1. Exercise Physiology McArdle, Katch, & Katch – Ch. 16
Body Composition
Exercise Physiology
McArdle, Katch, & Katch – Ch. 16

2. Gross Composition of Human Body
Body composition analysis often focuses on the tissue and whole body levels of multi-component model.

3. Behnke’s Reference Man
12% storage, 3% essential for men
Storage fat averages ___% of body mass for young men.
Essential fat averages ___% of body mass for young men.

4. Reference Woman Storage fat averages ___% for young adult women.
15% storage and 12% essential for women
Storage fat averages ___% for young adult women.
Essential fat averages ___% for young adult women.
Four times greater essential fat for females relates to child-bearing.

5. Gross Composition of Body
Essential fat: fat in organs, muscle, CNS, bone marrow. Also includes sex-specific essential fat necessary for survival.
Storage fat: energy reserve includes visceral adipose tissue & larger subcutaneous depots.
Fat Free Body Mass and Lean Body Mass
In vivo (within a living organism), it isn’t possible to differentiate between essential and non-essential fat.
LBM =FFM (bone, muscle, organs, connective tissue) + essential fat. LBM is an in vivo entity.
Density of human fat is .901 g/cm3. FFM varies.
Essential fat amount of fat necessary for survival

6. Gross Composition of Body
Density of FFM lower in children than adults.
Female density of FFM is lower at each age than male.
Percentage of FFM that is composed of water is higher in children.

7. Gross Composition of Body
Minimal body mass
What is suggested “healthy” lower level % fat in ? 3%
In females, includes 3% essential fat (same as ) + 9% sex-specific essential fat = 12%.
Optimal range of body fat should be established for each sport.
Elite female athletes in ballet, gymnastics, rowing, skating, track running events, triathlon body fat 8-15%
Underweight ≠ thin; appearance may average 18.2% body fat.

8. Leanness, Exercise, and Menstrual Irregularity
Lean:fat ratio may play role normal menstrual function.
Peripheral fat’s role in angrogens to estrogen
Production of leptin in adipose tissue
Factors associated with menstrual irregularity
High levels chronic physical stress causes hormone cascade
Nutritional inadequacy to sustain pregnancy
Too little fat triggers metabolic disturbances
Regional fat deposition

9. Methods of Body Composition
Direct Assessment
Chemical dissolution: dissolves body into fat and fat-free components
Physical dissection: extensive dissection of cadavers.

10. Indirect Body Composition
Hydrostatic Weighing
Air Displacement
Skinfolds
Girth Measurements
Bioelectrical Impedance Analysis
Dual-Energy X-Ray Absorptiometry
Near Infrared Interactance
Ultrasound
Computed Tomography
Magnetic Resonance Imaging

11. Hydrostatic Weighing
How is Archimedes principle of water displacement used to evaluate body composition?
Loss of weight in water equals weight of water displaced which yields volume of water any temperature.
Example: 50 kg  F
F = 48,000 cm3
50 kg ÷ 48,000 cm3 = g/cm3

12. Hydrostatic Weighing Body Density = Mass ÷ Volume
Computing % body fat using population specific equation.
Limitations and Errors.
Air compartments in body.
Densities of FFM vary due to race, age, and athletic experience.

13. Air Displacement Air displaced = Body Volume
Body density = mass ÷ volume
High validity compared to hydrostatic weighing

14. Skinfolds Common field method
Relationships among selected skinfold sites and body density
Caliper exerts constant tension of 10 g/mm2
Sum of skinfolds indicates relative fatness of individual

15. Girth Measurements Uses 3 sites: see Appendix F
Men: right forearm, abdomen, right upper arm (<27) or buttocks (27+)
Women: abdomen, right thigh, right forearm (<27) or right calf (27+)
Pattern of fat distribution
Predicting Body Fat

16. Bioelectrical Impedance
Hydrated, fat-free body tissues and extracellular water facilitate electrical flow compared to fat tissue because of greater electrolyte content of fat-free component.

17. Dual Energy X-Ray Absorptiometry
Two distinct x-ray energies penetrate into bone & soft tissue areas to depth of 30 cm. Computer software reconstructs an image of underlying tissue.
Quantifies bone mineral content, total fat mass, and FFM.

18. Body Mass Index
Importance of this easy to obtain index is its curvilinear relationship to all-cause mortality.

19. Near-Infrared Interactance
Uses technology developed by U.S. Dept. Agriculture to assess body composition of livestock and lipid content of grains.
Does not accurately predict human body fat across broad range of body fat levels.

20. Ultrasound Measures: Assess thickness of different tissues
Obtain image of deeper tissues, e.g. muscle’s cross sectional area
It works by converting electrical energy through a probe into high frequency pulsed sound waves that penetrate the skin surface to fat-muscle interface.

21. Computed Tomography
Generates detailed cross-sectional, 2 dimensional radiographic images.
Passes x-ray beam through tissues of different densities.
Provides quantitative information on:
Total tissue area
Total fat and muscle area
Thickness and volume of tissues w/i organ

22. Magnetic Resonance Imaging
Electromagnetic radiation, not ionizing radiation, in strong magnetic field excites hydrogen nuclei of body’s water and lipid molecules. Nuclei then project detectable signal to visually represent various body tissues.
Provides quantitative information on total and subcutaneous adipose tissue.

23. Average Values for Body Composition
Average young male possesses between __ and __% fat.
Average young female possesses between ___ and ___ % fat.
Men = 12-15%
Women = 25-28%

24. Goal Weight
Goal weight should be based on body composition not stature.
Goal Weight = Fat Free Body ÷ (100 -% Desired Body Fat)
Desirable Fat Loss = Present body weight – Goal body weight

25. Percentage of Body Fat Ballet dancers: 13-20 Body builders: 10-15
Triathlon: 10-15
Jumpers: 10-18

26. Illustration References
McArdle, William D., Frank I. Katch, and Victor L. Katch Essentials of Exercise Physiology 2nd ed. Image Collection. Lippincott Williams & Wilkins.
Plowman, Sharon A. and Denise L. Smith Digital Image Archive for Exercise Physiology. Allyn & Bacon.