kinesiology exam 1

type of bone found in the center of bone with high porosity is

trabecular

During adolescence, bone growth occurs primarly at the _____.

epiphyseal plate

Which type of bone makes up the hard, outer covering of bones?

cortical

Which of the following are cells that breakdown and resorb bone?

osteoclasts

what are triggers for bone remodeling to occur?

low blood calcium levels

skeletal damage

change in balance or mass requirements

The outer connective tissue that surrounds a bone is known as the _______

periosteum

Jumping jacks are a motion that occur in which anatomical plane?

frontal

Flexion and extension of the wrist occur in which anatomical plane?

sagittal

Hip flexion occurs in which anatomimcal plane of motion?

sagittal

flexion/extension runs parallel to the ____ plane

sagittal

abduction/adduction runs parallel to the _____ plane

frontal

internal/external rotation runs parallel to the ____ plane

transverse

axes of rotation

an imaginary line around which a body segment rotates during movement

axis is like the rod at the top of a swing, with the body part moving around that rod

all human movement occurs around one of these axes

plane vs axis

motion happens along a plane, but around an axis

anteroposterior (AP) axis

runs from anterior to posterior; like a rod is pushed straight through your body from chest to back

common movements are from side to side (adduction/abduction) → jumping jacks, side leg raises, arm movements out to the side

mediolateral (ML) axis

runs medial to lateral (left to right); like a rod going hip to hip

common movements include flexion and extension: bicep curls, squats, walking or running (knee and hip flexion/extension)

vertical/longitudinal axis

runs vertically, from top to bottom (rod from head to torso)

common movements: rotation → turning head, trunk rotations, spinning in a chair

osteogenesis

the process of bone growth and formation

bone matrix

initial framework where bone begins to grow

bone continues to be built on this matrix over time

key bone cells

osteoblasts - build bone

osteoclasts - break down (resorb) bone

osteocytes - mature bone cells (former osteoblasts) that maintain bone tissue

what triggers bone to form

loading stress; bone shape and strength depend on how it is loaded

without stress, bone weakens

degeneration

occurs when osteoclasts resorb bone

happens with lack of mechanical stress (immobility), low calcium levels, and injury

as a result, bones become porous and brittle, and can lead to osteoporosis

structure of bones

bones are strong and light because they are made of two types of tissue (compact and cancellous/trabecular bone)

compact bone

dense outer layer that provides strength and protection

cancellous (trabecular) bone

spongy, lattice-like inner bone

provides flexibility and shock absorption

more metabolically active (breaks down faster in osteoporosis)

medulla

open central cavity of bone

contains bone marrow

contributes to blood volume and production

compact bone contains…

osteons (structural units of bone)

haversian canals (channels that allow blood flow and nourishment)

osteocytes (live within osteons and maintain bone)

articular cartilage

smooth, hard cartilage covering the epiphysis (ends of bone)

reduces friction and supports join movement

epiphyseal plate

cartilage plate between epiphysis and diaphysis

primary site of bone length growth: over time, growth plate calcifies → turns into compact bone → growth in length stops

x ray interpretation of epiphyseal plate

bright white → calcified bone (plate closing or closed)

dark area → cartilage (growth plate still open)

age of epiphyseal closure

vertebrae: 25 yrs

humerus: 16-20 yrs

femur: 18-20 yrs

tibia: 18-20 yrs

pelvis/acetabulum: 20-25 yrs

pelvis (pubis and ischium): 7-8 yrs

sex differences between female and male closure of epiphyseal plate

females experience earlier slowing and closure of growth

skeletal degeneration (aging) + diff between male and female

peak bone mass is at 30-35 yrs

after 40: gradual bone loss with age

females: sharp dip in bone mass around 50 yrs (menopause); higher risk of osteoporosis

males: more gradual, steady decline

**exercise and mechanical stress are critical to slow bone loss, especially in older adults

osteoporosis

decrease in bone density, especially trabecular bone

common diagnostic sites: femoral neck and vertebrae (high weight-bearing and force transfer areas)

