Kin 121 Lec 13 +14- kinanthropomety and muscle fibers

What are the 4 ways of kinanthropometry?

• size

• proportionality

• composition

• shape

What percentage of excess fat does it become a chronic health risk at

Woman= over 30%, men= over 20-25%

kinanthropometry

different ways to asses the body and physique

Under and overweight BMI

Over 30= overweight , under 18.5= underweight

ways to measure size

• sitting or standing stature

• mass or weight

• lengths (limbs, segments, bones)

• girths

• widths

ways to measure proportionality

• stature proportions

• BMI

• Length proportions

• girth proportions

• width proportions

stature proportions

sitting height relative to standing height; females generally have longer trunks relative to leg length

BMI

weight relative to height; weight/height squared, BMI under 25 =increased risk of disease, BMI over or equal to 30 is considered obese

very controversial as it is not useful for children, teens, pregnant woman, or muscular people

length proportions

• crural index (lower leg relative to upper leg)

• brachial index (lower arm relative to upper arm)

• arm span relative to height

• trunk length relative to leg length

girth proportions

hip relative to waist

width proportions

shoulders relative to hips, androgyny index

surface area relative to volume

children have larger surface area relative to volume so they are more cold sensitive, as your height increases, your surface area squares but volume cubes

2 components of body composition

lean body mass and fat body mass

lean body mass

skeletal muscle, bone, water

fat body mass

storage fat, essential fat

storage fat

accumulates as a dispose, serves as a energy reserve, cushions and protects organs, mainly subcutaneous distribution

male=12% female=15%

essential fat

central nervous system; bone marrow, heart, lungs, liver, spleen, kidneys, intestines, muscle

comprises 12% of body weight for females, and 3% for males

height/ weight charts

used to assess body composition, assumption that if you weigh more than the normal for your height then you are fat so it is not reliable

waist to hip ratio

gynoid(pear) shape= female

android(apple) shape= male

obese individuals with excess abdominal fat leads to an increased risk of :

• coronary disease

• hypertension

• type 2 diabetes

waist girth

a very strong indicator of a health risk

hydrostatic

is the gold standard for all methods of body composition calculations

archimedes principle

he realized that the amount of water that spilled was equal in volume to the space that his body occupied. This fact suddenly provided him with a method for differentiating a mixed silver and gold crown from a pure gold crown.

air displacement( bod pod)

density= mass/volume

measure the volume of water or air displaced, have to correct for air in the lungs or GI tract

Bioelectric impedance

based on differences in electrical conductivity between fat free and fat mass, influenced by hydration level

Dual energy X-ray Abdorptiometry (DXA)

a painless medical scan that uses 2 different x ray beams to measure bone density, often in the hip and spine

skinfold thickness

% body fat calculations, sum of skinfolds 

somatotyping

used for shape; the human shape can be divided into

-endomorphy

-mesomorphy

-ectomorphy

changes over time

3 somatotypes

• endomorphy= roundness

• mesomorphy= muscularity

• ectomorphy= linearity

sex differences in somatotypes

males are more mesomorphic and females are more endomorphic

myofilaments

myosin and actin (comprise the sarcomere unit)

sarcomere

functional unit of a muscle fibre

a muscle contraction

many sarcomeres shortening (actin sliding over the myosin)= the sliding filament theory

crossbridge formation

a signal comes from the motor nerve activating the fibre 

the heads of the myosin filaments temporarily attach themselves to the actin filaments

cross bridge movement

similar to the stroking of the oars and movement of rowing shell

movement of myosin filaments in relation to actin filaments

shortening of the sarcomere

shortening of each sarcomere is additive

anatomy of a single myofibril contracting

sarcomeres should be optimal distance apart so an optimal number of cross bridges is formed

what happens when sarcomeres are stretched farther apart than optimal

fewer cross bridges can form= less force produced

what happens when the sarcomeres are too close together

cross bridges interfere with one another as they form= less force produced

name of outer membrane

sarcolema

name of thin contractile protein

actin

sarcoplasmic reticulum

(net like) labryinth of tubules inside fiber

T- tubules

(transverse tubules) connect sarcoplasmic reticulum to the outer membrane (sarcolemma)

connective tissue

comprised mainly of protein collagen surrounds all myofibrils, muscle fibers and muscle fiber bundles. it is continuous with, and a part of, the tendons that join muscle to bone.

what is attached to the bones to create movement

muscles

strong fibrous tissues that attach muscle to bone

tendons

neural impulse- also called an action potential

“drive mechanism” for a muscle to contract; electrical currents that pass along nerve fibres

Each motor nerve innervates many muscle fibres and is called a?

motor unit

synapses

impulse cross gaps between adjoining nerves

motor end plate

impulse cross gaps to innervate muscle

both gaps crossed using this neurotransmitter

acetylcholine

Where do impulses arrive at neuro- muscular junction?

motor endplate

how is calcium released in muscle contraction

impulse travels over the sarcolemma, through the T-tubules, causing calcium to be released from storage in sarcoplasmic reticulum

what does the release of calcium from sarcoplasmic reticulum cause?

molecular cross bridging of actin and myosin

what happens in the absence of a neural impulse?

calcium is reabsorbed into sarcoplasmic reticulum, thus stopping the contraction

Are all skeletal muscle fibers the same?

No. there are two types: type 1 or type 2

type 1 fibres

also called slow twitch fibres; contract slowly, fatigue slowly

type 2 fibers

also called fast twitch fibers; contract and fatigue quickly

what type of contractions will muscles that are mostly slow twitch fibers produce?

less powerful, but will be able to repeat the contraction many more times before fatigue

what type of contractions will muscles made of mostly fast twitch fibers produce?

more forceful contractions

examples of activities that would require activation of fast twitch fibres

running, jumping

examples of activities that would require activation of slow twitch fibers

walking, distance running, any type of endurance event

What type of fiber is suited for repeated contractions , requiring a force output of under 20-25% of max force output

slow twitch fibers

what fiber has a significantly greater force and speed generating capability and is well suited for activities involving high power

Fast twitch fibers

which genetic proportion are greatly advantaged in some sports

those with high % of fast twitch fibers

How long for a slow twitch fiber to reach peak and how many muscle fibers are innervated?

110 milliseconds to reach peak and approx 100 muscle fibers

How long for fast twitch fibers to reach peak and how many muscle fibers innervated?

50 milliseconds to reach peak and approx 500+ muscle fibers innovated

Muscle fibers under a microscope

slow: red fibers, small diameter, capillaries “oxidative”

fast: white, large diameter, dense packed myofibrils “glycogenic”

fast/slow twitch fiber distribution

• no sex or age differences

• non-athletes: 47-50% of each

• distance athletes: 70-80% slow twitch

• sprinters: 30-35% slow twitch

What type of muscle fibers do everyday activities use?

slow twitch

what do trained athletes in endurance activities vs fast explosive activities use

endurance activities= very efficient slow twitch

fast explosive activities= more efficient fast twitch

what fiber recruits first and then second

first- slow twitch

second- fast twitch

training effects on fiber type

• increased capillarization and aerobic capacity (more efficient slow twitch)

• increased motor unit activation of the desired muscle fibers