EXSS3071 Week 6 Lecture

Slide 1 – Lecture Title & Contributors

EXSS3071+Body+Composition+2025+S1.pdf](file-service://file-UNYypUZrTedW3jk6snDvVy)

• Topic: Body Composition (EXSS3071 — 2025 S1).

• Lecturer: Kenneth Daniel (APD, AFHEA).

• Acknowledgements: A/Prof Janelle Gifford, A/Prof Helen O’Connor, Ms Alison Miles.

• Sets the scene for a methods-heavy exploration of how, why and when to measure body composition in sport and health contexts.

Slide 2 – Mental-Health Support Services

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• Lists on- and off-campus resources (CAPS, USYD crisis line, Butterfly Foundation, headspace, Lifeline, Beyond Blue, Batyr).

• Key point: discussions about physique can trigger anxiety or disordered-eating concerns; practitioners must recognise red-flag behaviour and refer promptly.

Slide 3 – Ethical Imperative

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• Quotation (Swimming Australia 2023): body-comp assessment should occur only with a clear rationale.

• Implies duty of care and avoidance of unnecessary physique monitoring, especially in adolescents and aesthetic sports.

Slide 4 – Why Measure Body Composition?

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• Health risk prediction: distinguishes over-weight vs over-fat.

• Monitoring change: growth, ageing, training, rehab, supplements/meds.

• Performance optimisation: aligning mass distribution with force/acceleration demands; strategic periodisation.

• Clinical utility: tracking muscle loss post-injury or during cachexia.

Slide 5 – Periodisation Example

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• Case study: 9-year body-composition periodisation of an Olympic 1500 m runner (Stellingwerff 2018).

• Athlete cycles through race-weight phases and muscle-accrual phases, proving body-comp targets must sync with macro- and micro-cycle goals.

Slide 6 – Lecture Overview

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1. Compartment models (2-, 3-, 4-C).

2. Lab, 2-C: densitometry (UWW) & plethysmography (Bod Pod).

3. Field, 2-C: skinfolds, BIA.

4. Other technologies (DXA, MRI, CT, dilution methods).

5. Somatotyping.

• Density equation preview D = M/V.

Slide 7 – Part 1 Intro (Lab 2-C Methods)

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• Announces underwater weighing (UWW) and air-displacement plethysmography (ADP/Bod Pod) as gold-standard density measures requiring controlled lab settings.

Slide 8 – Body-Compartment Categorisation

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• Graphic (Shaw et al 2015) divides body into FM, FFM, bone, organs, etc.

• Emphasises that 2-C splits (FM vs FFM) assume fixed density & hydration values.

Slide 9 – Key Terminology

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• FM, FFM, LBM, VAT, SAT, BMC, BMD, BD defined with chemical/functional distinctions.

• Note: FFM ≈ 73 % water & 68 mmol K⁺ kg⁻¹.

Slide 10 – Two-Compartment Model Assumptions

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• Violations (e.g., growth, ageing, osteoporosis) introduce systematic error.

Slide 11 – Archimedes’ Principle Refresher

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• Buoyant force equals weight of displaced water.

• Forms the theoretical basis for UWW; densities corrected to 4 °C reference.

Slide 12 – Underwater Weighing Equipment

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• Photo of hydrostatic tank with seat & scale.

• Key hardware: load cell (±0.01 kg), thermometer (water density adjustment), N₂ wash-out system for lung volume.

Slide 13 – UWW Workflow Graphic

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• Stepwise: measure mass in air → subject exhales to RV → submerge & record mass in water → repeat for reliability.

Slide 14 – UWW Density Equations

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BD = \frac{M_{\text{air}}}{M_{\text{air}} - M_{\text{water}} - (RV - GG)} \times \rho_{\text{water}}

• RV = residual lung volume; GG = gut gas (~0.1 L).

• Siri (1956): %BF = 495/BD − 450.

• Brozek (1963): %BF = 497.1/BD − 451.9.

Slide 15 – Correction Factors

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• Water temperature alters density (0.999 g cm⁻³ at 22 °C vs 0.997 at 35 °C).

• Accurate RV measurement essential (He dilution or N₂ wash-out).

• Menstrual-cycle phase & bone-mineral density can shift BD slightly.

Slide 16 – %Body-Fat Conversion

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• Siri & Brozek equations reliable within BD range 1.03–1.10 g cm⁻³.

• Outside range (children, sarcopenic elderly) require multicomponent models.

Slide 17 – UWW Standardisation

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• Overnight fast, avoid gas-producing foods 12 h, tight swimwear, same cycle phase, prior technique coaching.

• Calibrate scales + gas analysers before session; perform ≥3 trials within 0.1 kg SD.

Slide 18 – UWW Pros & Cons

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Pros: inexpensive, high precision, time-efficient vs isotope dilution.

Cons: discomfort, full submersion difficult for obese/elderly, scale drift, claustrophobia, lower BMD may bias low.

