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Effect of running speed and leg prostheses on mediolateral foot placement and its variability.

Arellano CJ, McDermott WJ, Kram R, Grabowski AM - PLoS ONE (2015)

Bottom Line: We quantified ML foot placement relative to the body's midline and its variability.We interpret our results with respect to a hypothesized relation between ML foot placement variability and lateral balance.We infer that greater ML foot placement variability indicates greater challenges with maintaining lateral balance.

View Article: PubMed Central - PubMed

Affiliation: Integrative Physiology Department, University of Colorado, Boulder, Colorado, United States of America.

ABSTRACT
This study examined the effects of speed and leg prostheses on mediolateral (ML) foot placement and its variability in sprinters with and without transtibial amputations. We hypothesized that ML foot placement variability would: 1. increase with running speed up to maximum speed and 2. be symmetrical between the legs of non-amputee sprinters but asymmetrically greater for the affected leg of sprinters with a unilateral transtibial amputation. We measured the midline of the body (kinematic data) and center of pressure (kinetic data) in the ML direction while 12 non-amputee sprinters and 7 Paralympic sprinters with transtibial amputations (6 unilateral, 1 bilateral) ran across a range of speeds up to maximum speed on a high-speed force measuring treadmill. We quantified ML foot placement relative to the body's midline and its variability. We interpret our results with respect to a hypothesized relation between ML foot placement variability and lateral balance. We infer that greater ML foot placement variability indicates greater challenges with maintaining lateral balance. In non-amputee sprinters, ML foot placement variability for each leg increased substantially and symmetrically across speed. In sprinters with a unilateral amputation, ML foot placement variability for the affected and unaffected leg also increased substantially, but was asymmetric across speeds. In general, ML foot placement variability for sprinters with a unilateral amputation was within the range observed in non-amputee sprinters. For the sprinter with bilateral amputations, both affected legs exhibited the greatest increase in ML foot placement variability with speed. Overall, we find that maintaining lateral balance becomes increasingly challenging at faster speeds up to maximum speed but was equally challenging for sprinters with and without a unilateral transtibial amputation. Finally, when compared to all other sprinters in our subject pool, maintaining lateral balance appears to be the most challenging for the Paralympic sprinter with bilateral transtibial amputations.

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(a) Rear view of a sprinter with a left-side transtibial amputation running on a force-measuring treadmill.A side-view illustration of the running-specific prosthesis is provided as an inset. For measurements of ML foot placement relative to the body’s midline, we measured the position of the center of pressure at peak vertical ground reaction force for both biological legs and the legs using the running-specific prosthesis.
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pone.0115637.g001: (a) Rear view of a sprinter with a left-side transtibial amputation running on a force-measuring treadmill.A side-view illustration of the running-specific prosthesis is provided as an inset. For measurements of ML foot placement relative to the body’s midline, we measured the position of the center of pressure at peak vertical ground reaction force for both biological legs and the legs using the running-specific prosthesis.

Mentions: After emulating their pre-race warm-up (i.e. jogging, stretching, and short sprints), each subject performed brief running trials on a high-speed 3D force-sensing motorized treadmill (Fig. 1; Treadmetrix, Park City, UT). The treadmill is a custom designed lightweight treadmill with 3D force transducers (MC3A AMTI, Watertown, MA) at each corner that interface with amplifiers (MSA6 AMTI, Watertown, MA). During each trial, we simultaneously collected 3D ground reaction forces and moments (2400 Hz) and whole body kinematics from the 3D positions of reflective markers placed on the body (200 Hz; Motion Analysis Corporation, Santa Rosa, CA). We used a full-body custom marker set to define the position of the subject’s head, trunk, arms, legs, and running-specific prosthesis. Each subject began the series of trials at 3 m/s and we incremented the speed by 1 m/s until subjects approached their maximum speed. We then used smaller speed increments until the subject reached maximum speed, defined as the fastest speed at which the subject could maintain the same position on the treadmill for at least 20 consecutive steps. All subjects had experience with treadmill running and sprinting and were familiar with this task. During each trial, subjects lowered themselves from handrails onto the treadmill belt, which was moving at the testing speed. Handrails were placed along the front and sides of the treadmill and each subject had practice holding and then releasing the handrails when achieving maximum treadmill sprinting speeds (for clarity, handrails are not shown in Fig. 1).


