{"216371":{"#nid":"216371","#data":{"type":"news","title":"Model Finds Common Muscle Control Patterns Governing the Motion of Swimming Animals","body":[{"value":"\u003Cp\u003EWhat do swimmers like trout, eels and sandfish lizards have in common? According to a new study, the similar timing patterns that these animals use to contract their muscles and produce undulatory swimming motions can be explained using a simple model. Scientists have now applied the new model to understand the connection between electrical signals and body movement in the sandfish.\u003C\/p\u003E\u003Cp\u003EMost swimming creatures rely on an undulating pattern of body movement to propel themselves through fluids. Though differences in body flexibility may lead to different swimming styles, scientists have found \u201cneuromechanical phase lags\u201d in nearly all swimmers. These lags are characterized by a wave of muscle activation that travels faster down the body than the wave of body curvature.\u003C\/p\u003E\u003Cp\u003EA study of the sandfish lizard \u2013 which \u201cswims\u201d through sand \u2013 led to development of the new model, which researchers believe could also be used to study other swimming animals. Beyond assisting the study of locomotion in a wide range of animals, the findings could also help researchers design efficient swimming robots.\u003C\/p\u003E\u003Cp\u003E\u201cA graduate student in our group, Yang Ding, who is now at the University of Southern California, was able to develop a theory that could explain the kinematics of how this animal swims as well as the timing of the nervous system control signals,\u201d said \u003Ca href=\u0022https:\/\/www.physics.gatech.edu\/user\/daniel-goldman\u0022\u003EDaniel Goldman\u003C\/a\u003E, an associate professor in the \u003Ca href=\u0022http:\/\/www.physics.gatech.edu\/\u0022\u003ESchool of Physics\u003C\/a\u003E at the Georgia Institute of Technology. \u201cFor animals swimming in fluids using an undulating movement, there are basic physical constraints on how they must activate their muscles. We think we have uncovered an important mechanism that governs this kind of swimming.\u201d\u003C\/p\u003E\u003Cp\u003EThe research was reported June 3 in the early edition of the journal \u003Cem\u003EProceedings of the National Academy of Sciences\u003C\/em\u003E. It was sponsored by the National Science Foundation\u2019s Physics of Living Systems program, the Micro Autonomous Systems and Technology (MAST) program of the Army Research Office, and the Burroughs Wellcome Fund.\u003C\/p\u003E\u003Cp\u003EUndulatory locomotion is a gait in which thrust is produced in the opposite direction from a traveling wave of body bending. Because it is so commonly used by animals, this mode of locomotion has been widely used for studying the neuromechanical principles of movement.\u003C\/p\u003E\u003Cp\u003ESarah Sharpe, the paper\u2019s second author and a graduate student in Georgia Tech\u2019s Interdisciplinary Bioengineering Program, led laboratory experiments studying undulatory swimming in sandfish lizards. She used X-ray imaging to visualize how the animals swam through sand that was composed of tiny glass spheres.\u003C\/p\u003E\u003Cp\u003EAt the same time their swimming movements were being tracked, a set of four hair-thin electrodes implanted in the lizards\u2019 bodies were providing information on when their muscles were activated. The two information sources allowed the researchers to compare the electrical muscle activity to the lizards\u2019 body motion.\u003C\/p\u003E\u003Cp\u003E\u201cThe lizards propagate a wave of muscle activations, contracting the muscles close to their heads first, then the muscles at the midpoint of their body, then their tail,\u201d said Sharpe. \u201cThey send a wave of muscle of contraction down their bodies, which creates a wave of curvature that allows them to swim. This wave of activation travels faster than the wave of curvature down the body, resulting in different timing relationships, known as phase differences, between muscle contracts and bending along the body.\u201d\u003C\/p\u003E\u003Cp\u003ESand acts like a frictional fluid as the sandfish swims through it. However, a sandfish swimming through sand is simpler to model than a fish swimming through water because the sand lacks the vortices and other complex behavior of water \u2013 and the friction of the sand eliminates inertia.\u003C\/p\u003E\u003Cp\u003E\u201cTheoretically, it is difficult to calculate all of the forces acting on a fish or an eel swimming in a real fluid,\u201d said Goldman. \u201cBut for a sandfish, you can calculate pretty much everything.\u201d\u003Cbr \/\u003EThe relative simplicity of the system allowed the research team \u2013 which also included Georgia Tech professor Kurt Wiesenfeld \u2013 to develop a simple model showing how the muscle activation relates to motion. The model showed that combining synchronized torques from distant points in the lizards\u2019 bodies with local traveling torques is what creates the neuromechanical phase lag.\u003C\/p\u003E\u003Cp\u003E\u201cThis is one of the simplest, if not the simplest, models of swimming that reproduces the neuromechanical phase lag phenomenon,\u201d Sharpe said. \u201cAll we really had to pay attention to was the external forces acting on an animal\u2019s body. We realized that this timing relationship would emerge for any undulatory animal with distributed forces along its body. Understanding this concept can be used as the foundation to begin understanding timing patterns in all other swimmers.