Bone, Joint, Muscle Biomechanics Flashcards
What is the function of bone?
- stability- provide a frame to support body
- mobility- attachment for muscle sites and therefore moving limbs
- protection- spinal cord
What are the two types of bone?
- corticol (hard)- dense, forms outer layer
2. trabecular (spongy bone)- low density, fills interior
How do we fracture a bone?
apply excessive amount of force to the bone
How do we get compression fracture?
two forces move to each other in same line of action
ex. compression fracture
How do we get torsion fracture?
two torques rotate the object in different directions
ex. tibia fracture- turning the tibia forcefully while foot is on ground
How do we get tension fracture?
two forces move away from each other in same line of action
ex. transverse patella fracture
How do we get bending fracture?
compression force applies to one side of the object while tension force applies to the other side of object
ex. FOOSH, colles fracture
How do we get shear fracture?
two forces move towards or away from each in different lines of action
ex. tibia fracture- blow to tibia while foot is planted
Wolff’s law
if loading on a particular bone increases the bone will remodel itself overtime to become stronger to resist that sort of loading
What is stiffness in biomechanics terms?
stress/ strain
the object is stiff if a large amount of force can be applied and only a small amount of change in shape
Which bone is more stiff a normal bone or immobilized bone?
normal
What are the three types of joints?
- synarthrosis- joint that can hardly move (skull)
- ampiarthrosis- joints that can slight move usually fibrocartilage (IV discs, SI joint)
- diarthrosis- joints that can move freely and have DOF
In biomechanics how is DOF defined?
as the number of axis that the joint can rotate around
What is a plane joint?
articular surfaces are flat, allow gliding motions
ex. intercarpal bones
0 DOF
ligaments always support these joints
What is a hinge joint?
modeled like a door hinge
ex. humeroulnar joint
1 DOF
What is a pivot joint?
a ring shape bone rotates on the longitudinal axis of the other bone
ex. AA joint, supination/pronation
1 DOF, facilitates transverse rotation
What is a saddle joint?
joint surface looks like a saddle that has both convex-concave configurations
ex. CMC jt
allows 2 DOF
What is a condyloid joint?
an oval head sits on an elliptical cavity
ex. radiocarpal joints
allows 2 DOF
What is a ball and socket joint?
ball head sits on a round socket
ex. shoulder (deep) and hip (shallow)
allow 3 DOF
What factors contribute to joint stability?
- joint configuration- less mobility more stability
- Soft tissues- ligaments, muscles and jt capsule
- joint position
What does a close packed jt position mean?
the joint space is minimized
most ligaments and joints around joint are taut
ex. closed pack knee- full extension and ER
closed pack ankle- DF
What does a loose packed jt position mean?
jt space is maximized
most ligaments and capsule are loose around jt
ex. loose pack for knee= 25 flexion
this is important for joint mobs
What involves a muscle biggest to smallest?
muscle belly—–muscle fibers—-sacromere
What compromises a motor unit?
- alpha motor neuron
- axon
- muscle fiber innervated
CNS controls muscle activities through motor units
What determines the size of a motor unit?
defined by the number of muscle fibers it controls
What size are type 1 muscle fibers?
small
What size are type 2a muscle fibers?
medium
What size are type 2b muscle fibers?
large
What is Henneman’s size principle?
motor units are recruited smallest to largest
helps us preserve energy (self optimization)
What are type 1 fibers?
slow twitch oxidative fibers (use oxygen for energy)
high endurance, low power
What are type 2A fibers?
fast twitch, oxidative fibers
intermediate power and endurance
What are type 2B fibers?
fast twitch, glycolytic fibers (use glucose for energy)
high power, low endurance
Is atrophy greater in type 1 or 2 fibers?
type 2
What is the toe region in stress-strain curve?
fibers are realigned but not fully straightened
What is the elastic region in stress-strain curve?
fibers are straightened, can return to the original shape
final point of this region is yield point
What is the plastic region in stress-strain curve?
fibers now have irreversible change and permenent after being strecthed beyond yield point
What is the failure region in stress-strain curve?
fibers are torn
What is active insufficiency?
occurs when the agonist muscle fails to shorten enough, cannot achieve full ROM
What is passive insufficiency?
occurs when the antagonist muscle fails to lengthen far enough, Full ROM cannot be achieved
What is active tension?
when the muscle moves actively, it can produce the largest force when at resting length
What is passive tension?
when the muscle is being strecthed, there is a positive relationship between the muscle length and tension
In which position can we produce the greatest amount of force?
mid range of joint
ex. MMT
How can we produce passive tension on a muscle?
lengthen the muscle
Can we generate greater passive or active tension? How can we combine both active and passive tension?
passive tension, think eccentric contraction exercises
Why is strecthing so important in athletes?
so they can generate greater tension
What happens if we overstretch someone?
we are moving resting length
