Sudden turn during walking is impaired in people with Parkinson’s disease

The present study compared kinematic strategies for making sudden directional changes during walking between patients with Parkinson’s disease (PwPD) and age-matched controls. Ten PwPD and 10 healthy elderly were visually cued to walk straight or to turn either 30° or 60° to the left or right, at the mid-point of a 9-m walkway. Three-dimensional kinematic data recorded: (1) the onset time of body segments in response to the turning cue, and (2) step width at the first ipsilateral foot contact (IFC₁) marking the beginning of turn, the subsequent contralateral foot contact (CFC), and the second ipsilateral foot contact (IFC₂) marking the completion of turn. For both 30° and 60° turns, PwPD had later onset times for lateral foot displacement, and larger time lags between the onset of body CoM and the lateral foot translation than healthy subjects (P < 0.05). Furthermore, PwPD had a significantly narrower step width than healthy subjects (P < 0.05). Despite these differences, PwPD and control subjects scaled up turning speed and amplitude similarly for 30° and 60° turns. Our findings suggested that PwPD manifested specific difficulty in modifying their ongoing motor program to switch their locomotion from straight line to sideway direction, but their ability to scale movement speed and amplitude appeared to be preserved.     

Age-related modifications in steering behaviour: effects of base-of-support constraints at the turn point

This study investigated the effects of altering the base of support (BOS) at the turn point on anticipatory locomotor adjustments during voluntary changes in travel direction in healthy young and older adults. Participants were required to walk at their preferred pace along a 3-m straight travel path and continue to walk straight ahead or turn 40° to the left or right for an additional 2-m. The starting foot and occasionally the gait starting point were adjusted so that participants had to execute the turn using a cross-over step with a narrow BOS or a lead-out step with a wide BOS. Spatial and temporal gait variables, magnitudes of angular segmental movement, and timing and sequencing of body segment reorientation were similar despite executing the turn with a narrow or wide BOS. A narrow BOS during turning generated an increased step width in the step prior to the turn for both young and older adults. Age-related changes when turning included reduced step velocity and step length for older compared to young adults. Age-related changes in the timing and sequencing of body segment reorientation prior to the turn point were also observed. A reduction in walking speed and an increase in step width just prior to the turn, combined with a delay in motion of the center of mass suggests that older adults used a more cautious combined foot placement and hip strategy to execute changes in travel direction compared to young adults. The results of this study provide insight into mobility constraints during a common locomotor task in older adults.     

双任务介入对社区脑卒中患者步态参数及其对称性的影响

目的 对比社区脑卒中患者单任务步行与不同类型和不同负荷双任务步行时步态参数及其对称性的差异。方法 利用 Simi Motion 三维动作分析系统采集 20 名处于慢性恢复期的社区脑卒中患者在单任务步行及不同负荷认知双任务步行和运动双任务步行时步态参数,并间接计算出其对称指数。 采用单因素重复测量方差分析对比单任务步行与不同双任务步行时步态参数及其对称性差异。 结果 与单任务步行相比,社区脑卒中患者在高低负荷认知任务介入时步速、患侧步长、健侧摆动相占比均降低,困难认知任务介入时健侧步宽和健侧、患侧支撑相占增加、健侧步长和患侧摆动相占比降低,摆动相占比对称指数减小(P<0. 05)。 结论 社区脑卒中患者主要通过降低步速、缩减步长、降低摆动相占比、增加步宽和支撑相占比,改变步态模式来应对认知任务干扰,对于步态稳定性,高负荷认知任务的介入,会增加社区脑卒中患者摆动相占比的不对称性程度,降低其步态稳定性。     

Stroke-related differences in axial body segment coordination during preplanned and reactive changes in walking direction

This study quantitatively describes differences between participants with hemiparetic stroke and age-matched healthy participants in axial body segment and gait kinematics during a direction change task. Participants were required to change walking direction by 45°, either to their left or right, at the midpoint of a 6-m path. Participants were visually cued either at the start of the walk (pre-planned) or one stride before they reached the turn point (reactive). The sequence and inter-segmental timing of axial orientation onset was preserved in participants with stroke. Analysis of a subgroup of stroke survivors indicated that participants with lesions affecting the basal ganglia (BG) took significantly longer time than control participants to initiate the reorientation synergy when making turns to their non-paretic side. We hypothesize that these differences are a product of asymmetrical activity of dopaminergic pathways in the brain resulting from compromised BG function.     