DEXA scan

gold standard for measuring bone mineral density

uses low dose radiation

primarily used for bone density (not body comp)

how does DEXA measure bone density

by region: head, arms, legs, trunk, ribs, spine, pelvis

scores of DEXA scan

T-score: compares to healthy 30 year old of same sex

Z score: compares to people of the same age

what yields an osteoporosis diagnosis

greater than 2 standard deviations below the mean

wolff’s law

bone adapts to the stress placed upon it (more stress → stronger bone; less stress → bone loss)

this adaption happens in two ways: modeling and remodeling

• modeling forms new bone, changing bone shape and size

• remodeling is the continuous process of bone resorption and formation

triggers for bone remodeling

low blood calcium (body pulls calcium from bone)

skeletal microdamage (tiny tears or stress fractures)

changes in mechanical damage (sudden weight gain and new activity patterns) → aka stress needs (attained through exercise, like resistance training, running, and jumping)

ARF (Activation—Resorption—Formation)

Activation

• bone senses stress or damage

• signals osteoclasts to begin work

resorption

• osteoclasts break down bone

• calcium released into bloodstream

• happens relatively quickly

formation

• osteoblasts rebuild bone

• takes about 3x longer than resorption

**bone is lost faster than it is replaced if formation can’t keep up → reason for aging, hormonal changes, and lack of stress causing an increased osteoporosis risk

mechanical stress and bone loss (astronauts)

1 month in space: 60-70% calcium loss

1-2% bone density loss per month

recovery can take about 1 year

other bone loss situations include: bed loss and immobilization

female athlete triad

consists of (1) low energy availability / disordered eating, (2) bone loss / osteoporosis, and (3) menstrual disturbances / amenorrhea

sex hormones help maintain bone mass; hormone disruption → higher stress fracture risk; long term risk for osteoporosis later in life

RED-S (Relative Energy Deficiency in Sport

newer format of the female athlete triad, including areas for immunological, endocrine, metabolic, gastrointestinal, cardiovascular, psychological, and growth and development

males can be included too

In sport, you are generally more active than ACSM recommendations for exercise to have good health. RED-S shows that you are most likely nutrient deficient as well

three types of joints

diarthrosis, synarthrosis, ampiarthrosis

diarthrosis

knee, hip, shoulder (freely movable → synovial)

• has articular capsule with articular cartilage + synovial fluid

  • articular cartilage is very smooth and hard

• osteoarthritis → when there is injury to this cartilage

synarthrosis

sutures in skull (immovable → fibrous)

ampiarthrosis

pubic symphysis, SI joints (semimovable → cartilagenous)

diarthrosis articulations

arthrodial/gliding, hinge, pivot, saddle, ball and socket, condyloid

arthrodial/gliding joints

irregular surfaces, flat, or slightly curved

permits gliding movements (limits rotation movement) → intercarpal joints

hinge joints

convex/concave surfaces, uniaxial, permits flexion/extension → elbow

pivot joint

peg like pivot, or other that permits long axis rotation → atlantoaxial (C1 and C2)

condyloid joint

oval or egg shape convex surface fits into a reciprocal concave surface, biaxial, permits flexion/extension, ab and adduction, and circumduction → radiocarpal (wrist)

saddle joint

modification of condyloid, both surfaces are convex and concave, biaxial, permits flexion/extension, ab and adduction, and circumduction (thumb)

ball and socket joint

head of one bone fits into the cup of the other bone (Shoulder/hip)

what is joint stability dictated by?

