Biomechanics and Pedagogy Notes

Biomechanics and Pedagogy

• This week's focus: biomechanics and pedagogy.
• Topics to be covered:
  • History of biomechanics and its evolution.
  • Different branches of biomechanics.
  • Biomechanics related to exercise and sport.
  • Rehabilitation from injury.
  • Areas of study within the discipline.
  • Vector quantities.
  • Trigonometry.
  • Introduction to second-year review expectations.
  • Data analysis.

What is Biomechanics?

• Examines the relationship between physics and mechanics.
• Applies physics principles to biological structures and their interaction with the environment, often the human body.
• Aims to improve performance; requires understanding of:
  • Motor control: Neuromuscular pathways influencing movement.
  • Exercise physiology: Chemical processes creating movement.
  • Physics: Application of physics principles to movement.
  • Engineering and mathematics.
• Kinesiology:
  • A parent discipline focused solely on human movement.
  • In America, kinesiology is the primary term for studying human movement.
  • Biomechanics is the more accepted term in Europe, Australia, and worldwide.

History of Biomechanics

• Aristotle: First to discuss the gait cycle and mechanics of running and walking.
• Archimedes: Studied flotation and movement in water.
• Leonardo da Vinci: Examined anatomy and its application to mechanics of movement.
• Galileo: Studied falling bodies, laying the groundwork for human movement analysis by considering:
  • Effects of gravity.
  • Aerodynamic forces.
• Barelli: Wrote the first biomechanical text.
• Sir Isaac Newton: Developed the three laws of mechanics, which will be discussed throughout the lecture.

Modern History

• 19th Century: Development of measuring techniques.
  • Force transducers and strain gauges: Measure force using electrical circuits and resistance, proportional to applied force (typically tensile).
  • Electromyography (EMG): Measures muscle activation using electrodes to detect electrical signals under the skin.
  • Photography: Used to analyze movement; modern high-speed cameras determine joint velocities.
    • Markers placed on rigid segments (e.g., elbow and wrist for forearm velocity) to create a rigid model.
    • Capturing high-frequency images over short periods enables determination of limb/segment velocity.
• Late 20th Century: Increased biomechanics research.
  • Origination of the Journal of Biomechanics.
  • Founding of the International Society of Biomechanics in the 1970s.

Branches of Biomechanics

• Statics and Dynamics

Statics:

• Deals with bodies at rest or in equilibrium.
• Equilibrium: Maintained when there is no net acceleration acting on the body, meaning no net force is applied to change its velocity.
• The resisting forces of a body equals the acceleration forces of a body, maintaining constant velocity.

Dynamics:

• Investigates bodies, masses, and forces in motion.
• Deals with accelerating or decelerating motion.
• Example: Muscle contraction applying force to the femur, causing acceleration of the leg segment.
• Subcategories:
  • Temporal analysis
  • Kinematics
  • Kinetics

Temporal Analysis:

• Uses time as the basis for analysis.
• Examines the timing of events within a movement.
• Analyzes ratios of durations within a single or cyclical movement (e.g., running).
• Example: Comparing stance phase to swing phase duration in running.
• Example: Analyzing the duration of phases in a throw (wind-up, arm cocking, acceleration, deceleration, follow-through).

Kinematics:

• Investigates motion without reference to mass or forces.
• Focuses on:
  • Displacement of a body or segment.
  • Velocity of movement.
  • Acceleration of movement.
• Describes how something is moving (how fast, how far).

Kinetics:

• Relates to mass and forces.
• Investigates the actions of forces in producing or changing motion of masses.
• Force is required to change motion (initiate movement or create acceleration).
• Explores the "why" of movement by examining forces causing changes in velocity or initiation of movement.

Areas of Study within Biomechanics

• Developmental biomechanics
• Biomechanics of exercise and sport
• Rehabilitative biomechanics
• Occupational biomechanics
• Forensic biomechanics

Developmental Biomechanics:

• Focuses on evaluating essential movement patterns across the lifespan.
• Quantifies developmental motor skills and movement patterns.
• Examples: Crawling to walking, gait development, running, jumping, throwing.
• Describes typical activity patterns for different age groups, focusing on children and the elderly.

Focus on Children

• Used to diagnose movement disorders.
• Helps determine appropriate therapies.
• Compares a child's movement patterns to normative values to identify deviations.

