EXSS3071 Week 8 Lecture

Slide 1 – Title

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• Dietary Protein Requirements of Athletes (EXSS3071, 2025 S1).

• Lecturer: Kenneth Daniel (APD, AFHEA); acknowledgements to Parker, Gifford, O’Connor, Miles, Hay.

• Lecture frames protein as performance-limiting nutrient when poorly managed.

Slide 2 – Lecture Outline

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1. Context/history. 2. Protein metabolism in exercise. 3. Timing, type & other modulators. 4. High vs low intakes. 5. Evidence-based recommendations.

• Visual of trail runner emphasises training–nutrition synergy.

Slide 3 – Part 1 Introduction

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• Sets the historical and cultural backdrop for protein fascination in physique sports.

Slides 4-7 – Brief History of Bodybuilding

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• Ancient Greece: Milo of Croton demonstrates progressive overload ideology.

• Grecian Ideal calculator: classical anthropometry targets.

• Eugene Sandow (late 1800s) establishes modern bodybuilding shows.

• Arnold Schwarzenegger era (1970s) popularises “golden-age” hypertrophy plus high-protein eating.

• Citations to Mitchell et al. 2017 & Spendlove et al. 2015 highlight gap between practice and evidence.

Slide 8 – Pharmacology & Physique

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• Atlantic article graphic depicts impact of anabolic drugs on extreme muscularity—context for “natural” protein limits.

Slide 9 – Evolution of Swimmer Physique

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• Dawn Fraser (1950s) → Shane Gould (1970s) → Libby Trickett (2000s): increasing muscle mass mirrors advances in resistance training and recovery nutrition.

Slide 10 – Protein RDI vs Athletic Needs

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• Australian NRVs: 0.84 g kg⁻¹ d⁻¹ (men) / 0.75 (women) meet adequacy for 98 % of general population.

• Athletes aim for optimal, not merely adequate, intake.

Slides 11-12 – Dietary Protein Sources

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• Meat & alternatives: lean beef, poultry, fish, eggs, tofu, legumes, nuts/seeds.

• Dairy & alternatives: milk, yoghurt, cheese, soy drink.

• Emphasis on combining plant and animal proteins for leucine thresholds.

Slide 13 – RDI vs EAR & Individualisation

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• RDI ≠ personal requirement. EAR meets only 50 % of population.

• Athletic “higher needs” drivers: tissue repair, immune function, lean-mass accrual.

Slide 14 – Do Athletes Need More Protein?

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• Tarnopolsky meta-analysis: strength & endurance training each elevate nitrogen losses and synthetic demands.

Slide 15 – Quantitative Targets

‡EXSS3071+Protein+Requirements+Lecture+2025+S1.pdf](file-service://file-7FYPXAX7Hng5dmV7fVZUSo)

• Consensus range 1.2-2.0 g kg⁻¹ d⁻¹.

• Practical pattern: 0.3 g kg⁻¹ (≈15-25 g) per meal and immediately after key sessions; supplies ≈10 g EAAs.

• Periodise within micro- and macro-cycles.

Slide 16 – Beyond Quantity

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• Critical modifiers: timing relative to exercise & CHO, even distribution, protein quality (PDCAAS/DIAAS), total energy availability.

Slide 17 – Part 2 Introduction

‡EXSS3071+Protein+Requirements+Lecture+2025+S1.pdf](file-service://file-7FYPXAX7Hng5dmV7fVZUSo)

• Shifts focus to molecular roles and turnover dynamics during exercise.

Slide 18 – Protein Functions in Sport

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• Structural (collagen, titin), contractile (actin, myosin), metabolic (mitochondrial enzymes), haematological (Hb/albumin).

• Training remodels each pool; diet must support synthesis.

Slide 19 – Essential vs Non-Essential AAs

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• 20 proteinogenic AAs; 9 essential for adults; branched-chain (Leu, Ile, Val) highlighted.

Slide 20 – Peptide Bond & Side-Chain Diversity

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• Diagram shows alpha-carbon, amine, carboxyl groups and unique R-chains; peptide bonds form via condensation reaction.

Slide 21 – Daily AA Recycling

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• Endogenous turnover ≈300 g d⁻¹; exercise accelerates flux; majority of catabolised N lost as urea.

Slide 22 – Measuring Requirements

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• Classic nitrogen balance: Protein (g) ÷ 6.25 = N (g).

• Modern tracer & biopsy techniques (¹³C-leucine oxidation, FSR) give higher precision.

Slide 23 – Protein Use During Exercise

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• BCAAs preferentially oxidised; GDH activity rises from 5-8 % (rest) to 20-25 % (exercise).

Slide 24 – Regulation of GDH

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• Activated by low ATP/low glycogen/high ADP; suppressed by CHO loading or intra-workout CHO, which spares muscle protein.

Slide 25 – Quantifying Oxidation in Endurance

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• AA supply 2-6 % of exercise energy; oxidation ↑ with intensity, glycogen depletion, higher dietary protein and in males.

Slide 26 – Training-Induced Protein Sparing

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• 38-day endurance program ↓ leucine oxidation & GDH activity, reflecting metabolic shift to lipid & glycogen preservation.

Slide 27 – Protein Balance & Resistance Exercise

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• Feeding turns negative balance positive; RT further elevates synthesis for up to 48 h post-bout.

Slide 28 – Fed vs Fasted × RT Matrix

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• Best-case: fed + RT → maximal net balance; fasting blunts MPS despite RT stimulus.

Slide 29 – Novice vs Trained Anabolism

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• Untrained athletes display larger absolute synthesis & breakdown; can gain 0.25-0.5 kg lean wk⁻¹ with adequate protein/energy.

