EXSS3071 Week 9 Lecture

Slide 1 – Lecture Title & Acknowledgements

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Unit EXSS3071 “Nutrition for Exercise & Health” ― focus: Hydration & Thermoregulation.

• Presenter Mr Kenneth Daniel (APD). Contributors: Gifford, O’Connor, Miles, Guo.

• Sets expectation that fluid balance, heat stress and performance will be integrated from physiology to applied guidelines.

Slide 2 – Road-Map of the Session

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Five thematic blocks:
  

  1. Basic fluid concepts & body-water compartments.

  2. Fluid availability, sweat/heat exchange.

  3. Hyperthermia & hypohydration effects.

  4. Prevention strategies & athlete-specific recommendations.

  5. Composition and use-cases of rehydration solutions.

• Students are warned each section loops back to practice.

Slide 3 – Hydration Terminology

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Euhydration = normal body-water content.

• Hyperhydration = surplus body water.

• Hypohydration = chronic deficit; dehydration = the process of losing water.

• % body-water varies by life-stage (infant ~75 % vs older adult ~55 %).

• Establishes that even 1 % BW change is physiologically meaningful.

Slide 4 – Fluid Distribution & Typical Losses

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Body water split ≈ 2/3 intracellular, 1/3 extracellular (plasma + interstitial).

• Thermoregulation consumes ≈ 0.52 mL water · kcal⁻¹ of metabolic heat; resting losses ~1 mL·kcal⁻¹ of REE.

• Sets baseline for estimating exercise-derived sweat needs.

Slide 5 – GI Absorption & Endocrine Feedback

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Enterocyte model: Na⁺/glucose co-transport drags water paracellularly.

• Posterior pituitary senses ↑ plasma osmolality → AVP release → kidney water reabsorption; baroreceptors modulate via RAAS.

• Highlights why sodium plus fluid is superior to water alone for rapid rehydration.

Slide 6 – Human Water-Restriction Study

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• 9 adults; 1 L day⁻¹ vs 6.8 L day⁻¹ crossover.

• Markers: Posm > 300 mOsm kg⁻¹ & Uosm ≥ 295 mOsm kg⁻¹ define hypohydration/dehydration.

• AVP and renal concentrating ability surge under restriction, illustrating hormonal cost of fluid deficit.

Slide 7 – The Five Blocks Revisited

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Slide refreshes session outline to reinforce cognitive scaffolding before moving to thermoregulation.

Slide 8 – Temperature & Sport: Core vs Shell

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Core tissues (thoraco-abdominal, cranial) tightly regulated near 37 °C; shell (skin, muscle, fat) permits wider fluctuation.

• Heat accumulation = production > dissipation.

• Risk modifiers: age, sex, BMI, environment, clothing, fitness, pre-exercise hydration.

Slide 9 – Same Concept, Additional Sources

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Second graphic reiterates factors and cites clinical/field thermometry papers to emphasise measurement validity.

Slide 10 – Hyperthermia in Cool Weather Case

EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• 15 km road race, wet-bulb ≈ 11 °C; 15 % finishers reached exertional hyperthermia.

• Take-home: cool ambient ≠ safe; metabolic heat plus clothing can still push > 40 °C core T.

Slide 11 – Haemodynamic Chain During Exercise

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Muscle contractions ↑ capillary hydrostatic pressure → plasma shifts to interstitium → ↓ plasma volume.

• Simultaneous ↑ metabolic by-products elevates intramuscular osmotic load, drawing water inward; net effect = cardiovascular strain and earlier fatigue if fluid not replaced.

Slide 12 – Dehydration in Swimmers

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• 9 masters swimmers, 5 km distance at 25 m pool, three water temps.

• Body-mass loss used as proxy for sweat losses; even 28–32 °C pools can induce >1 % BW loss despite perceived “cool” medium.

Slide 13 – Section Divider Slide

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Signals shift to combined hyperthermia + hypohydration content.

