Lesson 14 · Fuelling the performance
Dietary and fluid requirements of athletes
An open-water swimmer finishing a five-hour race and a netballer finishing a 40-minute match need the same nutrients. Almost everything else about their plans is different, and the differences all come from three questions you can ask about any sport at all.
Two athletes finish at the same venue on the same day. One has swum 19 kilometres over five and a half hours. The other has played a 40-minute netball match. Both are told to "eat and drink properly".
Write down the three biggest differences in what those two people actually need, and beside each one write why. Then answer the question that decides the whole lesson: is the difference between them mainly about what they eat, or about when?
- State what each macronutrient contributes, and why carbohydrate dominates the discussion for most sports.
- Describe dietary requirements pre, during and post performance, and justify the timing as well as the content.
- Explain fluid intake requirements, including how sweat losses are estimated and why both under- and over-drinking carry risk.
- Analyse how requirements differ between athletes from different sports, tracing each difference to duration, intensity and the opportunity to refuel.
- Judge the quality of the research a nutrition claim rests on, which is what the dot point's opening words ask for.
- Macronutrient — carbohydrate, protein or fat, the nutrients required in large amounts and the only ones supplying energy.
- Glycogen — the storage form of carbohydrate in muscle and liver, and the limiting fuel in most prolonged high-intensity exercise.
- Glycogen resynthesis — the rebuilding of those stores after exercise.
- Carbohydrate loading — raising muscle glycogen above normal in the days before a prolonged event.
- Pre-performance meal — the meal eaten in the hours before competition, sized and timed so it is digested in time.
- Glycaemic index — a ranking of how quickly a carbohydrate food raises blood glucose.
- Hydration — the body's fluid balance.
- Dehydration — a fluid deficit large enough to impair function.
- Sweat rate — the volume of fluid lost through sweat per hour, estimated from body mass change plus fluid consumed.
- Electrolytes — dissolved minerals, principally sodium, lost in sweat and needed for fluid balance and nerve and muscle function.
- Hyponatraemia — an abnormally low blood sodium concentration, which can result from drinking far more fluid than is lost.
- Rehydration — the deliberate replacement of fluid, and of sodium, after exercise.
All three macronutrients matter, but they are not equally interesting for performance, and the reason connects straight back to the energy systems from Year 11.
| Macronutrient | Main role | Why it matters for performance |
|---|---|---|
| Carbohydrate | The body's preferred fuel for moderate and high-intensity work, stored as glycogen in muscle and liver | Stores are small relative to demand and can be emptied within a long or hard session, at which point intensity must fall. It is the only macronutrient whose store limits performance in a single event |
| Protein | Repair, remodelling and growth of tissue, including the adaptations of Lesson 8 | It supports adaptation between sessions rather than fuelling the session itself, and contributes little energy during exercise in a well-fuelled athlete |
| Fat | The dominant fuel at low intensities and a large energy store | Stores are effectively unlimited even in a lean athlete, so fat is rarely the limiting factor. Its oxidation is too slow to support high intensity |
Read that table as one argument. Fat is abundant and slow; carbohydrate is limited and fast. That single sentence explains why the entire pre-during-post structure of this dot point is organised around carbohydrate, why an athlete "hits the wall" rather than gradually slowing, and why protein belongs mostly to the recovery conversation rather than the fuelling one.
One correction worth making now, because it recurs in Lesson 16. Eating more protein does not build muscle by itself. Protein supplies the material; the training supplies the stimulus. Without the stimulus the extra protein is simply used for energy or stored, which is why a resistance program plus adequate protein produces hypertrophy and additional protein alone does not.
Carbohydrate is the fuel that runs out. Almost every practical nutrition decision in this dot point is a decision about when to put carbohydrate in, relative to when it will be needed.
