CSSD Body Composition 2 — Questions and Answers
Question 1: Which body composition assessment method is considered the gold standard for measuring body fat percentage in research settings?
- Dual-energy X-ray absorptiometry (DXA)
- Air displacement plethysmography (ADP)
- Hydrostatic weighing
- Four-compartment model (Correct answer)
Correct answer: Four-compartment model
The four-compartment model (4C) is the gold standard because it measures fat mass, water, mineral, and protein independently, minimizing assumptions about body composition.
Question 2: A female endurance athlete has a body fat percentage of 14%. According to sports nutrition guidelines, which statement best applies?
- This is within the healthy performance range for female endurance athletes (Correct answer)
- This is below the essential fat threshold and requires immediate intervention
- This level is associated with improved VO2max in all female athletes
- This percentage indicates low energy availability only if BMI is also below 18.5
Correct answer: This is within the healthy performance range for female endurance athletes
14% body fat falls within the accepted performance range for female endurance athletes (10–20%), and is above the essential fat threshold (~10–13%) for females.
Question 3: When using skinfold calipers, which condition most significantly reduces measurement reliability?
- Testing immediately post-exercise when the athlete is hydrated
- Using a 3-site versus 7-site protocol
- Measuring on the non-dominant side of the body
- Inter-tester variability between different assessors (Correct answer)
Correct answer: Inter-tester variability between different assessors
Inter-tester variability is the largest source of error with skinfold measurements; the same tester (intra-tester) should perform repeated assessments for reliable tracking.
Question 4: Fat-free mass (FFM) density is assumed to be 1.1 g/cc in the Siri two-compartment model. Which athlete population would most violate this assumption?
- Recreational distance runners
- Elite swimmers
- High-level weightlifters with high bone mineral density (Correct answer)
- Soccer players of average build
Correct answer: High-level weightlifters with high bone mineral density
Athletes with significantly higher bone mineral density, such as weightlifters, have a denser FFM than the assumed 1.1 g/cc, causing the 2C model to underestimate body fat.
Question 5: During the off-season, an American football lineman gains 8 kg. DXA shows 5 kg is fat mass and 3 kg is fat-free mass. What does this suggest about his off-season diet?
- His protein intake was sufficient but total calories were excessive (Correct answer)
- He was in negative energy balance throughout the off-season
- His fat-free mass gain indicates optimal hypertophy-phase nutrition
- The DXA results confirm he consumed adequate carbohydrate for glycogen storage
Correct answer: His protein intake was sufficient but total calories were excessive
A gain predominantly of fat mass with a smaller FFM gain suggests a caloric surplus beyond what was needed to support lean tissue accretion, indicating excess total calorie intake.
Question 6: Bioelectrical impedance analysis (BIA) estimates body composition primarily by measuring:
- The absorption of two X-ray energy beams by different tissues
- The resistance of body tissues to a low-level electrical current (Correct answer)
- The difference between body weight in air and underwater
- The volume of air displaced when an athlete sits in a sealed chamber
Correct answer: The resistance of body tissues to a low-level electrical current
BIA passes a small electrical current through the body and measures impedance (resistance + reactance); fat-free mass, which contains more water and electrolytes, conducts electricity better than fat mass.
Question 7: A sports dietitian tracks a wrestler's body composition throughout a season. Which metric is most clinically meaningful to monitor for health and performance risk?
- Absolute fat mass in kilograms
- Body mass index (BMI)
- Minimum wrestling weight (MWW) and rate of weight loss (Correct answer)
- Waist-to-hip ratio
Correct answer: Minimum wrestling weight (MWW) and rate of weight loss
Minimum wrestling weight and rate of weight loss are the most clinically relevant metrics for wrestlers because rapid, extreme weight cutting increases health risks and impairs performance.
