Muscle strength and stiffness in resistance exercise: Force transmission in tissues.

Physical therapists and osteopaths want to know the quantitative force transmitted in the tissues during resistance exercise and also the relationship between tissue strength and the specific type of resistance exercise of the skeletal muscles. This paper uses the strain energy function for large deformations associated with the active and passive response of transversely isotropic skeletal muscle tissue to evaluate muscle strength and force transmitted in tissues during resistance exercises for the quadriceps muscle at the knee during isometric training exercise at different knee angles in vivo. It is found that after an exercise program, the muscle stiffness is halved when the bending angle of the knee increases from 50° to 100°. The muscle strength generated is marginally greater at 100° than at 50°. The stress transmitted in the lateral direction for 100° bending is double that for 50°.

Deformations experienced in the human skin, adipose tissue, and fascia in osteopathic manipulative medicine.

CONTEXT: Osteopathic manipulative medicine techniques involve compressive and tangential forces to target the fascia. These forces are transmitted to the skin and adipose tissue before the fascia is encountered. Knowing the extent of deformation of these 2 tissue layers relative to the fascia will assist osteopathic physicians in evaluating techniques for manual therapies and adjusting these therapies to reduce patient discomfort and improve results. OBJECTIVE: To determine the magnitude of the forces transmitted to the skin, adipose tissue, and fascia, and to determine the magnitude of deformation produced in the skin and adipose tissue relative to the fascia using a mathematical model. METHODS: The large deformation theory of elasticity, valid for 3-dimensional deformations, was used to evaluate the forces that need to be applied such that a specified deformation is produced in any region of the skin, adipose tissue, or fascia layers. Similarly, if the forces are specified, then the deformation produced can be determined. RESULTS: The normal and tangential forces required to produce a deformation of 9% compression and 4% shear for the skin were 50 N and 11 N, respectively. Normal and tangential forces of about 100 N and 22 N were found for a similar deformation of fascia. For adipose tissue, these forces were 36 N and 8 N, respectively. In addition, the skin experienced more compression and shear-about 1.5 times as much as the fascia, and the adipose tissue experienced about 2.5 to 3.5 times the deformation of the fascia and 50% more than the skin when a given force was applied to the skin. CONCLUSION: The forces applied to the surface of the skin were transmitted through this layer and the adipose layer entirely to the fascia. Therefore, the skin and adipose tissue experienced the same magnitude of force as the fascia. However, the skin and adipose tissue experienced more compression and shear than the fascia.

Mathematical analysis of the flow of hyaluronic acid around fascia during manual therapy motions.

CONTEXT: More research is needed to understand the flow characteristics of hyaluronic acid (HA) during motions used in osteopathic manipulative treatment and other manual therapies. OBJECTIVE: To apply a 3-dimensional mathematical model to explore the relationship between the 3 manual therapy motions (constant sliding, perpendicular vibration, and tangential oscillation) and the flow characteristics of HA below the fascial layer. METHODS: The Squeeze Film Lubrication theory of fluid mechanics for flow between 2 plates was used, as well as the Navier-Stokes equations. RESULTS: The fluid pressure of HA increased substantially as fascia was deformed during manual therapies. There was a higher rate of pressure during tangential oscillation and perpendicular vibration than during constant sliding. This variation of pressure caused HA to flow near the edges of the fascial area under manipulation, and this flow resulted in greater lubrication. The pressure generated in the fluid between the muscle and the fascia during osteopathic manipulative treatment causes the fluid gap to increase. Consequently, the thickness between 2 fascial layers increases as well. Thus, the presence of a thicker fluid gap can improve the sliding system and permit the muscles to work more efficiently. CONCLUSION: The mathematical model employed by the authors suggests that inclusion of perpendicular vibration and tangential oscillation may increase the action of the treatment in the extracellular matrix, providing additional benefits in manual therapies that currently use only constant sliding motions.

Squeeze film lubrication for non-Newtonian fluids with application to manual medicine.