Quick check: Carbohydrate dominates sports nutrition advice mainly because:
The dot point names three windows, and each has a different job. The content follows from the job, not the other way round.
| Window | Purpose | Content and timing | The mistake to avoid |
|---|---|---|---|
| Pre-performance | Arrive with full glycogen stores, adequate hydration and no digestive discomfort | A carbohydrate-rich, moderate-protein, low-fat and low-fibre meal roughly three to four hours before, with a smaller carbohydrate snack closer if needed. Fluid taken steadily rather than in one large volume | A large, fatty or high-fibre meal too close to the start, which slows gastric emptying and causes discomfort. Also: trying anything new on competition day |
| During performance | Delay glycogen depletion, maintain blood glucose, and limit the fluid deficit | For events beyond roughly an hour, carbohydrate in a form that is easy to consume and tolerate, plus fluid matched approximately to sweat loss. For short events, generally nothing is required | Consuming carbohydrate during a 40-minute match as though it were an ultramarathon, and assuming the opportunity to eat exists when the sport may not allow it |
| Post-performance | Replace glycogen, provide protein for repair and adaptation, and restore fluid and sodium | Carbohydrate soon after finishing, especially when the next session is close, with protein alongside it for repair, and fluid volume greater than the deficit because some is lost as urine | Treating recovery nutrition as urgent for every athlete. It is urgent when the next effort is hours away, and much less so when it is days away |
Two points of precision separate a good answer from an average one. First, the urgency of post-performance carbohydrate depends entirely on how soon the next effort is. Glycogen resynthesis is fastest in the first hours after exercise, which matters enormously for a swimmer with a second race that afternoon and hardly at all for a footballer whose next match is in six days. Second, carbohydrate loading is not for everybody. It suits prolonged continuous events, typically beyond about ninety minutes, where glycogen depletion is the actual limiter. Loading before a 40-minute match solves a problem that match does not have, and the associated water storage adds mass for no benefit.
Nothing new on competition day
Every part of a nutrition plan has to be trialled in training, including the exact products, volumes and timing. The gut adapts to what it is repeatedly asked to absorb, and a strategy that works for one athlete can cause another real distress. This is the single most practical rule in the whole dot point, and it is also why a research finding averaged across a group cannot simply be applied to an individual.
True or false: Rapid post-exercise carbohydrate intake is far more important for a swimmer with a second race the same afternoon than for a footballer whose next match is six days away.
Sweating is how the body loses heat during exercise, so fluid loss is the price of temperature regulation rather than a malfunction. Sweat rates vary enormously between athletes and with conditions, which is why fluid advice cannot be a single number for everyone.
Dehydration impairs performance through a chain worth being able to state: fluid loss reduces plasma volume, so stroke volume falls and heart rate must rise to maintain cardiac output, blood flow to skin and muscle competes, core temperature climbs faster, and perceived effort rises. Cognitive function and skill execution deteriorate too, which matters as much in a netball final as in a marathon.
But the opposite error is real and more dangerous. Hyponatraemia occurs when an athlete drinks far more fluid than they lose, diluting blood sodium. It is most often seen in slower participants in long events who drink at every station regardless of need, and in severe cases it is life-threatening. So the goal is not "drink as much as possible" but replace approximately what is lost.
| Step | What to do | Why |
|---|---|---|
| 1 | Weigh the athlete before the session, in minimal dry clothing | Body mass change over a session is dominated by fluid loss |
| 2 | Record all fluid consumed during the session | Fluid taken in offsets part of the loss and must be added back |
| 3 | Weigh again immediately afterwards, towelled dry | Retained sweat on skin and clothing would otherwise hide the loss |
| 4 | Sweat loss is the mass lost plus the fluid consumed; divide by the hours to get a rate | An hourly rate is what a during-performance plan can actually be built on |
| 5 | Repeat in different conditions | Sweat rate rises in heat and humidity, so one measurement describes one set of conditions |
Two extras. Sodium is lost in sweat and matters for large losses and long events: replacing fluid without sodium can make dilution worse, which is why sports drinks contain it and why post-event rehydration is more effective with sodium present. And the opportunity to drink is a real constraint — a marathon runner passes aid stations, a netballer has quarter breaks, and a swimmer in a five-hour open-water event must be fed from a boat. The plan is limited by the sport, not only by the physiology.
Fill the gaps. The storage form of carbohydrate in muscle and liver is . An abnormally low blood sodium concentration caused by drinking far more than is lost is called . Sweat rate is estimated from the change in body mass plus the during the session.
