Int. J. Exergy, Vol. 25, No. 1, 2018 1 Copyright © 2018 Inderscience Enterprises Ltd. Assessment of the work efficiency with exergy method in ageing muscles and healthy and enlarged hearts Jale Çatak* Department of Nutrition and Dietetics, Yeditepe University, Istanbul, 34755, Turkey Email: jale.catak@yeditepe.edu.tr *Corresponding author Mustafa Özilgen Department of Food Engineering, Yeditepe University, Istanbul, 34755, Turkey Email: mozilgen@yeditepe.edu.tr Ali Bahadır Olcay Department of Mechanical Engineering, Yeditepe University, Istanbul, 34755, Turkey Email: bahadir.olcay@yeditepe.edu.tr Bayram Yılmaz Faculty of Medicine, Department of Physiology, Yeditepe University, Istanbul, 34755, Turkey Email: byilmaz@yeditepe.edu.tr Abstract: Thermodynamic aspects of skeletal and cardiac muscle work performance are assessed with the data obtained from the literature. Since the second law muscle work efficiency decreases with declining metabolic energy conversion efficiency in the mitochondria, followed by structural failure of the muscles during ageing, the thermodynamic aspects of the muscle work ageing process were simulated by incorporating the decreasing second law muscle work efficiency with the exercise data obtained with the healthy young adults. Within limits of the data analysed here, glucose utilisation ability of the cardiac muscle appears to be the most critical factor determining its work performance. The left and the right ventricles of the enlarged heart had the ability of utilising approximately 3.5 and 2.7 times less glucose, respectively, than their healthy counterparts. The work performance and the entropy generation by the enlarged and the healthy hearts maintained the same ratios.