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.
Font type and specific tension
Maximum force production is proportional to it’s cross-sectional area.
Specific tension is force of contractuon per unit area N/cm2, x cross-sectional area cm2 = force of muscle N
Fast twitch = 22 N/cm2
Slow twitch = 15 N/cm2
Whole muscles have variable specific tensions. Muscle that have predominantly fast twitch will have only a higher slightly higher specific tension that muscles that are predominantly slow twitch. However fast-twitch fibers tend to be a larger than slow-twitch fibers so the absolute tension they can develop is greater.
Recruitment
Intramuscularly - Force can be increased by increasing the firing frequency of the motor unit, increasing the number of motor units recruited, and recruiting progressively larger motor units.
Intermuscularly - Force can be increased by increasing the activation of the agonists and synergists, decreasing the activation of antagonists, or both.
Much of the improvement in strength gains occur through neural adaptation during the first few weeks of training
Time history of activation
Maximal muscle force can take up to .5 sec. To develop.
Rate of force development-the ratio of the change in force over the change in time. It can be improved with:
resistance exercise.
Stretch-shortening cycle SSC ( an eccentric muscle exercise immediately followed by a concentric muscle action. Attributed to storage of elastic energy and enhanced neural drive. Pre-forcing
Moment arms and levers
A perdón with a larger lever arm (tendinous insertion farther away from the joint) can produce a greater torque. Yet greater torque is produced at some points in the ROM than at others.
Sine all points along the forearm move at the same angular velocity the more distal points have higher linear velocity.
Strength and sticking points
Strength is the maximal force muscle or muscle group can produce at a specific velocity.
Sticking points is where the extern resistance has the greatest mechanical advantage compared to the muscle.
Closed kinetic chain
The movement of one joint causes the the other joints to move in a predictable manner
This includes bench press and and traditional leg press.
The torques at the joints are coupled.
Weakness or limitations at one joint will affect the others.
Open kinetic chain
Movement at one joint doesn’t necessarily cause movement at another joint.
Steindler
Describes the umami kinetic chain in the mid 1950’s
Kinetic vs kinematic
Used interchangeably. Kinematic change is technically correct.
6 step algorithm for any joint movement
Identify
1 movement or position.
2 effect of the external force if there were no active muscles
3 type of muscle action. Opposite direction is concentric. Same direction is eccentric. No movement is isometric. Movement across gravity is concentric in order to pull the segment against its own inertia.
4 plane of movement and axis of rotation to identify which side of the joint the muscles controlling the movement cross.
5 on which side of the joint are the muscles lengthening and on which side are they shortening
6 combine the info rom steps 3 and 5 to determine which muscles are producing or controlling movement.
Pectineus
Hip flexion. Adduction
Adductor Magnus
Adduction
Hip Extension with posterior fibers
Flexion flexion, and IR with anterior superior fibers
Adductor brevis and longus
Addiction, flexion ,IR
Tensor fascia latae
Abduction. Flexion. IR
Deep hip external rotators
Piriformis.
Gemellus superior and inferior
Obturator externus and internus
Quadratus femoris
Knee IR
Popliteus. Semimembranosus. Semitendinosus. Sartorius. Gracilis
Knee lateral rotation
Biceps femoris
Plantarflexion
Gastrocnemius. Soles. Plantaris. Tibialis posterior. FHL. FDL. PL. PB
DF
EHL. EDL. TA. PT.
Inv
TA. TP. Plantaris. FHL. FDL gastrocnemius. Soleus.
Eversion
PT. PL. PB. EDL
Shoulder girdle elevation
Levator scapula. Upper trapezius. Rhomboids
Shoulder girdle depression
Lower trapezius
Pectoralis minor
Retraction
Rhomboids
Middle trapezius
Protraction
Pectoralis minor
Serratus anterior
Upward rotation
Trapezius
Serratus anterior
Downward rotation
Rhomboids
Levator scapula
Pectoralis minor
Shoulder flexion
Pec major clavicular portion
Anterior deltoid
Biceps brachii, short head
Coracobrachialis
Shoulder extension
Pec major. Sternal portion Lats Teres major Posterior deltoid Triceps brachii. Long head.
Sh add
Lats
Teres major
Pec major. Sternal portion.
Abd
Middle deltoid.
supraspinatus
Anterior deltoid
Biceps brachii
IR
Lats Teres major Subscapularis Anterior deltoid Pec major Biceps brachii. Sort head
ER
There’s minor
Infra spinet us
Posterior deltoid
Horizontal flexion
Pec major
Anterior deltoid
Coracobrachialis
Biceps brachii
Horizontal extension
Middle and posterior deltoid Teres minor Infraspinafus Teres major Lat Dorsi
3 considerations of the torque equation and human movement mechanics.
First - magnitude can be increased or sea teased by raising or lowering F and /or d.
2nd - force applied through the axis of rotation. No moment arm exists therefore no torque is produced. The force can be compressive. If too high, injurious.
3rd - most human movement involves multiple torques. The resulting movement is based on net torque or net moment.
Tnet = T1 + T2. If equal and in opposite directions then net torque is 0. External vs internal forces will determine movment outcome.
Elbow flexio
Biceps brachiibrachialis brachioradialis
Elbow ext
Triceps brachii
Anconeus
Radio ulnar supination
Biceps brachi
Supinator
Brachioradialis
Radioulnar pronation
Pronator teres
pronator quadratus
Brachioradialis
Wrist flexor
FCR, FCU. FDS. FDP. Palmaris longus
Wrist ext
ECR longus. ECR brevis. ECU. Extensor indicis. Extensor digiti minimi. Extensor digitorum
Radial deviation
FCR. ECR longus and brevis
Ulnar deviation
ECU FCU
Vertebral flexion
Rectus abs. EO. IO. Papas major lumbar region
LaterL flexion
EO. IO. QL. RA extensor spinae
Rotation same side
Rotation opposite side
IO. Erect spinae
EO. Mulifidii
Constant resistance devices
The force does not change throughout the ROM
Free weights
Fixed mass with no constraint The force (weight is constant by virtue of being in a gravitational field that is constant. The velocity is not constant but if it is sufficiently slow the acceleration is approximated as 0 keeping the resistance equal to its weight in mg. Fr = ma + W W is equal to 0 in all directions except vertical. The position if the lever arm(s) relative to the body and space determines at what angle the muscle is working the hardest.
Machines
Constrains the motion of the resistance.
The path can be linear, angular. The correction of the resistance is in the direction of the cable.
The external resistance does not change because of the use of a pulley and fixed axis.
