week 3

• Biomechanics


  The study of physical action and force as it relates to analysis, function and anatomy of biological systems (to know movement)
• Mechanics


  • Statics - study of systems that are in "constant state of motion", both in a stationary state and moving at a constant speed
  • Dynamics - study of "system in motion", with acceleration
• Mechanics


  • Kinematics - the effect of forces on the body during motion without considering the effect of forces causing motion
  • Kinetics - relationship between the motion of bodies and its causes, namely forces and torques
• Mechanics generally uses a small force, or added effort to move a larger resistance
• Mechanical advantage


  The ability of a machine to increase the force applied to it
• Machines


  • Used to increase profits
  • Considering every mechanical aspect of every body component in relation to components such as engines
  • The musculoskeletal system as a collection of simple machines
• Function of machines


  1. Balancing a set of forces

  2. Increases force to reduce the overall force required to overcome a resistance

  3. Increases the distance of movement and speed, so that a resistance can move further and faster than just the amount of force applied

  4. Changes the direction of the applied force
• Types of machines in the body

  • Lever/lever system (levers)
  • Wheel-axles
  • Pulleys
• Lever


  A rigid bar that turns about an axis of rotation or a fulcrum
• Lever components


  • Axis (A) - as a rotation point
  • Style (F) - application of force (muscle movement)
  • Prisoner (R) - resistance or load application (center of gravity of the lever or location of external load)
• Lever arrangements


  • 1st class lever - axis (A) between force (F) & load (R)
  • 2nd class lever - load (R) between axis (A) & force (F)
  • 3rd class lever - force (F) between axis (A) & load (R)
• First class levers


  • Produces balanced movement when the axis is right in the middle (seesaw)
  • Produces the speed and distance of the movement if the axis approaches the force (triceps at elbow extension)
  • Produces force movement if the axis approaches the load (crowbar)
• Second class levers


  • Produces force movement, because large loads can be moved with relatively little effort
• Third class levers


  • Produces speed and distance
  • Most common in the human body
  • Requires quite a lot of power even to move a small load
• Factors in use of anatomical levers: can be used to get mechanical advantage, improve physical movements simple or complex, some people are used to using human-levers correctly and some often use it incorrectly
• Hand tools


  Physical items that can be used to achieve a goal
• Biomechanics of hand tools


  The study of the hand and its responses in relation to physical work objects used within grasping reach
• Disadvantages of hand-related work

  • Cumulative Trauma Disorder (CTD) - tendonitis, irritation and swelling of the tendons, tenosynivitis, inflammation of the tendons and membranes, carpal tunnel syndrome, pressure on the middle nerve due to swelling, trigger finger, vibration-induced white finger
• Factors to pay attention to in hand tool design

  • Burden muscle static, fatigue and pain
  • Position wrong hand
  • Pressure in tissues or joints
  • Vibration and disruption
  • Pinch point
• Hand anatomy


  • Wrist postures
  • Grip strength - maximum obtained when the tool opens about 75mm, when choosing a tool, consider to give something which is a little bigger for men and a little smaller for woman
  • Grip types - power grip, precision grip
• Improper design of hand tools can cause injuries that are more widespread than just injuries to the hand
• The new ergonomic hand tool design shows the hand position better than the conventional design
• Risks and prevention for hand tool use

  • Repetition
  • Excessive force
  • Poor posture
  • Direct pressure on nerves
  • Vibration
  • Cold and Heat
  • Poor physical condition
• Guidelines for ergonomic hand tool design

  • Provide the proper grip - thickness, form, surface
  • Provide the proper work - reduce repetition, maintain neutral wrist position, reduce force/energy/effort, reduce vibration
• The 3D-printed tool handles were found to be more comfortable and convenient rather than the commercial ones
• The adequate length of tool handles may also vary according to functions and not rely alone on the average hand measurements