Slide 14 – Hyperthermia & Hypohydration Interaction

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Exercise heat production 15–20 × resting; without cooling, core temp can climb 1 °C every 5 min.

• Fluid deficits >3–5 % BW → ↓ sweat rate & skin blood flow, compounding heat storage and slashing time-to-exhaustion.

Slide 15 – Heat Illness Prevalence: Atlanta ‘96

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• 80 % RH, 19–35 °C; 12.8 % medical admissions heat-related; volunteers/audience affected even more than athletes.

• Reinforces duty of care for support staff and spectators.

Slide 16 – Preventing Heat Illness

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Key message: “adequate fluids before, during, after”.

• Electrolyte replacement accelerates recovery.

• Refers practitioners to SMA Hot Weather Guidelines and Racinais 2015 consensus for protocol detail.

Slide 17 – Duplicate Prevention Slide (Emphasis)

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Reiteration underlines high-stakes consequences; ensures guidelines URL is noticed.

Slide 18 – 2021 SMA Extreme Heat Policy

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Highlights proactive risk assessment: WBGT thresholds, mandatory cooling breaks, event modification/cancellation triggers.

Slide 19 – IOC 2023 Statement Teaser

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Key actions: start hydration days before, individual monitoring, practice strategies in training; caution against over-drinking.

Slide 20 – Exercise-Associated Hyponatraemia (EAH): Definition & Mechanisms

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Serum Na⁺ < 135 mmol L⁻¹ during/after prolonged activity.

• Drivers: fluid intake > renal clearance, persistent AVP, impaired dilution.

• Behavioural aspect: fear of dehydration leads to over-consumption.

Slide 21 – EAH Clinical Manifestations

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Progression: headache → nausea → confusion → seizures → respiratory arrest.

• Emphasises the need for on-site medical triage able to differentiate EAH from heat stroke (opposite serum [Na⁺]).

Slide 22 – Hyperthermia’s Macro Effect on Sport

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• SDA 2020 position: performance decrements depend on sport geometry (indoor, aquatic, open-road) and clothing.

• Highlights integrated approach: acclimation, fluid, cooling, pacing.

Slide 23 – Hypohydration & Endurance Performance

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Temperate 20 °C: ≤2 % BW loss <90 min → trivial; >2 % or >90 min → impaired.

• Hot 31–32 °C: 2 % loss >60 min: significant impairment.

• Pre-start deficit ≥1.7 % BW predicts VO₂-peak reductions.

Slide 24 – Sprint/Power/Strength Outcomes

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Running & jumping tolerate 2–3 % BW loss with minor effects; >3 % can ↓ bar-bell velocity and MMA vertical jump.

• Research scarce for repeated-sprint contexts; girard 2015 points to combined heat + dehydration synergy.

Slide 25 – Repeated Cycle Sprints Study

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• 3 % dehydration via hot-water immersion ↑ RPE, ↓ mean & peak power, ↑ sprint time above 90 rpm.

• Graph visualises direct link between plasma volume loss and neuromuscular output.

Slide 26 – Water Sports Hydration

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Surfing: 0.9–1.2 % BW loss, wetsuit heat retention complicates.

• Swimming: ~0.4 % loss; hydration mostly a comfort rather than performance limiter unless >90 min.

• Water-polo: average −0.3 % but high-intensity phases may impact shooting accuracy.

Slide 27 – Cricket Accuracy & Speed

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• 30 players, 28–32 °C, high RH. High-fluid (4.2–4.9 L) vs restricted (0.9–1.1 L): bowling speed & accuracy maintained only in high-fluid group.

• Demonstrates motor-skill degradation under modest (∼2 %) dehydration.

Slide 28 – Cognitive Performance Meta-analysis

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Dehydration ≥2 % BW consistently impairs working memory, executive function and mood.

• Effect sizes largest in heat/high-intensity combinations.

Slide 29 – Team-Sport Cognition Review

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• 2021 SSE review: fluid loss >2 % compromises decision accuracy and fine motor skill in intermittent sports; suggests pre-planned breaks and flavour-enhanced drinks to boost adherence.

