The biomechanics of the fastest sprinter with a unilateral transtibial amputation

People have debated whether athletes with transtibial amputations should compete with nonamputees in track events despite insufficient information regarding how the use of running-specific prostheses (RSPs) affect athletic performance. Thus, we sought to quantify the spatiotemporal variables, ground reaction forces, and spring-mass mechanics of the fastest athlete with a unilateral transtibial amputation using an RSP to reveal how he adapts his biomechanics to achieve elite running speeds. Accordingly, we measured ground reaction forces during treadmill running trials spanning 2.87 to 11.55 m/s of the current male International Paralympic Committee T44 100- and 200-m world record holder. To achieve faster running speeds, the present study’s athlete increased his affected leg (AL) step lengths ( P < 0.001) through longer contact lengths ( P < 0.001) and his unaffected leg (UL) step lengths ( P < 0.001) through longer contact lengths ( P < 0.001) and greater stance average vertical ground reaction forces ( P < 0.001). At faster running speeds, step time decreased for both legs ( P < 0.001) through shorter ground contact and aerial times ( P < 0.001). Unlike athletes with unilateral transtibial amputations, this athlete maintained constant AL and UL stiffness across running speeds ( P ≥ 0.569). Across speeds, AL step lengths were 8% longer ( P < 0.001) despite 16% lower AL stance average vertical ground reaction forces compared with the UL ( P < 0.001). The present study’s athlete exhibited biomechanics that differed from those of athletes with bilateral and without transtibial amputations. Overall, we present the biomechanics of the fastest athlete with a unilateral transtibial amputation, providing insight into the functional abilities of athletes with transtibial amputations using running-specific prostheses.NEW & NOTEWORTHY The present study’s athlete achieved the fastest treadmill running trial ever attained by an individual with a leg amputation (11.55 m/s). From 2.87 to 11.55 m/s, the present study’s athlete maintained constant affected and unaffected leg stiffness, which is atypical for athletes with unilateral transtibial amputations. Furthermore, the asymmetric vertical ground reaction forces of athletes with unilateral transtibial amputations during running may be the result of leg length discrepancies.

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Prosthetic model, but not stiffness or height, affects the metabolic cost of running for athletes with unilateral transtibial amputations

Journal of Applied Physiology ◽

10.1152/japplphysiol.00896.2016 ◽

2017 ◽

Vol 123 (1) ◽

pp. 38-48 ◽

Cited By ~ 10

Author(s):

Owen N. Beck ◽

Paolo Taboga ◽

Alena M. Grabowski

Keyword(s):

Lower Limb ◽

Metabolic Cost ◽

Ground Reaction Forces ◽

Ground Contact ◽

Limb Stiffness ◽

Leg Stiffness ◽

In Series ◽

Reaction Forces ◽

Vertical Ground ◽

Vertical Ground Reaction Forces

Running-specific prostheses enable athletes with lower limb amputations to run by emulating the spring-like function of biological legs. Current prosthetic stiffness and height recommendations aim to mitigate kinematic asymmetries for athletes with unilateral transtibial amputations. However, it is unclear how different prosthetic configurations influence the biomechanics and metabolic cost of running. Consequently, we investigated how prosthetic model, stiffness, and height affect the biomechanics and metabolic cost of running. Ten athletes with unilateral transtibial amputations each performed 15 running trials at 2.5 or 3.0 m/s while we measured ground reaction forces and metabolic rates. Athletes ran using three different prosthetic models with five different stiffness category and height combinations per model. Use of an Ottobock 1E90 Sprinter prosthesis reduced metabolic cost by 4.3 and 3.4% compared with use of Freedom Innovations Catapult [fixed effect (β) = −0.177; P < 0.001] and Össur Flex-Run (β = −0.139; P = 0.002) prostheses, respectively. Neither prosthetic stiffness ( P ≥ 0.180) nor height ( P = 0.062) affected the metabolic cost of running. The metabolic cost of running was related to lower peak (β = 0.649; P = 0.001) and stance average (β = 0.772; P = 0.018) vertical ground reaction forces, prolonged ground contact times (β = −4.349; P = 0.012), and decreased leg stiffness (β = 0.071; P < 0.001) averaged from both legs. Metabolic cost was reduced with more symmetric peak vertical ground reaction forces (β = 0.007; P = 0.003) but was unrelated to stride kinematic symmetry ( P ≥ 0.636). Therefore, prosthetic recommendations based on symmetric stride kinematics do not necessarily minimize the metabolic cost of running. Instead, an optimal prosthetic model, which improves overall biomechanics, minimizes the metabolic cost of running for athletes with unilateral transtibial amputations.NEW & NOTEWORTHY The metabolic cost of running for athletes with unilateral transtibial amputations depends on prosthetic model and is associated with lower peak and stance average vertical ground reaction forces, longer contact times, and reduced leg stiffness. Metabolic cost is unrelated to prosthetic stiffness, height, and stride kinematic symmetry. Unlike nonamputees who decrease leg stiffness with increased in-series surface stiffness, biological limb stiffness for athletes with unilateral transtibial amputations is positively correlated with increased in-series (prosthetic) stiffness.