• Clinician must weigh validity vs participant burden.

Slide 19 – Transition to Air-Displacement Plethysmography (ADP)

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• BOD POD exploits Boyle’s law to derive volume from pressure change; %BF via Siri/Brozek after BD computed.

• Accepts individuals up to ≈225 kg.

Slide 20 – PEA POD (Infant ADP)

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• Neonatal analogue measuring FM/FFM in <5 min; critical for low-birth-weight growth monitoring.

Slide 21 – Gas-Law Physics Behind ADP

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• Boyle: P_1V_1 = P_2V_2; Poisson (adiabatic adjustment).

• Chamber oscillates air at two frequencies to isolate thoracic gas volume.

Slide 22 – ADP Standardisation

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• Fasted, euhydrated, void bladder.

• Clothing: men—compression shorts; women—shorts + seam-free sports bra; swim-cap flattens hair.

• Calibrate digital scale weekly & 50 L cylinder each session.

Slide 23 – ADP Pros & Cons

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Pros: 2 × 30 s scans, non-invasive, portable, accommodates larger users, TEM 0.4–1.2 %BF.

Cons: clothing/hair/moisture artefacts, claustrophobia, relies on 1950-60s density equations, predicted lung-volume error.

Slide 24 – Part 2 Intro (Field 2-C Methods)

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• Moves to skinfolds and bio-electrical impedance (BIA): practical for clinics, teams, large cohorts.

Slide 25 – Anthropometry Defined

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• Measurement of mass, stature, breadths, lengths, girths, skinfolds to describe phenotype; valued for talent ID, growth tracking, weight-category sports.

Slide 26 – Basic Anthropometric Kit

‡EXSS3071+Body+Composition+2025+S1.pdf](file-service://file-UNYypUZrTedW3jk6snDvVy)

• Stadiometer, digital scale, Harpenden calipers, segmometer, non-stretch tape.

• Illustration: climber study (Smith 2017) shows niche-sport profiling.

Slide 27 – Practical Profile (ISAK-Level Measures)

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• 8-site skinfold sum, selected girths, biepicondylar breadths; enables physique trend monitoring across seasons.

Slide 28 – Applications & Limitations of Anthropometry

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• Direct, cheap, rapid; but depends on strict landmarks and technician skill; %BF estimation requires population-specific equations.

Slide 29 – Subject Considerations & Consent

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• Privacy, cultural sensitivity, minimal clothing, option for chaperone, avoid painful/injured sites; never compromise physical or emotional welfare.

Slide 30 – AIS Position on Disordered-Eating Risk

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• AIS 2020 guideline: certain presentations (under-age, active eating disorder) contra-indicate measurement; flags for referral pathways.

Slide 31 – Skinfold Technique Illustration

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• Demonstrates parallel vs diagonal pinch, 1 cm jaw placement, 2 s read time; recommends duplicate measures within 0.5 mm.

Slide 32 – Converting Skinfolds to %Fat

‡EXSS3071+Body+Composition+2025+S1.pdf](file-service://file-UNYypUZrTedW3jk6snDvVy)

1. Apply population regression (e.g., Durnin-Womersley) to predict BD.

2. Convert BD to %BF via Siri/Brozek.

• Emphasise using sum of skinfolds for longitudinal athlete monitoring to avoid prediction error.

Slide 33 – Assumptions & Error Sources

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• Constant skin compressibility, fixed fat distribution, uniform FM/FFM densities.

• Technical error of measurement (TEM) + biological error (hydration, menstrual phase) + UWW reference error.

Slide 34 – Interpreting Change Over Time

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• Figure shows that weight loss with stable skinfolds likely reflects FFM loss; decreasing sum with stable mass indicates FM loss; both metrics needed for nuanced feedback.

Slide 35 – Anatomical Landmarks Protocol

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• Palpate, release, remark; use fine-tip pen; confirm in anatomical position.

• Landmarks underpin ISAK reliability thresholds (TEM < 1 mm for skinfolds).

Slide 36 – Landmark Accuracy Study

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• Hume 2008: inter-tester TEM improves from 9 % to 4 % after standardised ISAK training.

Slide 37 – Technical Error of Measurement (TEM)

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• Defines random-error quantification; small TEM is prerequisite for detecting “real” physique changes (≥2 × TEM).

Slide 38 – “Real Change?” Case

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• Graph shows skinfold fluctuations across three sessions; only change exceeding 2SD flagged as true adaptation.

Slide 39 – Bio-Electrical Impedance (BIA) Overview

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• Sends 50 kHz, 800 µA current.

• Resistance ↑ in fat (14–22 % water); conductance ↑ in lean (73 % water).

• Multi-frequency & segmental devices improve prediction of TBW & skeletal muscle.

Slide 40 – BIA Considerations

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• Hydration, food, exercise, skin temp, electrode placement alter impedance.

