Gait analysis and energy consumption of below-knee amputees wearing three different prosthetic feet

Effects of treadmill cushion and running speed on plantar force and metabolic energy consumption in running

BACKGROUND

Repetitive loading with high impact forces are considered as a primary risk factor for overuse injuries. Cushion was proposed in running surface and shoe manufacturing to reduce impact forces and prevent injuries in running.

RESEARCH QUESTION

To investigate the effects of treadmill cushion and running speed on plantar force and metabolic energy consumption in treadmill running.

METHODS

Plantar force data and metabolic data were collected for 20 men during running at 8 km/h and 10 km/h on the treadmill with and without cushion. Two-way ANOVAs with repeated measures were performed to determine the treadmill effects and the speed effects.

RESULTS

Participants significantly decreased peak plantar force on the fore foot at both 10 km/h (P = 0.001) and 8 km/h (P = 0.001) and peak plantar force on the mid foot only at 10 km/h (P = 0.011) while running on the treadmill with cushion compared to the treadmill without cushion. The reduction of peak plantar force at 10 km/h was greater than that at 8 km/h while running on the treadmill with cushion. Participants significantly increased metabolic energy consumption while running on the treadmill with cushion compared to the treadmill without cushion (P = 0.007).

SIGNIFICANCE

Running on the treadmill with cushion significantly decreased plantar force on the fore foot and mid foot, and increased metabolic energy consumption. Running on the treadmill with cushion may be a useful method in the prevention of fore foot injuries and increasing exercise effects.

A lightweight robotic ankle prosthesis with non-backdrivable cam-based transmission

Below-knee level amputation significantly impacts the ability of an individual to ambulate. Transtibial amputees are typically prescribed energetically passive ankle-foot prostheses that behave as a spring or controlled damper, and therefore cannot fully replace the function of the missing limb. More recently, fully-powered devices have been proposed to more closely match the power generation ability of intact limbs. However, these fully-powered devices are significantly heavier than passive devices, thus increasing the stress on the socket-residual limb interface. An alternative solution consists of using a motorized mechanism to actively reposition the foot during non-weight-bearing phases. By using this approach, the Össur© PROPRIO FOOT® showed promising outcomes such as improved gait energetics at self-selected speed, symmetry, and comfort. However, this device cannot be used by many transtibial amputees due to large build height (180 mm). Moreover, its weight has been shown critical for socket suspension. To address these limitations, we propose a novel non-backdrivable cam-based transmission. Based on this novel transmission, we developed a compact, lightweight ankle foot prosthesis. Bench-top testing and preliminary experiments with an able-bodied subject show that the proposed design can actively reposition the foot in swing as necessary to increase foot clearance, while adapting the ankle position to the ground inclination in stance.

Comparison of the Otto Bock solid ankle cushion heel foot with wooden keel to the low-cost CR-Equipements™ solid ankle cushion heel foot with polypropylene keel: A randomized prospective double-blind crossover study assessing patient satisfaction and energy expenditure

BACKGROUND

The International Committee of the Red Cross supports a worldwide program of prosthetic fitting and rehabilitation. In this context, a prosthetic foot was developed and widely distributed in least developed countries.

STUDY DESIGN

Prospective, randomized, double-blind, controlled study.

OBJECTIVE

To compare patient satisfaction and energy expenditure during ambulation between a low-cost prosthetic foot designed with a polypropylene keel (CR-Equipements^™ solid ankle cushion heel, International Committee of the Red Cross) to a well-recognized solid ankle cushion heel foot with a wooden keel (solid ankle cushion heel foot, Otto Bock).

METHODS

A total of 15 participants with unilateral transtibial amputation were evaluated using the two prosthetic feet in a randomized prospective double-blind crossover study. Main outcomes were patient satisfaction questionnaires (Satisfaction with Prosthesis Questionnaire and prosthetic foot satisfaction) and energy expenditure (oxygen consumption-mL/kg/min, oxygen cost-mL/kg/m, and heart rate-bpm).

RESULTS

There were no significant differences between the two prosthetic feet for satisfaction and energy expenditure.

CONCLUSION

The low-cost solid ankle cushion heel foot with polypropylene keel provides comparable satisfaction and similar energy expenditure as the solid ankle cushion heel foot with wooden keel. Clinical relevance The results of this study support the application and widespread use of the CR-Equipements^™ solid ankle cushion heel foot. From a cost-effectiveness standpoint, patients are well satisfied and exhibit similar outcomes at a substantially lower cost.

