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

Paolo Taboga,Owen N Beck,Alena M Grabowski,Emily K Drees

doi:10.1038/s41598-019-56479-8

Abstract

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 (vmax) and the underlying biomechanics. Ten athletes with unilateral TTAs ran at 3 m/s to vmax on a force-measuring treadmill. vmax 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). vmax 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 vmax (p < 0.05). Thus, RSP geometry (J-shape versus C-shape), but not stiffness or height, affects vmax in athletes with unilateral TTAs.

Highlights

The running-specific prosthetic (RSP) configuration used by athletes with transtibial amputations (TTAs) likely affects performance
Use of an Ottobock 1E90 Sprinter (OBK1) RSP resulted in 6.6% (β1 = 0.46, p < 0.05) faster vmax compared to use of an OSR2 RSP
When accounting for differences in vmax, we found that use of FDM3 resulted in 3.4% faster step frequencies than use of OBK1 and OSR2 RSPs (β1 = −0.088 and β2 = −0.088, both p < 0.05; Fig. 3A, Table 2), and the step frequencies were non-different between use of OBK1 and OSR2 RSPs (p = 0.99)

Summary

Introduction

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. RSP geometry (J-shape versus C-shape), but not stiffness or height, affects vmax 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. Running velocity equals the product of step frequency, stance average vertical GRF, and contact length. Greater vertical GRFs increase the vertical CoM velocity at the end of ground contact, resulting in longer aerial time, and increasing the forward CoM distance traveled for each step at a given running velocity. Non-amputees and athletes with TTAs exhibit directionally similar changes in stance average vertical GRFs and spatiotemporal variables to increase running velocity, but biomechanics differ between the AL versus UL6,7. Athletes with unilateral TTAs decrease AL stiffness, while UL stiffness remains constant from 3.0 m/s up to maximum running velocity (vmax)[6], leg stiffness values between the AL and UL are more asymmetric at faster velocities

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