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Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: potential index of lateral force transmission.

ABSTRACT: The strain rate (SR) tensor measures the principal directions and magnitude of the instantaneous deformation; this study aims to track age-related changes in the 2D SR tensor in the medial gastrocnemius during passive joint rotation and active isometric contraction.SR tensors were derived from velocity encoded magnetic resonance phase-contrast images in nine young (28 years) and eight senior (78 years) women. Strain rates along and in the cross-section of the fiber were calculated from the SR tensor and used to derive the out-plane SR. Age-related and regional differences in the SR eigenvalues, orientation, and the angle between the SR and muscle fiber (SR-fiber angle) were statistically analyzed.SR along the fiber was significantly different between the cohorts during isometric contraction with higher values in the young (P?

SUBMITTER: Sinha U

PROVIDER: S-EPMC4287463 | biostudies-literature | 2015 May

REPOSITORIES: biostudies-literature

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Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: potential index of lateral force transmission.

Sinha Usha U Malis Vadim V Csapo Robert R Moghadasi Ali A Kinugasa Ryuta R Sinha Shantanu S

Magnetic resonance in medicine 20140708 5

<h4>Purpose</h4>The strain rate (SR) tensor measures the principal directions and magnitude of the instantaneous deformation; this study aims to track age-related changes in the 2D SR tensor in the medial gastrocnemius during passive joint rotation and active isometric contraction.<h4>Methods</h4>SR tensors were derived from velocity encoded magnetic resonance phase-contrast images in nine young (28 years) and eight senior (78 years) women. Strain rates along and in the cross-section of the fibe ...[more]

PMID: 25046255

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Project description:BACKGROUND:Strain rate (SR) is a measure of the rate of regional deformation that can be computed by analyzing velocity-encoded phase-contrast 2D images. Recent studies have explored the changes in normal components of the strain tensor in aging muscle, while shear strain may also provide valuable information. PURPOSE:To compute the shear SR from velocity-encoded MRI of the lower leg and to study the correlation of SR parameters measured in the medial gastrocnemius (MG) to muscle force in a cohort of young and senior subjects. STUDY TYPE:Prospective cohort study. SUBJECTS:Six young (26.1?±?2.3 years) and six senior (76.7?±?8.3 years) healthy females; two other subjects were scanned on three separate occasions for repeatability studies. FIELD STRENGTH/SEQUENCE:1.5T using a single oblique sagittal slice with velocity-encoding in three directions (velocity-encoded phase contrast gradient echo sequence). ASSESSMENT:Age-related and regional differences in the SR eigenvalues (SRfiber , SRin-plane ), normal SRs (SRff , SRcc ), and shear SRs (SRfc , SRfc_max ) were statistically analyzed. STATISTICAL TESTS:Difference between young and senior cohorts were assessed using two-way analysis of variance (ANOVAs). The coefficient of variation and repeatability coefficient were calculated from repeat studies. Univariate and stepwise multivariable linear regression was performed to identify predictors of force. RESULTS:During isometric plantarflexion contraction, SRs in the principal basis (SRfiber , SRin-plane ) and maximum shear SR (SRfc_max ) was significantly lower in the senior cohort (P < 0.05). On multiple variable regression, maximum shear SR (SRfc_max ) and normal SR in the fiber cross-section (SRcc ) were significantly associated with force (R?=?0.681, F?=?14.034, P < 0.001). DATA CONCLUSION:This study establishes that computation of shear strain is feasible and is a significant predictor of force variability with age. LEVEL OF EVIDENCE:2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1351-1357.

Project description:Enhanced muscle weakness is commonly experienced following stroke and may be accompanied by increased susceptibility to fatigue. To examine the contributions of central and peripheral factors to isometric muscle fatigue in stroke survivors, this study investigates changes in motor unit (MU) mean firing rate, and action potential duration during, and directly following, a sustained submaximal fatiguing contraction at 30% maximum voluntary contraction (MVC). A series of short contractions of the first dorsal interosseous muscle were performed pre- and post-fatigue at 20% MVC, and again following a 10-min recovery period, by 12 chronic stroke survivors. Individual MU firing times were extracted using surface EMG decomposition and used to obtain the spike-triggered average MU action potential waveforms. During the sustained fatiguing contraction, the mean rate of change in firing rate across all detected MUs was greater on the affected side (-0.02 ± 0.03 Hz/s) than on the less-affected side (-0.004 ± 0.003 Hz/s, p = 0.045). The change in firing rate immediately post-fatigue was also greater on the affected side than less-affected side (-13.5 ± 20 and 0.1 ± 19%, p = 0.04). Mean MU firing rates increased following the recovery period on the less-affected side when compared to the affected side (19.3 ± 17 and 0.5 ± 20%, respectively, p = 0.03). MU action potential duration increased post-fatigue on both sides (10.3 ± 1.2 to 11.2 ± 1.3 ms on the affected side and 9.9 ± 1.7 to 11.2 ± 1.9 ms on the less-affected side, p = 0.001 and p = 0.02, respectively), and changes in action potential duration tended to be smaller in subjects with greater impairment (p = 0.04). This study presents evidence of both central and peripheral fatigue at the MU level during isometric fatiguing contraction for the first time in stroke survivors. Together, these preliminary observations indicate that the response to an isometric fatiguing contraction differs between the affected and less-affected side post-stroke, and may suggest that central mechanisms observed here as changes in firing rate are the dominant processes leading to task failure on the affected side.

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Dataset Information

Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: potential index of lateral force transmission.

Publications

Age-related differences in strain rate tensor of the medial gastrocnemius muscle during passive plantarflexion and active isometric contraction using velocity encoded MR imaging: potential index of lateral force transmission.

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