Chronic low back pain in traumatic lower limb amputees

Objective: To ascertain the prevalence of back pain amongst traumatic lower limb amputees attending a regional rehabilitation centre and to determine the possible causes of back pain.

Design: All traumatic lower limb amputees given a semi-structured questionnaire to complete and a comparative subgroup of amputees with back pain and without back pain underwent physical examination, gait analysis, magnetic resonance scanning (MRI) and gait/standing stability analysis.

Setting: A subregional amputee rehabilitation centre.

Results: Transfemoral amputees were more likely to suffer from back pain (81%) than transtibial amputees (62%) (p≤0.05) and of those suffering from severe back pain, 89% and 81% also suffered from severe pain in the phantom limb and severe stump pain respectively. In two comparative subgroups of amputees there was no significant difference between back pain and pain-free groups except those with pain were more likely to have a body mass index (BMI) ratio above 50% of the recommended ratio. No difference in degeneration or disc disease between the groups on MR scans was found. Impact ground reaction forces during walking, irrespective of limb, were significantly greater (p≤0.05) in the pain-free group than in the pain group, as was walking speed. Gait asymmetry measures were similar in both groups. Centre of pressure displacement measures during standing were greater in the pain group than in the pain-free group.

Conclusions: Low back pain in amputees is a significant problem equal to that of pain in the phantom limb and a biomechanical (myofascial) rather than a degenerative aetiology is suggested.

Energetic consequences of using a prosthesis with adaptive ankle motion during slope walking in persons with a transtibial amputation

BACKGROUND

Technological advances in prosthetic design include the use of microprocessors that adapt device performance based on user motion. The Proprio ankle unit prepositions the foot to adjust for walking on slopes and increases foot clearance during swing to minimize gait deviations.

STUDY DESIGN

Comparative analysis.

OBJECTIVES

To investigate the effect of a prosthesis with adaptive ankle motion on physiological gait performance during slope walking.

METHODS

Six persons with a unilateral transtibial amputation completed treadmill walking tests at three slopes (-5°, 0°, and 5°). The participants were tested wearing a customary device, active Proprio (Pon), and an identical inactivated Proprio (Poff).

RESULTS

Metabolic energy expenditure, energy cost for walking, and rating of walking difficulty were not statistically different between the Pon and Poff for all tested slopes. However, for slope descent, energy expenditure and energy cost for walking improved significantly by an average of 10%-14% for both the Pon and Poff compared to the customary limb. Rating of walking difficulty also showed an improvement with slope descent for both the Pon and Poff compared to the customary device. An improvement with slope ascent was found for Pon compared to the customary limb only.

CONCLUSIONS

Adaptive ankle motion provided no meaningful physiological benefit during slope walking. The Proprio was, however, less demanding than the customary device for slope descent. Differences in the mechanical properties of the prosthetic feet likely contributed to the changes.

CLINICAL RELEVANCE

While the adaptive ankle motion did not affect metabolic energy expenditure or energy cost for walking, the results suggest close attention should be paid to the mechanical properties of the foot component. Assessment of gait on nonlevel surfaces is recommended to better understand the implications of different prosthetic design features.

Antagonistic active knee prosthesis. A metabolic cost of walking comparison with a variable-damping prosthetic knee

This paper examines the impact of a biomimetic active knee prosthesis on the metabolic costs associated with a unilateral transfemoral amputee walking at self selected speed. In this study we compare the antagonistic active knee prosthesis developed at MIT to an electronically controlled, variable-damping commercial knee prosthesis, the Otto Bock C-leg. Use of the active knee prosthesis resulted in both, a 17% increase in an amputee's average self selected walking speed from 1.12 m/s to 1.31 m/s, and a 6.8% reduction in metabolic cost. The results of this study suggest that an agonist-antagonist active knee prosthesis design with variable impedance control can offer walking energetic advantages over commercially available systems.