• Requires population-specific equations (athletes vs sedentary, ethnicity).

• Best used for within-subject monitoring under strict standardisation.

Slide 41 – Part 3 Intro (Other Techniques)

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• Transitions to multi-compartment and imaging methods for high-precision research and clinical diagnostics.

Slide 42 – Technique Inventory

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• DXA, MRI, CT, deuterium TBW, D₃-creatine (skeletal muscle mass), 4-C modelling, laser scanning, ultrasound.

Slide 43 – Dual-Energy X-Ray Absorptiometry (DXA)

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• Simultaneously quantifies bone mineral, FM, and lean soft tissue; low radiation (≤5 µSv).

• Scan time 5–30 min depending on beam type; expensive and size-limited.

Slide 44 – DXA Beam Technology

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Slide 45 – DXA Report Example

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• Colour map showing android/gynoid fat %, regional lean mass; used for RED-S screening and limb muscle balance in return-to-play.

Slide 46 – MRI & CT Imaging

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• MRI: ~30 min, high soft-tissue contrast, no ionising radiation; contraindications (pacemaker).

• CT: excellent VAT quantification but whole-body dose ≈8 years background radiation—research use limited.

Slide 47 – NMR Spectroscopy Advances

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• ¹H-NMR permits in-vivo IMCL and liver fat quantification; emerging athlete-monitoring tool for overtraining & metabolic health.

Slide 48 – Deuterium Dilution

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• Measures total body water; assumes tracer distributes only in water, equilibrates quickly, not metabolised.

• FM calculated: Body Mass − FFM; FFM = TBW/0.732.

Slide 49 – Four-Compartment (4-C) Model

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• Combines mass + volume (UWW/Bod Pod) + TBW (dilution/BIA) + BMC (DXA); considered modern gold standard; random error minimised as assumptions are distributed.

Slide 50 – Standardisation Essentials

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• Technical + biological control reduces noise: overnight fast, rested, euhydrated, void, no exercise 12 h, same menstrual phase.

• Video link provides demonstration checklist.

Slide 51 – Food/Fluid Intake Effects

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• Kerr 2017: breakfast (750 kcal) increases DXA fat-mass estimate by ~0.3 kg; hydration shifts lean estimate.

• Interpretation of change must consider presentation variability.

Slide 52 – Selecting the Right Technique

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• Decision matrix: Why, What, Who, required validity/reliability, cost, time, access, operator skill.

• Differentiate accuracy (validity) vs precision (repeatability).

Slide 53 – Part 4 Intro (Somatotyping)

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• Moves from quantitative mass to shape descriptors using Heath-Carter system.

Slide 54 – Physique & Sport Performance

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• Figure contrasts endurance, sprint, and aesthetic sport norms; highlights sport-specific somatotype “windows.”

Slide 55 – Somatotype Definition

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• Three-number rating: Endomorphy (fatness), Mesomorphy (musculo-skeletal), Ectomorphy (linearity).

• Rating scale: 1 = very low, 7 = very high (e.g., 3-5-2).

Slide 56 – Rating Summary Table

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• Provides interpretive categories: moderate 3-5, high 5.5-7, very high ≥7.5.

Slide 57 – Three-Factor Examples

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• Photos: Strongman (6-2-2), AFL forward (1-7-2), NBA centre (1-2-7); visualises somatotype spectrum.

Slide 58 – Heath-Carter Anthropometric Method

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• 10 measures: stature, mass, four skinfolds, biepicondylar breadths (humerus/femur), flexed-arm & calf girths.

• Equipment list; calculations for each component.

Slide 59 – Somatotype Applications

‡EXSS3071+Body+Composition+2025+S1.pdf](file-service://file-UNYypUZrTedW3jk6snDvVy)

• Track growth, monitor training adaptations, compare sexes, assess body-image perception, talent ID.

• Somatochart plotting: X = Ectomorph − Endomorph, Y = 2 × Mesomorph − (Ecto + Endo).

Slide 60 – Triathlon Performance Study

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• Ironman (165 M, 22 F): lower endomorphy & higher ectomorphy correlate with faster total time; strongest in run leg (30 % variance).

• Suggests physique acts as performance modulator even after training normalisation.

Slide 61 – End Slide (Thank You)

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• Signals conclusion; invites questions.

Slides 62–67 – Topic Objectives

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• Key learning outcomes (total 26) grouped under:
  

  1. Technique identification & principles (UWW, Bod Pod, DXA, BIA, MRI).

  2. Calculations (BD, %BF via Siri/Brozek).

  3. Model distinctions (2- vs 3- vs 4-C; cadaver validation).

  4. Practical measurement skills (landmarks, ISAK protocol, precision vs accuracy).

  5. Professional conduct (modesty, consent, confidentiality).

  6. Interpretation & application (athlete vs obese populations, change monitoring).

  7. Somatotype theory and utilisation.