AdventHelath 1 article published in JoVE Biochemistry Measuring Mitochondrial Electron Transfer Complexes in Previously Frozen Cardiac Tissue from the Offspring of Sow: A Model to Assess Exercise-Induced Mitochondrial Bioenergetics Changes Daniel Barrera1, Sierra Upton2, Megan Rauch3, Tara Notarianni4, Ki Suk Eum5, Megan Liberty6, Sarmila Venkoba Sah7, Robert Liu8, Sean Newcomer9, Linda E. May10, Emre Agbas11, Jessica Sage12, Edina Kosa7, Abdulbaki Agbas7,13 1AdventHelath, 2University of Illinois Chicago School of Public Health, 3Lincoln Memorial University, 4Cincinnati Children’s Hospital Medical Center, 7Kansas City University, 8Roblex Rex Veterans Affairs Medical Center, 9California State University San Marcos, 10East Carolina University, 11Massachusetts Institute of Technology, 12Boehringer Ingelheim Norway KS, 13Heartland Center for Mitochondrial Medicine Preparation of mitochondria-enriched samples from previously frozen archived solid tissues allowed the investigators to perform both functional and analytical assessments of mitochondria in various experimental modalities. This study demonstrates how to prepare mitochondria-enriched preparations from frozen heart tissue and perform analytical assessments of mitochondria.