Recurrence quantification analysis of gait in normal and hypovestibular subjects

The study of postural control processes during locomotion may provide useful outcome measures of stability for people with unilateral vestibular hypofunction (UVH). Since nonlinear analysis techniques can characterize complex behaviour of a system, this may highlight mechanisms underlying dynamic stability in locomotion, although only few efforts have been made. In particular, there have been no studies that use recurrence quantification analysis (RQA), which can be applied even to short and non-stationary data. The purpose of this study was to develop a new method for walking balance assessment measuring the complexity of head, trunk and pelvis three-dimensional accelerations and angular velocities during normal overground locomotion by means of RQA in normal subjects and UVH patients. The results showed differential effect of upper body parts on pattern regularity, with better head than pelvis stabilization in both groups of subjects. The RQA outputs such as percent determinism and recurrence were nevertheless significantly lower in the UVH group for all measures, suggesting that body accelerations and angular velocities, although not significantly different in amplitude, were more chaotic in patients. The observed lower regularity of upper body movements in UVH is consistent with an important role of the vestibular system in controlling dynamic stability during walking. The findings suggest that RQA can be used as a quantitative tool to assess walking performance and rehabilitation outcome in patients with different balance disorders.     

Reducing gait speed affects axial coordination of walking turns

Turning is a common feature of daily life and dynamic coordination of the axial body segments is a cornerstone for safe and efficient turning. Although slow walking speed is a common trait of old age and neurological disorders, little is known about the effect of walking speed on axial coordination during walking turns. The aim of this study was to investigate the influence of walking speed on axial coordination during walking turns in healthy elderly adults. Seventeen healthy elderly adults randomly performed 180° left and right turns while walking in their self-selected comfortable pace and in a slow pace speed. Turning velocity, spatiotemporal gait parameters (step length and step time), angular rotations and angular velocity of the head and pelvis, head-pelvis separation (i.e. the angular difference in degrees between the rotation of the head and pelvis) and head-pelvis velocity were analyzed using Wilcoxon signed-rank tests. During slow walking, turning velocity was 15% lower accompanied by shorter step length and longer step time compared to comfortable walking. Reducing walking speed also led to a decrease in the amplitude and velocity of the axial rotation of the head and pelvis as well as a reduced head-pelvis separation and angular velocity. This study demonstrates that axial coordination during turning is speed dependent as evidenced by a more ‘en bloc’ movement pattern (i.e. less separation between axial segments) at reduced speeds in healthy older adults. This emphasizes the need for matching speed when comparing groups with diverse walking speeds to differentiate changes due to speed from changes due to disease.     

Compensatory balance reactions during forward and backward walking on a treadmill

Previous work suggests that balance perturbations to the body opposing the direction of progression during walking lead to larger amplitude corrective reactions than perturbations concurrent with walking direction. To test this hypothesis, subjects received forward and backward perturbations applied to the pelvis through a padded harness, while walking forwards or backwards on a treadmill. Contrary to our hypothesis, the greatest responses were associated with backward perturbations regardless of the direction of walking.     

Trunk sway measures of postural stability during clinical balance tests: effects of a unilateral vestibular deficit