The dot point says athletes from different sports, and the way to answer it is not to memorise four sports. It is to notice that almost every difference between them reduces to three variables: duration, intensity, and the opportunity to refuel. Get those three and you can reason about a sport you have never studied.
| Athlete | Duration, intensity, opportunity | Pre | During | Post |
|---|---|---|---|---|
| Open-water swimmer, 19 km | Five hours or more, moderate to high, feeding possible only at scheduled boat stops | Carbohydrate loading is genuinely indicated; full hydration | Substantial carbohydrate and fluid at every feed, rehearsed in training; sodium matters over this duration | Full refuelling, but not usually urgent, since the next event is not the same day |
| Netballer, 40 minutes plus breaks | Under an hour of play, high intermittent intensity, quarter and half-time breaks only | Normal well-fuelled diet; a light carbohydrate meal three to four hours before | Fluid at breaks; carbohydrate largely unnecessary for a single match | Matters most in a tournament with a second match the same day; otherwise ordinary meals suffice |
| Sprinter, under 30 seconds with heats | Seconds of maximal effort, repeated across a day | Light, easily digested, well hydrated; a full meal too close is worse than useless | Fluid between rounds; fuel is not the limiter within a single race | Between rounds the priority is fluid, comfort and readiness rather than glycogen replacement |
| Multi-day tournament player | Repeated efforts over consecutive days, opportunity between matches but not during | Consistent daily fuelling rather than a single pre-event meal | Fluid and carbohydrate in every available break | The most urgent case of all, because the recovery window is also the preparation window for tomorrow |
The bottom row is the one worth carrying. In a multi-day event or a tournament, post-performance nutrition is pre-performance nutrition, and the two windows collapse into one. That reframing answers a large class of exam questions.
And it settles card 01. The difference between the swimmer and the netballer is much more about when than about what: both need carbohydrate, fluid and protein, but the swimmer's demand is spread across five hours with feeding built into the event, while the netballer's is concentrated into a short high-intensity window with only breaks to work with.
Duration, intensity, opportunity. Ask those three questions about any sport and the pre, during and post plan writes itself.
Odd one out. Three of these athletes have a genuine need for carbohydrate during performance. Which one does not?
This dot point begins Using research, and it is assessed by outcome HM-12-10. Sports nutrition is one of the areas where the gap between what is claimed and what is evidenced is widest, so knowing how to judge a source is part of the content.
| Question | Why it matters | What a weak answer looks like |
|---|---|---|
| Who produced it, and do they benefit? | A manufacturer's own material is marketing, whatever it looks like | A product page citing "studies" without naming them, or research funded by the seller with no independent replication |
| Who was studied? | Findings from trained adult males in a laboratory may not transfer to a 16-year-old in a school competition | A result from eight elite cyclists presented as advice for everyone |
| What was actually measured? | A change in a laboratory measure is not the same as a change in competitive performance | "Improves recovery" where the measured outcome was a blood marker, not the next day's performance |
| How large was the effect, and compared with what? | A real but tiny effect can be true and useless, and a claim with no comparison group shows nothing | A percentage improvement quoted with no control condition and no measure of variability |
Apply this to the estimating method in card 06 and something useful emerges. The sweat-rate protocol is strong evidence for that athlete in those conditions and weak evidence about anyone else, because sweat rate varies so much between people. That is the general shape of good sports-nutrition reasoning: the physiology is general, and the numbers are individual.
Finally, keep the hierarchy straight. National sporting-institute and professional dietetic guidance sits above a coach's experience, which sits above a product's marketing. And an individual athlete's own tested response sits above all of them for that athlete, which is exactly why nothing is tried for the first time on competition day.
Two truths and a lie. One of these statements is false. Find it.
Activities · build and defend a fuelling plan
For each athlete, write duration, intensity and opportunity to refuel first. Only then write what they need pre, during and post.
A 17-year-old rowing a 2000 m race in the morning and a final in the afternoon.
A cyclist in a four-and-a-half-hour road race on a 34-degree day.
A touch football player at a three-day carnival with four matches a day.
A gymnast competing on four apparatus across ninety minutes, with long waits between routines.
Match each term to its meaning.
