The Contractors

Vince Bendotti

Chris Hoepfner

Taylor Stephenson

Cory Worthey
Why is muscle important?

Muscle contractions provide the basis for all
human movement.

-Muscle tissue produces force because of the
interaction of its basic contractile elements
(myofilaments), which are composed primarily of
protein.

-The function of the muscle tissue ultimately
depends on the type of muscle tissue involved.
Types of muscle
tissue

Skeletal- Voluntary, Striated, Multinucleated

Smooth- Involuntary, Non-Striated, Single nucleus

Cardiac muscle- Involuntary, Striated, Single
nucleus
Skeletal muscle

Function

1) Provides skeletal movement for the body

Contractions, move bones

2)Maintain Posture and body position

3)Homeostasis- Regulates
body temperature

4) Stores nutrient reserves

Protein
Smooth Muscle

Located in the walls of hollow organs such as the digestive
tract, bladder, blood vessels, reproductive tracts

Functions

Contract in the intestines to push food through the body

Contract in the bladder to expel urine

Contract to push food to the stomach
Cardiac Muscle

Located in the heart muscle
 Functions
 Contracts
the Atria and ventricles of
the heart to regulate blood flow
throughout the body
Changes in muscle with
growth & maturation:

Infancy

Fiber types are undifferentiated until ~30 weeks
(gestational age)

By infancy,

15% are still undifferentiated,

40% Type I,


35% Type IIA,
10% Type IIx.
Changes in muscle with
growth and maturation


Adulthood

50% Type I,

30% Type IIa,

20% Type IIx,
showing a shift in fiber type coming from
undifferentiated fibers towards Type I and IIx fiber
types (ref. 1).
Changes in muscle with
growth and maturation

The first two attached pictures show absolute fatfree mass estimates from birth to young adulthood
using total body water and total body density,
respectively.

Boys and girls have similar fat-free mass values
until the ages of puberty, when FFM steadily
increases and begins to level-off in women

while men experience a marked increase in FFM
until it begins to level-off at about age 20. (ref. 2)
Changes in muscle with
growth and maturation

After a peak in FFM between the ages of 18-34,
men experience a steady decrease in FFM with
age,

average decrease of 12.4% (+/- 9.5%) between the
age categories of 18-34 and 75+.

On average, women experience a 10.0% (+/- 9.5%)
decrease over that same time period (ref. 3).
Changes in muscle with
growth and maturation

The third attached picture shows FFM estimates
during growth.

At birth, 15% of an infant's body mass is protein.

This number steadily increases throughout
childhood and adolescence until it reaches ~19%
during young adulthood (ref. 1).
Increasing of muscle

Myogenesis - The formation of muscle fibers and
muscles

- Satellite cells become activated and expressed
and then become myoblasts

-These cells fuse together to generate new
myofibers during regeneration of torn and
damaged skeletal muscle
Increasing muscle

Hypertrophy- An increase in the size of existing
muscle cells


-This occurs with progressive overload resistance
training
proper nutrition

carbohydrates and protein,

genetics

Hormones

testosterone

Hgh

Androgens

IGF-1
Decreasing

Atrophy- Decrease in muscle cell size.

-Can occur from disease, immobilization, lack of
physical activity, aging and lack of nutrients.

-Decreases in protein synthesis and increases in
protein degradation both have been shown to
contribute to muscle protein loss due to disuse
Decreasing muscle size

Diseases that lead to Atrophy

Examples of diseases affecting the nerves that
control muscles:

Amyotrophic lateral sclerosis (ALS or Lou Gehrig's
disease)

Guillain-Barre syndrome

Neuropathy

Polio (poliomyelitis)

Parkinson’s
References

1. Heymsfield, S. (2005). Variation in body composition associated with
sex and ethnicity. In: Human Body Composition (Vol. 918, p. 278).
Champaign, IL: Human Kinetics.

2. Malina, R. M., Bouchard, C., & Bar-Or, O. (2004). In: Growth,
Maturation, and Physical Activity (pp. 144-146). Champaign, IL: Human
Kinetics.

3. Kyle, U. G., Genton, L., Hans, D., Karsegard, L., Slosman, D. O., &
Pichard, C. (2001). Eur J Clin Nutr, 55, 663-72.