Body Composition

ÒKnowing a person's body composition is more valuable for predicting performance potential than merely knowing height and weight

Densitometry is one of the best methods for assessing body composition and has long been considered the most accurate Densitometry involves calculating the density of the athlete's body by dividing body mass by volume, which is typically determined via hydrostatic weighing or air displacement

Body weight standards should be based on body composition, emphasizing relative body fat rather than total body mass

For each sport, a range of values should be established, recognizing the importance of individual variation, methodological error, and sex differences

POTENTIAL CAUSES OF OBESITY

Genetic predisposition Physiological, psychological, or emotional trauma Hormonal imbalances Cultural or familial factors Diet composition Physical inactivity

dehydration

Impairs kidney and cardiovascular function Losses of 2-4% of body weight through dehydration can impair performance

Menstrual dysfunction

Likely the body's natural adaptation to a prolonged energy deficit

Chronic Fatigue

May be due to substrate (glycogen) depletion Symptoms mimic overtraining

GUIDELINES FOR EXERCISE PRESCRIPTION FOR WEIGHT LOSS

Mode: Group I or II aerobic activities Duration: 30-60 min Intensity: moderate to vigorous (40% to 60% VO2 reserve - for beginners and eventual progression to 50% to 75% VO2 reserve ) Kcal Expenditure: 250 to 300 kcal or 4 kcal/kg of body weight per exercise session Frequency: 5 days/week or more Length of program: depended on desired weight loss

Disordered eating and eating disorders (e.g., anorexia nervosa, bulimia nervosa)

Pathological behaviors to control body weight Especially prevalent among women

Bone mineral disorders

Serious consequence of menstrual dysfunction

FIELD TECHNIQUES

Skinfold fat thickness -Sum of three or more sites used in a quadratic or curvilinear equation to estimate body density Bioelectrical impedance - Tends to overestimate relative body fat in lean athletic populations

Many sports enforce weight standards

Unfortunately athletes often turn to questionable, ineffective, or even dangerous methods of weight loss to reach weight goals

ETIOLOGY OF OBESITYFAT CELLS (ADIPOSE TISSUE)

With modest weight gain, fat cells increase in size. With significant weight gain, fat cells increase in size and number. With weight loss, fat cells decrease in size but not in number.

Anatomical model

adipose tissue, muscle, organs, bone, other

Fat-free mass

all body tissues that are not fat, including bone, muscle, organs, and connective tissue

RISKS WITH SEVERE WEIGHT LOSS

dehydration, chronic fatigue, eating disorders, menstrual dysfunction, bone mineral loss, female athlete triad

two component model

fat mass and fat free mass

Chemical Model

fat, protein, CHO, water, mineral

Density of fat

lower than the density of water

Dual-energy X-ray absorptiometry

originally developed for estimating bone density and bone mineral content, is now capable of providing accurate estimates of total body composition

RECOMMENDED NUTRIENT CONTENT OF A WEIGHT-REDUCING DIET

protein 15% Carb less than 55 fat less than 30

Fatigue can also be caused by

substrate depletion

Densitometry involves calculating

the density of the athlete's body by dividing body mass by volume, which is typically determined via hydrostatic weighing or air displacement

Fat mass

the total body mass that is composed of fat

Relative Body Fat

•A high relative body fat is generally detrimental to performance •Maintaining a low body fat is desirable in sports in which the body weight is moved through space (e.g., running and jumping)

ACHIEVING OPTIMAL WEIGHT

•Avoid fasting and crash dieting •Work toward achieving the upper-end goal weight slowly •Lose no more than 0.5-1.0 kg (1.1-2.2 lb) per week •When the upper-end goal weight is achieved, further weight reduction should be achieved at an even slower rate (<0.5 kg or 1.1 lb per week) •Reduce caloric intake by 200 to 500 kcal per day •Eat at least 3 balanced meals per day •Use moderate resistance and endurance training

ESTABLISHING APPROPRIATE WEIGHT STANDARDS

•Based on body composition instead of weight •Sport and event specific •Optimal ranges for relative body fat should be established •Sex and individual differences should be considered •Methodological errors in body composition measurement should be considered

DENSITOMETRY

•Body density = body mass ÷ body volume

Maximizing Fat-Free Mass

•Desirable for athletes involved in strength, power, and muscular endurance types of activities •May be undesirable for endurance athletes or jumping sports (horizontal movement)

BODY COMPOSITION VS. HEIGHTAND WEIGHT IN ATHLETES

•Generally, an athlete's body composition is of greater concern than total body size and weight •Standard height and weight tables do not provide accurate estimates of what an athlete should weigh because they do not take into account the composition of the weight

OTHER LABORATORY TECHNIQUESTO ASSESS BODY COMPOSITION

•Radiography •Computed tomography (CT) •Magnetic resonance imaging •Hydrometry •Total body electrical conductivity •Neutron activation •Dual-energy X-ray absorption (DEXA) •Air displacement

Density of fat-free mass

•higher than the density of water

•Increases in body fat might possibly be of benefit for:

-Heavyweight weightlifters because it lowers their center of gravity -Sumo wrestlers -Swimmers because fat improves buoyancy

Body composition refers to the chemical composition of the body

1.Chemical model 2.Anatomical model 3.Two-compartment model

1.The density of each tissue constituting the fat-free mass is known and remains constant

1.Each tissue type represents a constant proportion of the fat-free mass (e.g., bone always represents 17% of the fat-free mass)

Thermogenic effect of a meal

10 %

lower than the density of water

495 ÷ body density) - 450