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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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Average linear regression lines for ML foot placement (top) and ML foot placement variability (bottom) across normalized speed.Across speed, non-amputees exhibited symmetrical foot placement patterns between their right leg (RL) and left leg (LL). As non-amputee sprinters approached maximum speed, they placed their feet closer to the midline of the body; however, each leg exhibited greater ML foot placement variability (left column). In contrast, sprinters with unilateral transtibial amputations exhibited asymmetrical foot placement patterns between the affected leg (AL) and unaffected leg (UL). They tended to place the AL closer to the midline as compared to the UL, but the AL exhibited greater ML foot placement variability (middle column). The sprinter with bilateral transtibial amputations also exhibited asymmetrical foot placement patterns. Although he tended to place the right affected leg (RAL) closer to the midline of the body as compared to the left affected leg (LAL), ML foot placement was similar across speed. Both the LAL and RAL exhibited dramatic increases in ML foot placement variability at faster running speeds up to maximum sprint speed (right column). For each variable, we present the equation and r values from a least-squares linear regression analysis that included the individual data points across normalized speed for each sprinter. For the Non-Amputee and Unilateral group, the shaded regions represent the 95% lower and upper confidence bands. Since n = 1, we do not include the confidence bands for the Bilateral case. For clarity, individual data points are not shown.
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pone.0115637.g005: Average linear regression lines for ML foot placement (top) and ML foot placement variability (bottom) across normalized speed.Across speed, non-amputees exhibited symmetrical foot placement patterns between their right leg (RL) and left leg (LL). As non-amputee sprinters approached maximum speed, they placed their feet closer to the midline of the body; however, each leg exhibited greater ML foot placement variability (left column). In contrast, sprinters with unilateral transtibial amputations exhibited asymmetrical foot placement patterns between the affected leg (AL) and unaffected leg (UL). They tended to place the AL closer to the midline as compared to the UL, but the AL exhibited greater ML foot placement variability (middle column). The sprinter with bilateral transtibial amputations also exhibited asymmetrical foot placement patterns. Although he tended to place the right affected leg (RAL) closer to the midline of the body as compared to the left affected leg (LAL), ML foot placement was similar across speed. Both the LAL and RAL exhibited dramatic increases in ML foot placement variability at faster running speeds up to maximum sprint speed (right column). For each variable, we present the equation and r values from a least-squares linear regression analysis that included the individual data points across normalized speed for each sprinter. For the Non-Amputee and Unilateral group, the shaded regions represent the 95% lower and upper confidence bands. Since n = 1, we do not include the confidence bands for the Bilateral case. For clarity, individual data points are not shown.

Mentions: To determine the direction and strength of the relation between variables, we followed the repeated measures MANOVAs with separate linear regression and correlation analyses for each dependent variable (i.e. ML foot placement and ML foot placement variability) with normalized speed as the independent variable. Linear regression and correlation (Pearson’s r) analyses were performed separately for non-amputee sprinters (n = 12) and sprinters with a unilateral amputation (n = 6). To elucidate the individual and group trends between ML foot placement, ML foot placement variability, and normalized speed, we present the linear regression equations denoting the slope, intercept, Pearson’s r values, and range (Figs. 3, 4, and 5). The range is defined in brackets, expressed in units of centimeters, and denotes the ML foot placement (or its variability) value at the individual’s minimum and maximum normalized speed. Statistical significance for all analyses was set at an α level = 0.05 (SPSS Inc., Chicago, IL).


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)

Average linear regression lines for ML foot placement (top) and ML foot placement variability (bottom) across normalized speed.Across speed, non-amputees exhibited symmetrical foot placement patterns between their right leg (RL) and left leg (LL). As non-amputee sprinters approached maximum speed, they placed their feet closer to the midline of the body; however, each leg exhibited greater ML foot placement variability (left column). In contrast, sprinters with unilateral transtibial amputations exhibited asymmetrical foot placement patterns between the affected leg (AL) and unaffected leg (UL). They tended to place the AL closer to the midline as compared to the UL, but the AL exhibited greater ML foot placement variability (middle column). The sprinter with bilateral transtibial amputations also exhibited asymmetrical foot placement patterns. Although he tended to place the right affected leg (RAL) closer to the midline of the body as compared to the left affected leg (LAL), ML foot placement was similar across speed. Both the LAL and RAL exhibited dramatic increases in ML foot placement variability at faster running speeds up to maximum sprint speed (right column). For each variable, we present the equation and r values from a least-squares linear regression analysis that included the individual data points across normalized speed for each sprinter. For the Non-Amputee and Unilateral group, the shaded regions represent the 95% lower and upper confidence bands. Since n = 1, we do not include the confidence bands for the Bilateral case. For clarity, individual data points are not shown.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4295868&req=5

pone.0115637.g005: Average linear regression lines for ML foot placement (top) and ML foot placement variability (bottom) across normalized speed.Across speed, non-amputees exhibited symmetrical foot placement patterns between their right leg (RL) and left leg (LL). As non-amputee sprinters approached maximum speed, they placed their feet closer to the midline of the body; however, each leg exhibited greater ML foot placement variability (left column). In contrast, sprinters with unilateral transtibial amputations exhibited asymmetrical foot placement patterns between the affected leg (AL) and unaffected leg (UL). They tended to place the AL closer to the midline as compared to the UL, but the AL exhibited greater ML foot placement variability (middle column). The sprinter with bilateral transtibial amputations also exhibited asymmetrical foot placement patterns. Although he tended to place the right affected leg (RAL) closer to the midline of the body as compared to the left affected leg (LAL), ML foot placement was similar across speed. Both the LAL and RAL exhibited dramatic increases in ML foot placement variability at faster running speeds up to maximum sprint speed (right column). For each variable, we present the equation and r values from a least-squares linear regression analysis that included the individual data points across normalized speed for each sprinter. For the Non-Amputee and Unilateral group, the shaded regions represent the 95% lower and upper confidence bands. Since n = 1, we do not include the confidence bands for the Bilateral case. For clarity, individual data points are not shown.
Mentions: To determine the direction and strength of the relation between variables, we followed the repeated measures MANOVAs with separate linear regression and correlation analyses for each dependent variable (i.e. ML foot placement and ML foot placement variability) with normalized speed as the independent variable. Linear regression and correlation (Pearson’s r) analyses were performed separately for non-amputee sprinters (n = 12) and sprinters with a unilateral amputation (n = 6). To elucidate the individual and group trends between ML foot placement, ML foot placement variability, and normalized speed, we present the linear regression equations denoting the slope, intercept, Pearson’s r values, and range (Figs. 3, 4, and 5). The range is defined in brackets, expressed in units of centimeters, and denotes the ML foot placement (or its variability) value at the individual’s minimum and maximum normalized speed. Statistical significance for all analyses was set at an α level = 0.05 (SPSS Inc., Chicago, IL).

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.

Show MeSH
Related in: MedlinePlus