When is Higher Level Cognitive Control Needed for Locomotor Tasks Among Patients with Parkinson’s Disease?

Turning has been implicated as a complex task that requires both motor and cognitive resources. Accumulating evidence shows that patients with Parkinson’s disease (PD) require more steps and more time to complete a turn, however, the role of the prefrontal cortex during turning is not clear. Forty nine patients with PD without freezing of gait (mean age 71.7?±?1.0 years; 67% men, disease duration 9.7?±?1.3 years) performed motor and cognitive tests. Prefrontal activation, specifically in Brodmann area 10 (BA10), during turning and usual walking was measured using functional near infrared spectroscopy (fNIRS). The patients with PD were further divided into two subgroups with high and low functional status based on limitations in community ambulation. General Linear Model analysis adjusted for age, gender, disease duration and turn duration was used to assess differences between tasks and subgroups of patients with PD. In addition, Pearson’s correlation was performed to assess association between BA10 activation and motor and cognitive scores. Activation in BA10 increased during walking (p?<?0.001), while it decreased during turning (p?=?0.006). A comparison between the two subgroups of patients with PD revealed that patients with relatively better ambulation decreased prefrontal activation during turning, as compared to patients with relatively worse ambulation (p?<?0.001). These findings are the first to show that BA10 plays a different role during turning and walking and that ambulation status may alter BA10 activation during turning. Higher prefrontal activation during turning in the subgroup of patients with relatively worse ambulation may reflect a compensatory attempt at improving performance.     

Effects of head immobilization on the coordination and control of head and body reorientation and translation during steering

Changing the direction of locomotion involves lateral translation of the body in addition to body reorientation to align with the new travel direction. We designed this study to investigate the CNS control of these postural adjustments. The specific aims of the study were: first, to test the hypothesis that anticipatory head movements towards the new travel path are proactively controlled by the CNS to provide a stable frame of reference for body reorientation and, second, to investigate the relative contribution of foot placement and other mechanisms to the control of lateral body translation during steering. We achieved these aims by carrying out a comprehensive biomechanical analysis of participants performing a steering paradigm and observing the effects of immobilizing the head (by fixing it to the trunk) on postural control and the sequencing of body segment reorientation. Participants performed a task whereby they were visually cued to change their direction of walking by 30° or 60°, left or right, at the midpoint of a 9-m path. The temporal sequence of body reorientation was consistent with previous findings that the head starts to turn in the direction of travel before the rest of the body. Translation of the centre of mass (COM) in the new travel direction was achieved both through alternate placement of the contralateral foot prior to the turn step and use of a hip strategy to control the body pendulum during swing. Immobilizing the head resulted in the following significant changes: earlier onset of trunk yaw with respect to cue delivery, later trunk roll onset and a reduction in trunk roll amplitude. These results provide valuable information regarding the biomechanics of steering and support the hypothesis that aligning the head with motor or locomotor goals using vision provides the CNS with a stable frame of reference, independent of gaze, that can be used to control the repositioning of the body in space. Electronic Publication     

Motor planning ability is not related to lesion side or functional manual ability in children with hemiplegic cerebral palsy

Optimal task performance requires anticipatory planning to select the most appropriate movement strategy. There is conflicting evidence for hemispheric specialisation of motor planning, with some suggesting left hemisphere dominance, claiming that children with right hemiplegic cerebral palsy (HCP) are therefore disproportionally affected. An alternative view is that there is a positive relationship between functional ability (rather than side of lesion) and motor planning skill. We aimed to compare children with right and left HCP on motor planning ability and to explore its relationship with functional manual ability. Participants were 76 children with HCP (40 left HCP; 30 female), aged 4–15 years (Mean 9.09, SD 2.94). Motor planning was assessed using a measure of end-state comfort, which involved turning a hexagonal handle 180° without readjusting grasp. This is difficult, or in some cases impossible, to achieve unless an appropriate initial grasp is adopted. Children completed 24 turns (12 clockwise), which were video recorded for offline scoring. Functional manual ability was assessed with the ABILHAND-Kids questionnaire, completed by parents. Contrary to the existing literature, no differences were observed between right and left HCP. However, a significant interaction between direction of turn and side of hemiplegia indicated a preferential bias for turns in the medial direction, consistent with the “medial over lateral advantage”. There was no relationship between functional ability and motor planning. Therefore, motor planning may not be a priority for therapeutic intervention to improve functional ability in HCP.     