Energy cost of walking measurements in subjects with lower limb amputations: a comparison study between floor and treadmill test

Measuring the energy cost of walking (ECW) is a valid way of assessing the walking efficiency of subjects who were prosthetic users following lower limb amputation. The aim of this study was to determine whether, in these subjects, treadmill and floor ECW measurements are comparable. We tested 24 subjects who had undergone unilateral lower limb amputations for vascular diseases as they walked at a self-selected comfortable speed on the floor and on a treadmill. The tests were conducted at the end of rehabilitative treatment to fit prosthesis. Eight subjects underwent transtibial and 16 transfemoral amputation. The measurements were taken with a portable gas analyzer. The self-selected comfortable speed on the treadmill was significantly lower than that on the floor, where the patients adopted the aid they normally used for walking; oxygen consumption was the same in the two tests. Therefore, for both transtibial and transfemoral patients, ECW was greater during walking on the treadmill. Steady-state heart rate did not differ in the two tests. The data show that the ECW values of the amputated subjects obtained on the treadmill at the end of rehabilitation did not correspond with those they obtained on the floor. The floor test is the one that may better reflect walking with prostheses and aids in everyday life, in subjects with dysvascular lower limb amputation, using the prosthesis for a short time.

Walking patterns change rapidly following asymmetrical lower extremity loading

The purpose of this study was to determine the amount of time needed for individuals to become well accommodated to asymmetrical changes in lower extremity inertial properties. Participants walked at 1.57 m s(-1) during four separate data collection sessions over the period of eight days. On days 1 and 7, participants completed a 60 min treadmill protocol consisting of both overground (motion and ground reaction force recorded) and treadmill (vertical ground reaction force recorded) walking. On day 1, 1.95 kg was attached distally to one shank prior to the start of the 60 min treadmill protocol and was not removed until day 7. On day 7, the load was permanently removed prior to the 60 min treadmill protocol. On days 2 and 8 participants completed three overground walking trials and walked on the treadmill for approximately 5 min. Stance and swing time asymmetries appeared immediately and were complete following initial assessment after the load was attached. Net joint moments at the knee and hip were altered and continued to change beyond initial exposure to the load, but these changes were complete within 5 min. Overall, results suggest that changes in walking symmetry due to asymmetrical lower extremity loading are immediate and complete within 5 min of exposure to the load. We recommend that at least 5 min of walking or other normal activity be used to accommodate individuals to novel asymmetrical lower extremity loading.

High Failure Rates When Avoiding Obstacles During Treadmill Walking in Patients With a Transtibial Amputation

OBJECTIVE

To investigate if and to what extent patients with a transtibial amputation are less successful in avoiding unexpected obstacles while walking than healthy adults.

DESIGN

Experimental 2-group design.

SETTING

Dutch rehabilitation center.

PARTICIPANTS

Eleven patients with a transtibial amputation and 14 healthy controls.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Subjects walked on a treadmill at .56m/s. In 2 series of 12 trials each, an obstacle was dropped in front of the prosthetic or the nonprosthetic leg of the amputation group and the left leg of the control group at different phases during the step cycle. It was noted which avoidance strategy was used (a long step strategy [LSS] or a short step strategy [SSS]) and whether the obstacle was avoided successfully or not. These data were expressed as a percentage of the total number of trials completed by each subject.

RESULTS

With either leg, the amputation group made significantly more errors than the control subjects (prosthetic leg, 24%+/-17%; nonprosthetic leg, 21%+/-17% vs 2%+/-2% for the control group). Highest failure rates were in the amputation group when time pressure was high, requiring an SSS, especially on the prosthetic side. An LSS under time pressure, however, nearly always resulted in failure for both the prosthetic and nonprosthetic legs. Subjects with the longest time since amputation were most successful in avoiding unexpected obstacles.

CONCLUSIONS

Under time pressure, patients with a lower-leg prosthesis perform best when they use their nonprosthetic leg as the lead limb in an SSS. The fact that some subjects with the longest time since amputation made no errors suggests that over many years it is possible to relearn the appropriate avoidance reactions sufficiently fast.