Slide 30 – Part 3 Introduction

‡EXSS3071+Protein+Requirements+Lecture+2025+S1.pdf](file-service://file-7FYPXAX7Hng5dmV7fVZUSo)

• Explores practical ingestion variables: timing, dose, distribution, type.

Slide 31 – Timing: Pre/During Exercise

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• Little evidence that pre protein boosts acute performance, but may supply AA pool for recovery.

• Endurance bouts >90 min: small protein + CHO during work may reduce endogenous oxidation and later soreness.

• RT sessions >2 h: during-protein may help.

Slides 32-33 – Timing: Post Exercise

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• MPS elevated for 24 h; “anabolic window” optimal 0-2 h.

• Meta-analysis (Schoenfeld et al. 2013) finds timing matters when total daily protein is not already high.

Slide 34 – Optimal Single Dose

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• Dose-response plateaus at ~20 g high-quality protein (~10 g EAAs) for average-size athlete; larger bodies may need 0.4 g kg⁻¹.

Slide 35 – Distribution Strategies

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• Bolus (2 × 40 g), Pulse (8 × 10 g), Intermediate (4 × 20 g).

• Intermediate every 3 h produced greatest 12 h myofibrillar synthesis (Areta et al. 2013).

Slides 36-37 – Pre-Sleep Protein

‡EXSS3071+Protein+Requirements+Lecture+2025+S1.pdf](file-service://file-7FYPXAX7Hng5dmV7fVZUSo)

• 30-40 g casein ~30 min before bed augments overnight MPS and long-term hypertrophy, especially in evening-trained athletes.

Slide 38 – Is Whey the Way?

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• Whey is rapid-digesting, leucine-rich; studies (Hartman 2007, Cribb 2006) show superior lean-mass gains vs soy/casein when post-exercise.

Slide 39 – Leucine Trigger Mechanism

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• Leucine (≥2-3 g) activates mTORC1 → ↑ translation initiation and MPS.

Slide 40 – Energy & Macronutrient Needs for Hypertrophy

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• Energy surplus 1500-2000 kJ d⁻¹ plus ~1.6 g kg⁻¹ protein maximises muscle gain; adequate CHO supports RT performance.

Slide 41 – Hormonal Modulators: Testosterone

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• Supra-physiological doses ↑ lean mass even without exercise; resistance training magnifies effect; WADA banned.

Slide 42 – Hormonal Modulators: Insulin

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• Insulin amplifies AA uptake and MPS; rationale for CHO + protein co-ingestion in early recovery phase.

Slide 43 – Part 4 Introduction

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• Examines risks and special situations: excess intake, low intake, ageing, energy deficit, injury.

Slide 44 – Risks of Excessive Intake

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• Intakes 1.4-1.9 g kg⁻¹ typical; >3 g kg⁻¹ may displace other nutrients and waste money; no strong evidence of kidney/bone harm in healthy adults.

Slide 45 – Athletes at Risk of Low Intake

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• Weight-category sports, aesthetic sports, extreme vegetarians, eating-disorder cohorts.

Slide 46 – Older Athletes

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• Anabolic resistance: suggest ≥1.2 g kg⁻¹, 35-40 g leucine-rich doses, and resistance exercise; adjust downward with renal impairment.

Slide 47 – Negative Energy Balance

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• Energy deficit ↓ MPS; increase per-meal protein to 0.3-0.4 g kg⁻¹, maintain RT to spare lean mass.

Slide 48 – Injury & Bed Rest

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• 7 d bed rest can cut lean mass by 1.4 kg and insulin sensitivity by 29 %; neuromuscular electrical stimulation + pre-sleep casein mitigates loss.

Slide 49 – Part 5 Introduction

‡EXSS3071+Protein+Requirements+Lecture+2025+S1.pdf](file-service://file-7FYPXAX7Hng5dmV7fVZUSo)

• Translates evidence into field practice.

Slide 50 – Position Statements

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• Key references: ACSM/AND/CSEP 2016, IAAF 2019—provide sport-specific protein guidelines.

Slide 51 – Practice Tips

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• Strength phase: 1.6-1.7 g kg⁻¹; distribute evenly; prioritise 0-2 h post-exercise; excess beyond 2.2 g kg⁻¹ offers no added benefit.

Slide 52 – Do Athletes Meet Targets?

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• Survey data show most exceed RDI but distribution and timing often sub-optimal.

Slide 53 – Whole-Food Emphasis

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• Dietitians favour minimally processed lean meats, dairy and legumes before defaulting to supplements.

Slide 54 – Milk vs Protein Powder Economics

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| Item (per 20 g protein) | Cost (AUD) | Notes |

| Skim milk | ≈$0.60 | Includes CHO, Ca²⁺, fluids |

| Skim milk powder | ≈$0.50 | Portable |

| Whey powder | ≈$2.00 | Rapid digestion, higher leucine |

Slide 55 – Timing Graphic

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• Reinforces 4 × 20 g pattern plus casein before sleep for maximal daily MPS.

Slides 56-59 – Sport-Specific Applications

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• Middle/Long-Distance Running: 1.2-1.6 g kg⁻¹, focus on recovery snack + mixed meals; monitor energy availability.

• Swimming/Rowing: high-volume training—multi-snack strategy, protein-CHOC milk post-pool, evening casein; account for early-morning sessions.

Slide 60 – End / Thank You

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• Invites questions.

Slides 61-62 – Lecture Objectives (Recap)

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• Essential AA count (20 AAs; 9 EAA).

• BCAA identification.

• Conditions increasing AA oxidation.

• Training-specific protein needs.

• Interaction of CHO/energy with lean-mass gain.

• Timing strategies, risks of excess, groups prone to deficiency, nitrogen-balance basics, whey vs casein differences.