Walking along curved paths of different angles: the relationship between head and trunk turning

Walking along a curved path requires coordinated motor actions of the entire body. Here, we investigate the relationship between head and trunk movements during walking. Previous studies have found that the head systematically turns into turns before the trunk does. This has been found to occur at a constant distance rather than at a constant time before a turn. We tested whether this anticipatory head behavior is spatially invariant for turns of different angles. Head and trunk positions and orientations were measured while participants walked around obstacles in 45°, 90°, 135° or 180° turns. The radius of the turns was either imposed or left free. We found that the head started to turn into the direction of the turn at a constant distance before the obstacle (~1.1 m) for turn angles up to 135°. During turns, the head was consistently oriented more into the direction of the turn than the trunk. This difference increased for larger turning angles and reached its maximum later in the turn for larger turns. Walking speeds decreased monotonically for increasing turn angles. Imposing fixed turn radii only affected the point at which the trunk started to turn into a turn. Our results support the view that anticipatory head movements during turns occur in order to gather advance visual information about the trajectory and potential obstacles.     

Mobile-bearing total knee arthroplasty: More rotation is evident during more demanding tasks

BackgroundSome reports showed few but significant more axial femorotibial rotation in favor of mobile-bearing (MB) versus fixed-bearing (FB) total knee arthroplasty (TKA), mostly during knee bend fluoroscopic studies. The goal of the current study was to submit MB and FB groups of TKA patients to a turning activity, in which additional rotation was to be expected.MethodsTwo consecutive cohorts of patients after TKA (10 FB and 11 MB knees in a total of 18 patients) were assessed using motion analysis five year postoperatively, while performing gait and sit-to-walk (STW) movements with and without turning steps.ResultsMean range of rotation in the FB group increased from 9.7° during gait, to 11.7° during STW straight, and to 14.3° during STW turning. Mean range of rotation in the MB group increased from 13.4° during gait to 21.0° during STW straight, and stayed at 21.1° during STW turning.ConclusionsToo many uncontrolled variables in the current study hinder a meaningful discrimination of MB from FB TKA rotation. However, the study does illustrate how more demanding task loads could be helpful in exploring the geometric constraints of TKA variants.Level of EvidenceLevel III, therapeutic study.     

Cognitive Processing for Step Precision Increases Beta and Gamma Band Modulation During Overground Walking

The aim of this study was to investigate whether cognitive processing for defining step precision during walking could induce changes in electrocortical activity. Ten healthy adults (21–36 years) were asked to walk overground in three different conditions: (1) normal walking in a straight path (NW); (2) walking in a pre-defined pathway forcing variation in step width and length by stepping on green marks on the floor (only one color: W1C), and (3) walking in the same pre-defined W1C pathway while evaluating different combinations among the colors green, yellow and red, in which only one color was the footfall target (evaluating two colors: W2C). Walking speed, stride duration and scalp electroencephalography (EEG) were recorded from all conditions. Event-related spectral perturbation was calculated for channels Fz, Cz, C3, C4, Pz and Oz in each condition, which were all time-normalized in relation to the gait cycle. The results showed that walking speed was reduced and stride duration was increased for W2C when compared to both NW and W1C (p?<?0.01). Moreover, Event-related spectral perturbation analysis revealed significant changes (p?<?0.05) during mid-stance in the frontal lobe and motor/sensorimotor regions, a phase in the gait cycle in which participants define the correct foot placement for the next step. These results suggest that greater cognitive demands during precision stepping influences electrocortical dynamics especially towards step transitions. Therefore, increased electrocortical activity in cognitive, motor and sensorimotor areas may be relevant to produce patterned and safe locomotion through challenging paths.     

