imposed head rotations, visual-vestibular interaction during the wearing of telescopic spectacles can markedly augment gain of the vestibulo-ocular reflex (VOR). The present study was conducted to determine whether the wearing of these aids for the visually impaired is associated with similar visual-vestibular interaction during more natural activities. Angular eye and head movements of unrestrained normal volunteers were measured using magnetic search coils. In some subjects, head translations and rotations were also monitored by a flux gate magnetometer array. Measurements were performed of the VOR in darkness, and of the visually enhanced VOR (VVOR) in lit conditions, during three natural activities: 1) standing quietly; 2) walking in place; 3) running in place. These data were compared with similar measurements during repetitive voluntary head oscillations at 0.8 Hz in pitch or yaw. During VVOR, subjects viewed a target placed 6 to 10 m away and remembered this target during VOR trials in darkness. To assess the effects of altering visual-vestibular interactions, VVOR testing during normal vision was augmented by wearing of binocular telescopic spectacles of 2X, 4X, and 6X powers. Dorsoventral and mediolateral head translations were consistently phase-locked with pitch and yaw head rotations, respectively, such that head translation at least partially compensated for rotational disturbances of gaze. Angular velocity of the head was greater during walking than during standing, and was greater still during running, with a greater increase in each case for pitch as compared with yaw. Eye movements were phase compensatory for head movements. VOR gain (eye velocity divided by head velocity) was near 1.0 in both pitch and yaw during standing and during actively generated head rotation. During walking and running there was a significant decrease in angular VOR gain in pitch to approximately 0.75 (P < 0.0005). During ambulatory activities, normal and magnified vision were associated with VVOR gain enhancement in pitch and yaw that was statistically significant, but substantially less than was telescope magnification and markedly lower than was the corresponding VVOR gain measured during active head rotation. Measurements of unmagnified VOR and VVOR during walking and running showed that gain was lower than the "ideal" value of 1.0. However, since translational head perturbations during these activities partially offset the visual effects of angular disturbances, lower gains may nevertheless be associated with retinal image stability at typical indoor target distances. In contrast with performance during repetitive, uniplanar motion, vision has very limited influence on VOR gain during natural activities.

Head stabilization during various locomotor tasks in humans

This experiment, which extends a previous investigation (Pozzo et al. 1990), was undertaken to examine how head position is controlled during natural locomotor tasks in both normal subjects (N) and patients with bilateral vestibular deficits (V). 10 normals and 7 patients were asked to perform 4 locomotor tasks: free walking (W), walking in place (WIP), running in place (R) and hopping (H). Head and body movements were recorded with a video system which allowed a computed 3 dimensional reconstruction of selected points in the sagittal plane. In order to determine the respective contribution of visual and vestibular cues in the control of head angular position, the 2 groups of subjects were tested in the light and in darkness. In darkness, the amplitude and velocity of head rotation decreased for N subjects; these parameters increased for V subjects, especially during R and H. In darkness, compared to the light condition, the mean position of a line placed on the Frankfort plane (about 20-30 degrees below the horizontal semi-circular canal plane) was tilted downward in all conditions of movement, except during H, for N subjects. In contrast, this flexion of the head was not systematic in V subjects: the Frankfort plane could be located above or below earth horizontal. In V subjects, head rotation was not found to be compensatory for head translation and the power spectrum analysis shows that head angular displacements in the sagittal plane contain mainly low frequencies (about 0.3-0.8 Hz). The respective contribution of visual and vestibular cues in the control of the orientation and the stabilization of the head in space is discussed.

Effect of Telescopic Spectacles on Head Stability in Normal and Low Vision

Telescopic spectacles, highly magnifying visual aids mounted in spectacle frames, markedly alter the visual consequences of head movements. To evaluate the effect of this altered visual feedback on head stability, angular head velocity of normally sighted and low vision subjects was measured in the roll, pitch, and yaw axes. Measurements were made under two postural conditions: (1) quiet standing; and (2) walking in place, as well as three visual conditions: (1) eyes closed; (2) unmagnified vision; and (3) vision with 4 x binocular telescopic spectacles. For normal subjects during quiet standing, both unmagnified vision and vision with telescopic spectacles tended to reduce spontaneous head velocity in all axes as compared to the eyes-closed condition. However, in low vision subjects neither unmagnified vision nor vision with telescopic spectacles produced significant changes in values of head velocity relative to those measured with eyes closed. Spontaneous head velocities for standing low vision subjects tended to be higher than in normal subjects, although not all differences were statistically significant. During walking in place, Fourier analysis demonstrated prominent frequency components related to harmonics of the walking frequency under all viewing conditions. In normal subjects, vision with telescopic spectacles, to a greater degree than unmagnified vision, reduced head velocity during walking in the roll and yaw, but not the pitch, axes. For low vision subjects, significant reductions in head velocity during walking were observed only during vision with telescopic spectacles. These findings indicate that vision reduces angular instability of the head during standing and walking. Magnification produced by telescopic spectacles further improves head stability under some conditions, although the effect of vision is least evident in the pitch axis. The stabilizing effect of vision is reduced in low vision subjects.

Head stabilization during various locomotor tasks in humans

Head kinematics were studied in ten normal subjects while they executed various locomotor tasks. The movement of the body was recorded with a video system which allowed a computer reconstruction of motion of joint articulations and other selected points on the body in three dimensions. Analyses focus on head translation along the vertical axis and rotation in the sagittal plane. This was done by recording the displacement of a line approximating the plane of horizontal semi-circular canals (the Frankfort plane: F-P). Four conditions were studied: free walking (W) walking in place (WIP) running in place (R) and hopping (H). In the 4 experimental conditions, amplitude and velocity of head translation along the vertical axis ranged from 1 cm to 25 cm and 0.15 m/s to 1.8 m/s. In spite of the disparities in the tasks regarding the magnitude of dynamic components, we found a significant stabilization of the F-P around the earth horizontal. Maximum amplitude of F-P rotation did not exceed 20 degrees in the 4 situations. Vertical angular velocities increased from locomotion tasks to the dynamic equilibrium task although the maximum values remained less than 140 degrees/s. Predominant frequencies of translations and rotations in all the tasks were within the range 0.4-3.5 Hz and harmonics were present up to 6-8 Hz. During walking in darkness, mean head position is tilted downward, with the F-P always below the earth horizontal. Darkness did not significantly influence the amplitude and velocity of head angular displacement during W, WIP and R, but during H the amplitude decreased by 37%. Residual head angular displacement is found to compensate for head translation during the 4 conditions. Our study emphasizes the importance of head stabilization as part of the postural control system and described as a basis for inertial guidance.