Researchers at the University of Washington demonstrated that muscle power is generated by forces in multiple directions, not just straight up and down the muscle as was previously thought, according to a study published in Proceedings of the Royal Society B.
Muscles generate power through contractions of filaments of myosin tugging on filaments of actin, which has been understood for more than 50 years. However, the researchers discovered that approximately 20% to 50% of power is also created through the filament lattice spacing, the radial distance between actin and myosin filaments, created as a muscle bulges.
The researchers made this discovery while using computer modeling to test the geometry and physics of muscle force, and the computer results were validated through X-ray diffraction experiments on moth flight muscles, which are very similar to human cardiac muscles.
“The predominant thinking of the last 50 years is that 100% of the muscle force comes from changes as muscles shorten and myosin and actin filaments overlap,” C. David Williams, PhD, study author and a postdoctoral researcher at Harvard University, stated in a news release. “But when we isolated the effects of filament overlap we only got about half the change in force that physiologists know muscles are capable of producing.”
According to Williams, the rest of the force is a result of the latticework of filaments as it expands outward in bulging muscle.
“One of the major discoveries that David Williams brought to light is that force is generated in multiple directions, not just along the long axis of muscle as everyone thinks, but also in the radial direction,” Thomas Daniel, UW professor of biology and co-author on the paper, stated in the release. “This aspect of muscle force generation has flown under the radar for decades and is now becoming a critical feature of our understanding of normal and pathological aspects of muscle.”
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