\u201d\u003C\/p\u003E\u003Cp\u003EThe sandfish swims using a simple single-period sinusoidal wave with constant amplitude. A key finding that facilitated the model\u2019s development was that the sandfish\u2019s body is extremely flexible, allowing internal forces \u2013 body stiffness \u2013 to be ignored.\u003C\/p\u003E\u003Cp\u003E\u201cThis animal turns out to be like a little limp noodle,\u201d said Goldman. \u201cHaving that result in the theory makes everything else pop out.\u201d\u003C\/p\u003E\u003Cp\u003EThe model shows that the waveform used by the sandfish should allow it to swim the farthest with the least expenditure of energy. Swimming robots adopting the same waveform should therefore be able to maximize their range.\u003C\/p\u003E\u003Cp\u003EGoldman and his colleagues have been studying the sandfish, a native of the northern African desert, for more than six years.\u003C\/p\u003E\u003Cp\u003E\u201cSandfish are among the champions of all sand diggers, swimmers and burrowers,\u201d said Goldman. \u201cThis lizard has provided us with an interesting entry point into swimming because its environment is surprisingly simple and behavior is simple. It turns out that this little sand-dweller may be able to tell us things about swimming more generally.\u201d\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research has been supported by the National Science Foundation Physics of Living Systems (PoLS) under grants PHY-0749991 and PHY-1150760, by the U.S. Army Research Laboratory\u2019s (ARL) Micro Autonomous Systems and Technology (MAST) Program under cooperative agreement W911NF-11-1-0514, and by the Burroughs Wellcome Fund Career Award. Any conclusions are those of the authors and do not necessarily represent the official views of the NSF or ARL.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Yang Ding, Sarah Sharpe, Kurt Wiesenfeld and Daniel Goldman, \u201cEmergence of the advancing neuromechanical phase in resistive force dominated medium,\u201d (Proceedings of the National Academy of Sciences, 2013).\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia\u0026nbsp; 30332-0181\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E)\u003Cbr \/\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003Cbr \/\u003E\u003Cbr \/\u003E\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EWhat do swimmers like trout, eels and sandfish lizards have in common? According to a new study, the similar timing patterns that these animals use to contract their muscles and produce undulatory swimming motions can be explained using a simple model. Scientists have now applied the new model to understand the connection between electrical signals and body movement in the sandfish.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"A new study shows that swimming animals use similar timing patterns to contract their muscles"}],"uid":"27303","created_gmt":"2013-06-04 15:36:53","changed_gmt":"2016-10-08 03:14:20","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2013-06-04T00:00:00-04:00","iso_date":"2013-06-04T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"216341":{"id":"216341","type":"image","title":"X-ray of Sandfish Swimming","body":null,"created":"1449180114","gmt_created":"2015-12-03 22:01:54","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"X-ray of Sandfish Swimming","file":{"fid":"197119","name":"sandfish5.jpg","image_path":"\/sites\/default\/files\/images\/sandfish5_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/sandfish5_0.jpg","mime":"image\/jpeg","size":253357,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/sandfish5_0.jpg?itok=HyTzMGzh"}},"216351":{"id":"216351","type":"image","title":"Sandfish Lizard","body":null,"created":"1449180114","gmt_created":"2015-12-03 22:01:54","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"Sandfish Lizard","file":{"fid":"197120","name":"sandfish54.jpg","image_path":"\/sites\/default\/files\/images\/sandfish54_1.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/sandfish54_1.jpg","mime":"image\/jpeg","size":741621,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/sandfish54_1.jpg?itok=ifnOfwQl"}},"216361":{"id":"216361","type":"image","title":"Sandfish Lizard","body":null,"created":"1449180114","gmt_created":"2015-12-03 22:01:54","changed":"1475894882","gmt_changed":"2016-10-08 02:48:02","alt":"Sandfish Lizard","file":{"fid":"197121","name":"sandfish77.jpg","image_path":"\/sites\/default\/files\/images\/sandfish77_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/sandfish77_0.jpg","mime":"image\/jpeg","size":792900,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/sandfish77_0.jpg?itok=qTYF-Xey"}}},"media_ids":["216341","216351","216361"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"146","name":"Life Sciences and Biology"},{"id":"152","name":"Robotics"}],"keywords":[{"id":"12040","name":"Daniel Goldman"},{"id":"169581","name":"sandfish"},{"id":"166937","name":"School of Physics"},{"id":"167350","name":"swimming"},{"id":"67541","name":"undulatory swimming"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"},{"id":"39521","name":"Robotics"}],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}