What is Biomechanics
- The Study of STRUCTURE and FUNCTION of Biological Systems by looking at the Statics, Dynamics, and the Mechanics of MATERIALS (What they’re like when Still, when in Motion, and how they Work TOGETHER)
We need Biomechanics to Undertand Human Physical Performance
- How MOTIONS are Performed
- How we Control Motion
- How FORCES (Internal and External) affect the Human Body and Tissues
Leonardo Da Vinci
- First to study Anatomy in the context of Mechanics
- Analyze muscle forces as acting along points of attachment and Joint Function
Giovanni Alfonso Borelli
- Walking, Running, Jumping, Heart Action
- CENTER of GRAVITY
- Inspired and Expired AIR VOLUME
- INSPIRATION is MUSCLE DRIVEN
- EXPIRATION is due to TISSUE ELASTICITY
A.T. Still
- Among other things, was a MILLWRIGHT and applied the PRINCIPLES of MECHANICS to HUMAN AFFLICTIONS
- Millwright: A person who maintains and cares for Mechanical Equipment
- This includes tasks such as LEVELING, ALIGNING, and INSTALLING Machinery on FOUNDATIONS or BASE PLATES and Setting, Leveling, and Aligning!
- Their job requires a thorough KNOWLEDGE of the LOAD-BEARING CAPABILITIES of the EQUIPMENT they use!!!
Structure and Function
1) STRUCTURE: 3 Dimensional, Responsive to APPLIED FORCES in EACH DIMENSION
2) FUNCTION: Various STRUCTURES respond to FORCES APPLIED in DIFFERENT WAYS!!!
***There is an INTERCONNECTION between STRUCTURES!!!! (Core Element of Kinesiology)
Motion and Movement
- MOTION is usually described in ONE BODY PLANE, however, SYNOVIAL JOINTS can have movement in ALL THREE PLANES (Trade off between Stability and ROM)!!!!!!!!!!!!!!!!
- Joints are where we TRANSFER FORCE between BODY SEGMENTS
1) Direction of MOVEMENT of the BODY SEGMENT is thus Defined by the STRUCTURE of the JOINTS between THEM!!!
Machines
- Used to Increase MECHANICAL ADVANTAGE!!!!
FUNCTIONS:
1) Balance Multiple FORCES
2) Enhance FORCE in an ATTEMPT to REDUCE TOTAL FORCE needed to OVERCOME a RESISTANCE
3) Enhance RANGE of MOTION and SPEED of Movement so that RESISTANCE may be moved FURTHER or FASTER than APPLIED FORCE
4) ALTER resulting DIRECTION of the APPLIED FORCE
Three Types of Machines Seen in the Body:
1) LEVERS (Most Common)
- Torque and Length
2) WHEEL AXLES
- Function as a FORM of LEVER
3) PULLEYS
- Change effective DIRECTION of FORCE APPLICATION
- Ex: Knee Cap
Biomaterial are Classified into Two Groups
1) HARD
- BONE: Undergoes Mechanical Deformation and may be analyzed with the THEORY of LINEAR ELASTICITY
***WOLF'S LAW: Bone INCREASES where it is NEEDED and REABSORBED where it is NOT!!!!! (Heel Spur!!!!!)
2) SOFT
- Can undergo large deformations
- Cartilage, Tendon, Muscle, Skin
1) CARTILAGE wearing leads to STRUCTURAL DISRUPTION of Matrix: LOSES ELASTICITY. There is a LIMITED CAPACITY to REGENERATE/ REPAIR!!!!!!2) LIGAMENTS become STRONGER and STIFFER with REPEATED STRESS. They become WEAKER and LESS STIFF with a REDUCTION of STRESS!!!!!!
Breakdown of Levers
1) FIRST CLASS (Neck)
- AXIS (Fulcrum) is BETWEEN the FORCE and RESISTANCE
2) SECOND CLASS (Calf Raises)
- Axis is at one end, Force is at the Other: RESISTANCE is in the MIDDLE!!!!
- FORCE and RESISTANCE move in the SAME DIRECTION!!!!!!!!
3) THIRD CLASS (Bicep Curl)
- Axis is at one END, Resistance is at the Other; FORCE is in the MIDDLE
- FORCE and RESISTANCE move in the SAME DIRECTION!!!!!!!
**** MOST COMMON for in the HUMAN BODY!!!!!!!!!
Relaxation
- Only a PARTIAL CONTRACTION may be Required to accomplish the DESIRED MOTION
- As the Matrix of the SEGMENT REACHES a NEUTRAL POSITION, the LOAD Necessary to MAINTAIN that SHAPE (Length) DECREASES
- Aka: When a MUSCLE is More RELAXED, it is EASIER to keep it the LENGTH that it IS! The more RELAXED a Muscle is, the FULLER TTHE RANGE of MOTION IS!!!!!!
- Thus, RELAXATION is Equivalent to FLEXIBILITY. (This is FAIRLY IMPORTANT to consider when considering Somatic Dysfunctions!!!!)
Strength
- The amount of FORCE needed to CONTRACT a MUSCLE
Moment
- FORCE being APPLIED plus the MOMENT ARM (Aka WORK- Force x Distance)
Joint Reaction Force
- Sum of MOMENTS and the FORCE of CONTRACTING MUSCLE
- This applies a STRESS to the JOINT during MOVEMENT. Stress can be ABSORBED or REDISTRIBUTED. All structure have some ELASTICITY and BEND to help them ACCOMPLISH THIS!!!
Stiffness
- The Amount of FORCE NECESSARY to BEND an OBJECT
Viscosity
- Related to ITS WATER CONTENT. Rapid STRETCH has INCREASED RESISTANCE. Slower Stretch (CREEP) has DECREASED RESISTANCE
Stress
1) Tension:
- STRETCHING
2) Compression
3) Shearing:
- PARALLEL Force
4) Beinding:
- FOLDING about an AXIS!!!
5) Torsion:
- TWISTING around an AXIS!!!
Load
- The sum of STRESSES on an OBJECT
- Can result in TISSUE DEFORMATION
Fatigue
- Repeated APPLICATION of STRESSES can result in BREAKDOWN of the STRUCTURE
Callus/ Stress Fracture
- Repeated Stress can also result in an INCREASED MASS of the TISSUE!!!
Somatic Dysfunction
- An INAPPROPRIATE response to STRESS
Applied Forces
1) EXTERNAL: Pressure applied to an OBJECT at REST; PASSIVE FORCE form the Perspective of the PATIENT.
- Magnitude and Combination of VECTORS LEADS to a RESULTANT APPLIED FORCE
- Produced from OUTSIDE the BODY and Originate from Gravity, Inertia, or Direct Contact
GROUND REACTIVE FORCES*
2) INTERNAL: Force generated to ACHIEVE LIMB MOVEMENT. Also includes VERTICAL LOAD (Summative Weight Transmitted through KINETIC CHAIN to the Ground) and FRICTION!
***VERTICAL LOAD!!!!!!
- Muscle GENERATE the ACTIVE INTERNAL FORCES; Tendons, Connective Tissues, Ligaments, and Joint Capsules generate PASSIVE INTERNAL FORCES!!!!!
***TISSUE Deformation can result from EITHER TYPE!!!!
Static
- The study of Systems that are in Constant State of MOTION (no Acceleration, whether at rest or at Constant Velocity)
Dynamic
- Study of Systems with Acceleration