Gait adaptations to simultaneous cognitive and mechanical constraints

Previous studies have shown that walking is not a purely automatic motor task but places demands on sensory and cognitive systems. We set out to investigate whether complex walking tasks, as when walking down a steeper gradient while performing a concurrent cognitive task, would demand gait adaptation beyond those required for walking under low-challenge conditions. Thirteen healthy young individuals walked at their self-selected speed on a treadmill at different inclinations (0, −5 and −10%). Gait spatio-temporal measures, pelvis angular excursion, and sacral centre of mass (CoM) motion were acquired while walking or while walking and performing a mental tracking task. Repeated-measures ANOVAs revealed that decreasing treadmill inclination from 0 to −10% resulted in significant decreased walking speed (P < 0.001), decreased stride length (P < 0.001), increased pelvis tilt (P = 0.006) and obliquity variability (P = 0.05), decreased pelvis rotation (P = 0.02), and increased anterio-posterior (A-P) CoM displacement (P = 0.015). Compared to walking alone, walking under dual-task condition resulted in increased step width (P < 0.001), and increased medio-lateral (M-L) CoM displacement (P = 0.039) regardless of inclination grade, while sagittal plane dynamics did not change. Findings suggest that gait adapts differently to cognitive and mechanical constraints; the cognitive system is more actively involved in controlling frontal than sagittal plane gait dynamics, while the reverse is true for the mechanical system. Finally, these findings suggest that gait adaptations maintain the ability to perform concurrent tasks while treadmill walking in healthy young adults.     

Locomotor adjustments for circumvention of an obstacle in the travel path

Independent living requires the navigation of a surrounding environment which is often cluttered with obstacles. When walking around an obstacle in the travel path, safe clearance requires some degree of body-segment reorientation. While body-segmental coordination strategies have been well studied for steering tasks that require moving the body in a new walking direction, it has never been established just what coordination strategies are used in different walking tasks. To address this issue, the current study was designed to investigate the timing of body segment coordination strategies and whole-body anticipatory locomotor adjustments employed when circumventing an obstacle placed in the travel path. Six healthy adults were asked to walk at their natural pace during unobstructed walking, as well as during avoidance to the right or left of a cylindrical obstacle (OBS) located in the travel path. Data analyzed were center of mass (COM) clearance from the OBS, forward velocity, step length and width, yaw angles of the head and trunk, roll angle of the trunk, and medial-lateral COM displacement. Onset of change in these variables from unobstructed walking was calculated as the time from OBS crossing. Avoidance involved two equally used strategies: lead limb close to or away from the OBS during the crossing step. Medial-lateral COM deviations were controlled by changes in step width without changes in trunk roll. There were no differences in the onset times of body segment reorientation for path deviation. These results are in contrast to previous studies on change in travel direction where the head segment initiates the body reorientation. Contrary to a steering task, circumventing an obstacle requires a different coordination for a transient change in COM trajectory with the underlying travel-direction maintained.     

Differential effects of absent visual feedback control on gait variability during different locomotion speeds

Healthy persons exhibit relatively small temporal and spatial gait variability when walking unimpeded. In contrast, patients with a sensory deficit (e.g., polyneuropathy) show an increased gait variability that depends on speed and is associated with an increased fall risk. The purpose of this study was to investigate the role of vision in gait stabilization by determining the effects of withdrawing visual information (eyes closed) on gait variability at different locomotion speeds. Ten healthy subjects (32.2 ± 7.9 years, 5 women) walked on a treadmill for 5-min periods at their preferred walking speed and at 20, 40, 70, and 80 % of maximal walking speed during the conditions of walking with eyes open (EO) and with eyes closed (EC). The coefficient of variation (CV) and fractal dimension (α) of the fluctuations in stride time, stride length, and base width were computed and analyzed. Withdrawing visual information increased the base width CV for all walking velocities (p < 0.001). The effects of absent visual information on CV and α of stride time and stride length were most pronounced during slow locomotion (p < 0.001) and declined during fast walking speeds. The results indicate that visual feedback control is used to stabilize the medio-lateral (i.e., base width) gait parameters at all speed sections. In contrast, sensory feedback control in the fore-aft direction (i.e., stride time and stride length) depends on speed. Sensory feedback contributes most to fore-aft gait stabilization during slow locomotion, whereas passive biomechanical mechanisms and an automated central pattern generation appear to control fast locomotion.     

Effects of postural threat on walking features of Parkinson's disease patients

This study investigated whether or not gait kinematics among healthy older individuals and Parkinson's disease (PD) patients are influenced by postural threat. Eight healthy older individuals and eight PD patients were examined while walking at self-selected velocities, under three conditions of postural threat: unconstrained floor; constrained floor (19 cm wide); constrained and elevated floor (19 cm wide by 10 cm high). Independent of the surface conditions, due to motor disturbances caused by the PD these patients walked slower, with shorter strides, and spent more time in the double support phase and less time in the swing phase than did their matched controls. Increases in postural threat resulted in altered gait kinematics for all subjects. Specifically, stride length, stride velocity, cadence, and heel contact velocity decreased, and stride duration and double support duration increased relative to increases in postural threat. All gait alterations were the result of participants’ attempts to facilitate locomotion control and maintain stability. The results of this study reveal that width and height constraints effectively perturbed the balance of all of the walking older individuals. The PD patients were able to modulate gait parameters when faced by a postural threat task.     