In this paper, we computed fluid pressure and force on fascia sheets during manual therapy treatments using Squeeze Film Lubrication theory for non-Newtonian fluids. For this purpose, we developed a model valid for three dimensional fluid flow of a non-Newtonian liquid. Previous models considered only one-dimensional flows in two dimensions. We applied this model to compare the one-dimensional flow of HA, considered as a lubricating fluid, around or within the fascia during sliding, vibration, and back-and-forth sliding manipulation treatment techniques. The fluid pressure of HA increases dramatically as fascia is deformed during manual therapies. The fluid force increases more during vertical vibratory manipulation treatment than in constant sliding, and back and forth motion. The variation of fluid pressure/force causes HA to flow near the edges of the fascial area under manipulation in sliding and back and forth motion which may result in greater lubrication. The fluid pressure generated in manual therapy techniques may improve sliding and permit muscles to work more efficiently.

Measurement of balance in computer posturography: Comparison of methods--A brief review.

Some symptoms related to disequilibrium may not be detected by a clinical exam. Therefore, objective study is important in assessing balance. In this paper, methods to measure balance in computer posturography are compared. Center of pressure (COP) displacement, equilibrium score (ES) and postural stability index (PSI), the main measures of assessing balance are described and their merits and disadvantages are discussed. Clinicians should apply that measure which suits the specific strategies in a specific situation. Measuring devices such as Force plate, Balance Master and Equitest are also discussed. Although the Balance Master and Equitest devices are more costly compared to the force plate only, they are more useful for assessing balance relevant to daily life activities that might result in falls.

Mathematical analysis of applied loads on skeletal muscles during manual therapy.

CONTEXT: Because of the lack of accurate values for mechanically applied forces in osteopathic manipulative treatment, osteopathic physicians must apply mechanical forces intuitively. However, excessive loading and high velocity maneuvers carry risks for patients. OBJECTIVE: To determine the loads required to produce compression, shear, extension, and twist on biceps muscle during manual therapy. METHODS: A mathematical analysis valid for the in vivo state of biceps muscle was performed to determine the loads produced in a simple elastic biceps muscle model and a more realistic viscoelastic biceps muscle model. RESULTS: Loads of 7% lesser pressure were needed to produce 10% deformation of biceps muscle using the viscoelastic model, compared with the elastic model. In the viscoelastic model, there was stress relaxation of 18% of maximum pressure when muscle was deformed by 10% over 60 seconds and maintained in that state for 200 seconds. With quick maneuvers, the viscoelasticity effect was decreased. CONCLUSION: The biceps muscle is 15 times stiffer in the direction parallel to the muscle fibers than in the direction perpendicular to the fibers. The results of the present study may be used by osteopathic physicians to adjust their manual techniques to match viscoelastic properties of specific tissues. Because biceps muscle is viscoelastic, the results obtained with the viscoelastic model would be more useful than the results obtained with the elastic model for determining viscoelastic loads on this muscle.

Three-dimensional mathematical model for deformation of human fasciae in manual therapy.

CONTEXT: Although mathematical models have been developed for the bony movement occurring during chiropractic manipulation, such models are not available for soft tissue motion. OBJECTIVE: To develop a three-dimensional mathematical model for exploring the relationship between mechanical forces and deformation of human fasciae in manual therapy using a finite deformation theory. METHODS: The predicted stresses required to produce plastic deformation were evaluated for a volunteer subject's fascia lata, plantar fascia, and superficial nasal fascia. These stresses were then compared with previous experimental findings for plastic deformation in dense connective tissues. Using the three-dimensional mathematical model, the authors determined the changing amounts of compression and shear produced in fascial tissue during 20 seconds of manual therapy. RESULTS: The three-dimensional model's equations revealed that very large forces, outside the normal physiologic range, are required to produce even 1% compression and 1% shear in fascia lata and plantar fascia. Such large forces are not required to produce substantial compression and shear in superficial nasal fascia, however. CONCLUSION: The palpable sensations of tissue release that are often reported by osteopathic physicians and other manual therapists cannot be due to deformations produced in the firm tissues of plantar fascia and fascia lata. However, palpable tissue release could result from deformation in softer tissues, such as superficial nasal fascia.