Comparison of Rectified and Unrectified Sockets for Transtibial Amputees

The current method for fabricating prosthetic sockets is to modify a positive mold to account for the non-homogeneity of the residual limb to tolerate load (i.e., rectified socket). We tested unrectified sockets by retaining the shape of the residual limb, except for a distal end pad, using an alginate gel process instead of casting. This investigation compared rectified and unrectified sockets. Forty-three adults with unilateral transtibial amputations were tested after randomly wearing both rectified and unrectified sockets for at least 4 weeks. Testing included a gait analysis, energy expenditure and Prosthesis Evaluation Questionnaire (PEQ). Results indicated no differences between sockets for gait speed and timing, gait kinematics and kinetics, and gait energy expenditure. There were also no differences in the Prosthetic Evaluation Questionnaire and 16 subjects selected the rectified socket, 25 selected the unrectified socket, and 2 subjects selected to use both sockets as their exit socket. Results seemed to indicate that more than one paradigm exists for shaping prosthetic sockets, and this paradigm may be helpful in understanding the mechanisms of socket fit. The alginate gel fabrication method was simpler than the traditional method. The method could be helpful in other countries where prosthetic care is lacking, may be helpful with new amputees, and may be helpful in typical clinics to reduce costs and free the prosthetist to focus more time on patient needs.

Usability of gait analysis in the alignment of trans-tibial prostheses: a clinical study

The purpose of the study was to investigate which systematic effects of prosthetic misalignment could be observed with the use of the SYBAR system. The alignment of the prosthesis of five well-trained unilateral trans-tibial amputees was changed 15 degrees in magnitude in varus, valgus, flexion, extension, endorotation, exorotation, dorsal flexion, and plantar flexion. Subjects walked over a distance of 8 m at a self-selected walking speed with the alignment of the prosthesis as it was at the start of the experiment (reference) and with each changed alignment. Two video cameras (frontal and sagittal) and a force plate of the SYBAR system (Noldus Information Technology, The Netherlands) were used to capture gait characteristics of the subjects. Temporal and spatial characteristics, the magnitude and timing of the ground reaction force (GRF), and the external joint moments were derived from these data. Despite the substantial perturbations to prosthetic alignment, only a few effects were observed in the temporal and spatial characteristics of gait, the magnitude and timing of the GRF, and the external joint moments. Only the pattern of the ground reaction force in the mediolateral direction and the joint moment around the ankle in the frontal plane during terminal stance showed a systematic effect when the alignment was set into varus and valgus or exorotation. It was concluded that using the SYBAR system in this study revealed little effect of perturbations in prosthetic alignment, for this group of patients, and for the selected parameters. It was questioned whether this is due to the relatively low resolution of the SYBAR system or the capacity of the well-trained subjects to compensate for the disturbance in alignment. It was suggested that the usability of the SYBAR system in clinical settings should be further explored.

Prosthetic prescription in the Netherlands: an interview with clinical experts

In the process of guideline development for prosthetic prescription in the Netherlands the authors made a study of the daily clinical practice of lower limb prosthetics. Besides the evidence-based knowledge from literature the more implicit knowledge from clinical experts is of importance for guideline development. In order to obtain this information the authors performed both an observational study of clinical practice and an interview study with 11 clinical experts from the three key disciplines in this field. The latter study is presented here as a descriptive and qualitative study. The combination of the opinions on prescription criteria given in these semi-structured interviews appeared divided with regard to various options in the prescription of a lower limb prosthesis. However, the implicit knowledge is considered by the authors of importance for the consensus procedure on guideline development. Prosthetic prescription criteria seem to be based on local experience and partly on assumptions. A consensus procedure can lead to improvement of the knowledge about prosthetic prescription.

Strength and endurance training of an individual with left upper and lower limb amputations

PURPOSE

The purpose of this article is to describe the development of a strength and endurance training programme designed to prepare an individual with a left glenohumeral disarticulation and transtibial amputation for a bike trip across the USA.

METHOD

The subject was scheduled for training three times per week over a two-month period followed by two times per week for an additional two months. Training consisted of a resistance training circuit using variable resistance machines, cycling using a recumbent stationary bike, and core stability training using stability ball exercises. Changes in strength were assessed using 10 RM tests on the resistance machines and changes in peak VO(2) were monitored utilizing the Cosmed K4b pulmonary function tester.

RESULTS

The subject demonstrated a 30.3% gain in peak VO(2). The subject's 10 RM for left single limb leg press increased 36.8% and gains of at least 7.7% were seen for all other muscle groups tested.

CONCLUSION

The strength and endurance training programme adapted to compensate for this subject's limb losses was effective in increasing both strength and peak VO(2). Adapting exercise programmes to compensate for limb loss may allow individuals with amputations to participate in physically challenging activities that otherwise may not be available to them.

