Changes in Dynamic Mean Ankle Moment Arm in Unimpaired Walking Across Speeds, Ramps, and Stairs.

Understanding the natural biomechanics of walking at different speeds and activities is crucial to develop effective assistive devices for persons with lower-limb impairments. While continuous measures such as joint angle and moment are well-suited for biomimetic control of robotic systems, whole-stride summary metrics are useful for describing changes across behaviors and for designing and controlling passive and semi-active devices. Dynamic mean ankle moment arm (DMAMA) is a whole-stride measure representing the moment arm of the ground reaction impulse about the ankle joint-effectively, how "forefoot-dominated" or "hindfoot-dominated" a movement is. DMAMA was developed as a target and performance metric for semi-active devices that adjust once per stride. However, for implementation in this application, DMAMA must be characterized across various activities in unimpaired individuals. In our study, unimpaired participants walked at "slow," "normal," and "fast" self-selected speeds on level ground and at a normal self-selected speed while ascending and descending stairs and a 5-degree incline ramp. DMAMA measured from these activities displayed a borderline-significant negative sensitivity to walking speed, a significant positive sensitivity to ground incline, and a significant decrease when ascending stairs compared to descending. The data suggested a nonlinear relationship between DMAMA and walking speed; half of the participants had the highest average DMAMA at their "normal" speed. Our findings suggest that DMAMA varies substantially across activities, and thus, matching DMAMA could be a valuable metric to consider when designing biomimetic assistive lower-limb devices.

Socket-residuum coupling integrity affects perception of external stimuli: Effects of altering the transtibial interface using vacuum-assisted suspension.

BACKGROUND: Relative movement between the socket and residual limb can impair function in prosthesis users. It is plausible that, in addition to its mechanical effect, the integrity of the socket-residuum interface influences the ability of an individual to sense tactile cues through the prosthesis. Vacuum-assisted suspension (VAS) has been shown to reduce relative movement at this interface, providing a means to test this premise. The purpose of this pilot study was to assess the effects of altering socket-residuum interface integrity through the VAS pressure level on the thresholds of perception of an externally applied vibration stimulus. METHODS: Seven unilateral transtibial prosthesis users participated. Socket-residual limb integrity was altered using the VAS subatmospheric (vacuum) pressure level. Vibration perception tests were conducted at low, mid, and high vacuum levels, targeting 0, 8, and 19 in Hg respectively, and performed in partially loaded and fully loaded conditions. Vibration intensity was increased using a dial until participants delivered a verbal signal indicating it was perceptible, and the nominal intensity was recorded. RESULTS: Intensity thresholds decreased (ie, sensitivity increased) from low to high vacuum settings when fully loaded ( P = 0.008). Differences when partially loaded were nonsignificant and variable across participants. CONCLUSION: This study provides preliminary evidence that altering the integrity between the socket and residual limb by modifying the vacuum level affects sensation related to the external environment experienced through the prosthesis, although translation of these findings to real-world stimuli remains to be tested.

Biomechanically-Consistent Skin Stretch as an Intuitive Mechanism for Sensory Feedback: A Preliminary Investigation in the Lower Limb.

The proprioceptive loss accompanied by lower limb amputation can impair function and mobility. We explore a simple, mechanical skin-stretch array configured to generate superficial tissue behaviour that might occur with movement about an intact joint. Four adhesive pads attached around the circumference of the lower leg were connected via cords to a remote "foot" mounted on a ball joint attached to the underside of a fracture boot, such that "foot" reorientation would result in skin stretch. In two discrimination experiments performed with and without the connection, with no view of the mechanism, and with minimal training, unimpaired adults (i) estimated foot orientation following passive foot rotations (eight directions), either with or without contact between the lower leg and boot, and (ii) actively lowered the "foot" to estimate slope orientation (four directions). In (i), 56-60% of responses (depending on contact condition) were correct and 88-94% were either correct or one of the two adjacent choices. In (ii), 56% of responses were correct. In contrast, without the connection, participants performed near or no different to chance. A biomechanically-consistent skin stretch array may be an intuitive means to convey proprioceptive information from an artificial or poorly innervated joint.

Effects of footwear on the gait kinematics of women with unilateral transtibial amputation: an observational case series.