Effect of running speed and leg prostheses on mediolateral foot placement and its variability.

Arellano CJ, McDermott WJ, Kram R, Grabowski AM - PLoS ONE (2015)

(a) Rear view of a sprinter with a left-side transtibial amputation running on a force-measuring treadmill.A side-view illustration of the running-specific prosthesis is provided as an inset. For measurements of ML foot placement relative to the body’s midline, we measured the position of the center of pressure at peak vertical ground reaction force for both biological legs and the legs using the running-specific prosthesis.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4295868&req=5

pone.0115637.g001: (a) Rear view of a sprinter with a left-side transtibial amputation running on a force-measuring treadmill.A side-view illustration of the running-specific prosthesis is provided as an inset. For measurements of ML foot placement relative to the body’s midline, we measured the position of the center of pressure at peak vertical ground reaction force for both biological legs and the legs using the running-specific prosthesis.
Mentions: After emulating their pre-race warm-up (i.e. jogging, stretching, and short sprints), each subject performed brief running trials on a high-speed 3D force-sensing motorized treadmill (Fig. 1; Treadmetrix, Park City, UT). The treadmill is a custom designed lightweight treadmill with 3D force transducers (MC3A AMTI, Watertown, MA) at each corner that interface with amplifiers (MSA6 AMTI, Watertown, MA). During each trial, we simultaneously collected 3D ground reaction forces and moments (2400 Hz) and whole body kinematics from the 3D positions of reflective markers placed on the body (200 Hz; Motion Analysis Corporation, Santa Rosa, CA). We used a full-body custom marker set to define the position of the subject’s head, trunk, arms, legs, and running-specific prosthesis. Each subject began the series of trials at 3 m/s and we incremented the speed by 1 m/s until subjects approached their maximum speed. We then used smaller speed increments until the subject reached maximum speed, defined as the fastest speed at which the subject could maintain the same position on the treadmill for at least 20 consecutive steps. All subjects had experience with treadmill running and sprinting and were familiar with this task. During each trial, subjects lowered themselves from handrails onto the treadmill belt, which was moving at the testing speed. Handrails were placed along the front and sides of the treadmill and each subject had practice holding and then releasing the handrails when achieving maximum treadmill sprinting speeds (for clarity, handrails are not shown in Fig. 1).

Bottom Line: We quantified ML foot placement relative to the body's midline and its variability.We interpret our results with respect to a hypothesized relation between ML foot placement variability and lateral balance.We infer that greater ML foot placement variability indicates greater challenges with maintaining lateral balance.

View Article: PubMed Central - PubMed

Affiliation: Integrative Physiology Department, University of Colorado, Boulder, Colorado, United States of America.

ABSTRACT
This study examined the effects of speed and leg prostheses on mediolateral (ML) foot placement and its variability in sprinters with and without transtibial amputations. We hypothesized that ML foot placement variability would: 1. increase with running speed up to maximum speed and 2. be symmetrical between the legs of non-amputee sprinters but asymmetrically greater for the affected leg of sprinters with a unilateral transtibial amputation. We measured the midline of the body (kinematic data) and center of pressure (kinetic data) in the ML direction while 12 non-amputee sprinters and 7 Paralympic sprinters with transtibial amputations (6 unilateral, 1 bilateral) ran across a range of speeds up to maximum speed on a high-speed force measuring treadmill. We quantified ML foot placement relative to the body's midline and its variability. We interpret our results with respect to a hypothesized relation between ML foot placement variability and lateral balance. We infer that greater ML foot placement variability indicates greater challenges with maintaining lateral balance. In non-amputee sprinters, ML foot placement variability for each leg increased substantially and symmetrically across speed. In sprinters with a unilateral amputation, ML foot placement variability for the affected and unaffected leg also increased substantially, but was asymmetric across speeds. In general, ML foot placement variability for sprinters with a unilateral amputation was within the range observed in non-amputee sprinters. For the sprinter with bilateral amputations, both affected legs exhibited the greatest increase in ML foot placement variability with speed. Overall, we find that maintaining lateral balance becomes increasingly challenging at faster speeds up to maximum speed but was equally challenging for sprinters with and without a unilateral transtibial amputation. Finally, when compared to all other sprinters in our subject pool, maintaining lateral balance appears to be the most challenging for the Paralympic sprinter with bilateral transtibial amputations.

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