- Glycogen
- Hyponatraemia
- Sweat rate
- Carbohydrate loading
- The storage form of carbohydrate in muscle and liver
- An abnormally low blood sodium concentration, which drinking far more than is lost can cause
- Fluid lost per hour, estimated from body mass change plus fluid consumed
- Raising muscle glycogen above normal in the days before a prolonged event
Three players from the same squad were measured across the same 90-minute session in the same conditions.
| Player | Mass before, kg | Mass after, kg | Fluid consumed, litres |
|---|---|---|---|
| A | 72.4 | 71.2 | 0.9 |
| B | 84.0 | 83.7 | 0.4 |
| C | 66.8 | 66.9 | 1.8 |
Answer five things. Calculate each player's sweat loss and hourly sweat rate. Which player has the largest fluid deficit at the end, and what is it? What is notable about player C, and what would you check? A supplement company's material states that "athletes lose 2 litres per hour and must drink accordingly" — evaluate that claim against this data using the four questions from card 08. Finally, write one sentence of individual advice for each player.
Lock it in. In one sentence, explain why post-performance nutrition is urgent for a tournament player and much less so for a footballer with a match once a week.
Analyse the dietary and fluid requirements of athletes before, during and after performance.
Analyse asks for the parts and how they relate. Three time points are named, so the answer must show what each is for and how they connect rather than listing foods.
Plan: identify the components, state the constraint linking them, work through the three phases, then draw the implication.
Three requirements operate across the three phases: fuel availability, principally muscle and liver glycogen; hydration and electrolyte balance; and the protein and energy required for repair and adaptation after the session.
They are linked by a single constraint: the digestive system cannot absorb at the rate the working muscle consumes. Fuel and fluid must therefore be positioned before they are needed and replaced after they are lost, because intake during performance can only slow depletion rather than prevent it — which is why the three phases are one strategy rather than three separate decisions.
Before performance the aim is to maximise glycogen stores and begin fully hydrated. Carbohydrate intake is increased in the days beforehand, with endurance athletes loading most aggressively because their event depletes glycogen most completely, and a meal several hours prior is high in carbohydrate and low in fat and fibre so it empties from the stomach in time. Fluid is consumed steadily rather than in bulk immediately beforehand, since rapid intake is excreted rather than retained.
During performance the aim is to slow depletion. Events beyond about an hour benefit from carbohydrate intake, and fluid replacement with electrolytes matters where sweat losses are high, since replacing sodium alongside fluid is what allows that fluid to be retained rather than excreted. Hyponatraemia is a separate hazard with the opposite cause: it arises when an athlete drinks substantially more than they have lost and dilutes their blood sodium, which is why the aim is to replace approximately what a measured sweat rate says was lost rather than to drink as much as possible. After performance the aim is restoration: carbohydrate replaces glycogen most rapidly in the period immediately afterwards when muscle uptake is elevated, protein supplies the amino acids for repair and adaptation, and fluid must exceed the volume lost because some is excreted rather than retained.
The requirements differ by sport in proportion to how much they deplete each component. An endurance athlete's dominant problem is glycogen and fluid; a strength athlete's is protein and total energy; and an athlete in a weight-category or aesthetic sport faces a genuine conflict between fuelling for performance and meeting a weight target, which is where the greatest risk of inadequate intake and disordered eating arises. Nutrition is therefore not a general prescription but an allocation matched to what a given sport actually depletes.