Effect on gait and socket comfort in unilateral trans-tibial amputees after exchange to a polyurethane concept

Trans-tibial amputees with different indications for amputation often have stump problems. Many active amputees have limits in daily life and sports activities because of pressure ulcers, friction, allergic dermatitis or volume changes. Many methods and materials have been tried to make a well-fitted socket. A new polyurethane concept had been designed with a shock absorbing effect. The purpose of this prospective study was to compare a conventional suspension with a polyurethane concept with regard to the amputees' satisfaction, socket comfort, physical capacity and to analyse the long-term effect. The total material includes 29 unilateral trans-tibial amputees. They answered a questionnaire after 2 months use of the polyurethane concept and were interviewed after 3 and 5 years. After 3 years 22 amputees and after 5 years 20 amputees used the polyurethane concept. Gait was registered in 7 amputees. Speed and symmetry index (SI) for temporal, stride and kinematics variables were used to evaluate gait. The amputees reported that the polyurethane concept was better or much better in physical capacity in 117 (67%) and socket comfort was better or much better in 119 (82%) compared with the conventional suspension. There was no obvious symmetry difference in gait variables in speed, step length, step time or single support or in kinematics knee variables. The amputees tended to walk faster, decrease in symmetry in temporal and stride variables and increase in symmetry in kinematics variables with the polyurethane concept. After 5 years 6 had died and 20 amputees of the surviving 23 used the polyurethane concept.

CONCLUSIONS

The polyurethane concept increased comfort considerably and physical activity increased when the trans-tibial amputees changed from conventional suspension. Gait registration was not useful to evaluate the amputees' satisfaction or socket comfort.

Prescription of prosthetic ankle-foot mechanisms after lower limb amputation

BACKGROUND

A correct prosthetic prescription can be derived from adapting the functional benefits of a prosthesis to the functional needs of the prosthetic user. For adequate matching, the functional abilities of the amputees are of value, as well as the technical and functional aspects of the various prosthetic ankle-foot mechanisms. There seems to be no clear clinical consensus on the precise prescription criteria for the various prosthetic ankle-foot mechanisms related to the functional abilities of amputees.

OBJECTIVES

To obtain information about aspects of prosthetic ankle-foot mechanisms and daily functioning of amputees with a prosthesis, for appropriate prosthetic prescription criteria.

SEARCH STRATEGY

We searched the Cochrane Musculoskeletal Injuries Group specialised register of trials (April 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library issue 1, 2003), MEDLINE (1966 to April 2003), EMBASE (1983 to April 2003), CINAHL (1982 to April 2003) and reference lists of articles. No language restrictions were applied.

SELECTION CRITERIA

All randomised controlled trials and quasi-randomised controlled trials comparing different prosthetic devices for lower limb amputation in adults. No language restrictions were applied.

DATA COLLECTION AND ANALYSIS

Two reviewers independently identified potential articles from the literature search. Methodological quality was assessed using a checklist comprising 13 criteria. The reviewers extracted data using pre-defined extraction forms.

MAIN RESULTS

Twenty-three trials were included, with a total of 217 participants. The methodological quality was moderate. Only one study was of high quality. No classical RCT's were identified, yet, all included studies used cross-over designs allowing sufficient control for confounding. In high activity transfemoral amputees, there is limited evidence for the superiority of the Flex foot during level walking compared with the SACH foot in respect of energy cost and, gait efficiency. This benefit has only been confirmed in transtibial amputees during decline and incline walking and increased walking speeds.

REVIEWER'S CONCLUSIONS

There is insufficient evidence from high quality comparative studies for the overall superiority of any individual type of prosthetic ankle-foot mechanism. In high activity transfemoral amputees, there is limited evidence for the superiority of the Flex foot during level walking compared with the SACH foot in respect of energy cost and, gait efficiency. This benefit has only been confirmed in transtibial amputees during decline and incline walking and increased walking speeds. In prescribing prosthetic-ankle foot mechanisms for lower-limb amputees, practitioners should take into account availability, patient functional needs, and cost.