PURPOSE: Prosthesis geometry and behaviour limit the footwear options available to women. Using a commercially available prosthetic foot that permits user-alignment to accommodate shoes with different heel heights, we investigated the effect of footwear on gait kinematics, with and without adjustment for differences in heel-forefoot differential. MATERIALS AND METHODS: Three women with transtibial amputation walked at a self-selected pace, first in an athletic shoe (prosthetist-aligned; baseline condition), then (i) in a flatter shoe without realigning the prosthesis, and (ii) in flat and heeled shoes following user re-alignment. Kinematics in each condition were compared to baseline. RESULTS: Baseline gait patterns were highly variable across participants. Gait was slower in comparison to baseline in all conditions, but movement compensations varied across participants. An increased lower limb extension tendency was evident with the misaligned prosthesis. With user re-alignment to accommodate the shoe there were fewer deviations from baseline, however kinematic differences remained in both the flat and heeled shoes. CONCLUSIONS: The user-alignment feature of the prosthetic foot reduced the effect of a change in footwear on kinematics, and permitted walking in heeled shoes when it might otherwise not be possible. Persistence of some deviations suggests differences in walking task demand remained despite adjustment.Implications for rehabilitationPermitting prosthesis users to don footwear of choice may improve body image, well-being and quality of life following amputation.Prosthetic feet that permit user ankle adjustment can reduce gait deviations associated with a change in footwear heel height, although kinematic adaptations are individual.

Comparison of clinical and biomechanical characteristics between individuals with lower limb amputation with and without lower back pain: A systematic review and meta-analysis.

BACKGROUND: Lower back pain is a debilitating condition common to individuals with lower limb amputation. It is unclear what risk factors contribute to the development of back pain. This study systematically reviewed and analyzed the available evidence regarding the clinical and biomechanical differences between individuals with amputation, with and without lower back pain. METHODS: A literature search was conducted in PubMed, Web of Science, Scopus, and CINAHL databases in November 2020 and repeated in June 2021 and June 2022. Studies were included if they reported comparisons of demographic, anthropometric, biomechanical, and other clinical variables between participants with and without LBP. Study quality and potential for reporting bias were assessed. Meta-analyses were conducted to compare the two groups. FINDINGS: Thirteen studies were included, with aggregated data from 436 participants (239 with LBP; 197 pain free). The median reporting quality score was 37.5%. The included studies enrolled participants who were predominantly male (mean = 91.4%, range = 77.8-100%) and with trauma-related amputation. Meta-analyses showed that individuals with LBP exhibited moderate (3.4 out of 10) but significantly greater pain than those without LBP. We found no between-group differences in age, height, weight, BMI, and time since amputation (p = 0.121-0.682). No significant differences in trunk/pelvic kinematics during gait were detected (p = 0.07-0.446) between the groups. INTERPRETATION: Demographic, anthropometric, biomechanical, and simple clinical outcome variables may be insufficient for differentiating the risk of developing back pain after amputation. Investigators should be aware of the existing gender bias in sampling and methodological limitations, as well as to consider incorporating psychosocial measures when studying LBP in this clinical population.

Systematic Assessment of Prosthesis Stiffness on User Biomechanics Using the Lower Leg Trajectory Error Framework and Its Implication for the Design and Evaluation of Ankle-Foot Prostheses.

Advances in understanding the effects the mechanical characteristics of prosthetic feet on user biomechanics have enabled passive prostheses to improve the walking pattern of people with lower limb amputation. However, there is no consensus on the design methodology and criteria required to maximize specific user outcomes and fully restore their mobility. The Lower Leg Trajectory Error (LLTE) framework is a novel design methodology based on the replication of lower leg dynamics. The LLTE value evaluates how closely a prosthetic foot replicates a target walking pattern. Designing a prosthesis that minimizes the LLTE value, optimizes its mechanical function to enable users to best replicate the target lower leg trajectory. Here, we conducted a systematic sensitivity investigation of LLTE-optimized prostheses. Five people with unilateral transtibial amputation walked overground at self-selected speeds using five prototype energy storage and return feet with varying LLTE values. The prototypes' LLTE values were varied by changing the stiffness of the participant's LLTE-optimized design by 60%, 80%, 120%, and 167%. Users most closely replicated the target able-bodied walking pattern with the LLTE-optimized stiffness, experimentally demonstrating that the predicted optimum was a true optimum. Additionally, the predicted LLTE values were correlated to the user's ability to replicate the target walking pattern, user preferences, and clinical outcomes including roll-over geometries, trunk sway, prosthetic energy return, and peak push-off power. This study further validates the use of the LLTE framework as a predictive and quantitative tool for designing and evaluating prosthetic feet.

