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Adaptation and prosthesis effects on stride-to-stride fluctuations in amputee gait.

Wurdeman SR, Myers SA, Jacobsen AL, Stergiou N - PLoS ONE (2014)

Bottom Line: There was also a significant effect for the time point in the adaptation period (F2,46 = 3.164, p = 0.050).Through the adaptation period, a freezing and subsequent freeing of dynamic degrees of freedom was seen as the λ at the ankle decreased at the midpoint of the adaptation period compared to the initial prosthesis fitting (p = 0.032), but then increased at the end compared to the midpoint (p = 0.042).No differences were seen between the initial fitting and the end of the adaptation for λ (p = 0.577).

View Article: PubMed Central - PubMed

Affiliation: Biomechanics Research Building, University of Nebraska at Omaha, Omaha, Nebraska, United States of America; Advanced Prosthetics Center, Omaha, Nebraska, United States of America.

ABSTRACT
Twenty-four individuals with transtibial amputation were recruited to a randomized, crossover design study to examine stride-to-stride fluctuations of lower limb joint flexion/extension time series using the largest Lyapunov exponent (λ). Each individual wore a "more appropriate" and a "less appropriate" prosthesis design based on the subject's previous functional classification for a three week adaptation period. Results showed decreased λ for the sound ankle compared to the prosthetic ankle (F1,23 = 13.897, p = 0.001) and a decreased λ for the "more appropriate" prosthesis (F1,23 = 4.849, p = 0.038). There was also a significant effect for the time point in the adaptation period (F2,46 = 3.164, p = 0.050). Through the adaptation period, a freezing and subsequent freeing of dynamic degrees of freedom was seen as the λ at the ankle decreased at the midpoint of the adaptation period compared to the initial prosthesis fitting (p = 0.032), but then increased at the end compared to the midpoint (p = 0.042). No differences were seen between the initial fitting and the end of the adaptation for λ (p = 0.577). It is concluded that the λ may be a feasible clinical tool for measuring prosthesis functionality and adaptation to a new prosthesis is a process through which the motor control develops mastery of redundant degrees of freedom present in the system.

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Stride-to-stride fluctuations for the ankle were significantly decreased for the sound leg compared to the prosthetic leg.The “more appropriate” prosthesis design also yielded decreased stride-to-stride fluctuations compared to the “less appropriate” prosthesis. Through the adaptation, a significant U-shaped quadratic trend was present, with significantly increased stride-to-stride fluctuations at the initial visit and final visit compared to the middle of the adaptation period. (mean ± SEM) SL: sound leg; PL: prosthetic leg; MA: “more appropriate” prosthesis; LA: “less appropriate” prosthesis; V1: initial visit; V2: second visit; V3: final visit. *Sig. at p<0.05.
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pone-0100125-g001: Stride-to-stride fluctuations for the ankle were significantly decreased for the sound leg compared to the prosthetic leg.The “more appropriate” prosthesis design also yielded decreased stride-to-stride fluctuations compared to the “less appropriate” prosthesis. Through the adaptation, a significant U-shaped quadratic trend was present, with significantly increased stride-to-stride fluctuations at the initial visit and final visit compared to the middle of the adaptation period. (mean ± SEM) SL: sound leg; PL: prosthetic leg; MA: “more appropriate” prosthesis; LA: “less appropriate” prosthesis; V1: initial visit; V2: second visit; V3: final visit. *Sig. at p<0.05.

Mentions: At the ankle, there were significant main effects for leg, prosthesis, and visit (Figure 1). The sound leg ankle had significantly reduced λ compared to the prosthetic ankle (F1,23 = 13.897, p = 0.001) with an observed power of 0.946. The “more appropriate” prosthesis resulted in reduced λ when compared to the “less appropriate” prosthesis design (F1,23 = 4.849, p = 0.038) with an observed power of 0.559. For visit there was also a significant effect (F2,46 = 3.164, p = 0.050) with an observed power of 0.578. Post-hoc analysis showed the initial visit (i.e. initial fitting) to have a significantly increased λ compared to the second visit (i.e. middle of 3 week period; p = 0.032), and the final visit (i.e. end of adaptation period) had a significantly increased λ compared to the second visit (p = 0.042). The λ values for the initial and final visits were not statistically different (p = 0.577). This yielded a significant U-shaped quadratic trend across the adaptation period (p = 0.013). There were no significant interactions.


