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Frequency dependence of power and its implications for contractile function of muscle fibers from the digital flexors of horses.

Title: Frequency dependence of power and its implications for contractile function of muscle fibers from the digital flexors of horses.
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Name(s): Butcher, Michael T, author
Bertram, John E A, author
Syme, Douglas A, author
Hermanson, John W, author
Chase, P Bryant, author
Type of Resource: text
Genre: Journal Article
Text
Date Issued: 2014-10-07
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: The digital flexors of horses must produce high force to support the body weight during running, and a need for these muscles to generate power is likely limited during locomotion over level ground. Measurements of power output from horse muscle fibers close to physiological temperatures, and when cyclic strain is imposed, will help to better understand the in vivo performance of the muscles as power absorbers and generators. Skinned fibers from the deep (DDF) and superficial (SDF) digital flexors, and the soleus (SOL) underwent sinusoidal oscillations in length over a range of frequencies (0.5-16 Hz) and strain amplitudes (0.01-0.06) under maximum activation (pCa 5) at 30°C. Results were analyzed using both workloop and Nyquist plot analyses to determine the ability of the fibers to absorb or generate power and the frequency dependence of those abilities. Power absorption was dominant at most cycling frequencies and strain amplitudes in fibers from all three muscles. However, small amounts of power were generated (0.002-0.05 Wkg(-1)) at 0.01 strain by all three muscles at relatively slow cycling frequencies: DDF (4-7 Hz), SDF (4-5 Hz) and SOL (0.5-1 Hz). Nyquist analysis, reflecting the influence of cross-bridge kinetics on power generation, corroborated these results. The similar capacity for power generation by DDF and SDF versus lower for SOL, and the faster frequency at which this power was realized in DDF and SDF fibers, are largely explained by the fast myosin heavy chain isoform content in each muscle. Contractile function of DDF and SDF as power absorbers and generators, respectively, during locomotion may therefore be more dependent on their fiber architectural arrangement than on the physiological properties of their muscle fibers.
Identifier: FSU_pmch_25293602 (IID), 10.14814/phy2.12174 (DOI), PMC4254099 (PMCID), 25293602 (RID), 25293602 (EID), 2/10/e12174 (PII)
Keywords: Absorption, Deep digital flexor, Skinned fiber, Superficial digital flexor, Workloop
Grant Number: R01 HL063974
Publication Note: This NIH-funded author manuscript originally appeared in PubMed Central at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4254099.
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_pmch_25293602
Owner Institution: FSU
Is Part Of: Physiological reports.
2051-817X
Issue: iss. 10, vol. 2

Choose the citation style.
Butcher, M. T., Bertram, J. E. A., Syme, D. A., Hermanson, J. W., & Chase, P. B. (2014). Frequency dependence of power and its implications for contractile function of muscle fibers from the digital flexors of horses. Physiological Reports. Retrieved from http://purl.flvc.org/fsu/fd/FSU_pmch_25293602