Biomechanical evaluation over level ground walking of user-specific prosthetic feet designed using the lower leg trajectory error framework.

The walking pattern and comfort of a person with lower limb amputation are determined by the prosthetic foot's diverse set of mechanical characteristics. However, most design methodologies are iterative and focus on individual parameters, preventing a holistic design of prosthetic feet for a user's body size and walking preferences. Here we refined and evaluated the lower leg trajectory error (LLTE) framework, a novel quantitative and predictive design methodology that optimizes the mechanical function of a user's prosthesis to encourage gait dynamics that match their body size and desired walking pattern. Five people with unilateral below-knee amputation walked over-ground at self-selected speeds using an LLTE-optimized foot made of Nylon 6/6, their daily-use foot, and a standardized commercial energy storage and return (ESR) foot. Using the LLTE feet, target able-bodied kinematics and kinetics were replicated to within 5.2% and 13.9%, respectively, 13.5% closer than with the commercial ESR foot. Additionally, energy return and center of mass propulsion work were 46% and 34% greater compared to the other two prostheses, which could lead to reduced walking effort. Similarly, peak limb loading and flexion moment on the intact leg were reduced by an average of 13.1%, lowering risk of long-term injuries. LLTE-feet were preferred over the commercial ESR foot across all users and preferred over the daily-use feet by two participants. These results suggest that the LLTE framework could be used to design customized, high performance ESR prostheses using low-cost Nylon 6/6 material. More studies with large sample size are warranted for further verification.

Subthreshold Vibration Influences Standing Balance but Has Unclear Impact on Somatosensation in Persons With Transtibial Amputations.

Stochastic resonance has been successfully used to improve human movement when using subthreshold vibration. Recent work has shown promise in improving mobility in individuals with unilateral lower limb amputations. Furthering this work, we present an investigation of two different signal structures in the use of stochastic resonance to improve mobility in individuals with unilateral lower limb amputations. Cutaneous somatosensation and standing balance measures using spatial and temporal analysis were assessed. There were no differences in the somatosensation measures, but differences in the temporal characteristics of the standing measures were seen with the various vibration structures when compared to no vibration, one of which suggesting mass may play an important role in determining who may or may not benefit from this intervention. Stochastic resonance employed with subthreshold vibration influences mobility in individuals with unilateral amputations, but the full direction and extent of influence is yet to be understood.

Irregular Metronomes as Assistive Devices to Promote Healthy Gait Patterns.

Older adults and people suffering from neurodegenerative disease often experience difficulty controlling gait during locomotion, ultimately increasing their risk of falling. To combat these effects, researchers and clinicians have used metronomes as assistive devices to improve movement timing in hopes of reducing their risk of falling. Historically, researchers in this area have relied on metronomes with isochronous interbeat intervals, which may be problematic because normal healthy gait varies considerably from one step to the next. More recently, researchers have advocated the use of irregular metronomes embedded with statistical properties found in healthy populations. In this paper, we explore the effect of both regular and irregular metronomes on many statistical properties of interstride intervals. Furthermore, we investigate how these properties react to mechanical perturbation in the form of a halted treadmill belt while walking. Our results demonstrate that metronomes that are either isochronous or random break down the inherent structure of healthy gait. Metronomes with statistical properties similar to healthy gait seem to preserve those properties, despite a strong mechanical perturbation. We discuss the future development of this work in the context of networked augmented reality metronome devices.

Inter-limb coupling in individuals with transtibial amputation during bilateral stance is direction dependent.

We investigated the control of upright standing in individuals with unilateral transtibial amputation (TTA) by assessing the inter-limb coupling and the coupling between the center of pressure beneath both limbs combined (COPNET) and the center of pressure (COP) beneath the prosthetic limb and the intact limb. Twenty-one adults with TTA and eighteen unimpaired adults completed 90 s of standing on two parallel force plates. The inter-limb coupling and the coupling between the COP beneath each limb and the COPNET were assessed by quantifying the synchronization of the COP signals. This included the number of epochs with synchronized signals, the total duration of signal synchronization and the relative phase and deviation phase between the signals. Additionally, magnitude and temporal characteristics of the COP displacements were quantified. Individuals with TTA exhibited looser inter-limb coupling in the anterior-posterior direction, characterized by more shifts between epochs with synchronized signals, shorter total duration of signal synchronization, less in-phase coordination patterns and a higher deviation phase between the two limbs, compared to unimpaired individuals. This coincided with a larger and more irregular postural sway in the TTA group. No group difference was observed in the mediolateral direction. The coupling between the COPNET and the COP beneath the individual limbs was similarly direction dependent, and tighter for the intact side, suggesting that an intact limb-driven strategy was utilized.