Interaction of the body, head, and eyes during walking and turning

Body, head, and eye movements were measured in five subjects during straight walking and while turning corners. The purpose was to determine how well the head and eyes followed the linear trajectory of the body in space and whether head orientation followed changes in the gravito-inertial acceleration vector (GIA). Head and body movements were measured with a video-based motion analysis system and horizontal, vertical, and torsional eye movements with video-oculography. During straight walking, there was lateral body motion at the stride frequency, which was at half the frequency of stepping. The GIA oscillated about the direction of heading, according to the acceleration and deceleration associated with heel strike and toe flexion, and the body yawed in concert with stepping. Despite the linear and rotatory motions of the head and body, the head pointed along the forward motion of the body during straight walking. The head pitch/roll component appeared to compensate for vertical and horizontal acceleration of the head rather than orienting to the tilt of the GIA or anticipating it. When turning corners, subjects walked on a 50-cm radius over two steps or on a 200-cm radius in five to seven steps. Maximum centripetal accelerations in sharp turns were ca.0.4 g, which tilted the GIA ca.21 degrees with regard to the heading. This was anticipated by a roll tilt of the head of up to 8 degrees. The eyes rolled 1-1.5 degrees and moved down into the direction of linear acceleration during the tilts of the GIA. Yaw head deviations moved smoothly through the turn, anticipating the shift in lateral body trajectory by as much as 25 degrees. The trunk did not anticipate the change in trajectory. Thus, in contrast to straight walking, the tilt axes of the head and the GIA tended to align during turns. Gaze was stable in space during the slow phases and jumped forward in saccades along the trajectory, leading it by larger angles when the angular velocity of turning was greater. The anticipatory roll head movements during turning are likely to be utilized to overcome inertial forces that would destabilize balance during turning. The data show that compensatory eye, head, and body movements stabilize gaze during straight walking, while orienting mechanisms direct the eyes, head, and body to tilts of the GIA in space during turning.     

An apparent contradiction: increasing variability to achieve greater precision?

To understand the relationship between variability of foot placement in the frontal plane and stability of gait patterns, we explored how constraining mediolateral foot placement during walking affects the structure of kinematic variance in the lower-limb configuration space during the swing phase of gait. Ten young subjects walked under three conditions: (1) unconstrained (normal walking), (2) constrained (walking overground with visual guides for foot placement to achieve the measured unconstrained step width) and, (3) beam (walking on elevated beams spaced to achieve the measured unconstrained step width). The uncontrolled manifold analysis of the joint configuration variance was used to quantify two variance components, one that did not affect the mediolateral trajectory of the foot in the frontal plane (“good variance”) and one that affected this trajectory (“bad variance”). Based on recent studies, we hypothesized that across conditions (1) the index of the synergy stabilizing the mediolateral trajectory of the foot (the normalized difference between the “good variance” and “bad variance”) would systematically increase and (2) the changes in the synergy index would be associated with a disproportionate increase in the “good variance.” Both hypotheses were confirmed. We conclude that an increase in the “good variance” component of the joint configuration variance may be an effective method of ensuring high stability of gait patterns during conditions requiring increased control of foot placement, particularly if a postural threat is present. Ultimately, designing interventions that encourage a larger amount of “good variance” may be a promising method of improving stability of gait patterns in populations such as older adults and neurological patients.     

Constraining eye movement when redirecting walking trajectories alters turning control in healthy young adults

Humans use a specific steering synergy, where the eyes and head lead rotation to the new direction, when executing a turn or change in direction. Increasing evidence suggests that eye movement is critical for turning control and that when the eyes are constrained, or participants have difficulties making eye movements, steering control is disrupted. The purpose of the current study was to extend previous research regarding eye movements and steering control to a functional walking and turning task. This study investigated eye, head, trunk, and pelvis kinematics of healthy young adults during a 90° redirection of walking trajectory under two visual conditions: Free Gaze (the eyes were allowed to move naturally in the environment), and Fixed Gaze (participants were required to fixate the eyes on a target in front). Results revealed significant differences in eye, head, and trunk coordination between Free Gaze and Fixed Gaze conditions (p < 0.001). During Free Gaze, the eyes led reorientation followed by the head and trunk. Intersegment timings between the eyes, head, and trunk were significantly different (p < 0.05). In contrast, during Fixed Gaze, the segments moved together with no significant differences between segment onset times. In addition, the sequence of segment rotation during Fixed Gaze suggested a bottom-up postural perturbation control strategy in place of top-down steering control seen in Free Gaze. The results of this study support the hypothesis that eye movement is critical for the release of the steering synergy for turning control.     