Adaptation and prosthesis effects on stride-to-stride fluctuations in amputee gait.

Wurdeman SR, Myers SA, Jacobsen AL, Stergiou N - PLoS ONE (2014)

Stride-to-stride fluctuations for the ankle were significantly decreased for the sound leg compared to the prosthetic leg.The “more appropriate” prosthesis design also yielded decreased stride-to-stride fluctuations compared to the “less appropriate” prosthesis. Through the adaptation, a significant U-shaped quadratic trend was present, with significantly increased stride-to-stride fluctuations at the initial visit and final visit compared to the middle of the adaptation period. (mean ± SEM) SL: sound leg; PL: prosthetic leg; MA: “more appropriate” prosthesis; LA: “less appropriate” prosthesis; V1: initial visit; V2: second visit; V3: final visit. *Sig. at p<0.05.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4067312&req=5

pone-0100125-g001: Stride-to-stride fluctuations for the ankle were significantly decreased for the sound leg compared to the prosthetic leg.The “more appropriate” prosthesis design also yielded decreased stride-to-stride fluctuations compared to the “less appropriate” prosthesis. Through the adaptation, a significant U-shaped quadratic trend was present, with significantly increased stride-to-stride fluctuations at the initial visit and final visit compared to the middle of the adaptation period. (mean ± SEM) SL: sound leg; PL: prosthetic leg; MA: “more appropriate” prosthesis; LA: “less appropriate” prosthesis; V1: initial visit; V2: second visit; V3: final visit. *Sig. at p<0.05.
Mentions: At the ankle, there were significant main effects for leg, prosthesis, and visit (Figure 1). The sound leg ankle had significantly reduced λ compared to the prosthetic ankle (F1,23 = 13.897, p = 0.001) with an observed power of 0.946. The “more appropriate” prosthesis resulted in reduced λ when compared to the “less appropriate” prosthesis design (F1,23 = 4.849, p = 0.038) with an observed power of 0.559. For visit there was also a significant effect (F2,46 = 3.164, p = 0.050) with an observed power of 0.578. Post-hoc analysis showed the initial visit (i.e. initial fitting) to have a significantly increased λ compared to the second visit (i.e. middle of 3 week period; p = 0.032), and the final visit (i.e. end of adaptation period) had a significantly increased λ compared to the second visit (p = 0.042). The λ values for the initial and final visits were not statistically different (p = 0.577). This yielded a significant U-shaped quadratic trend across the adaptation period (p = 0.013). There were no significant interactions.

Bottom Line: There was also a significant effect for the time point in the adaptation period (F2,46 = 3.164, p = 0.050).Through the adaptation period, a freezing and subsequent freeing of dynamic degrees of freedom was seen as the λ at the ankle decreased at the midpoint of the adaptation period compared to the initial prosthesis fitting (p = 0.032), but then increased at the end compared to the midpoint (p = 0.042).No differences were seen between the initial fitting and the end of the adaptation for λ (p = 0.577).

View Article: PubMed Central - PubMed

Affiliation: Biomechanics Research Building, University of Nebraska at Omaha, Omaha, Nebraska, United States of America; Advanced Prosthetics Center, Omaha, Nebraska, United States of America.

ABSTRACT
Twenty-four individuals with transtibial amputation were recruited to a randomized, crossover design study to examine stride-to-stride fluctuations of lower limb joint flexion/extension time series using the largest Lyapunov exponent (λ). Each individual wore a "more appropriate" and a "less appropriate" prosthesis design based on the subject's previous functional classification for a three week adaptation period. Results showed decreased λ for the sound ankle compared to the prosthetic ankle (F1,23 = 13.897, p = 0.001) and a decreased λ for the "more appropriate" prosthesis (F1,23 = 4.849, p = 0.038). There was also a significant effect for the time point in the adaptation period (F2,46 = 3.164, p = 0.050). Through the adaptation period, a freezing and subsequent freeing of dynamic degrees of freedom was seen as the λ at the ankle decreased at the midpoint of the adaptation period compared to the initial prosthesis fitting (p = 0.032), but then increased at the end compared to the midpoint (p = 0.042). No differences were seen between the initial fitting and the end of the adaptation for λ (p = 0.577). It is concluded that the λ may be a feasible clinical tool for measuring prosthesis functionality and adaptation to a new prosthesis is a process through which the motor control develops mastery of redundant degrees of freedom present in the system.

Show MeSH
Related in: MedlinePlus