Knee Swing Phase Flexion Resistance Affects Several Key Features of Leg Swing Important to Safe Transfemoral Prosthetic Gait.

We systematically investigate in-vivo the effect of increasing prosthetic knee flexion damping on key features of the swing phase of individuals with transfemoral amputation during walking. Five experienced prosthesis users walked using a prototype device in a motion capture laboratory. A range of interchangeable hydraulic rotary dampers was used to progressively modify swing phase flexion resistance in isolation. Toe clearance (TC; vertical distance toe to floor), effective leg length (ELL; distance hip to toe), and knee flexion angle during swing phase were computed, alongside the sensitivities of vertical toe position to angular displacements at the hip, knee and ankle. Key features of these profiles were compared across 5 damping conditions. With higher damping, knee extension occurred earlier in swing phase, promoting greater symmetry. However, with implications for toe catch, minimum TC reduced, and minimum TC and maximum ELL occurred earlier; temporally closer to mid-swing, when the limb must pass the stance limb. Further, TC became less sensitive to changes in hip flexion, suggesting a lesser ability to control toe clearance without employing proximal or contralateral compensations. There is a trade-off between key features related to gait safety when selecting an appropriate resistance for a mechanical prosthetic knee. In addition to highlighting broader implications surrounding swing phase damping selection for the optimization of mechanical knees, this work reveals design considerations that may be of utility in the formulation of control strategies for computerized devices.

Rhythmic auditory stimuli modulate movement recovery in response to perturbation during locomotion.

The capacity to recover after a perturbation is a well-known intrinsic property of physiological systems, including the locomotor system, and can be termed 'resilience'. Despite an abundance of metrics proposed to measure the complex dynamics of bipedal locomotion, analytical tools for quantifying resilience are lacking. Here, we introduce a novel method to directly quantify resilience to perturbations during locomotion. We examined the extent to which synchronizing stepping with two different temporal structured auditory stimuli (periodic and 1/f structure) during walking modulates resilience to a large unexpected perturbation. Recovery time after perturbation was calculated from the horizontal velocity of the body's center of mass. Our results indicate that synchronizing stepping with a 1/f stimulus elicited greater resilience to mechanical perturbations during walking compared with the periodic stimulus (3.3 s faster). Our proposed method may help to gain a comprehensive understanding of movement recovery behavior of humans and other animals in their ecological contexts.

Stochastic Resonance Reduces Sway and Gait Variability in Individuals With Unilateral Transtibial Amputation: A Pilot Study.

Sub-threshold (imperceptible) vibration, applied to parts of the body, impacts how people move and perceive our world. Could this idea help someone who has lost part of their limb? Sub-threshold vibration was applied to the thigh of the affected limb of 20 people with unilateral transtibial amputation. Vibration conditions tested included two noise structures: pink and white. Center of pressure (COP) excursion (range and root-mean-square displacements) during quiet standing, and speed and spatial stride measures (mean and standard deviations of step length and width) during walking were assessed. Pink noise vibration decreased COP displacements in standing, and white noise vibration decreased sound limb step length standard deviation in walking. Sub-threshold vibration positively impacted aspects of both posture and gait; however, different noise structures had different effects. The current study represents foundational work in understanding the potential benefits of incorporating stochastic resonance as an intervention for individuals with amputation.

To walk or to run - a question of movement attractor stability.

During locomotion, humans change gait mode between walking and running as locomotion speed is either increased or decreased. Dynamical systems theory predicts that the self-organization of coordinated motor behaviors dictates the transition from one distinct stable attractor behavior to another distinct attractor behavior (e.g. walk to run or vice versa) as the speed is changed. To evaluate this prediction, the present study investigated the attractor stability of walking and running across a range of speeds evoking both self-selected gait mode and non-self-selected gait mode. Eleven subjects completed treadmill walking for 3 min at 0.89, 1.12, 1.34, 1.56, 1.79, 2.01, 2.24 and 2.46 m s-1 and running for 3 min at 1.79, 2.01, 2.24, 2.46, 2.68, 2.91, 3.13 and 3.35 m s-1 in randomized order while lower limb joint angles and sacrum displacements was recorded. Attractor stability was quantified by continuous relative phase and deviation phase of lower limb segment angles, and the largest Lyapunov exponent, correlation dimension and movement variability of the sacrum marker displacement and the hip, knee and ankle joint angles. Lower limb attractor stability during walking was maximized at speeds close to the self-selected preferred walking speed and increased during running as speed was increased. Furthermore, lower limb attractor stability was highest at a particular gait mode closest to the corresponding preferred speed, in support of the prediction of dynamical systems theory. This was not the case for the sacrum displacement attractor, suggesting that lower limb attractor behavior provides a more appropriate order parameter compared with sacrum displacement.