Slide 30 – Section Divider (Back to Basics)

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

Slide 31 – General Water Requirements

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Day-to-day TBW fluctuates ±1 % BW (600–900 mL).

• Adequate Intake (AI): men 3.4 L, women 2.8 L total fluids.

• Hydration status depends on intake and renal/ADH regulation, not volume alone.

Slide 32 – Consequences & Individualisation

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Hypohydration elevates HR, core T, lowers gastric emptying, mental and physical outputs, and raises GI syndrome risk under heat stress.

• Athletes develop personalised sweat maps and replacement plans (genetics, environment, kit).

Slide 33 – Pre-Exercise Hydration Goals

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• 5–10 mL·kg⁻¹ fluid in the 2–4 h pre-start → pale urine & chance to void.

• Salted snacks enhance fluid retention.

• Emphasises euhydration not over-drinking.

Slide 34 – Hyper-Hydration Strategies

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Salt + glycerol loading raises TBW and gastric volume; useful before ultra-endurance or extreme heat with large predicted losses.

• Needs athlete-specific fine-tuning to avoid GI upset.

Slide 35 – AIS Glycerol Infographic Highlights

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Protocol example: 1.2 g glycerol kg⁻¹ + 26 mL water kg⁻¹ over 60 min, 2–3 h pre-event, delivers ~1 L extra water retained.

Slide 36 – Creatine as Fluid Retention Aid

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Creatine draws water intracellularly; meta-analysis shows no deterioration of heat tolerance; may pair with glycerol for dual-compartment storage.

Slide 37 – During-Exercise Hydration Objectives

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Prevent >2 % BW loss & large electrolyte swings without net gain (avoid over-hydration).

• Drinking pattern: “opportunities” (bench, breaks) and gut-priming sips during play.

Slide 38 – Practical On-Field Strategies

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Use squeeze bottles, camelbacks, cold slushies; train gut to tolerate 400–600 mL h⁻¹ depending on sweat rate.

Slide 39 – Electrolyte Content of Sweat

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Na⁺ range 10–90 mmol L⁻¹; extremes demand testing.

• 2023 modelling: sodium replacement priority rises with fluid-intake ratio; >90 % fluid replacement + salty sweater (>1 g L⁻¹) → aim for 70–85 % Na⁺ replacement.

Slide 40 – Sodium Replacement Decision Tree

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• <70 % fluid loss replaced: “season to taste”.

• 70–80 %: replace 30–65 % Na⁺ if high sweater.

• ≥90 %: aggressive Na⁺ replacement, otherwise 30–40 % for low sweaters.

Slide 41 – Factors Slowing Gastric Emptying

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• ↑ CHO % (>8 %), ↑ osmolality, high energy density, large bolus, intense exercise, thermal stress, cold drinks if hypothermic, carbonation.

• Guides beverage formulation (6–8 % CHO, 10–35 mmol L⁻¹ Na⁺).

Slide 42 – Post-Exercise Rehydration Principles

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Fluid + electrolyte replacement goal set by deficit magnitude and time window.

• Routine meals suffice if >12 h till next session.

Slide 43 – Aggressive Rehydration Protocol

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• For <12 h recovery: ingest 1.25–1.5 L per kg BW lost within 2–4 h, with Na⁺ ≥ 50 mmol L⁻¹ to restore plasma osmolality and drive thirst suppression.

Slide 44 – Alcohol & Rehydration

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Beer provides water, CHO, Na⁺/K⁺ but EtOH >4 % inhibits AVP → diuresis; <2 % EtOH has milder effect, especially when hypohydrated.

• Also perturbs thermoregulation; advisable to alternate with non-alcoholic saline beverages.

Slide 45 – Field Hydration Assessment Tools

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Urine colour chart (8-point), USG refractometry (<1.020 euhydrated), body-mass tracking, thirst VAS.

• Stress multidisciplinary approach: combine two markers for accuracy.

