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 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 ). 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,