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 fat-free 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.