Prosthetic prescription in the Netherlands: an observational study

Prosthetic prescription for lower limb amputees and the methodology used are primarily based on empirical knowledge. Clinical expertise plays an important role that can lead to an adequate prescription; however, a clear evidence based motivation for the choices made cannot be given. This can lead to local prescription variations with regard to overuse or underuse of prosthetic care and a lack of transparency for consumers and health insurance companies. Hence a clinical guideline may lead to a more consistent and efficient clinical practice and thus more uniformly high quality care. The purpose of this study was to get insight into potential similarities in prescription criteria in clinical practice in the Netherlands. Secondly, the authors were interested to know if prosthetic prescription was primarily based on the level of activity or intended use of the prosthesis. As part of the development of a consensus-based clinical guideline a multi-centred, cross-sectional study was carried out in order to observe the prosthetic prescription for a group of lower limb amputees. Therefore prescription data were collected from 151 amputees with trans-femoral amputation, knee disarticulation or trans-tibial amputation. Results of the multiple logistic regression show no relationship between the activity level and any of the variables included in the equation such as the hospital or medical doctor in Physical and Rehabilitation Medicine (MD in P&RM), prosthetic components, age of the amputee or reason of amputation. The criteria used are merely based on the clinical expertise and local experience whereas the actual prescriptions differ from location to location. In conclusion the development of a clinical guideline for prosthetic prescription in lower limb amputation is recommended. The information gained from this observational study will be used in a clinical guideline procedure for prosthetic prescription in the Netherlands.

Energy expenditure and biomechanical characteristics of lower limb amputee gait: the influence of prosthetic alignment and different prosthetic components

In this study, the influence of different prosthetic alignments and components on oxygen consumption and the important biomechanical characteristics of the normal gait pattern of leg amputees was investigated. With 15 transtibial and 12 transfemoral amputees, the oxygen consumption during walking on a treadmill was analyzed and biomechanical parameters during walking on even ground at a self-selected speed were defined. The amputation of all patients was caused by trauma. Variations of the prosthetic alignment affect the energy consumption of transfemoral amputees more significantly than that of transtibial amputees. Comparison of different prosthetic feet worn by transtibial amputees did not show significant differences regarding metabolic parameters. Compared with conventional hydraulic knee controls, the oxygen consumption of transfemoral amputees provided with an electronically controlled hydraulic knee joint is reduced. All investigated variations can be clearly characterized by the sagittal moments acting on the joints of the prosthetic limb during gait.

Energy storage and return prostheses: does patient perception correlate with biomechanical analysis?

The development and prescription of energy storage and return prosthetic feet in favor of conventional feet is largely based upon prosthetist and amputee experience. Regretfully, the comparative biomechanical analysis of energy storage and return and conventional prosthetic feet is rarely a motivation to either the technical development or clinical prescription of such devices. The development and prescription of prosthetic feet without supportive scientific evidence is likely due to the conflicting or non-significant results often presented in the scientific literature. Despite the sizeable history of comparative prosthetic literature and continued analysis of prosthetic components, the link between clinical experience and scientific evidence remains largely unexplored.A review of the comparative analysis literature evaluating energy storage and return and conventional prosthetic feet is presented to illustrate consistencies between the perceptive assessments and the objective biomechanical data. Results suggest that while experimental methodologies may limit the statistical significance of objective gait analysis results, consistent trends in temporal, kinetic, and kinematic parameters correlate well with perceptive impressions of these feet. These correlations provide insight to subtle changes in gait parameters that are deemed neither clinically nor statistically significant, yet are perceived by amputees to affect their preference for and performance of prosthetic feet during locomotion. Acknowledging and targeting areas of perceptive significance will help researchers develop more structured protocols for energy storage and return prosthesis evaluation as well as provide clinicians with information needed to enhance the appropriateness of their clinical recommendations. Expanding test environments to measure activities of perceived improvement such as high-velocity motions, stair ascent/descent, and uneven ground locomotion will provide a more appropriate assessment of the conditions for which energy storage and return prosthetic feet were designed. Concentrating research to specific test populations by age or amputation etiologies can overcome statistical limitations imposed by small study samples. Finally, directing research toward the areas of gait adaptation, heel performance, and the temporal release of energy in energy storage and return feet may reinforce the selection and utilization of advanced prosthetic components. These enhancements to current biomechanical analyses may serve to reduce the boundaries of perceptive significance and provide clinicians, designers, and researchers with the supportive data needed to prescribe, design, and evaluate energy storage and return prosthetic feet.