This research evaluated whether quantified measures of trunk sway during clinical balance tasks are sensitive enough to identify a balance disorder and possibly specific enough to distinguish between different types of balance disorder. We used a light-weight, easy to attach, body-worn apparatus to measure trunk angular velocities in the roll and pitch planes during a number of stance and gait tasks similar to those of the Tinetti and CTSIB protocols. The tasks included standing on one or two legs both eyes-open and closed on a foam or firm support-surface, walking eight tandem steps, walking five steps while horizontally rotating or pitching the head, walking over low barriers, and up and down stairs. Tasks were sought, which when quantified might provide optimal screening for a balance pathology by comparing the test results of 15 patients with a well defined acute balance deficit (sudden unilateral vestibular loss (UVL)) with those of 26 patients with less severe chronic balance problems caused by a cerebellar-pontine-angle-tumour (CPAT) prior to surgery, and with those of 88 age- and sex-matched healthy subjects. The UVL patients demonstrated significantly greater than normal trunk sway for all two-legged stance tasks especially those performed with eyes closed on a foam support surface. Sway was also greater for walking while rotating or pitching the head, and for walking eight tandem steps on a foam support surface. Interestingly, the patients could perform gait tasks such as walking over barriers almost normally, however took longer. CPAT patients had trunk sway values intermediate between those of UVL patients and normals. A combination of trunk sway amplitude measurements (roll angle and pitch velocity) from the stance tasks of standing on two legs eyes closed on a foam support, standing eyes open on a normal support surface, as well as from the gait tasks of walking five steps while rotating, or pitching the head, and walking eight tandem steps on foam permitted a 97% correct recognition of a normal subject and a 93% correct recognition of an acute vestibular loss patient. Just over 50% of CPAT patients could be classified into a group with intermediate balance deficits, the rest were classified as normal. Our results indicate that measuring trunk sway in the form of roll angle and pitch angular velocity during five simple clinical tests of equilibrium, four of which probe both stance and gait control under more difficult sensory conditions, can reliably and quantitatively distinguish patients with a well defined balance deficit from healthy controls. Further, refinement of these trunk sway measuring techniques may be required if functions such as preliminary diagnosis rather than screening are to be attempted.     

Concern about falling is associated with segmental control when turning in older adults

BackgroundHealthy young adults typically exhibit a progressive ‘top-down’ reorientation of body segments (i.e., head, trunk, then pelvis) during turning. This behaviour is less evident in older adults at risk of falling, who often reduce angular displacement between body segments during turns. The potential functional and psychological contributors to this so-called ‘en-bloc’ turning strategy are not yet understood.Research questionAre there associations between concern about falling and variables representing en-bloc turning (i.e., increased coupling between body segments)?MethodsTwenty-one older adults were assessed while turning during an adaptive walking task. We collected data from markers forming the head, trunk, and pelvis segments, while gait velocity throughout the turn was calculated from a sternum marker. We correlated several variables with concern about falling alone, as well as while controlling for functional balance ability.ResultsCorrelation analyses revealed that concern about falling was related to en-bloc turning strategies and slower gait velocity throughout the turn, when analysed independently of functional balance. When controlling for balance ability, en-bloc turning strategies between the head and trunk, as well as the head and pelvis, remained significantly associated with concern about falling.SignificanceFindings offer an insight into the potential role that psychological characteristics may have in determining older adults’ turning behaviour and associated risk of falling.     

Movement strategies for head stabilization during incline walking

Changes in body orientation with respect to space during incline walking can alter vestibular information requiring a different solution to the problem of head stabilization. Eleven young adults walked along a level walkway, and ascended and descended an inclined surface. Head, neck and trunk angular positions in space were collected. Changes in the gravitoinertial vector imposed by the inclined surface, produced concomitant changes in body segment orientation that decreased head stability during the inclined walking tasks. Head, neck and trunk segments were least stable while ascending the incline creating the greatest challenge to head stability during this task. Movement strategies reflected adjustments of head–neck and neck–trunk patterns to accommodate changes in the gravitoinertial vector and insure balance of the head over the trunk.     