Three requirements operate across the three phases: fuel availability, principally muscle and liver glycogen; hydration and electrolyte balance; and the protein and energy needed for repair and adaptation. They are linked by one constraint — the digestive system cannot absorb at the rate the working muscle consumes — so fuel and fluid must be positioned before they are needed and replaced after they are lost, since intake during performance only slows depletion rather than preventing it, which makes the three phases one strategy rather than three decisions. Before performance the aim is to maximise glycogen and begin fully hydrated: carbohydrate intake rises in the preceding days, most aggressively for endurance athletes whose events deplete glycogen most completely, and a meal several hours prior is high in carbohydrate and low in fat and fibre so it empties from the stomach in time, while fluid is taken steadily rather than in bulk immediately beforehand, since rapid intake is excreted rather than retained. During performance the aim is to slow depletion, so events beyond about an hour benefit from carbohydrate intake, and fluid replacement with electrolytes matters where sweat losses are high, because replacing sodium alongside fluid is what allows it to be retained; hyponatraemia is the opposite failure, caused by drinking substantially more than has been lost and diluting blood sodium, so the aim is to replace approximately the measured loss rather than to maximise intake. After performance the aim is restoration: carbohydrate replaces glycogen fastest in the period immediately afterwards when muscle uptake is elevated, protein supplies amino acids for repair and adaptation, and fluid intake must exceed the volume lost because some is excreted. Requirements then differ by sport in proportion to what each depletes — glycogen and fluid dominate for endurance athletes, protein and total energy for strength athletes, while weight-category and aesthetic sports create a genuine conflict between fuelling for performance and meeting a weight target, which is where inadequate intake and disordered eating most often arise. Nutrition is therefore an allocation matched to what a sport actually depletes, not a general prescription.
Explain how dehydration impairs both physiological function and performance.
Explain asks for the causal chain from fluid loss to reduced performance. The stem names two outcomes — physiological and performance — so both need reaching.
Plan: name the principle, follow the chain through the systems, then reach performance and safety.
Sweat is drawn from body water including plasma, so fluid loss reduces blood volume. Because blood simultaneously delivers oxygen to muscle and carries heat to the skin, a fall in blood volume forces those two functions into direct competition.
Reduced plasma volume lowers venous return and therefore stroke volume, so heart rate must rise to maintain cardiac output at the same workload — cardiovascular drift — which means the athlete works at a higher proportion of maximum for the same external intensity and fatigues sooner.
As dehydration progresses the body prioritises central blood pressure, so blood flow to the skin is reduced and sweat rate falls, which means heat loss declines exactly when heat production is highest and core temperature rises further — a positive feedback loop ending in heat illness if uninterrupted.
Fluid loss also impairs concentration, reaction time and decision-making before the athlete reports feeling thirsty, so skill execution and tactical judgement decline while the athlete still believes they are performing normally — which is why thirst is an unreliable guide and scheduled fluid intake is preferred.
Sweat is drawn from body water including plasma, so fluid loss reduces blood volume, and because blood simultaneously delivers oxygen to working muscle and carries heat to the skin, a fall in blood volume forces those two functions into direct competition. Reduced plasma volume lowers venous return and therefore stroke volume, so heart rate must rise to maintain cardiac output at the same workload — cardiovascular drift — meaning the athlete works at a higher proportion of maximum for the same external intensity and fatigues sooner. As dehydration progresses the body prioritises central blood pressure, so skin blood flow is reduced and sweat rate falls, and heat loss declines exactly when heat production is highest, raising core temperature further in a positive feedback loop that ends in heat illness if uninterrupted. Fluid loss also impairs concentration, reaction time and decision-making before the athlete reports feeling thirsty, so skill execution and tactical judgement decline while the athlete still believes they are performing normally. Dehydration therefore reduces performance through two independent routes — cardiovascular strain limiting sustainable intensity and cognitive impairment degrading skill and decisions — and because thirst lags the impairment, fluid intake must be scheduled rather than left to sensation.
Go back to card 01. Both athletes need the same things — carbohydrate, fluid, protein and sodium — so the difference is mostly about when, and it is generated by three variables: the swimmer's event lasts more than five hours at moderate to high intensity with feeding built into it, while the netballer's is under an hour of intermittent high intensity with only quarter breaks. That is why carbohydrate loading and during-event feeding are central for one and largely irrelevant for the other. Check your three differences against duration, intensity and opportunity, and note any that you cannot trace to one of them.
