Biomechanics Flashcards
Biomechanics
Applies mechanical principles to understand the function of living organisms and systems
Functional anatomy
The study if how body systems cooperate to perform certain tasks
Linear motion
- rectilinear
- curvilinear
The body moves in a s
- Straight line
- curved path
Angular motion or rotational motion
The body rotates about a fixed line known as the axis of rotation, fulcrum , or pivot.
General motion
A combination of linear and angular motion
Kinematics
Study of movement from a descriptive perspective without regard to the underlying forces.
Involves spatial and timing characteristics of movement .
5 variables: timing or temporal(sec). Position or location(at given deg) Displacement(deg of move). Velocity(deg/sec). Acceleration or change on velocity(deg /sec2).
Kinetics
Movt assessment in regards to forces involved. Forces are the cause of motion. Internal forces- muscle External forces - gravity Kinetic variables - force, torque ...
Units of measure conversions
File: table 4.1
How many ways is kilograms used
In the SI system Kg is the unit of mass with weight measured in newtons of force. (Quantity of matter or kgm)
Also used as units of force. (Kg plates in a weight room or kgf)
Force
A mechanical action or effect applied to a body that tends to produce acceleration. Internal and external forces. SI unit is N ( newton). 1 lb = 4.45 N Affected by: Magnitude- how much force. Location - where is it applied Direction - where is force directed Duration - how long is the force applied Frequency - how many times in a given priod if time Variability- does the magnitude change over the application period Rate - how quickly the force is produced
Sir isaac Newton (1643-2727) his laws of motion
1st- a body at rest or in motion tens to stay at rest or in motion unless acted upon by an outside force.
2nd - a net force acting on a body produces an acceleration proportional to the force according to the equation F=m x a
3rd - for every action there is an equal and opposite reaction.
Momentum
Quantity of motion
The larger and faster the body is, the greater the momentum.
Linear momentum is a product of size and velocity.
Angular momentum is the product of moment of inertia (resistance to change) and angular velocity.
Inertia - body mass and the distribution of mass relative to the axis of rotation.
Transfer of momentum
Momentum is transferred from one body to another. ie. throwing a ball
Impulse
Changes momentum.
Force x time
Torque
Torque = force x moment arm T(N•m) = F(N) x d(m)
Moment arm is the perpendicular distance from the axis to the line of force action
Lever is typically the
The (Fa) applied forces is
The (Fr) resistance force is
Bone
Muscle
Gravity. Weights. Friction…,
First-class lever
The fulcrum is located between the two forces A first class lever, the forearm, extending the elbow concentrically and flexing eccentrically against resistance.
Second-class lever
The Fr is located between the fulcrum and Fa
Fa is the calf muscle
Fr is the body weight and gravity coming down the tib-fib
The fulcrum is the ball of the foot.
The moment arm of the muscle force is longer than the moment arm of the resistive force. Therefore the Fa is less than Fr.
Third-class lever
The Fa lies between the fulcrum
And the Fr.
Joints in the body are primarily third class.
Because the moment a if the applied force is shorter the the moment arm of the resistive force the Fa is much greater than the Fr
Work
W = F x d
= force x distance
Standard unit of work is
1 J = 1N•m
Power
P= W / t 1W = 1J / 1s Or P = F x v The rate at which the work is performed.
Energy (mechanical)
The ability or capacity to perform work. In human movement, kinetic energy (energy of motion) or potential energy (energy of position or deformation).
Linear kinetic energy:
LKE=1/2 x m x v2
=1/2 x mass x linear velocity squared.
Angular kinetic energy:
AKE = 1/2 x l x w2
= 1/2 x moment of inertia x angular velocity squared
Importance of squared: a runner who increases his speed from 5m/s to 6 m/s (20%) would increase his LKE by 44%.
Potential kinetic energy
Two forms:
Gravitational potential energy- the potential to perform mechanical work as a function of a body’s height above a reference level
PE = m x g x h
Mass x gravitational acceleration x height
Deformational energy - stored in the body when it is deformed. When the force is removed the body returns to its original configuration, releasing energy in the process. Some of the energy is lost as heat.
Biomechanical efficiency
How much output (work) can be produced with the use of a given amount of metabolic input.
The ratio of mechanical output to metabolic input.
The skeletal muscle is 25% efficient . Therefore 1/4 of thee tabloid energy goes to skeletal muscle. The rest goes to heat conversion or the recovery process.
Total m event inefficiencies
26% skeletal muscle. Muscular coactivation. Jerky movements to accel or decel. Movt. Extraneous movements. Isometrics. Excessive SOG excursion .
What percent IOC body weight is muscle?
Functions?
4 distinguishing characteristics.
49-45
Movement. Protection. Heat production.
Excitability. Contractility. Extensilibility. Elasticity.
The functional unit for force production within the myofibril
Sarcomere
Arrangement of muscle fibers
Fusiform - parallel to a Line between the origin and insertion
Pennation angled muscle - Unipennate semimembranosus. Bipennate rectus femoris. Mulitpennate deltoid.
Types of muscle action
Isomeric with a net torque of 0. No joint movement. By definition no work
Concentric the net torque produced by the muscle is greater than the external torque. Positive work. Muscle force and displacement are in the same direction.
Eccentric - the external net torque is greater. Negative work. Muscle force and displacement are in opposite directions.
Length tension
It’s 3 components
The combined effect of all the muscle’s structural elements.
Detained in part by the muscle’s length.
Active - if too short then complete overlap between actin filaments, myosin filament pressure against the z-lines, and diminishe capacity for myosin binding. As the sarcomere lengthen it reaches a point if optimal filament overlap and maximal force production. Further lengthening decreases overlap and force production drops.
Passive - the muscle us stretched passed its resting length, the non contractile elements want to recoil and produce resistive tension.
Total force production - The musculotendinous unit force production is the summation of active contractile and passive non contractile components.
Functional range - the optimal positioning in the length tension relationship.
Force velocity
The maximal force a muscle can produce at a given velocity.
Concentric- faster muscle velocities are associated with lower force production
Isometric - mor force is produced.
Eccentric - the most force is produced and is less affected by momentum.