KIN 240 – Introduction to kinesiology Biomechanics of Physical Activity

What is biomechanics? Biomechanics is the application of mechanical laws of physics and engineering to motion, structure and function of all living systems Structure refers to anatomy while function refers to being able to accomplish a specific purpose How do we produce forces to generate movement? How do forces (e.g. – gravity) affect the functioning of body tissues? How do forces affect the structure of our body?

What do biomechanists do? Biomechanics researcher Perform experiments on problems of interest and/or assist with product development Footwear design, equipment design Clinical biomechanist Perform biomechanical analyses in medical settings to guide care for patients Gait analysis in cerebral palsy patients to determine if surgery warranted and/or to prescribe physical therapy techniques Performance enhancement specialist Analysis of techniques to improve performance and/or prevent and identify injury mechanisms Usually associated with elite/professional athletes

What do biomechanists do? Ergonomist Experts at improving efficiency and safety of employees Design of tools, job sites, task and/or behavior modifications College/university professor Teach biomechanics related courses in Kinesiology, Engineering and/or Medicine Conduct research on biomechanics issues Orthotist/prosthetist Use biomechanical concepts to design/fit custom devices to support injuries and medical conditions Development of prosthetic devices secondary to amputation

Goals of biomechanics To understand how people use and are affected by the fundamental principles of mechanical physics and engineering that explain how forces influence our structure and function What factors influence the composition and strength of damaged ligamentous tissue? To apply theoretical understanding gained through attainment of first goal to determine how best to Improve performance effectiveness (function) How to improve jumping movements? Increase safety and health of those body tissues that are affected by forces or those tissues involved in physical activity (structure) How to prevent baseball pitching injuries?

History of biomechanics Early beginnings Aristotle investigated biomechanical questions when analyzing animal motion and human walking pattern in 300’s BC DaVinci credited with developing first systematic examination of mechanical principles of human and animal movement (15th & 16th centuries) Industrial revolution in early 20th century provided inventions such as cameras to measure movements 1920’s saw investigation of efficiency of human movement in sport and industrial settings Post-WWI (and later WWII) used biomechanics to design prosthetics for war veterans who lost limbs 1950’s saw study of anthropometry (study of physical dimensions of people) as it related to auto, space and transportation industries Design of seats, instrument panels, etc.

History of biomechanics Contemporary biomechanics Creation of professional organizations and graduate-level university programs developed in 1960’s Rapid growth in field of biomechanics in 1970’s American Society of Biomechanics International Society of Biomechanics Current university programs not only offer biomechanics courses but also undergraduate and graduate specializations in kinesiology, allied health and or engineering departments

Research methods in biomechanics A model for analysis – allows researchers to design experiments and practitioners to apply knowledge from research Step 1 – identify your question Step 2 – state performance goal/s Step 3 – consider influencing factors Step 4 – understand motions and mechanics Step 5 – determine relevant biomechanical principles and movement techniques Step 6 – observe or measure Step 7 – assessment, evaluation and interpretation

Research methods in biomechanics Biomechanical instrumentation and tools Motion measurement devices High-speed digital cameras and other motion detection technology Can be used to track motion of body segments using reflective markers and/or LEDs – can determine positions, velocities, acceleration/deceleration Golf swing analysis, etc. Force measurement devices Force transducers can be attached to (humans) or implanted in (animals) body to measure forces exerted on body causing motion and/or injury Force platform/plate measure ground reaction forces for gait analysis to determine appropriate footwear and/or orthotics Electromyography (EMG) used to estimate muscle forces using surface electrodes to measure electrical activity in contracting muscles

Overview of knowledge How do external forces act on performers? Gravity pulls us toward earth – force of gravity = weight Ground reaction force generated any time you push against the ground (action) because the ground pushes back (reaction) Can be created in any direction – without GRF, you can’t go anywhere – you must push against the ground so that it can move you in opposite direction Friction is force needed to make sure individual doesn’t slip when ground pushes back Air/fluid forces produce resistance (force) to movement too – greater speed of movement increases resistance

Overview of knowledge How do internal forces act on performers? Tissue biomechanists study internal forces acting on body to understand mechanisms of injury and/or how to increase force production by muscles and tendons Compressive loading pushes tissues together Significantly greater GRF when landing from jump vs. walking Shear loading causes tissues to slide against another tissues Abrasive skin injuries Tensile loading pulls tissues apart Arm motion with overhead throw wants to pull shoulder joint apart and imparts huge load to muscles, tendons, ligament & joint capsules of the shoulder complex

Overview of knowledge Assessment and evaluation of performers Performance assessment in physical activities Investigate biomechanics of elite/highly skilled athletes to determine optimal techniques for performance Use those techniques to improve performance in novice/less skilled individuals to ensure optimal outcome Due to individuals differences, unreasonable to expect that techniques for given movement identical for people of all shapes, sizes, strengths and antomical variations Clinical assessment Investigate biomechanical values of general population to identify normative data Can help identify dysfunctional movement and/or whether or not rehabilitation intervention has been successful