Multiple choice · 5 questions
MC 1. The main reason carbohydrate dominates sports nutrition advice is that:
- A. it is the only nutrient absorbed during exercise
- B. its stores are small relative to demand and it is the fast fuel, so depletion forces intensity to fall
- C. it repairs muscle tissue more effectively than protein
- D. fat cannot be oxidised during exercise
MC 2. A pre-performance meal three to four hours before competition should be:
- A. high in fat and fibre, to slow digestion and provide sustained energy
- B. as large as the athlete can manage, to maximise fuel available
- C. entirely liquid, regardless of the sport
- D. carbohydrate-rich, moderate in protein, and low in fat and fibre
MC 3. Carbohydrate loading is appropriate before:
- A. a 100 m sprint final
- B. a 40-minute netball match
- C. a prolonged continuous event beyond about ninety minutes, where glycogen depletion is the limiter
- D. any competition, since more stored fuel is always better
MC 4. An athlete in a long event drinks at every station regardless of need and finishes heavier than they started, feeling unwell. The most likely explanation is:
- A. hyponatraemia, caused by drinking far more fluid than was lost and diluting blood sodium
- B. severe dehydration
- C. glycogen depletion
- D. an excessive sweat rate
MC 5. A supplement company states that "athletes lose 2 litres of sweat per hour and must drink accordingly". The strongest criticism is that:
- A. sweat losses are never that large in any athlete
- B. fluid replacement is unnecessary in events under three hours
- C. sodium is more important than fluid volume in all circumstances
- D. sweat rate varies greatly between individuals and with conditions, and the source benefits from athletes drinking more
Short answer · exam style
SA 1. Understand Band 4 Explain the purpose of pre, during and post performance nutrition, and state one factor that determines how urgent the post-performance window is. (4 marks)
SA 2. Analyse Band 5 Explain how dehydration impairs performance, and explain why "drink as much as possible" is nonetheless poor advice. (5 marks)
SA 3. Evaluate Band 6 Using research, analyse the dietary and fluid requirements of athletes from two contrasting sports. Explain each difference, and comment on the quality of the evidence available for the advice you give. (7 marks)
📖 Comprehensive answers (click to reveal)
Multiple choice: 1 → B. 2 → D. 3 → C. 4 → A. 5 → D.
Activity 1, indicative answers: 1 → Rower: about six minutes of near-maximal effort, twice in one day, with several hours between. Pre: a familiar carbohydrate-based meal three to four hours before the heat, low in fat and fibre, well hydrated. During: nothing is needed within a six-minute race; fluid between rounds. Post: this is the critical window, because the final is the same day, so carbohydrate and fluid soon after the heat, with the recovery meal treated as preparation for the final. 2 → Cyclist: four and a half hours, moderate to high, with continuous opportunity to eat and drink on the bike. Pre: carbohydrate loading is justified, plus a substantial pre-race meal. During: regular carbohydrate throughout and a fluid plan built on a measured sweat rate, which in 34 degrees will be high; sodium matters at this duration and in this heat. Post: full refuelling and rehydration with sodium, urgency depending on whether there is a stage tomorrow. 3 → Touch player: short matches at high intermittent intensity, four a day for three days, with opportunity between matches but almost none during. Pre: consistent daily fuelling rather than one pre-event meal. During: fluid at every break, with carbohydrate in the longer gaps. Post: the most urgent of the four, because each recovery window is also the preparation window for the next match and the next day. 4 → Gymnast: total work is brief and highly explosive but spread over ninety minutes with long waits. Duration of effort is short, so fuel is not the limiter, but the elapsed time is long and the waits allow cooling and loss of readiness. Pre: light, familiar, comfortable, since a full stomach impairs the movements required. During: small amounts of fluid and, if the wait is long, a small easily digested carbohydrate snack. Post: ordinary. What makes it unusual is that elapsed time and working time diverge sharply, so the plan is driven by the schedule rather than by fuel demand.
