Characterizing the Mechanical Properties of Running-Specific Prostheses

Beck, Owen N.; Taboga, Paolo; Grabowski, Alena M.

doi:10.1371/journal.pone.0168298

Cited by 61 publications

(122 citation statements)

References 28 publications

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“…2, it seems that the use of a prosthetic knee and foot results in a large amount of energy loss (hysteresis) in the vGRF-COM displacement curves during ground contact. Therefore, as demonstrated by past findings 7,14,19 , the stiffness of each prosthetic component should be addressed to determine stiffness regulation during running using RSPs. Second, in our study, each participant ran at different f step at a given running speed, which differed depending on the participant.…”

Section: And Prostheticmentioning

confidence: 97%

Effect of step frequency on leg stiffness during running in unilateral transfemoral amputees

Hobara

Sakata

Namiki

et al. 2020

Sci Rep

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Spring-like leg behavior is a general feature of mammalian bouncing gaits, such as running and hopping. Although increases in step frequency at a given running speed are known to increase the stiffness of the leg spring (k leg) in non-amputees, little is known about stiffness regulation in unilateral transfemoral amputees. In this study, we investigated stiffness regulation at different step frequencies at a given running speed in unilateral transfemoral amputees. We recruited nine unilateral transfemoral amputees wearing running-specific prostheses. They were asked to perform the action of running across a range of step frequencies (±20, ±15, ±10, ±5, and 0% of their preferred step frequency) at a given speed on an instrumented treadmill. The k leg values were calculated using ground reaction force data in both the affected and unaffected limbs. It was found that k leg increased with increasing step frequency for the unaffected limb, but not for the affected limb. Consequently, the unilateral transfemoral amputees attained the desired step frequency in the unaffected limb, but were unable to match the three highest step frequencies using their affected limbs. These results suggest that the stiffness regulation strategy during running differs between the affected and unaffected limbs.

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Section: And Prostheticmentioning

confidence: 97%

Effect of step frequency on leg stiffness during running in unilateral transfemoral amputees

Hobara

Sakata

Namiki

et al. 2020

Sci Rep

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“…Stiffness curve and damping response is fixed and depends on material properties, shape, and thickness [5,6]. Feet are prescribed to patients in stiffness categories, primarily based on weight and activity levels [7,8].…”

Section: Introductionmentioning

confidence: 99%

Use of Dynamic FEA for Design Modification and Energy Analysis of a Variable Stiffness Prosthetic Foot

et al. 2020

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Different tasks and conditions in gait call for different stiffness of prosthetic foot devices. The following work presents a case study on design modifications of a prosthetic foot, aimed at variable stiffness of the device. The objective is a proof-of-concept, achieved by simulating the modifications using finite element modeling. Design changes include the addition of a controlled damping element, connected both in parallel and series to a system of springs. The aim is to change the stiffness of the device under dynamic loading, by applying a high damping constant, approaching force coupling for the given boundary conditions. The dynamic modelling simulates mechanical test methods used to measure load response in full roll-over of prosthetic feet. Activation of the element during loading of the foot justifies the damped effect. As damping is in contrast to the main design objectives of energy return in prosthetic feet, it is considered important to quantify the dissipated energy in such an element. Our design case shows that the introduction of a damping element, with a high damping constant, can increase the overall rotational stiffness of the device by 50%. Given a large enough damping coefficient, the energy dissipation in the active element is about 20% of maximum strain energy.

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“…We used the mean AL peak resultant GRFs measured in the current study and the reported RSP stiffness values from each device reported by Beck et al 4 (Supplementary Tables 1, 3 and 4) (k RSP ) to calculate RSP displacement (ΔRSP):…”

mentioning

confidence: 99%

Prosthetic model, but not stiffness or height, affects maximum running velocity in athletes with unilateral transtibial amputations

Taboga

Drees

Beck

et al. 2020

Sci Rep

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The running-specific prosthetic (RSP) configuration used by athletes with transtibial amputations (TTAs) likely affects performance. Athletes with unilateral TTAs are prescribed C-or J-shaped RSPs with a manufacturer-recommended stiffness category based on body mass and activity level, and height based on unaffected leg and residual limb length. We determined how 15 different RSP model, stiffness, and height configurations affect maximum running velocity (v max) and the underlying biomechanics. Ten athletes with unilateral TTAs ran at 3 m/s to v max on a force-measuring treadmill. v max was 3.8-10.7% faster when athletes used J-shaped versus C-shaped RSP models (p < 0.05), but was not affected by stiffness category, actual stiffness (kN/m), or height (p = 0.72, p = 0.37, and p = 0.11, respectively). v max differences were explained by vertical ground reaction forces (vGRFs), stride kinematics, leg stiffness, and symmetry. While controlling for velocity, use of J-shaped versus C-shaped RSPs resulted in greater stance average vGRFs, slower step frequencies, and longer step lengths (p < 0.05). Stance average vGRFs were less asymmetric using J-shaped versus C-shaped RSPs (p < 0.05). Contact time and leg stiffness were more asymmetric using the RSP model that elicited the fastest v max (p < 0.05). Thus, RSP geometry (J-shape versus C-shape), but not stiffness or height, affects v max in athletes with unilateral ttAs. Running-specific prostheses (RSPs) are passive-elastic devices typically made of carbon fiber that attach to a socket that surrounds the residual limb. The use of RSPs enable athletes with transtibial amputations (TTAs) to compete in running events including the Olympic games. RSP models are generally C-shaped or J-shaped. C-shaped RSPs attach distal to the socket and are recommended for distance running 1 (e.g. 10 km, half marathon, and marathon) and J-shaped RSPs attach posterior to the socket and are recommended for sprinting 1 (e.g. 100 m, 200 m, and 400 m). Despite different attachments and shapes, both types of RSPs act in-series with the residual limb. Athletes with TTAs are prescribed an RSP with a manufacturer-recommended stiffness category that is based on his or her body mass and activity level 1-3. Greater stiffness categories correspond with stiffer RSPs while considering prosthetic model 4. Further, for an athlete with a unilateral TTA, RSP height is set based on the athlete's contralateral unaffected leg length, stride kinematics, and their prosthetist's and personal preference 5. The height of a C-shaped RSP is adjusted by shortening or lengthening the pylon that connects the RSP to the socket, while the height of a J-shaped RSP is adjusted by changing its mounting position posterior to the socket (Fig. 1). An athlete's unloaded RSP height is adjusted so that their affected leg (AL) length is 2-8 cm taller than their unaffected leg (UL) length 6,7. The RSP configuration (i.e. model, stiffness category, height) used by athletes with TTAs likely affects their running performance, which is we...

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Characterizing the Mechanical Properties of Running-Specific Prostheses

Cited by 61 publications

References 28 publications

Effect of step frequency on leg stiffness during running in unilateral transfemoral amputees

Effect of step frequency on leg stiffness during running in unilateral transfemoral amputees

Use of Dynamic FEA for Design Modification and Energy Analysis of a Variable Stiffness Prosthetic Foot

Prosthetic model, but not stiffness or height, affects maximum running velocity in athletes with unilateral transtibial amputations

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