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

Abstract

Athletes with transtibial amputation (TTA) use running-specific prostheses (RSPs) to run. RSP configuration likely affects the biomechanics of such athletes across speeds. We determined how the use of three RSP models (Catapult, Sprinter and Xtend) with three stiffness categories (recommended, ±1), and three heights (recommended, ±2 cm) affected contact length ( L c ), stance average vertical ground reaction force ( F avg ), step frequency ( f step ) and asymmetry between legs for 10 athletes with unilateral TTA at 3–7 m s −1 . The use of the Xtend versus Catapult RSP decreased L c ( p = 2.69 × 10 −7 ) and F avg asymmetry ( p = 0.032); the effect on L c asymmetry diminished with faster speeds ( p = 0.0020). The use of the Sprinter versus Catapult RSP decreased F avg asymmetry ( p = 7.00 × 10 −5 ); this effect was independent of speed ( p = 0.90). The use of a stiffer RSP decreased L c asymmetry ( p ≤ 0.00033); this effect was independent of speed ( p ≥ 0.071). The use of a shorter RSP decreased L c ( p = 5.86 × 10 −6 ), F avg ( p = 8.58 × 10 −6 ) and f step asymmetry ( p = 0.0011); each effect was independent of speed ( p ≥ 0.15). To minimize asymmetry, athletes with unilateral TTA should use an Xtend or Sprinter RSP with 2 cm shorter than recommended height and stiffness based on intended speed.

A review of evidence on mechanical properties of running specific prostheses and their relationship with running performance

“…Eight studies assessed the relationship between the mechanical properties of RSPs and running performance indices, including running speed and cost of transport (CoT) ( 7 , 39 – 44 , 48 ). Stride or step frequency, GRF, and contact time were assessed in some of these studies.…”

“…The association between running speed and RSP stiffness was assessed in six studies ( 7 , 39 , 42 – 44 , 48 ). However, three studies ( 7 , 39 , 44 ) were based on the same data set.…”

“…The association between running speed and RSP stiffness was assessed in six studies ( 7 , 39 , 42 – 44 , 48 ). However, three studies ( 7 , 39 , 44 ) were based on the same data set. They measured the effect of prosthesis stiffness (using three manufacturer-defined RSP stiffness categories) on running outcomes such as temporal and spatial parameters, GRF, and leg stiffness.…”

“…Toboga et al ( 42 ) reported a similar finding in unilateral transtibial amputees using the same methods and same RSPs as their study in individuals with bilateral transtibial amputation. Nevertheless, in their recent publication, the same research team revealed that the step frequency rose in correlation with higher speeds, and this effect was mitigated when participants used a stiffer RSP compared to a less stiff one ( 44 ).…”