CSSD Body Composition 3 — Questions and Answers
Question 1: Which of the following BEST describes the concept of 'fat-free mass index' (FFMI) in the context of athlete assessment?
- Fat mass divided by height squared
- Fat-free mass divided by height squared (Correct answer)
- Total body weight minus fat mass
- The ratio of visceral fat to subcutaneous fat
Correct answer: Fat-free mass divided by height squared
FFMI is calculated as fat-free mass (kg) ÷ height (m)², providing a height-adjusted measure of muscularity useful for comparing lean mass across athletes of different statures.
Question 2: An athlete's DXA scan shows a T-score of -2.6 at the lumbar spine. Which diagnosis applies, and what is the primary nutrition concern?
- Osteopenia; inadequate calcium intake
- Osteoporosis; low bone mineral density increasing fracture risk (Correct answer)
- Normal bone density; no nutritional action needed
- Osteomalacia; severe vitamin D deficiency causing bone softening
Correct answer: Osteoporosis; low bone mineral density increasing fracture risk
A T-score of ≤ -2.5 meets the WHO diagnostic threshold for osteoporosis, which significantly elevates stress fracture risk in athletes.
Question 3: When using hydrostatic weighing (underwater weighing) to estimate body density, what correction factor must always be applied?
- Tare weight of the underwater scale
- Residual lung volume at the time of submersion (Correct answer)
- Resting metabolic rate of the subject
- Skin surface area relative to body weight
Correct answer: Residual lung volume at the time of submersion
Residual volume — the air remaining in the lungs after maximal exhalation — creates buoyancy and must be measured or estimated to accurately calculate body density.
Question 4: A strength and conditioning coach asks the sports dietitian why two athletes with identical body weight and height have very different DXA-derived body fat percentages. The most likely explanation is:
- DXA has poor test-retest reliability and the difference is measurement error
- Differences in fat distribution and lean mass between the two athletes (Correct answer)
- BMI predicts body fat percentage and both athletes should have the same value
- DXA overestimates fat mass in muscular athletes making the comparison invalid
Correct answer: Differences in fat distribution and lean mass between the two athletes
Body weight and height (and therefore BMI) do not capture differences in fat versus lean tissue distribution, so two athletes with the same BMI can have markedly different body fat percentages.
Question 5: The Jackson-Pollock 3-site skinfold equation for women uses which three sites?
- Chest, abdomen, thigh
- Tricep, suprailiac, thigh (Correct answer)
- Subscapular, suprailiac, abdomen
- Bicep, tricep, subscapular
Correct answer: Tricep, suprailiac, thigh
The Jackson-Pollock 3-site formula for females uses tricep, suprailiac, and thigh skinfolds, whereas the male version uses chest, abdomen, and thigh.
Question 6: Which variable most strongly confounds BIA measurements taken in an athletic population?
- Ambient room temperature during testing
- Hydration status of the athlete (Correct answer)
- Time of day the test is administered
- The brand of BIA device used
Correct answer: Hydration status of the athlete
BIA relies on fluid distribution to estimate lean mass; dehydration or hyperhydration significantly alters electrical conductance and produces inaccurate body fat estimates.
Question 7: In the context of body composition for weight-class sport athletes, what does 'optimal competition weight' refer to?
- The lowest possible weight an athlete can reach through dehydration
- A weight at which performance is maximized while maintaining health and adequate fat stores (Correct answer)
- The average weight of competitors in a given weight class
- Body weight at the start of the competitive season
Correct answer: A weight at which performance is maximized while maintaining health and adequate fat stores
Optimal competition weight balances performance capacity with health, ensuring the athlete retains sufficient fat stores (above essential fat) and is not chronically energy-deficient.
CSSD Body Composition 3
Which of the following BEST describes the concept of 'fat-free mass index' (FFMI) in the context of athlete assessment?