Human cardiomyocytes can be studied as a single cell on microposts or as a tissue on tissue posts. (A) To study engineered heart tissues, one post remains rigid, while the other is flexible to measure deflection. (B) In some cases, post deflection is measured by a GMR sensor which senses the movement of an embedded magnet inside the flexible post. (C) The graph shows correlation between the deflection measured optically and the deflection reported by the GMR sensor. (D) Tissue posts with braces to vary effective length and modify stiffness. (E) Post deflection, twitch force, twitch velocity, and twitch power for various post lengths. A, D, and E are adapted with permission.[130] Copyright 2018, Elsevier. B and C are adapted under the terms of Creative Commons Attribution 4.0 International Public License.[129] Copyright 2016, Mary Ann Liebert, Inc. publishers.