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Comparison of vertical ground reaction forces during overground and treadmill running. A validation study

BMC Musculoskeletal Disorders ◽

10.1186/1471-2474-13-235 ◽

2012 ◽

Vol 13 (1) ◽

Cited By ~ 54

Author(s):

Bas Kluitenberg ◽

Steef W Bredeweg ◽

Sjouke Zijlstra ◽

Wiebren Zijlstra ◽

Ida Buist

Keyword(s):

Validation Study ◽

Treadmill Running ◽

Ground Reaction Forces ◽

Reaction Forces ◽

Vertical Ground ◽

Vertical Ground Reaction Forces

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Effects of mild leg length discrepancy on vertical ground reaction forces in running

Journal of Biomechanics ◽

10.1016/s0021-9290(06)85237-1 ◽

2006 ◽

Vol 39 ◽

pp. S544

Author(s):

C.S. Pereira ◽

J.G.M. Silva ◽

I.C.N. Sacco

Keyword(s):

Leg Length Discrepancy ◽

Ground Reaction Forces ◽

Leg Length ◽

Length Discrepancy ◽

Reaction Forces ◽

Vertical Ground ◽

Vertical Ground Reaction Forces

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Leg stiffness of sprinters using running-specific prostheses

Journal of The Royal Society Interface ◽

10.1098/rsif.2011.0877 ◽

2012 ◽

Vol 9 (73) ◽

pp. 1975-1982 ◽

Cited By ~ 54

Author(s):

Craig P. McGowan ◽

Alena M. Grabowski ◽

William J. McDermott ◽

Hugh M. Herr ◽

Rodger Kram

Keyword(s):

Ground Reaction Forces ◽

Mass Model ◽

Leg Stiffness ◽

Reaction Forces ◽

Vertical Ground ◽

Stiffness Characteristics ◽

And Performance ◽

Vertical Ground Reaction Forces ◽

Transtibial Amputees ◽

Running Mechanics

Running-specific prostheses (RSF) are designed to replicate the spring-like nature of biological legs (bioL) during running. However, it is not clear how these devices affect whole leg stiffness characteristics or running dynamics over a range of speeds. We used a simple spring–mass model to examine running mechanics across a range of speeds, in unilateral and bilateral transtibial amputees and performance-matched controls. We found significant differences between the affected leg (AL) of unilateral amputees and both ALs of bilateral amputees compared with the bioL of non-amputees for nearly every variable measured. Leg stiffness remained constant or increased with speed in bioL, but decreased with speed in legs with RSPs. The decrease in leg stiffness in legs with RSPs was mainly owing to a combination of lower peak ground reaction forces and increased leg compression with increasing speeds. Leg stiffness is an important parameter affecting contact time and the force exerted on the ground. It is likely that the fixed stiffness of the prosthesis coupled with differences in the limb posture required to run with the prosthesis limits the ability to modulate whole leg stiffness and the ability to apply high vertical ground reaction forces during sprinting.

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