Impaired postural control of axial segments in children with cerebral palsy

BackgroundSensorimotor control of axial segments, which develops during childhood and is not mature until adolescence, is essential for the development of balance control during motor activities. Children with cerebral palsy (CP) have deficits in postural control when standing or walking, including less stabilization of the head and trunk which could affect postural control.Research questionIs dynamic stabilization of axial segments during an unstable sitting task deficient in children with CP compared to typically developing children? Is this deficit correlated with the deficit of postural control during standing?MethodSeventeen children with CP (GMFCS I-II) and 17 typically-developing children from 6 to 12 years old were rated on the Trunk Control Measurement Scale (TCMS). In addition, posturography was evaluated in participants while they maintained their balance in stable sitting, unstable sitting, and quiet standing, under “eyes open” and “eyes closed” conditions. In sitting tasks, the participants had to remain stable while being prevented from using the lower and upper limbs (i.e. to ensure the involvement of axial segments alone).ResultsChildren with CP compared to TD children had significantly larger surface area, mean velocity and RMS values of CoP displacements measured during the unstable sitting task and the standing task, under both “eyes open” and “eyes closed” conditions. No significant group effects were observed during the stable sitting task. The TCMS total score was significantly lower, indicating trunk postural deficit, in the CP group than in the TD group and was significantly correlated with postural variables in the sitting and standing tasks.SignificanceChildren with CP indeed have a specific impairment in the postural control of axial segments. Since the postural control of axial segments is important for standing and walking, its impairment should be taken into account in rehabilitation programs for children with CP.     

Kinetic analysis of forwards and backwards stair descent

The activity of descending stairs increases loading at the joints of the lower extremities as compared to walking, which may cause discomfort and or difficulties in completing the task. This study compared and contrasted the kinematics and kinetics of both forwards and backwards stair descent to those of level walking. We compared the support moments and moment powers of the lower limb joints while descending stairs forwards at a self-selected pace, backwards at a self-selected pace and forwards at the same pace as backwards. Participants were 10 healthy young adults (6 men and 4 women) aged 20–35 years. Sagittal plane kinematics and ground reaction forces were collected and moments of force computed using inverse dynamics. The ratio of stance/swing phase changed from 59:41 for normal level walking to between 65:35 and 70:30 for forward stair descent but backwards descent was 58:42. Stair descent produced larger double-peak support moments with reduced ankle plantar flexor and increased knee extensor moments as compared to level walking (>±95th-percentile confidence interval). The hip moments during stair descent were relatively small and highly variable. We observed significantly larger distances between the centres of pressure and the stair edges for backwards stair descent versus forwards stair descent. These results demonstrate that stair descent, even at a slower pace, requires greater power from the knee extensors than level walking but that backwards stair descent significantly reduced the peak knee power during midstance and provided a potentially safer means of descending stairs than forwards stair descent.     

Whole-body and segment angular momentum during 90-degree turns

BackgroundTurning is a frequently performed, asymmetric task of daily living. The asymmetric nature makes turning challenging to perform while maintaining balance.Research questionHow do healthy individuals maintain dynamic balance, quantified as whole-body angular momentum, during a 90-degree turn compared to straight-line walking?MethodsThe kinematics of sixteen healthy individuals were tracked during walking in a straight-line and during left and right 90-degree turns at a comfortable pace. Whole-body and segment angular momenta were calculated and the relative contributions of the legs, arms, pelvis and head/trunk to whole-body angular momentum were evaluated.ResultsAverage whole-body angular momentum was different during turning compared to straight-line walking in all planes of motion. The initiation of a turn required generation of whole body angular momentum in all three planes of motion, which was counteracted at the end of the turn by a generation of angular momentum in the opposite direction in the frontal and sagittal planes. Transverse plane momentum was always directed in the turn direction. All segment groups, except for the inside leg, had a greater magnitude of angular momentum during turning compared to straight-line walking. The outside leg and head/trunk segments were the largest contributors to frontal and transverse plane whole-body angular momentum.SignificanceUnderstanding how body segments contribute to maintaining balance during a 90-degree turn can be useful for designing rehabilitation paradigms for people who have difficulty turning or impaired balance.     

