An idea with its origins in ballistic prey catching\u2014the way toads and chameleons snatch food with their tongues\u2014may change fundamental views of muscle movement while powering a new approach to prosthetics.<\/p>\n
After a decade of work, lead author\u00a0Kiisa Nishikawa<\/strong>, Regents\u2019 professor of biology at Northern Arizona University, and an international team of collaborators have published their hypothesis about spring-loaded muscles. Their paper, \u201cIs Titin a \u2018Winding Filament\u2019? A New Twist on Muscle Contraction,\u201d appears\u00a0online<\/a>\u00a0in\u00a0Proceedings of the Royal Society B<\/em>.<\/p>\n The implications run deep in the world of movement neuroscience and hold promise for a burgeoning field of pioneers in bionics, exoskeleton robotic suits and prosthetics so advanced that the word \u201ctranshumanism\u201d is becoming common.<\/p>\n \u201cIt turns out that our bodies are interacting with the environment all the time and our muscles can manage that interaction in a smart way without any intervention from the brain,\u201d Nishikawa said. \u201cThere\u2019s never been a model that explained how muscles are able to do that until now.\u201d<\/p>\n Nishikawa\u2019s approach lends credence to one of the two schools of thought that attempts to explain how the brain controls movement; namely, that the body and muscles \u201chave a lot of passive-dynamic properties,\u201d Nishikawa said, \u201cand the job of the brain is to learn not to interfere with the passive dynamics.\u201d<\/p>\n To demonstrate the concept, Nishikawa and her team built a physical model over the summer that \u201ccaptures all the non-linear properties of muscle\u201d that allow it to adapt instantaneously to changes in the environment, she said. Nishikawa is working with NAU mechanical engineering associate professor\u00a0John Tester<\/strong>\u00a0to design a working prototype.<\/p>\n The practical applications extend to \u201cany device worn by humans where ultimate control comes from the human brain,\u201d Nishikawa said. \u201cThe potential to improve those devices using this idea is good because the human brain expects its actuators to be muscles, so if you make them work like muscles, it\u2019s bound to be more comfortable, efficient and stable.\u201d<\/p>\n Getting to the spring-property conclusion took 10 years of grant-funded research and a complete retooling of Nishikawa\u2019s lab, which had previously focused on the\u00a0study of feeding in toads and chameleons<\/a>\u00a0to understand the power amplification in muscles that produces ballistic movements.<\/p>\n \u201cWe started asking the question, \u2018What do muscles contribute to control?\u2019” Nishikawa said. \u201cBecause of the emphasis on fast movement, we were really interested in looking at and accounting for the spring-like properties of muscles.\u201d<\/p>\n Nishikawa explained that most muscle theory was developed from 1925-1975, based on the idea that muscles stretch tendons, and the recovery of energy from the tendons led to high-power movement. But in the 1980s, the relatively late discovery of titin, the largest protein ever found, raised questions about that conventional view. A few other researchers proposed early ideas about titin as a spring, but their perspective did not include Nishikawa\u2019s findings about titin winding.<\/p>\n \u201cOur arms and legs are chock-full of tendons,\u201d Nishikawa said, \u201cbut our heads and our jaws are not\u2014there are some, but they are small and short. So we thought there had to be a spring inside the actual working unit of muscle.\u201d<\/p>\n Titin, goes the hypothesis, is that spring. At a micron in length and 2 nanometers in diameter, it cannot be directly observed. \u201cBut we can model it,\u201d Nishikawa said, \u201cand it accounts for a lot of unexplained facts.\u201d The computer modeling was performed by Nishikawa\u2019s collaborators at the University of British Columbia.<\/p>\n Nishikawa pointed to recent prosthetics advances by\u00a0iWalk<\/a>\u00a0and\u00a0SpringActive<\/a>\u00a0as opportunities to put her ideas into action. \u201cI would love to partner with companies like these to provide actuation that\u2019s more compatible with how the human brain interacts with muscles,\u201d she said. \u201cHaving been a scientist who\u2019s done a lot of basic research, I\u2019m excited that something practical might come of it.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"