1. Biomechanists use simulations using muscle models as actuators to exert forces on mechanical skeletons. By combining advanced measurement technology and biomechanical modeling, studying the human locomotion can be objectively done. Based on these studies, physical limitations, muscle pathologies and movement optimization can be performed, which are of great interest to athletes, coaches, researchers and medical doctors. Modeling the musculoskeletal system provides a major insight into the working conditions of the human body which are used in ergonomic design. Muscle modeling may, therefore, revolutionize ergonomic design because its analytical approach is complementary to empirical investigations. The so called Man-Machine Interface (MMI) is the relationship between a human and a machine. MMI is studied in some areas of biomechanics to support investigations in robotics. Integrating humans and robotic machines in one system offers a lot of opportunities for creating a new generation of assistive technologies that can be used in biomedical, industrial and aerospace applications. Analysis of human locomotion Ergonomics Man-Machine Interface Acknowledgements: Prof. Miguel Tavares da Silva, Departamento de Engenharia Mecânica, IST The musculoskeletal system is crucial in locomotion. To improve the muscle movement one can use invasive methods but these can damage the body, so it’s better to use non- invasive methods, namely computational muscle models. This work shows how to understand the models that simulate the muscle dynamics, from a clinical point of view, exploring the muscle’s anatomy and physiology, and analyzing the muscle dynamics from an engineering perspective. Muscle modeling and its associated evolution it’s important to the development of current and future applications and models, which can improve the quality of life of impaired people. 1922 Sartorius muscle experiments: understanding biochemical reactions in muscles – The heat production. (by Hill) 1924 Discover of parity between muscle and a spring-like structure working in a linearly viscous manner (by Gasser and Hill) 1927 Isokinetic experiments – model of a damped spring-like property in series with an undamped string (by Levin and Wyman) 1938 H ILL ’ S M ODEL 19391949 CE in series and in parallel with passive, lightly-damped elastic tissue was understood. (by Katz) - Passive Element (PE) explains the muscle resistance to stretch. - Series Elastic Element (SEE) symbolizes the muscle elasticity, it’s seen as a spring. - Contractile Element (CE) generates muscle Force (F M ), depending on the muscle length (L M ), velocity (V M ) and activation rate (a(t)), and demonstrates, with SEE and PE contribution, the force-length (FL) and the force-velocity relation (FV). On the left: (a)Force Length Relationship (b) Force Velocity Relationship, explained by Hill’s equation On the right: (c) Representations of the force-length and force-velocity properties for the CE (a), the PE (b), the total muscle when fully activated (c), the whole muscle when only 50 % activated (d) Hill’s explicit definition and technique for estimating excitation-activation dynamics.(by Hill) Skeletal muscle is used to affect skeletal movement and maintaining posture. The skeletal muscles are disposed over the skeletal system, and are connected to the bones by tendons. A muscle contraction occurs when a muscle fiber generates tension through the action of actin-myosin cross-bridge cycling producing movement around the joints. Voluntary muscle contractions are initiated in the brain, sending electrochemical signals conducted through nervous cells, to skeletal muscular cells, through the neuromuscular junction in a procedure referred to as Excitation-Activation-Dynamics. The process of transformation of an activation state into muscular force production, is called Activation- Contraction Dynamics. Mathematical models are a very useful and completely non-invasive technique to study the muscle’s dynamics. This area has seen a fast growth, and several models have been proposed to model the musculoskeletal system. Considering all the aspects that have to be taken into account in muscle modeling, Hill’s Model continues to be the key model to perform these studies. AFONSO, Pedro, CHAGAS, Pedro, PINHEIRO, Pedro, RIBEIRO, Jonathan pedrommafonso@ist.utl.pt 65119 pedro.chagas@ist.utl.pt 65117 pedro.1.pinheiro@ist.utl.pt 65121 jonathan.ribeiro@ist.utl.pt 65107 pedrommafonso@ist.utl.pt 65119 pedro.chagas@ist.utl.pt 65117 pedro.1.pinheiro@ist.utl.pt 65121 jonathan.ribeiro@ist.utl.pt 65107