Acceleration patterns of the head and pelvis when walking on level and irregular surfaces

The aim of this study was to evaluate acceleration patterns at the head and pelvis while subjects walked on a level and an irregular walking surface, to develop an understanding of how the postural control system responds to challenging walking conditions. Thirty young, healthy subjects walked on a level corridor and on artificial grass underlain with foam and wooden blocks placed in an arbitrary manner. Temporo-spatial gait parameters and acceleration patterns at the head and pelvis were measured. The results revealed that when walking on the irregular surface, subjects were able to maintain their velocity, but adopted a slower and more variable cadence and a significantly longer stride length. The magnitude of pelvis accelerations increased, however head accelerations were not affected by the walking surface. When considered as an overall pattern of movement, these findings suggest that one of the primary objectives of the postural control system when walking on irregular surfaces is head control, and that subjects adapt their stepping pattern on irregular surfaces to ensure that the head remains stable.     

Effects of caloric vestibular stimulation on head and trunk movements during walking

The effects of vestibular stimulation on head and trunk movements were investigated during human walking (4.0 km/h). Vestibular stimulation was produced by irrigating an external auditory meatus with 4 °C ice water for 10 s. Using a 3-D motion analysis system, the linear (medial/lateral and vertical) translations and angular (yaw, pitch and roll) rotations were determined at the head, thorax, pelvis, knee, and foot. After caloric stimulation, waking trajectory deviated toward the stimulated side during dizziness. In addition, the amplitude of medial/lateral (M/L) linear translation and yaw rotation were significantly increased by caloric stimulation, especially at the head and thorax, whereas changes in vertical translation and pitch and roll rotations were not significant. The compensatory coordination (i.e., the yaw rotation to oppose the M/L linear translation) of the head was precisely maintained both before and after caloric stimulations, but it was decreased at the thorax and pelvis after stimulation. Our results suggested that vestibular sensory information, probably via the horizontal semicircular canals, contributes predominantly to the regulation of dynamic head and trunk movements in the M/L direction.     

Light touch and center of mass stability during treadmill locomotion

PURPOSE: To study the contributions of light fingertip touch on an earth-referenced object to body stability during treadmill locomotion. METHOD: Twenty young healthy adults were tested in two blocks of five testing conditions while walking on the treadmill at 3 km/h. In each condition, subjects were tested with eyes open (EO) and with eyes closed (EC). In each block, four separate conditions of heavy (H) or light (L) touch to either a left or to a right force sensor mounted on the respective side rail, as well as one condition of no touch (N), were randomly applied. The 3D positions of the center of mass (COM) and the midpoint of the posterior aspect of each leg were monitored via a kinematic ultrasonic system, while the anterior-posterior (AP) acceleration of the COM was measured with a uniaxial linear accelerometer. RESULTS: Light touch had a similar stabilizing effect as vision and as heavy touch on COM sway. Thus, COM sway and AP acceleration were comparable in conditions of eyes open and eyes closed as long as touch was applied. Conversely, without vision and touch, subjects drifted backwards, with complete disruption of the coordinated stepping pattern. CONCLUSIONS: Somatosensory fingertip input from an external reference provides spatial orientation, which, similar to vision, enables the sustaining of body stability during treadmill walking.     

Modulation of head movement control in humans during treadmill walking

The purpose of this study was to investigate the coordination of the head relative to the trunk within a gait cycle during gaze fixation. Nine normal subjects walked on a motorized treadmill driven at 1.79 m/s (20 s trials) while fixing their gaze on a centrally located earth-fixed target positioned at a distance of 2 m from their eyes. The net and relative angular motions of the head about the three axes of rotations, as well as the corresponding values for the moments acting on it relative to the trunk during the gait cycle were quantified and used as measures of coordination. The average net moment, as well as the average moments about the different axes were significantly different (P<0.01) between the high impact and low/no impact phases of the gait cycle. However, the average net angular displacement as well as the average angular displacement about the axial rotation axis of the head relative to the trunk was maintained uniform (P>0.01) throughout the gait cycle. The average angular displacement about the lateral bending axis was significantly increased (P<0.01) during the high impact phase while that about the flexion–extension axis was significantly decreased (P<0.01) throughout the gait cycle. Thus, the coordination of the motion of the head relative to the trunk during walking is dynamically modulated depending on the behavioral events occurring in the gait cycle. This modulation may serve to aid stabilization of the head by counteracting the force variations acting on the upper body that may aid in the visual fixation of targets during walking.     