Role of motor and visual experience during development of bipedal locomotion in chicks

The purpose of this research was to investigate the role of motor and visual experience during the development of locomotion in chicks. We have previously demonstrated that when locomotor activity is restricted immediately posthatching, chicks walk with shorter stride lengths and attenuated head bobbing movements. Head bobbing is an optokinetic response in birds, driven by the movement of the visual world across the retina (i.e., optic flow). During locomotion, optic flow is generated by forward translation, and we have shown that the magnitude of head bobbing movements and stride lengths are moderately correlated in walking chicks. In the present study, we investigated this relationship more closely by examining whether imposed changes in stride length could affect head excursions during head bobbing. We manipulated stride length by hobbling chicks immediately after hatching and subsequently quantified kinematic parameters, including step timing and head excursions, during walking. Imposition of shorter stride lengths induced chicks to take more frequent steps, spend less time in contact with the ground, and shortened head excursions during head bobbing. Nevertheless, the developmental changes in head excursions were not fully accounted for by altered stride lengths, so in a separate experiment, we investigated whether the development of head bobbing relies on the normal experience of optic flow. We raised chicks under stroboscopic illumination to eliminate chicks' experience of optic flow but found that this did not significantly alter head bobbing. These results are discussed along with related findings in other species and the possible neural and biomechanical constraints underlying development of walking and head bobbing in birds.     

Identifying axial and cognitive correlates in patients with Parkinson’s disease motor subtype using the instrumented Timed Up and Go

Parkinson’s disease (PD) is clinically highly heterogeneous, often divided into tremor dominant (TD) and postural instability gait difficulty (PIGD). To better understand these subtypes and to help stratify patients, we applied an objective marker, i.e., an instrumented version of the traditional “Timed Up and Go” test (iTUG). It is not known whether the iTUG is sensitive to PD motor phenotypes or what are its behavioral and cognitive correlates. Subjects performed the iTUG wearing a body-fixed sensor. Subcomponents were studied including walking, transitions and turning. Gait, balance and cognitive function and the associations between iTUG, behavioral and cognitive domains were assessed. We also compared two representative subtypes, with minimal symptom overlap, referred to here as predominant PIGD (p-PIGD) and predominant TD (p-TD). One hundred and six patients with PD performed the iTUG. Significant correlations were found between iTUG measures and the PIGD score, but not with TD score. Thirty p-PIGD and 31 p-TD patients were identified. Both groups were similar with respect to age and disease duration (p > 0.75). The p-PIGD patients took significantly longer to complete the iTUG (p = 0.026), used more steps (p = 0.031), albeit with similar step duration (p = 0.936). In the sit-to-stand transition, the p-PIGD patients exhibited lower anterior–posterior jerk (p = 0.04) and lower pitch range (p = 0.012). During the turn, the p-PIGD patients had a lower yaw amplitude (p < 0.038). Cognitive domains were correlated with iTUG measures in the p-PIGD patients, but not in the p-TD. These findings demonstrate that a single sensor can identify axial and cognitive correlates using subcomponents of the iTUG and reveals subtle alterations between the PD motor subtypes.     

Gait analysis of slope walking: a study on step length, stride width, time factors and deviation in the center of pressure

Determination was made of step length, stride width, time factors and deviation in the center of pressure during up- and downslope walking in 17 healthy men between the ages of 19 and 34 using a force plate. Slope inclinations were set at 3, 6, 9 and 12 degrees. At 12 degrees, walking speed, the product of step length and cadence, decreased significantly (p less than 0.01) in both up- and downslope walking. The most conspicuous phenomenon in upslope walking was in cadence. The steeper the slope, the smaller was the cadence. The most conspicuous phenomenon in downslope walking was in step length. The steeper the slope, the shorter was the step length.