Key result
Differences in maximum specific force across fast MHC isoforms were eliminated when controlled for half-sarcomere MHC content, but slow fibers produced less force per cross bridge than fast fibers.
Population
Single, Triton X-100-permeabilized rat diaphragm muscle fibers expressing different myosin heavy chain…
Comparison
Activation in the presence of a high-calcium… vs Comparison between fast and slow MHC isoforms
Design
Preclinical
Authors
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Slow fibers generate less force per cross-bridge than fast; leaves open relevance to human cardiac contractility.
The lower force produced by slow muscle fibers compared to fast fibers may be due to less force per cross bridge rather than just the number of cross bridges available.
Geiger et al. (2000) studied this question. MHC isoform composition (fast vs slow) vs. Different MHC isoforms was evaluated on Maximum specific force (force per cross-sectional area). Differences in maximum specific force across fast MHC isoforms were eliminated when controlled for half-sarcomere MHC content, but slow fibers produced less force per cross bridge than fast fibers.
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