Biomechanical Properties Of Muscles Research Articles

Relapse of clubfoot after treatment with the Ponseti method and the function of the foot abduction orthosis.

Ponseti clubfoot treatment has become more popular during the last decade because of its high initial correction rate. But the most common problem affecting the long-term successful outcome is relapse of the deformity. Non-compliance with Ponseti brace protocol is a major problem associated with relapse. Although more comfortable braces have been reported to improve the compliance, they all have the same design and no significant changes have been made to the protocols. After refinement in the Ponseti method and emphasizing the importance of brace to parents, the relapse rate has been markedly decreased. Nevertheless, there are patients who do not have any recurrence although they are not completely compliant with the brace treatment, whereas other patients have a recurrence even though they are strictly compliant with the brace treatment. The aim of this article is to review the relapse of clubfoot and the function of the brace and to develop an individualized brace protocol for each patient by analyzing the mechanism of the brace and the biomechanical properties of muscles, tendons, and ligaments.

Critical Damping Conditions for Third Order Muscle Models: Implications for Force Control

Experimental results presented in the literature suggest that humans use a position control strategy to indirectly control force rather than direct force control. Modeling the muscle-tendon system as a third-order linear model, we provide an explanation of why an indirect force control strategy is preferred. We analyzed a third-order muscle system and verified that it is required for a faithful representation of muscle-tendon mechanics, especially when investigating critical damping conditions. We provided numerical examples using biomechanical properties of muscles and tendons reported in the literature. We demonstrated that at maximum isotonic contraction, for muscle and tendon stiffness within physiologically compatible ranges, a third-order muscle-tendon system can be under-damped. Over-damping occurs for values of the damping coefficient included within a finite interval defined by two separate critical limits (such interval is a semi-infinite region in second-order models). An increase in damping beyond the larger critical value would lead the system to mechanical instability. We proved the existence of a theoretical threshold for the ratio between tendon and muscle stiffness above which critical damping can never be achieved; thus resulting in an oscillatory free response of the system, independently of the value of the damping. Under such condition, combined with high muscle activation, oscillation of the system can be compensated only by active control.

Third-Order Muscle Models: The Role of Oscillatory Behavior In Force Control.

This paper presents the analysis of a third-order linear differential equation representing a muscle-tendon system, including the identification of critical damping conditions. We analytically verified that this model is required for a faithful representation of muscle-skeletal muscles and provided numerical examples using the biomechanical properties of muscles and tendon reported in the literature. We proved the existence of a theoretical threshold for the ratio between tendon and muscle stiffness above which critical damping can never be achieved, thus resulting in an oscillatory free response of the system, independently of the value of the damping. Oscillation of the limb can be compensated only by active control, which requires creating an internal model of the limb mechanics. We demonstrated that, when admissible, over-damping of the muscle-tendon system occurs for damping values included within a finite interval between two separate critical limits. The same interval is a semi-infinite region in second-order models. Moreover, an increase in damping beyond the second critical point rapidly brings the system to mechanical instability.

The approach to rehabilitation in post-traumatic spasticity

Tone and biomechanical properties of muscles can be measured objectively, e.g., using a probe that applies a perpendicular brief pulse percussion to the underlying tissue. The tissue responds in the form of damped oscillations that can be recorded by sensor measuring kinematic variations. We performed a double-blind study of 40 patients (15 M, 25F) affected by spasticity, who were treated with BoNT (72.45±23.52 Botox U). The patients were evaluated before and after treatment using the modified Ashworth score (MAS); muscle tone, elasticity and stiffness were evaluated using Myoton ® , either at rest or during passive extension. Follow-up evaluations were performed 25–30 days and 4 months after treatment. Variations in MAS and physical variables were compared using 2-way ANOVA. Muscle tone was reduced at rest and during passive elongation, both at 25–30 days and at 4 months, compared to baseline ( p p

Biomechanical muscle properties and angiotensin-converting enzyme gene polymorphism: a model-based study

Previous studies reported an association of angiotensin-converting enzyme (ACE) I/D gene polymorphism with physical performance. The study was based on the hypothesis that certain individual biomechanical muscle properties could be associated with ACE genotype and that they could influence athletes' physical performance. Movement-independent individual biomechanical muscle properties of 62 sports students were determined by applying a mathematical model to experimental data. Subjects exerted concentric and isometric contractions at a leg-press. The model was based on a Hill-type muscle model, a function describing the geometrical arrangement of human leg extensor muscles, and an exponential function describing muscle activation. Mouthwash samples were taken to determine the ACE genotypes. Several combinations of experimentally determined biomechanical properties served as input variables for a discriminant analysis. We were able to show that individual biomechanical muscle properties correlated with ACE I/D gene polymorphism. With a combination of certain individual muscle parameters based on a Hill-type muscle model, we were able to separate three individual ACE genotypes (II, ID, DD) in a significant way (P<0.03) and correctly classify 89% of the cases using a discriminant analysis. We conclude that local biomechanical muscle properties are influenced by ACE genotype.