Subject-Specific Tendon-Aponeurosis Definition in Hill-Type Model Predicts Higher Muscle Forces in Dynamic Tasks

• Published in: PloS one Vol. 7; no. 8; p. e44406
• Main Authors: Gerus, Pauline, Rao, Guillaume, Berton, Eric
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 29.08.2012; Public Library of Science (PLoS)
• Subjects: Adult; Analysis; Ankle; Biology; Biomechanical Phenomena - physiology; Biomechanics; Calibration; Complexity; Decoupling; Electromyography; Engineering Sciences; Exercise; Gastrocnemius muscle; Genetic aspects; Humans; In vitro methods and tests; In vivo methods and tests; Life Sciences; Male; Mathematical models; Mechanical properties; Medicine; Models, Biological; Motion capture; Muscle contraction; Muscle Fibers, Skeletal - diagnostic imaging; Muscle Fibers, Skeletal - physiology; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - physiology; Muscles; Musculoskeletal system; Physical fitness; Physiological aspects; Physiology; Soleus muscle; Strain; Task Performance and Analysis; Tendons; Tendons - physiology; Ultrasonic imaging; Ultrasonography; Ultrasound; Ultrasound imaging; France
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0044406

Neuromusculoskeletal models are a common method to estimate muscle forces. Developing accurate neuromusculoskeletal models is a challenging task due to the complexity of the system and large inter-subject variability. The estimation of muscles force is based on the mechanical properties of tendon-aponeurosis complex. Most neuromusculoskeletal models use a generic definition of the tendon-aponeurosis complex based on in vitro test, perhaps limiting their validity. Ultrasonography allows subject-specific estimates of the tendon-aponeurosis complex's mechanical properties. The aim of this study was to investigate the influence of subject-specific mechanical properties of the tendon-aponeurosis complex on a neuromusculoskeletal model of the ankle joint. Seven subjects performed isometric contractions from which the tendon-aponeurosis force-strain relationship was estimated. Hopping and running tasks were performed and muscle forces were estimated using subject-specific tendon-aponeurosis and generic tendon properties. Two ultrasound probes positioned over the muscle-tendon junction and the mid-belly were combined with motion capture to estimate the in vivo tendon and aponeurosis strain of the medial head of gastrocnemius muscle. The tendon-aponeurosis force-strain relationship was scaled for the other ankle muscles based on tendon and aponeurosis length of each muscle measured by ultrasonography. The EMG-driven model was calibrated twice - using the generic tendon definition and a subject-specific tendon-aponeurosis force-strain definition. The use of subject-specific tendon-aponeurosis definition leads to a higher muscle force estimate for the soleus muscle and the plantar-flexor group, and to a better model prediction of the ankle joint moment compared to the model estimate which used a generic definition. Furthermore, the subject-specific tendon-aponeurosis definition leads to a decoupling behaviour between the muscle fibre and muscle-tendon unit in agreement with previous experiments using ultrasonography. These results indicate the use of subject-specific tendon-aponeurosis definitions in a neuromusculoskeletal model produce better agreement with measured external loads and more physiological model behaviour.