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Transverse Strains in Muscle Fascicles during Voluntary Contraction: A 2D Frequency Decomposition of B-Mode Ultrasound Images.

Wakeling JM, Randhawa A - Int J Biomed Imaging (2014)

Bottom Line: In pennate muscle, this transverse expansion results in the fibres rotating to greater pennation angle, with a consequent reduction in their contractile velocity in a process known as gearing.The transverse fascicle strains were calculated from their wavelengths within the images.These methods showed that the transverse strain increases while the longitudinal fascicle length decreases; however, the extent of these strains was smaller than expected.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6.

ABSTRACT
When skeletal muscle fibres shorten, they must increase in their transverse dimensions in order to maintain a constant volume. In pennate muscle, this transverse expansion results in the fibres rotating to greater pennation angle, with a consequent reduction in their contractile velocity in a process known as gearing. Understanding the nature and extent of this transverse expansion is necessary to understand the mechanisms driving the changes in internal geometry of whole muscles during contraction. Current methodologies allow the fascicle lengths, orientations, and curvatures to be quantified, but not the transverse expansion. The purpose of this study was to develop and validate techniques for quantifying transverse strain in skeletal muscle fascicles during contraction from B-mode ultrasound images. Images were acquired from the medial and lateral gastrocnemii during cyclic contractions, enhanced using multiscale vessel enhancement filtering and the spatial frequencies resolved using 2D discrete Fourier transforms. The frequency information was resolved into the fascicle orientations that were validated against manually digitized values. The transverse fascicle strains were calculated from their wavelengths within the images. These methods showed that the transverse strain increases while the longitudinal fascicle length decreases; however, the extent of these strains was smaller than expected.

No MeSH data available.


Related in: MedlinePlus

Error Analysis for the Selection of the Moment of Frequency, m. The correlation between the inclination angle determined by manual digitization, θd, and the inclination angle determined from the discrete Fourier transform, θF, is shown for different values of m (a). The root-mean-square error between these terms is shown in (b). Points show the mean ± SEM (n = 99).
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fig3: Error Analysis for the Selection of the Moment of Frequency, m. The correlation between the inclination angle determined by manual digitization, θd, and the inclination angle determined from the discrete Fourier transform, θF, is shown for different values of m (a). The root-mean-square error between these terms is shown in (b). Points show the mean ± SEM (n = 99).

Mentions: The estimates of the inclination angle based on the Fourier transform were dependent on the moment of frequency, m, selected. There was no significant effect of m on the correlation between the inclination angle determined by manual digitization, θd, and the inclination angle determined from the discrete Fourier transform, θF; however, there was a significant effect of m on the root-mean-square error between these values (Figure 3). A value of m = 5 resulted to be close to the greatest correlation and the lowest RMSE and so was selected for further analysis. When considered across all subjects, muscles, and contraction conditions, the RMSE for m = 5 was 3.4°. The error between the two measures of inclination was partly due to the smaller amplitude of change in inclination for the θF than for θd.


Transverse Strains in Muscle Fascicles during Voluntary Contraction: A 2D Frequency Decomposition of B-Mode Ultrasound Images.

Wakeling JM, Randhawa A - Int J Biomed Imaging (2014)

Error Analysis for the Selection of the Moment of Frequency, m. The correlation between the inclination angle determined by manual digitization, θd, and the inclination angle determined from the discrete Fourier transform, θF, is shown for different values of m (a). The root-mean-square error between these terms is shown in (b). Points show the mean ± SEM (n = 99).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4195266&req=5

fig3: Error Analysis for the Selection of the Moment of Frequency, m. The correlation between the inclination angle determined by manual digitization, θd, and the inclination angle determined from the discrete Fourier transform, θF, is shown for different values of m (a). The root-mean-square error between these terms is shown in (b). Points show the mean ± SEM (n = 99).
Mentions: The estimates of the inclination angle based on the Fourier transform were dependent on the moment of frequency, m, selected. There was no significant effect of m on the correlation between the inclination angle determined by manual digitization, θd, and the inclination angle determined from the discrete Fourier transform, θF; however, there was a significant effect of m on the root-mean-square error between these values (Figure 3). A value of m = 5 resulted to be close to the greatest correlation and the lowest RMSE and so was selected for further analysis. When considered across all subjects, muscles, and contraction conditions, the RMSE for m = 5 was 3.4°. The error between the two measures of inclination was partly due to the smaller amplitude of change in inclination for the θF than for θd.

Bottom Line: In pennate muscle, this transverse expansion results in the fibres rotating to greater pennation angle, with a consequent reduction in their contractile velocity in a process known as gearing.The transverse fascicle strains were calculated from their wavelengths within the images.These methods showed that the transverse strain increases while the longitudinal fascicle length decreases; however, the extent of these strains was smaller than expected.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada V5A 1S6.

ABSTRACT
When skeletal muscle fibres shorten, they must increase in their transverse dimensions in order to maintain a constant volume. In pennate muscle, this transverse expansion results in the fibres rotating to greater pennation angle, with a consequent reduction in their contractile velocity in a process known as gearing. Understanding the nature and extent of this transverse expansion is necessary to understand the mechanisms driving the changes in internal geometry of whole muscles during contraction. Current methodologies allow the fascicle lengths, orientations, and curvatures to be quantified, but not the transverse expansion. The purpose of this study was to develop and validate techniques for quantifying transverse strain in skeletal muscle fascicles during contraction from B-mode ultrasound images. Images were acquired from the medial and lateral gastrocnemii during cyclic contractions, enhanced using multiscale vessel enhancement filtering and the spatial frequencies resolved using 2D discrete Fourier transforms. The frequency information was resolved into the fascicle orientations that were validated against manually digitized values. The transverse fascicle strains were calculated from their wavelengths within the images. These methods showed that the transverse strain increases while the longitudinal fascicle length decreases; however, the extent of these strains was smaller than expected.

No MeSH data available.


Related in: MedlinePlus