Focus on Elderly

• Primarily concerned with stability to prevent injury and maintain quality of life.
• Age-related decline in force production and tissue tolerance increases slip and fall risks.
• Aims to increase stability through:
  • Gate-assisting devices: Walkers increase the base of support, making it harder for the center of gravity to fall outside of it.

$Base \space of \space Support$: The area within the points of contact with the ground.

$Line \space of \space Gravity$: An imaginary vertical line passing through the center of gravity.

• Widening stance: Applying horizontal force into the ground shifts the center of mass and stabilizes gravity.
• Maximizing base of support minimizes the likelihood of injury.

Biomechanics of Exercise and Sport:

• Focuses on postures, movement patterns, and equipment that:
  • Minimizes injury risk.
  • Improves performance.

Reducing Injury Risk

• Example: ACL injuries in netball/basketball players.
• Develop landing techniques to minimize injury risk.
• Internal vs external rotation of knee on landing:
  • Internal rotation of the femur relative to external rotation of the tibia creates a torsional stress on the ACL.
  • Landing with foot pointed outward and changing direction in the opposite direction causes twisting.
• Valgus knee position (knock-knees) is a risk factor.
• Strategies for minimizing injury:
  • Landing with bent knees: Muscles (glutes, quads, calves) absorb force.
  • Landing with straighter leg: More force transmitted back through the leg, stressing ligaments.
• Shoe design: Higher medial longitudinal arch minimizes foot collapse and pronation, reducing risk of ACL injury.

Improving Performance

• Focus on technique and equipment.

• Example: Pitching technique in baseball.

• Maximize release velocity by:

  • Increasing the distance from the central axis of rotation to the release point.
  • Full extension of the arm maximizes the radius length and ball release velocity.

• Equipment analysis:

  • Effects of skin garments.
  • Cycling helmets to reduce drag.

• Cricket example-Chucking:

  • The difference between throwing a ball and bowling it relates to the extension angle and change in extension angle of the elbow just prior to release of the ball.
  • If the extension angle changes by equal to or greater than 15 degrees just before the ball is released, then it's considered a throw, not a bowl.
    Matayam Muralidaran Case:

• Early 2000s: Muralidaran called for chucking.

• University of Western Australia analysis: Markers on upper body joint centers to measure elbow angle change.

• Findings: Elbow angle hardly changed; visual illusion due to large carry angle.

• Carry Angle: Angle formed by the humerus and ulna when the arm is extended and supinated.

Rehabilitative Biomechanics:

• Focuses on movement patterns of the injured and disabled.
• Determines differences in movement from healthy individuals to develop rehabilitation strategies.
• Interventions: Walkers, orthotics to restore normal walking mechanics.
• Example: Canes used after joint replacement to reduce load on the joint.
• After an injury, the tissue structure has been compromised and requires appropriate strategies to rehabilitate the person.

$Reduced \space Tensile \space Strength$: Leads to reinjury.

• Canes/walkers distribute force, minimizing load through the affected leg.
• Helps evaluate if surgical treatment is required or maybe a conservative therapy based treatment would be required.
• Evaluates surgical vs. therapy-based treatment needs for conditions like cerebral palsy, or Parkinson's by analyzing:
  Kinematic measures like video analysis.
  Kinetic measures like force production.
• Devices like canes can provide upper body propulsive force during gait.

Occupational Biomechanics:

• Development of safety equipment (helmets, footwear) for dangerous environments (e.g., warehouses).
• Addresses high-mass object contact risks by providing adequate protective equipment
• Application of ergonomics: Body positioning to facilitate health and prevent injury.
• Proper desk setup (hip angle, cervical spine position) prevents chronic injury.
  • Creep: Constant stress (e.g., neck flexion) causes tissue deformation over time, leading to failure and injury.
• Changing posture while working reduces injury risk.

Forensic Biomechanics:

• Used in litigation (court proceedings) to prove injury causation.
• Example: Car accident reconstruction analyzes car velocity, steering wheel material, seat belt resistance to determine forces and injury likelihood.
• Used when injury cause is disputed and witnesses are absent.
• This module will be split in two parts. The second part will cover vector and scalar quantities as well as the gait cycle.