Fine-wire electromyography of the transverse head of adductor hallucis during locomotion

BackgroundPrevious literature on the transverse head of adductor hallucis (AddH-T) has largely focused on muscle morphology. This data provides insight into muscle architecture, yet fails to inform it’s functional implication during walking. The role of the AddH-T, which runs parallel to the distal transverse metatarsal arch, has never been studied using fine-wire EMG during locomotion.Research questionThe purpose of this study is to explain a novel method of recording fine-wire EMG of the adductor hallucis muscle of the foot, and secondly, to report phasic AddH-T muscle activity during level walking on hard and soft surfaces.MethodsUltrasound-guided fine-wire EMG was recorded from the AddH-T of each foot, in ten asymptomatic young adults. Participants completed ten walking trials per experimental conditions (hard and soft surface). Ensemble averages were calculated from the time normalized linear-envelopes of each participant, and represented from 0 to 100 percent of the gait cycle.ResultsUsing the described ultrasound-guided fine-wire protocol, successful EMG signals were generated in 19 of 20 feet. When walking over hard or soft flooring, the AddH-T muscle has two bursts in EMG, occurring between 0–20 % and 50–65 % of the gait cycle. The magnitude of peak activity was often reduced at initial contact when walking over foam. 45 % of participants experienced a third burst in EMG activity at midstance, corresponding to 30–40 % of the gait cycle.SignificanceThis study has successfully explained a novel method of recording finewire electromyography (EMG) of the adductor hallucis (transverse head) muscle of the foot. Results suggest that the AddH-T stabilizes the forefoot at initial contact and toeoff, while further anchoring the hallux during propulsion. These results provide preliminary insight into the functional role of the AddH-T during human locomotion     

Directional effects of biofeedback on trunk sway during gait tasks in healthy young subjects

Biofeedback of trunk sway is a possible remedy for patients with balance disorders. Because these patients have a tendency to fall more in one direction, we investigated whether biofeedback has a directional effect on trunk sway during gait.Forty healthy young participants (mean age 23.1 years) performed 10 gait tasks with and without biofeedback. Combined vibrotactile, auditory and visual feedback on trunk sway in either the lateral or anterior–posterior (AP) direction was provided by a head-mounted actuator system. Trunk roll and pitch angles, calculated from trunk angular velocities measured with gyroscopes, were used to drive the feedback.A reduction in sway velocities occurred across all tasks regardless of feedback direction. Reductions in sway angles depended on the task. Generally, reductions were greater in pitch. For walking up and down stairs, or over barriers, pitch angle reductions were greater with AP than lateral feedback. For tandem and normal walking, reductions were similar in pitch and roll angles for both feedback directions. For walking while rotating or pitching the head or with eyes closed, only pitch angle was reduced for both feedback directions.These results indicate that the central nervous system is able to incorporate biofeedback of trunk sway from either the AP or lateral direction to achieve a reduction in both pitch and roll sway. Greater reductions in pitch suggest a greater ability to use this direction of trunk sway biofeedback during gait.     

Aging affects coordination of rapid head motions with trunk and pelvis movements during standing and walking