Slide 46 – SDA Position Paper (Hot Env.)

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Emphasises synergy of pre-cooling, fluid balance, sodium, and acclimation; underpins practical checklists for dietitians.

Slide 47 – Section Divider (Rehydration Solutions)

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

Slide 48 – AIS Electrolyte Infographic Motto

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Core advice: flavour & temperature drive voluntary intake; sodium “to taste” covers most scenarios barring extreme sweaters.

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Slide 49 – Sports Drink Pros

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Combined CHO-electrolyte-fluid delivery; improved palatability; may lower perceived effort and provide protein or caffeine in recovery-oriented formulas.

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Slide 50 – Sports Drink Cons

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Cost, added calories, dental erosion risk, FODMAP/GI intolerance, taste fatigue.

Slide 51 – Sensory Attributes Driving Choice

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Colour, flavour, aroma, mouth-feel, serving temperature collectively modulate ad-libitum intake.

Slide 52 – Comparative Nutrition Table

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Lists CHO %, Na⁺, K⁺ for Gatorade, Accelerade, Powerade variants, milk-based products; emphasises 6–8 % CHO and 20–40 mmol L⁻¹ Na⁺ as isotonic sweet-spot.

Slide 53 – Sports Drinks vs Other Beverages

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Matrix contrasts energy, protein, electrolytes for isotonic drink, milk, juice, coconut water, cola, water.

• Highlights milk’s superior K⁺ and protein for post-exercise but slower gastric emptying.

Slide 54 – 2024 Milk vs Sports Drink RCT

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Skim lactose-free milk achieved better net fluid balance than water or Gatorade at 150 % BW replacement, with mild GI discomfort.

• Suggests milk as viable recovery beverage in heat.

Slide 55 – PRIME™ Example

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Marketing case used to prompt critical thinking: compare label CHO %, electrolytes, caffeine to evidence-based targets.

Slide 56 – Post-Exercise Rehydration Checklist

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Aim for full rehydration within 4 h; spread intake, include electrolytes, pick palatable temp/flavour, avoid large alcohol doses; align beverage energy with overall diet.

Slide 57 – Crafting Hydration Strategy

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Factors: sport fluid access, sweat rate, environment, clothing, individual GI tolerance.

• Strategy must be rehearsed in training to avoid race-day surprises.

Slide 58 – Environmental Heat-Stress Scale (AO)

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Australian Open example: WBGT thresholds trigger roof closure, extended change-over; underscores the need to integrate event-level policies with personal plans.

Slide 59 – Belval et al. Practical Solutions

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Table ranks sports by fluid availability, intensity, hypohydration risk to prioritise education and logistics (e.g., wrestling high risk in training).

Slide 60 – Risk Matrix by Sport Segment

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Triathlon swim leg low fluid access vs bike/high; highlights modular planning.

Slide 61 – Summary: Before–During–After

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Before: start well-hydrated, perhaps hyper-hydrate for extreme heat.

• During: drink to limit BW loss <2 %; integrate Na⁺; temperature & flavour matter.

• After: replace 125–150 % of fluid lost with salty drinks/snacks; monitor urine.

Slide 62 – What to Drink? Decision Points

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• ≤2.5 h event: 30–60 g CHO h⁻¹; >2.5 h: up to 90 g blended CHO.

• Water sufficient for brief cooler sessions; sports drink or milk preferred when CHO and electrolytes also required.

Slide 63 – Additional Reading List

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Key papers and position stands for deeper exploration; encourages evidence-led practice.

Slide 64 – Lecture Objectives (14 Items)

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Ranges from sodium absorption physiology to practical sweat-rate assessment, sports-drink composition, gastric emptying factors and hyper-hydration methods.

Slide 65 – Questions Prompt

‡EXSS3071+W9+Hydration+2025+S1+student.pdf](file-service://file-LQeQrCgQ1wjbZbhiFX6FLP)

• Encourages application of lecture material to case scenarios.

Slide 66 – Thank-You / Closing

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• Signals end; invites discussion.