C H A P T E R 14 BODY WEIGHT, BODY COMPOSITION, AND SPORT

C H A P T E R 14 BODY WEIGHT, BODY COMPOSITION, AND SPORT

Learning Objectives Differentiate among body build, body size, and body composition. Find out what tissues of the body constitute fat-free mass. Discover how densitometry and several field techniques are used to assess body composition. Examine the relationship of relative leanness and fatness to performance in sport. (continued)

Learning Objectives Find out what guidelines best determine an athlete's goal weight. Learn why athletes should avoid crash dieting or fixating on a weight that is too low. Find out how much weight an overweight athlete can lose per week to maximize fat loss and minimize fat-free mass loss.

Body Build, Size, and Composition Body build is the form or structure of the body. Muscularity (mesomorphy) Linearity (ectomorphy) Fatness (endomorphy) Body size is determined by height and weight. Body composition refers to the chemical composition of the body. Fat mass Fat-free mass

MODELS OF BODY COMPOSITION

Did You Know? Fat-free mass is composed of all of the body's nonfat tissue including bone, muscle, organs, and connective tissue. Lean body mass includes all fat-free mass along with essential fat. Lean body mass is difficult to measure so the fat mass/fat-free mass model is most often used.

Did You Know? Body composition is a better indicator of fitness than body size and weight. Being overfat (not necessarily overweight) has a negative impact on athletic performance. Standard height-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. An athlete can be overweight according to these tables yet have very little body fat.

Assessing Body Composition Densitometry (hydrostatic weighing) Dual-energy X-ray absorptiometry Air plethysmography Skinfold fat thickness Bioelectric impedance

Densitometry Body density = Body mass Body volume Body mass = measured on a regular scale Body volume = measured using hydrostatic (underwater) weighing accounting for water density and air trapped in lungs % body fat = (495 body density) 450

UNDERWATER WEIGHING TECHNIQUE

Did You Know? Inaccuracies in densitometry are due to variation in the density of the fat-free mass from one individual to another. Age, sex, and race affect the density of fat-free mass.

Differences in the Density of Fat-Free Mass (D FFM ) in Three Female Athletes Edna Vicki Susan Body tissue D T % D P D T % D P D T % D P Muscle 1.065 46 0.490 1.065 41 0.437 1.065 46 0.490 Bone 1.350 17 0.229 1.350 22 0.297 1.260 17 0.214 Remainder 1.030 37 0.381 1.030 37 0.381 1.030 37 0.381 D FFM 1.100 1.115 1.085 Note. D T = density of the tissue; % = percent contribution of this tissue to the totalfat-free mass; D P = proportional density of the tissue (D T %); D FFM = density of the fat-free mass, which is the sum of the proportional densities.

DUAL-ENERGY X-RAY ABSORPTIOMETRY (DXA)

AIR PLETHYSMOGRAPHY

MEASURING SKINFOLD FAT THICKNESS

BIOELECTRIC IMPEDANCE TECHNIQUE

Body Composition and Performance Maximizing fat-free mass Desirable for strength, power, and muscular endurance Undesirable for endurance or jumping sports if result is a gain in weight Minimizing relative body fat Desirable, especially in sports in which the body weight is moved through space Improves speed, endurance, balance, agility, and jumping ability

Did You Know? Combining resistance training with the ingestion of carbohydrate, or carbohydrate and protein, during recovery from resistance training appears to be effective for increasing fat-free mass

The Effect of Relative Body Fat on Selected Performance Tests in Young Men Subject s level of fatness (% body fat) Performance test Low Moderate High (<10%) (10-15%) (>15%) 75-yd dash (s) 9.8 10.1 10.7 220-yd dash (s) 29.3 31.6 35.0 Standing long jump a (ft) 23.8 22.7 20.2 Sit-ups in 2 min 43.4 41.6 36.2 Note. The men in this study were classified into three levels of fatness: low, moderate, and high. a Sum of three trials.

RELATIVE BODY FAT IN ELITE TRACK AND FIELD ATHLETES

Risks With Severe Weight Loss Dehydration Chronic fatigue Disordered eating and eating disorders Menstrual dysfunction Bone mineral disorders

Appropriate Weight Guidelines Maximize performance within the specific sport Are based on body composition Emphasize relative body fat rather than total body mass Use a range of relative fat values that are considered acceptable for the athlete s age, sex, and sport/event

Computing a Weight Goal for Performance for a Female Swimmer Parameter Measure Weight 72.6 kg (160 lb) Relative fat 25% Fat weight 18.2 kg (40 lb) (weight 25%) Fat-free weight 54.4 kg (120 lb) (weight fat weight) Relative fat goal 18% (= 82% fat-free) Weight goal 66.3 kg (146 lb) (fat-free weight 82%) Weight loss goal 6.3 kg (14 lb)

COMPOSITION OF WEIGHT LOSS

Achieving Optimal Weight Combine proper diet with exercise. Lose no more than 0.5 to 1.0 kg (1 to 2 lb) per week. Reduce caloric intake by 200 to 500 kcal less than daily energy expenditure. Use moderate resistance and endurance training. Decrease fat mass and increase fat-free mass