1. bony and cartilaginous structure (passive stability)

2. muscles/tendons (dynamic stability → tighten muscles to provide protections; ex = rotator cuff)

3. ligaments (passive stability; don’t have to activate for them to work)

4. fascia/skin

5. atmospheric pressure (synovial joint is at a lower pressure than the outside air, acting like a vacuum to hold bones together and increase stability)

6. propioception (getting feedback to know what position your joint is in → don’t need to look at feet to know where they are/where to step)

ligaments vs tendons

ligaments - bone to bone

tendons - muscle to bone

plantarflexion and dorsiflexion at the ankle occur in which anatomical plane?

sagittal

inversion and eversion of the ankle occur in which plane and around which axis?

frontal plane, anteroposterior axis

what plane and axis does pronation/supination take place in

transverse plane, longitudinal axis

what plane and axis does lateral flexion take place in

frontal plane, anteroposterior axis

what plane and axis does radial deviation take place in

frontal plane, anteroposterior axis

articular cartilage absorbs what when not weight bearing?

synovial fluid

primary responsibilities of fibrocartilage discs

absorb shock, increase joint stability, distribute load

hip internal rotation occurs around the ___ axis

longitudinal

rotation vs flexion/extension vs abduction/adduction for what axis they occur around

rotation - longitudinal

flexion/extension - mediolateral

abduction/adduction - anteroposterior

example of an open kinetic chain activity

synchronized swimming

example of closed kinetic chain activity

squatting

___muscles on opposite sides of the joint may contract at the same time to increase joint stability

antagonist

if standing flat footed, raising up onto your toes requires your ankle to ___

plantarflex

kinetic chain

how forces move through the body when a segment is fixed vs free

closed kinetic chain (ckc)

distal end of the limb is fixed against an external surface (ground, wall, bar, etc)

forces in a ckc

ground reaction force pushes up into the distal segment; body weight pushes down through proximal joints (creates compressive forces at joints)

• increased joint compression = increased joint stability

examples of ckc

squatting, walking/running, pushups, cartwheels

open kinetic chain (okc)

distal end is free moving (not fixed to anything); forces come mostly from muscle contraction, not ground reaction

• less joint compression, more isolated joint motion

okc examples

kicking, throwing a ball, leg extension machine

active range of motion

you move the joint using your own muscles

(moving your wrist back and forth → wrist deviation)

passive range of motion

joint is moved by an eternal force (PT or partner)

• muscles are relaxed, usually greater ROM than active

active vs passive ROM reveals…

can’t move actively but can move passively → muscular issue

limited both actively and passively → joint, ligament, or bony issue

factors that affect ROM

muscle and tendon length

ligament tightness

joint/bone shape

ROM in shoulder vs hip

shoulder → high ROM, low stability

hip → lower ROM, high stability

fascia

passive connective tissue; surrounds and penetrates muscle; continuous with the tendon

what does fascia contribute to?

force transmission, muscle extensibility, and overall joint stability

muscle fiber components

sarcomere, SR, t-tubules, mitochondria

sarcomere

functional unit of muscle made of actin and myosin; shortens during contraction

SR

stores calcium; calcium release = muscle activation

• calcium presence allows actin-myosin interaction → contraction occurs)

t tubules

carry electrical signals deep into the muscle fiber; ensure coordinated contraction

mitochondria

produce ATP via aerobic metabolism (more mitochondria = greater endurance capacity)

longitudinal fiber arrangement

strap-like (sartorius mm); long ROM, less force

quadrate fiber mm

rhomboids; broad origin and insertion → stronger

triangular mm fiber

pectoralis major; broad origin and narrow insertion; combines strength and ROM

fusiform mm fiber

brachioradialis; thick middle, tapered ends

pennate mm

tibialis posterior; short fibers, packed tightly

bipennate mm

rectus femoris; central tendon with fibers on both sides

multipennate mm

multiple tendons; deltoid

why are pennate mm strong?

more fibers are arranged side by side → greater physiological cross sectional area (PCSA)

physiological cross sectional area

area that cuts perpendicular to muscle fibers; directly related to force production; pennate mm → larger PCSA → high force, less ROM

muscle contractions

muscle contraction determines how much force a muscle can produce and how movement occurs at a joint

striated (skeletal) muscle characteristics

extensibility (ability of muscle to be stretched)

elasticity (ability to recoil back to resting length)

contractility (ability to shorten and generate force)

excitability (ability to respond to a stimulus - action potential)

line of pull

the direction a muscle’s force acts on a bone

• represented by an arrow that starts at the insertion, points toward the origin, and follows the midline of the muscle belly

**muscles always pull, never push