The head, containing the gravity sensors (vestibular system) and the visual system, must be stabilized in space to provide a steady reference. During walking, the head also needs to be free to move to allow scanning of surrounding objects and steering of locomotion. With aging, deteriorations in motor and sensory systems and their integration are commonly observed. Nevertheless, the strategies used by elderly subjects to complete challenging tasks that require precise sensorimotor integration, such as turning the head rapidly during gait, is not known. The objective of this study was to determine the effects of aging on the movement coordination of the head, trunk and pelvis when executing a rapid head motion in response to a visual signal. Elderly and young subjects turned their head rapidly (up, down, left, right or none) in response to a visual signal, during standing and walking. The 3-D positions of head, trunk and pelvis were recorded and analyzed. All subjects, young and old, successfully performed the task during both standing and walking without any loss of balance. Postural stability was maintained as large head motions were accompanied by relatively small trunk and pelvis movements. Horizontal plane movements associated with right and left head turns were significantly larger than sagittal plane movements associated with head up and down motions. Head motions were significantly slower and smaller in elderly subjects, and resulted in disrupted horizontal plane trunk-pelvis coordination during walking. We conclude that head, trunk and pelvis movements are coordinated in a task-dependent manner such that their movement amplitudes induced by rapid voluntary head motions are larger in walking than in standing. This task-dependent movement coordination is affected by aging.     

Comparisons of forward and backward gait between poorer and better attention capabilities in early Parkinson's disease

This study compared forward and backward gait between Parkinson's disease (PD) patients with poorer and better attention capabilities. PD and healthy control (HC) participants received a dual-stimuli attention task. The results were assessed using principal component analysis to quantify and rank attention capability. Accordingly, 22 PD and 42 HC subjects were equally divided into poorer (14 PD-P, 18 HC-P) and better (8 PD-B, 24 HC-B) attention capabilities. To analyze the spatiotemporal gait parameters, each participant walked forwards and backwards on a GAITRite^® walkway. Compared to HC, PD performed worse in the dual task and exhibited slower velocity, less swing, and shorter stride in both walking directions. Notably, PD-P experienced all these gait defects, regardless of directions. PD-B walked worse than HC-B backwards, and displayed comparable gait to HC-P in both directions. In PD and HC, velocity, stride, and swing decreased perceptibly when walking backwards compared to forwards, and the same was true for velocity and stride in PD-P and PD-B. Backward strides were reduced evidently more in PD-P than in PD-B. However, backward swing reductions in PD-P and PD-B were statistically insignificant. Cadence in both directions was similar within the groups and between the groups, and there were little alterations between directions within each group and between groups. These results suggest that attention capability may affect PD gait. Poorer attention exacerbates gait defects and better attention improves gait in both directions. These results may support the application of cuing strategies in PD to enhance attention capability and improve walking gait.     

Differences between trunk sway characteristics on a foam support surface and on the Equitest ankle-sway-referenced support surface

Clinicians have sought ways to increase trunk sway so that it is easily observed and a balance deficit more easily identified. One technique often used for this purpose is to reduce the efficacy of ankle proprioceptive inputs on sway. To achieve this reduction either a foam mat is used as an unstable support surface or the subject stands on a surface made unstable with servo-driven ankle-sway-referencing. The purpose of the current study was to investigate differences in trunk pitch and roll sway characteristics using these techniques. Trunk sway while standing quietly on two legs was measured in 25 normal subjects in the age range 20–35 years for three support-surface conditions. Each condition was tested twice for 20 s, once with eyes open and once with eyes closed. The three conditions were standing on a foam support surface, standing on a support surface with pitch (fore-aft) ankle-sway-referencing as used for the standard Sensory Organization Test (SOT) of the Neurocom Equitest System (SOT 4 and 5), and standing with roll (lateral) ankle-sway-referencing. The latter was achieved by having the subjects stand turned 90° to the standard SOT position. Two angular velocity sensors mounted on a belt measured trunk sway in the pitch and roll directions. Trunk roll angle and angular velocity amplitudes for pitch sway-referencing were reduced compared to either the foam or roll sway-referencing conditions, but trunk pitch angle and angular velocities amplitudes were greater. For roll sway-referencing, the trunk roll angle was greater than for the other stimulus conditions. Analyses of the trunk sway velocity in the frequency domain indicated that ankle-sway-referencing in the pitch direction increased trunk pitch sway at 1 Hz and decreased trunk roll sway between 2 and 5 Hz compared to foam support frequency spectra. Roll ankle-sway-referencing decreased trunk roll between 2 and 4 Hz only. These results indicate that using a foam support surface provides multidirectional trunk sway with velocity content across all frequencies in the range 0.8–5.2 Hz. Roll ankle-sway-referencing, but not pitch ankle-sway-referencing, yields trunk sway with similar characteristics to those with foam. Pitch ankle-sway-referencing forces pitch trunk resonance to be around 1 Hz and yields very different trunk sway from that obtained with a foam support surface. Roll sway-referencing is an alternative means to test multidirectional control of sway. Clinically though, foam is simpler to use and provides a more difficult balance task for the patient.     

