Biomechanics - BIOS 3100 Musculoskeletal Physiology AHW 2024 PDF

BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 1. Introduction 2. Measuring movements (kinematics) 3. Measuring force & speed (kinetics)...

BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 1. Introduction 2. Measuring movements (kinematics) 3. Measuring force & speed (kinetics) 1 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 CONTENTS 1. Introduction -mechanical descriptions of animal movements 2. Movements (kinematics) -types of movements about joints -angles -levers 3. Force & speed (kinetics) -the generation of muscle force -foot & ground reaction force -joint pressures 2 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Available online via Nusearch. 2nd & 3rd editions via Available online via Images in the presentation are largely Nusearch Nusearch. from Gray’s Anatomy, copyright is At Greenfield Med acknowledged. Library. https://en.wikipedia.org/wiki/List_of_skeletal_muscles_of_the_human_body#Lower_limb 3 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 1. Introduction - mechanical descriptions of animal movements (kinesiology, kinematics & kinetics) 4 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Biomechanics involves the application of engineering to descriptions of physiology, especially in humans (kinesiology). For example, it also considers the hydraulics of the cardiovascular system, but it is primarily concerned with movements about joints. The movements can be described in terms of angular extent, distances moved, speed of movement and force of movement. 5 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Whilst it is of scientific interest to quantify movements, biomechanics in the 20th century grew from the need to develop prosthetics for injured servicemen, post WW2. It includes a knowledge of tissue parameters, e.g., the ability of bone to withstand stress as well as the measurement of movement. Excessive or constant force can lead to tears, fractures and compression injuries. 6 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Even lying flat, the body is subject to stress due to gravity acting upon a mass of tissue. To stand, any animal must overcome the force generated by their weight, as in, F(N) = mass(k g) x acc’n(m/s2) Similarly, the forces acting about joints during a movement can be quantified. Forces can be measured in the laboratory using weights applied to specific movements and using dynamometers with isometric contraction. 7 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Shape can attenuate the force per unit area within a joint. The long bones typically have broader ends to improve stability and reduce forces. The knee is the largest joint in the human body consisting of the rounded femoral condyles and the flattened tibial condyles forming the tibial plateau. 8 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 2. Measuring movements (kinematics) -types of movements about joints -angles -levers 9 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Kinematics refers to movement about joints. There are several types of movement. The hinge type at the knee and the ball & socket of the hip & shoulder are well known but the rotational pivot of the elbow, the saddle joint of the thumb and the mortise & tenon of the ankle are less obvious. 10 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Angles are measured using goniometers (angle meter). It is important to know how to measure the angle, typically perpendicular to the resting plane. 11  BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 All biomechanical texts list the actions about joints in terms of the type of levers, 1-3. 1 & 2 can intrinsically be understood to increase the mechanical advantage. 12  BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Isotonic shortening of the biceps brachii is an example of a type 3 lever (where the MA is always less than 1). BUT/ this allows for a short contraction which results in a rapid & extensive movement (1:20). 13 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Mechanical advantage is a function of the lengths of the lever & load arms from the fulcrum. MA=Lever arm/Load arm For type 1 where the lever arm is say, 60mm and the load arm is 40mm, it is an advantage of 1.5x. For type 3 where the lever arm is relatively short, at say 0.05m and the load arm is 0.35m, MA is 0.143. IMA is the lever arm. EMA is the load arm, MF is muscle force & HW is head weight (IMA/EMA is internal or external moment arm) 14 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 An interesting example of leverage is the pulley effect of the patella at the human knee. 15 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 16 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 3. Measuring force & speed (kinetics) -the generation of muscle force -foot & ground reaction force -joint pressures 17 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 The muscle force required for movement depends upon the type of lever. Force is measured in Newtons, length in metres & weights converted to force in Newtons. The force at the end of the lever arm is also called the “moment” and can be calculated - example 3: MA = 0.05m/0.35m = 0.143 or (1/7) If wt is 6.8k g, i.e., 67 N then, 67 N/0.143 MA = 466 N muscle force required. From Neumann, Kinesiology of the Musculoskeletal System, 3 rd ed., Elsevier 2017 18 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 From Grays Anatomy Heel contact The force generated by the impact Push off of the distal limb can be measured using plate transducers. In humans it is referred to as the foot force. Due to Newtonian mechanics, there is an insistence that the equal & opposite ground reaction force is also considered. The measure may be in % body weight or Newtons. Pollard, Christine & Ter Har, Justin & Hannigan, J.J. & Norcross, Marc. (2018). Influence of Maximal Running Shoes on Biomechanics Before and After a 5K Run. Orthopaedic Journal of Sports Medicine. 6. 232596711877572. 19 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Taking the human knee as an example, studies suggest at full extension during heel strike in normal walking the pressure is 2-3x body weight. Walking downstairs or during impacts from jumps it will be considerably greater. ESB clinical biomechanics award 2008: Complete data of total knee replacement loading for level walking and stair climbing measured in vivo with a follow-up of 6–10 months Bernd Heinlein a,d,*, Ines Kutzner a, Friedmar Graichen a, Alwina Bender a,b, Antonius Rohlmann a, Andreas M. Halder c, Alexander Beier c, Georg Bergmann Clinical Biomechanics Volume 24, Issue 4, May 2009, Pages 315-326 20 BIOS 3100 Musculoskeletal Physiology Biomechanics AHW 2024 Summary Biomechanics of movement or kinesiology in humans, considers the nature of movements (kinematics) and the force/speed/energy of movement (kinetics) with reductive descriptions of complex actions about joints or of individuals. Considerable information is available in reference to man from both an academic & clinical perspective. Human gait is unique & distinctive. In addition, the range of distal forelimb movements is very extensive. The concept of levers are used as models for joint action. Biomechanical measurements have utility in both medicine and sports training. 21