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

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 (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...

Running-specific prosthesis model, stiffness and height affect biomechanics and asymmetry of athletes with unilateral leg amputations across speeds

“…From 3-7 m s −1 , the use of the Xtend RSP resulted in shorter affected leg L c compared with the other RSP models; the use of the Sprinter and Xtend RSPs increased affected leg F avg and decreased f step compared with the Catapult RSP, and these relationships between RSP models were independent of speed, which supported our hypothesis (1a). The results for affected leg L c , F avg and f step from 3 to 7 m s −1 are similar to overall L c , F avg and f step of previous studies at 2.5-3.0 m s −1 and maximum speed when athletes with unilateral TTA used different RSP models [1,2] and confirm that the relationships between RSP model and affected leg biomechanics are consistent across a range of speeds. The use of the J-shaped Sprinter and Xtend RSPs had different effects on affected leg L c compared with the C-shaped Catapult RSP.…”

“…Previous studies show that the configuration of an RSP (e.g. model) can affect performance, specifically the metabolic cost and maximum speed, of an athlete with TTA [1][2][3]. The model of an RSP is generally shaped like a 'C' or 'J' (figure 1).…”

“…Previous studies have examined the effects of different RSP model, stiffness category and height configurations on metabolic cost and maximum speed of athletes with unilateral TTA to determine how RSP configuration affects performance as well as the underlying biomechanics [ 1 , 2 ]. Overall, the use of J-shaped RSPs resulted in lower metabolic cost at 2.5 and 3 m s −1 and faster maximum speed compared with C-shaped RSPs, but RSP stiffness category and height did not affect performance [ 1 , 2 ].…”

“…Previous studies have examined the effects of different RSP model, stiffness category and height configurations on metabolic cost and maximum speed of athletes with unilateral TTA to determine how RSP configuration affects performance as well as the underlying biomechanics [ 1 , 2 ]. Overall, the use of J-shaped RSPs resulted in lower metabolic cost at 2.5 and 3 m s −1 and faster maximum speed compared with C-shaped RSPs, but RSP stiffness category and height did not affect performance [ 1 , 2 ]. At 2.5 and 3 m s −1 use of the J-shaped Ottobock 1E90 Sprinter (Duderstadt, Germany, figure 1 ) compared with the C-shaped Freedom Innovations Catapult FX6 (Irvine, CA, USA, figure 1 ) RSP did not change overall L c (average L c of the unaffected and affected legs), but increased overall F avg [ 1 ].…”

External Mechanical Work in Runners With Unilateral Transfemoral Amputation

“…Finally, participants in the present study used their own RSPs and prosthetic knee joints (Table 1) under several prosthetic configurations, such as RSP model, RSP shape, category of stiffness, and prosthetic alignments. According to previous studies (Beck et al, 2016;Beck et al, 2017a;Beck et al, 2017b;Migliore et al, 2020;Taboga et al, 2020), prosthetic configurations could affect the running biomechanics and performance in individuals with lower limb amputation. Future work should investigate the bouncing gait mechanism in runners with passive prostheses while considering different prosthetic configurations.…”