Activity 2, indicative answers: Sweat loss is mass lost plus fluid consumed. Player A lost 1.2 kg and drank 0.9 L, so sweat loss was about 2.1 L over 1.5 hours, a rate near 1.4 L per hour, and the end-of-session deficit is the 1.2 kg mass loss, roughly 1.2 L. Player B lost 0.3 kg and drank 0.4 L, so sweat loss was about 0.7 L, a rate near 0.47 L per hour, with a deficit of about 0.3 L. Player C gained 0.1 kg and drank 1.8 L, so sweat loss was about 1.7 L, a rate near 1.13 L per hour, and there is no deficit at all — C finished in fluid surplus. A has the largest deficit. Player C is notable because they drank more than they lost in the same conditions, and the things to check are whether the mass measurements were taken correctly, whether the drinking pattern is habitual, and whether C has any symptoms; in a long event this pattern is the one that leads towards hyponatraemia. On the company's claim: the source sells fluid products and therefore benefits from athletes drinking more, which fails the first question; the figure of 2 litres per hour is far above all three measured players, so the population it came from is not this one; a blanket instruction to "drink accordingly" specifies no measurement of the individual; and this data shows a threefold spread in sweat rate within a single squad in identical conditions, which is the direct evidence that a single number cannot be right for everyone. Advice: A should plan a higher during-session intake and finish with deliberate rehydration including sodium; B needs relatively little and should not be pushed to match the others; C should reduce intake towards their measured loss and be monitored, particularly before any long event.
SA 1 (4 marks): Pre [1]: to arrive with full muscle and liver glycogen stores, adequately hydrated and without digestive discomfort, which is why the meal is carbohydrate-rich, low in fat and fibre and taken about three to four hours before. During [1]: to delay glycogen depletion, maintain blood glucose and limit the fluid deficit, which matters in events beyond roughly an hour and is largely unnecessary in short ones. Post [1]: to replace glycogen, supply protein for repair and adaptation, and restore fluid and sodium. The factor setting urgency [1]: how soon the next effort is. Glycogen resynthesis is fastest in the hours immediately after exercise, so rapid refuelling is critical for a second race the same day or a tournament, and much less so when the next competition is several days away.
SA 2 (5 marks): The mechanism [3]: fluid loss reduces plasma volume [1], so stroke volume falls and heart rate must rise to maintain cardiac output, while blood flow is contested between skin for cooling and muscle for work [1]; core temperature therefore rises faster, perceived effort increases, and cognitive function and skill execution deteriorate, which affects decision-making sports as much as endurance ones [1]. Why the advice is still wrong [2]: drinking far more than is lost dilutes blood sodium and can cause hyponatraemia, which is most often seen in slower participants in long events who drink at every opportunity regardless of need and which can be life-threatening [1]; so the goal is to replace approximately what is lost, which requires the individual sweat rate to be measured rather than a single figure applied to everyone [1].
SA 3 (7 marks): Choose two genuinely contrasting sports and analyse both on duration, intensity and opportunity to refuel, since every difference traces to those three. Sport one, for example an open-water swim of five hours [2]: long duration at moderate to high intensity with feeding possible only at scheduled stops, so carbohydrate loading is genuinely indicated, substantial carbohydrate and fluid are needed at each feed with sodium relevant at this duration, and everything must be rehearsed in training because tolerance is individual. Sport two, for example a 40-minute netball match [2]: under an hour of intermittent high-intensity work with only quarter and half-time breaks, so a normal well-fuelled diet and a light carbohydrate meal three to four hours before are sufficient, carbohydrate during a single match is largely unnecessary, and fluid is taken at breaks; loading would add mass with no benefit. Explanation of the differences [2]: both athletes need the same nutrients, and the difference is mainly one of timing and quantity, generated by how long the event lasts, how hard it is, and whether the sport permits intake during it. A strong answer also notes the tournament case, where the post-performance window is simultaneously the pre-performance window for the next match. Evidence [1]: the physiological principles are well established and supported by institute and dietetic guidance, but the numbers are individual — the measured spread in sweat rate within a single squad in identical conditions shows why a population average cannot be prescribed to a person — and much supplement-adjacent material is produced by parties who benefit from its conclusions, is drawn from small samples of trained adult males, and reports laboratory markers rather than competitive performance.
This lesson opens the fourth inquiry question. It connects backwards to the Year 11 energy systems, which is where the primacy of carbohydrate comes from, and to Lesson 8, where protein's role in adaptation was established.
Take three things forward. Duration, intensity and opportunity generate every difference between sports. Fluid has two failure modes rather than one, and the target between them is individual. And the phrase using research is part of the dot point, so judging a source is part of the answer. Lesson 15 puts sleep alongside nutrition and hydration and treats the three as one system.
Mark lesson as complete
Tick when you've finished the practice and review.