Pt Pap 101- Force Systems 2024 PDF

PT PAP 101- FORCE SYSTEMS Dr Watson Arulsingh October 21, 2024 www.gmu.ac.ae COLLEGE OF ALLIED HEALTH SEIENCES Objectives At the end of this Lecture, the student should be able to Analyze components of fo...

PT PAP 101- FORCE SYSTEMS Dr Watson Arulsingh October 21, 2024 www.gmu.ac.ae COLLEGE OF ALLIED HEALTH SEIENCES Objectives At the end of this Lecture, the student should be able to Analyze components of forces in Human mechanics. Explain Anatomic pulleys and its implications in human body. Understand angle of muscle pull  Muscle force & components  Muscle force produces a torque around the center of rotation of the joint on which it is acting  Muscle force (Fms) can be broken into components to determine its actual effect on the joint.  Torque: A force that produces or tends to produce rotation or torsion  Rotatory & Translatory component [link]  A force applied towards the joint is called as ‘Compression Component’ which contributes to joint stability as it draws the contiguous joint surfaces together.  A translatory force away from the joint would separate the joint surfaces and is known as ‘Distraction Component’.  Components of muscle force  Rotatory component - the force that tries to turn the body segment around the proximal joint  Portion of force applied perpendicular to the lever is known as Rotatory component of force (fr)  Translatory (Stabilizing) component- the force that acts along the body segment forcing into, or pulling out of the joint  Portion of force applied parallel to the lever is known as Translatory component of force (ft) Muscle force & components  In fig a and d the translatory component is larger  At 90 there is no translatory component  The component changes not only in magnitude but also in direction during the course of elbow flexion  Translatory component is larger than the rotation component both at 35 of elbow flexion and at 145 of elbow flexion  At 35 of elbow flexion the translatory force is toward the joint (compression) where as at 145 it is away from the joint (distraction) 6 Importance of Rotatory Component  When any force is applied to a lever at 90 Fr (torque) will be maximum because it will be equivalent to the total force  At 90 of elbow flexion (c in above example) Fms is applied at 90 to the lever that is, Fms and Fr coincide and all force is applied to rotation with out translation  Magnitude of force applied to a lever at some angle other than 90will result in less torque than the same force applied at 90 Angle of Pull of a muscle  The angle between the vector representing muscle force and a straight line from the center of rotation of the joint to the muscle insertion  Is the angle between the line of pull of the muscle (action line) and the mechanical axis of the bone or segment involved  Mechanical axis of a bone = a straight line connecting the midpoints of the joints at both ends of the bone 9 Need- Angle of Pull  A force [Torque] is most effective when it is applied at right angles to the lever (90)  Similarly, when the muscle is inserted at right angles or when pull is exerted at right angle to the bone will produce highest torque  Efficiency or torque is decreased as the angle of pull is reduced or increased from right angle, because some of the force is used in pulling the bone of insertion towards the joint representing the fulcrum  Anatomic Pulleys When a muscle or muscle fiber is wrapped around a bone or deflected around a bony prominence the direction of pull of a muscle is altered and the bony prominence forms an anatomic pulley Pulleys change the direction without changing the magnitude of the applied force  Anatomic Pulleys Anatomic pulleys change the direction but not the magnitude of muscle force The change in direction of the muscle force, improves the ability of the muscles to generate torque. The change in direction or deflection of the action line of a muscle in an anatomic pulley is away from the axis of the joint being crossed. By deflecting the action line away from the joint axis, the MA of the muscle force in increased Pull of Quadriceps Pull of quadriceps without Patella with patella Patella changes the angle of muscle pull 14