Herzog, WalterJohnston, Kaleena2015-04-302015-06-222015-04-302015Johnston, K. (2015). An Examination of Sarcomere Length Non-uniformities in Actively Stretched Muscle Myofibrils (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/24879http://hdl.handle.net/11023/2195Residual force enhancement (RFE) is a characteristic of skeletal muscle describing the increase in isometric steady-state force following an active stretch, compared to the force of an isometric contraction at the same final length. It has been argued that RFE is a result of unstable sarcomeres on the descending limb of the force-length relationship, causing long, weak sarcomeres to lengthen more than short, strong sarcomeres when a myofibril is actively stretched, as described by the Sarcomere Length Non-uniformity Theory (SLNT). While the SLNT is currently the most popular explanation for RFE, its primary predictions have never been experimentally tested. In this research we performed experiments on rabbit psoas muscle myofibrils, comparing isometric contractions to isometric contractions following active stretch in order to examine the predictions of the SLNT. The results suggest that, while sarcomere length non-uniformities may play a role, the SLNT does not fully capture the mechanism of RFE.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.PhysiologyEngineering--BiomedicalSkeletal MuscleMyofibrilSarcomereResidual force enhancementNon-uniformityHistory dependencemaster thesis10.11575/PRISM/24879