Asymmetry of mass and motion affects the regulation of whole-body angular momentum in individuals with upper limb absence.

BACKGROUND: There is a high fall prevalence in individuals with upper limb absence, which may be related to a momentum imbalance resulting from the loss of all or part of one arm. The purpose of this study was to characterise whole-body angular momentum in individuals with upper limb absence during walking, and determine the effect of restoring the mass and inertial properties of the impaired side with a mock prosthesis. METHODS: Ten individuals with unilateral upper limb absence walked at self-selected speeds, with and without a mock prosthesis. For each condition, whole-body angular momentum range was computed during ten strides; in the first 50% of the stride bilaterally, and over the whole stride. Two-way repeated measures ANOVAs were used to assess the main effect of side and the interaction effect with prosthesis condition on the 50% range, and paired t-tests to determine the effect of prosthesis condition on the whole stride range (α = 0.05). FINDINGS: Sagittal plane 50% range was greater for the sound compared to the impaired side stride (P = .003), with no difference in the coronal or transverse planes (P ≥ .8). Coronal plane whole stride range was lower when wearing the mock prosthesis (P = .021), with no change in the sagittal or transverse planes (P ≥ .5). INTERPRETATION: Use of a prosthesis does not reduce a sagittal plane imbalance. There may be a greater risk of loss of balance in people with upper limb absence following a perturbation, particularly when it occurs during the sound side stance phase, during which whole-body angular momentum is elevated.

Changes in human walking dynamics induced by uneven terrain are reduced with ongoing exposure, but a higher variability persists.

During walking, uneven terrain alters the action of the ground reaction force from stride to stride. The extent to which such environmental inconsistencies are withstood may be revealed by the regulation of whole-body angular momentum (L) during walking. L quantifies the balance of momenta of the body segments (thigh, trunk, etc.) about their combined center of mass, and remains close to zero during level walking. A failure to constrain L has been linked to falls. The aim of this study was to explore the ability of young adults to orchestrate their movement on uneven terrain, illustrated by the range of L (LR) and its variability (vLR). In eleven male adults, we observed significant increases in sagittal plane LR, and vLR in all three planes of motion during walking on an uneven in comparison to a flat surface. No reductions in these measures were observed within a 12-minute familiarisation period, suggesting that unimpaired adults either are unable to, or do not need to eliminate the effects of uneven terrain. Transverse plane LR, in contrast, was lower on immediate exposure, and then increased, pointing to the development of a less restrictive movement pattern, and would support the latter hypothesis.

Locomotor patterns change over time during walking on an uneven surface.

During walking, uneven surfaces impose new demands for controlling balance and forward progression at each step. It is unknown to what extent walking may be refined given an amount of stride-to-stride unpredictability at the distal level. Here, we explored the effects of an uneven terrain surface on whole-body locomotor dynamics immediately following exposure and after a familiarization period. Eleven young, unimpaired adults walked for 12 min on flat and uneven terrain treadmills. The whole-body center of mass excursion range (COMexc) and peak velocity (COMvel), step length and width were estimated. On first exposure to uneven terrain, we saw significant increases in medial-lateral COMexc and lateral COMvel, and in the variability of COMexc, COMvel and foot placement in both anterior-posterior and medial-lateral directions. Increases in step width and decreases in step length supported the immediate adoption of a cautious, restrictive solution on uneven terrain. After familiarization, step length increased and the variability of anterior-posterior COMvel and step length reduced, while step width and lateral COMvel reduced, alluding to a refinement of movement and a reduction of conservative strategies over time. However, the variability of medial-lateral COMexc and lateral COMvel increased, consistent with the release of previously constrained degrees of freedom. Despite this increase in variability, a strong relationship between step width and medial-lateral center of mass movement was maintained. Our results indicate that movement strategies of unimpaired adults when walking on uneven terrain can evolve over time with longer exposure to the surface.

Selection Procedures for the Largest Lyapunov Exponent in Gait Biomechanics.

