title: In Vivo Sarcomere Length Measurement in Whole Muscles during Passive Stretch and Twitch Contractions.
abstract: Muscle force is dictated by micrometer-scale contractile machines called sarcomeres. Whole-muscle force drops from peak force production to zero with just a few micrometers of sarcomere length change. No current technology is able to capture adequate dynamic sarcomere data in vivo, and thus we lack fundamental data needed to understand human movement and movement disorders. Methods such as diffraction, endoscopy, and optical coherence tomography have been applied to muscle but are prohibitively invasive, sensitive to motion artifact, and/or imprecise. Here, we report dynamic sarcomere length measurement in vivo using a combination of our recently validated resonant reflection spectroscopy method combined with optical frequency domain interferometry. Using a 250-μm-wide fiber optic probe, we captured nanometer sarcomere length changes from thousands of sarcomeres on the sub-millisecond timescale during whole-muscle stretch and twitch contraction. We believe that this demonstrates the first large-scale sensing of sarcomere dynamics in vivo, which is a necessary first step to understand movement disorders and to create patient-specific surgical interventions and rehabilitation.
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California; VA San Diego Healthcare System, San Diego, California.
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Young
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California.
authors.forename: Bill P-P
authors.initials: BP
authors.lastname: Kuo
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, California.
authors.forename: Shawn M
authors.initials: SM
authors.lastname: O'Connor
authors.affiliation: Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California.
authors.forename: Stojan
authors.initials: S
authors.lastname: Radic
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, California; VA San Diego Healthcare System, San Diego, California; Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, California; Rehabilitation Institute of Chicago and Northwestern University, Chicago, Illinois. Electronic address: rlieber@ric.org.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Lieber
mesh_terms: D000818:Animals; D008954:Models, Biological; D009119:Muscle Contraction; D011817:Rabbits; D012518:Sarcomeres / Q000502:physiology*