Effect of changing visual condition and frequency of horizontal oscillations on postural balance of standing healthy subjects

The goal of this study was to describe the movement pattern of the body-segment rotations of healthy subjects in the horizontal plane while they were standing on a supporting platform that imposed steady sinusoidal horizontal rotations under three visual conditions: (a) eyes closed with no instructions (EC–NI), (b) eyes open with instructions to gaze at a stationary black dot located at eye level on a wall surface about four meters in front of them (EO–WI), and (c) eyes closed with instructions to imagine looking at the same target (EC–WI). The selected input signal was a sinusoid with an amplitude of ±45 deg at different frequencies equal to 0.25, 0.50 and 0.75 Hz, which were referred to as L, M and H. Bipedal balance measurements were taken in 10 adult subjects (mean age 30 ± 9 years; three men and seven women).Subjects’ kinematics were analyzed with an optoelectronic system. Under the three visual conditions, the movements of the pelvis, the trunk, and the head decreased and were inversely dependent on platform frequency; specifically, both the head and the trunk decreased their gain rotation of about 1.8–2.9 times from L to H, while the pelvis decreased its by about 1.3 times. However, the arm oscillations showed a gain and phase tendency opposite to that of the other body segments, with the gain rotation having increased of about 1.8–3.7 times from L to H.Comparing the three visual conditions, the finding suggests that the subjects were able to stabilize their head as a reference frame to maintain postural balance in a similar way under the EC–WI and EO–WI conditions. Instead, in the EC–NI trials, the subjects compensated less, in particular at the hip, the external perturbation producing higher absolute body rotations and lower relative body rotations. In fact, the head rotation was about four and three times the one showed in EC–WI and EO–WI, while for the trunk and the pelvis it was always equal to two and 1.5 times the correspondent rotation observed under the WI conditions. These results provide a quantitative assessment of compensatory balance reactions in healthy subjects to periodical horizontal perturbations.     

Age-related changes in upper body adaptation to walking speed in human locomotion

Assessments of changes in gait stability due to aging and disease are predominantly based on lower extremity kinematic and kinetic data. These gait changes are also often based on comparisons at preferred speed only. The purpose of this experiment was to: (1) examine age-related changes in range of motion and coordination of segments of the upper body during locomotion; and (2) investigate the effects of a systematic walking velocity manipulation on rotational motion and coordination. Participants (n=30) walked on a motor driven treadmill at speeds ranging from 0.2 to 1.8m/s and were divided into three groups with mean ages of 23.3, 49.3 and 72.6 years, respectively. Seven high-speed infrared cameras were used to record three-dimensional kinematics of the pelvis, trunk and head. Dependent variables were amplitude of segmental and joint rotations, as well as relative phase to assess coordination between segments. Although no differences in stride parameters were found between the groups, age-related changes in movement amplitude in response to speed manipulations were observed for all segments and joints. Pelvic rotations in sagittal, frontal and transverse planes of motion were systematically reduced with age. Older individuals showed reduced trunk flexion-extension in the sagittal plane and increased trunk axial rotation in the transverse plane. Coordination analysis showed reduced compensatory movement between pelvis and trunk in older individuals. These findings support the importance of systematic manipulation of walking velocity and three-dimensional upper body kinematics in assessing age-related changes in locomotor stability and adaptability.