Kinetics Principles of Muscle Contraction PDF

TOPIC 3: KINETIC PRINCIPLES OF MUSCLE CONTRACTION Kinetics Internal forces from structures located within the body: -Active: generated by stimulated muscle, generally but not necessarily under voluntary control. -Passive: generated by tension in stretched periarticular connective tissues. External f...

TOPIC 3: KINETIC PRINCIPLES OF MUSCLE CONTRACTION Kinetics Internal forces from structures located within the body: -Active: generated by stimulated muscle, generally but not necessarily under voluntary control. -Passive: generated by tension in stretched periarticular connective tissues. External forces: produced by forces acting outside the body. These forces usually originate from either gravity pulling on the mass of a body segment or an external load. Torque Forces exerted on the body: Translate a body segment (Linear) Applied at some distance perpendicular to the axis of rotation (Joints) -Moment arm: distance between axis of rotation and the force. -Torque: the product of a force and its moment arm. Muscle activation A muscle is considered activated when its stimulated by the nervous system: Isometric: muscle is producing a pulling force while maintaining a constant length. Muscle torque =external load. Concentric: muscle produces a pulling a force as it contracts (shortens). Muscle torque > external load. Eccentric: muscle produces a pulling force as it is being elongated by another more dominant force. Muscle torque < external load. Terminology related to the Actions of Muscles: Agonist: muscle group that is most directly related to the execution of a particular movement. Antagonist:opposite action of a particular agonist Synergistic: cooperate during the execution of a particular movement. Musculoskeletal levers