The present study was aimed at investigating the effectiveness of the Wolf et al. (LyE_W) and Rosenstein et al. largest Lyapunov Exponent (LyE_R) algorithms to differentiate data sets with distinctly different temporal structures. The three-dimensional displacement of the sacrum was recorded from healthy subjects during walking and running at two speeds; one low speed close to the preferred walking speed and one high speed close to the preferred running speed. LyE_R and LyE_W were calculated using four different time series normalization procedures. The performance of the algorithms were evaluated based on their ability to return relative low values for slow walking and fast running and relative high values for fast walking and slow running. Neither of the two algorithms outperformed the other; however, the effectiveness of the two algorithms was highly dependent on the applied time series normalization procedure. Future studies using the LyE_R should normalize the time series to a fixed number of strides and a fixed number of data points per stride or data points per time series while the LyE_W should be applied to time series normalized to a fixed number of data points or a fixed number of strides.

Uneven terrain exacerbates the deficits of a passive prosthesis in the regulation of whole body angular momentum in individuals with a unilateral transtibial amputation.

BACKGROUND: Uneven ground is a frequently encountered, yet little-studied challenge for individuals with amputation. The absence of control at the prosthetic ankle to facilitate correction for surface inconsistencies, and diminished sensory input from the extremity, add unpredictability to an already complex control problem, and leave limited means to produce appropriate corrective responses in a timely manner. Whole body angular momentum, L, and its variability across several strides may provide insight into the extent to which an individual can regulate their movement in such a context. The aim of this study was to explore L in individuals with a transtibial amputation, when challenged by an uneven surface. We hypothesized that, similar to previous studies, sagittal plane L would be asymmetrical on uneven terrain, and further, that uneven terrain would evoke a greater variability in L from stride to stride in individuals with amputation in comparison to unimpaired individuals, due to a limited ability to discern and correct for changing contours beneath the prosthetic foot. METHODS: We examined sagittal plane L in ten individuals with a unilateral transtibial amputation and age- and gender- matched control participants walking on flat (FT) and uneven (UT) treadmills. The average range of L in the first 50% of the gait cycle (LR), the average L at foot contact (LC) and their standard deviations (vLR, vLC) were computed over 60 strides on each treadmill. RESULTS: On both surfaces we observed a higher LR on the prosthetic side and a reduced LC on the sound side (p < 0.001) in the amputee cohort, consistent with previous findings. UT invoked an increase in LC (p = 0.006), but not LR (p = 0.491). vLR, and vLC were higher in individuals with amputation (p < 0.001, p = 0.002), and increased in both groups on UT (p < 0.001). CONCLUSIONS: These findings support previous assertions that individuals with amputation regulate L less effectively, and suggest that the deficits of the prosthesis are exacerbated on uneven terrain, potentially to the detriment of balance. Further, the results indicate that a greater demand may be placed on the unaffected side to control movement.

Dynamic balance changes within three weeks of fitting a new prosthetic foot component.

Balance during walking is of high importance to prosthesis users and may affect walking during baseline observation and evaluation. The aim of this study was to determine whether changes in walking balance occurred during an adaptation period following the fitting of a new prosthetic component. Margin of stability in the medial-lateral direction (MOSML) and an anterior instability margin (AIM) were used to quantify the dynamic balance of 21 unilateral transtibial amputees during overground walking. Participants trialled two prosthetic feet presenting contrasting movement/balance constraints; a Higher Activity foot similar to that of their own prosthesis, and a Lower Activity foot. Participants were assessed before (Visit 1) and after (Visit 2) a 3-week adaptation period on each foot. With the Higher Activity component, MOSML decreased on the prosthetic side, and increased on the sound side from Visit 1 to Visit 2, eliminating a significant inter-limb difference apparent at Visit 1 (Visit 1-sound=0.062m, prosthetic=0.075m, p=0.018; Visit 2-sound=0.066m, prosthetic=0.074m, p=0.084). No such change was seen with the Lower Activity foot (Visit 1-sound=0.064m, prosthetic=0.077m, p=0.007; Visit 2-sound=0.063m, prosthetic=0.080m, p<0.001). Significant changes in AIM were observed at Visit 2 (Visit 1: -0.16 (0.08) m, Visit 2: -0.17 (0.08) m; F=23.396, p<0.01). These findings suggest that changes in balance during walking can occur following the initial receipt of a device regardless of whether the component is of the same functional category as the one an individual is accustomed to using.