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86 m a s s a g e & b o d y w o r k m a y / j u n e 2 0 2 0 used in various movements helps you determine how muscle overload may have contributed to specific injuries. Multiple treatment techniques and assessment strategies also incorporate different types of muscle contractions, so you need to be familiar with these and understand them to be most effective. BIOMECHANICS Biomechanics is the study of how forces act on the body. It is an application of mechanical physics to our living organism. The term biomechanics is sometimes confused with body mechanics. The former term encompasses a broad application of mechanical physics, while the latter term defines how the body is used during massage treatments. There are components of biomechanics used to study body mechanics, but the two are not the same thing. The realm of biomechanics is often divided into two primary categories— kinematics and kinetics. Kinematics is the study of movement in space, especially as it relates to the fundamental concepts of velocity, direction, time, and acceleration or deceleration. The focus of kinematics is on motion. In kinetics, the focus is on the force and energy required to produce or limit that motion. Kinetic analysis involves an application of these key concepts: • Inertia indicates that an object will tend to stay in its current state, whether moving or at rest, unless acted upon by some outside force. You may remember this concept from science class as Newton's first law. • Mass is the amount of matter contained within an object. An object can be relatively small and still have a large mass. Consider the difference in mass between a shotput and a softball even though they are relatively the same size. The shotput has a much greater mass. • Force is the amount of effort required to accelerate or decelerate a mass. There are five different types of force we evaluate in the body. Let's take a look at all five, but keep in mind that the majority of soft-tissue injuries occur from one of the first two, either compression or tension. 1. Compression is a compressive force that occurs when two objects press against each other, such as two vertebrae compressing the disk between them. 2. Tension or tensile force occurs when two ends of an object are pulled away from each other. High tensile forces are responsible for muscle strains and ligament sprains. 3. Torsion occurs when an object is twisted, and is called a torsion force. Because soft tissues are attached at each end within the body and under the skin, it is hard to apply a torsion or twisting force to them. However, you could also Not only is kinesiology a much broader science than you may have realized, it is also an integral part of becoming a highly skilled soft-tissue therapist when working with pain and injury complaints. commonly associated with deceleration movements or slowly resisting gravity. • Isometric contractions are muscle contractions in which the muscle is getting a neurological stimulus, but the resistance is exactly matching the contraction stimulus, so there is no motion at the joint. Isometric contractions are most common for stabilizing a limb or resisting an ongoing opposing force. Contraction of the back-extensor muscles to maintain an upright posture against the force of gravity is a good example. Another crucial facet of neuromuscular physiology is the complex system of proprioception. Proprioception is the sensory feedback that comes back to the brain about the body's position in space, as well as information about the state of various tissues involved in movement. We often think of the most significant amount of sensory information coming back into the central nervous system from some of our primary sense organs, such as the eyes, nose, ears, or skin. However, our central nervous system actually receives the greatest amount of sensory nerves from the myofascial tissues. 1 Some of the most powerful effects of manual therapy are likely from neurological responses to pressure, movement, and quality of touch in our sessions. These are all factors that are monitored by various proprioceptors and give feedback to the central nervous system. Clinical Applications of Physiology It is unfortunate that understanding and recognizing different types of muscle contractions is often relegated to rote memorization and then forgotten. Analyzing different types of contractions