Nutrition and Hydration

Energy and carbohydrate needs track the training demand of the day, so intake sensibly varies across the week. This is a guiding principle rather than a precise formula.

Source: Sports nutrition position stands / general reference

Carbohydrate supplies the fuel that harder efforts depend on, and stores are small enough that intake matters. Repair material comes mainly from protein.

Source: Sports nutrition position stands / general reference

Persistently eating below the demands of training undermines the recovery that turns training into fitness. Adding load to an under-fuelled athlete usually makes it worse.

Source: Sports nutrition position stands / general reference

The 2016 ACSM/AND/DC joint position statement frames daily carbohydrate as g/kg body mass scaled to training load, with very high days going higher still. These are guidance ranges, not prescriptions for any individual.

Source: ACSM / Academy of Nutrition and Dietetics / Dietitians of Canada joint position statement (2016)

Eating well and eating enough are different questions, and only the second determines whether training is supported. Quality does not compensate for a shortfall in energy.

Source: Sports nutrition position stands / general reference

When the pre-session window is short, the previous evening's meal does much of the work, topped up by whatever is tolerated on the morning. Caffeine supplies no energy at all.

Source: Sports nutrition position stands / general reference

A rest day needs less fuel for work but the same support for repair, so carbohydrate flexes while protein and overall adequacy hold. The body still uses substantial energy at rest.

Source: Sports nutrition position stands / general reference

Refilling muscle glycogen is a process measured in hours, not minutes, so the day before a key session is part of fuelling it.

Source: Sports nutrition position stands / general reference

Repeatable session quality and recovery are the practical everyday signal. Steady in-season weight loss and constant hunger point the other way.

Source: Sports nutrition position stands / general reference

Food volume and satiety can become the limiting factor when energy needs are high, which is why some more energy-dense choices help in big blocks.

Source: Sports nutrition position stands / general reference

Fat is abundant but carbohydrate is scarce, and it is carbohydrate that hard intensities depend on, so carbohydrate runs out first. Both fuels are used throughout.

Source: Sports nutrition position stands / general reference

Glycogen is simply carbohydrate packed away for later, in the muscles that will use it and in the liver, which supplies the bloodstream.

Source: Sports nutrition position stands / general reference

Guidelines scale intake with duration and intensity, from little or none in short easy work up to substantially more per hour in long hard sessions. Treat published ranges as guidance, not rules.

Source: Sports nutrition position stands / general reference

Train-low describes manipulating carbohydrate availability for chosen sessions, not lowering intensity, weight or volume. It is applied to selected, usually lower-intensity sessions within an energy-adequate diet: hard sessions are still fuelled, which is why deliberately under-fuelling a hard day is not train-low.

Source: Sports nutrition position stands / general reference

You buy a possible adaptation signal at the cost of intensity and added stress, and the performance evidence remains mixed. Used repeatedly or unsupervised it can tip into low energy availability, so it is a selective tool rather than a default.

Source: Sports nutrition position stands / general reference

Higher fat oxidation does not change the rate limit: hard efforts need energy faster than fat can supply it. Very high fat intakes can also blunt the muscle's ability to burn carbohydrate at intensity, even though digestion is unaffected.

Source: Sports nutrition position stands / general reference

Liver glycogen, not muscle glycogen, maintains blood glucose overnight; muscle keeps its own store for its own use.

Source: Sports nutrition position stands / general reference

Intestinal carbohydrate transport is trainable to a degree, so habitual intake shapes tolerance. Individual variation remains large.

Source: Sports nutrition position stands / general reference

Loading combines several days of higher carbohydrate intake with reduced training and can raise muscle glycogen roughly one-and-a-half to two times normal. Below about 90 minutes, normal stores are not the limiter, so there is nothing to gain.

Source: Sports nutrition position stands / general reference

Once muscle stores run down the body cannot sustain the same intensity, and refilling takes hours, which is why fuelling has to start early.

Source: Sports nutrition position stands / general reference

Protein is primarily building and repair material, with training driving continual remodelling of tissue. Fuel comes mainly from carbohydrate and fat.

Source: Sports nutrition position stands / general reference

Repeated endurance work increases both repair demands and a small amount of protein use as fuel, so requirements sit above sedentary levels. Position stands give ranges rather than a single figure.

Source: Sports nutrition position stands / general reference

Each meal containing protein stimulates repair, so several moderate servings tend to serve an athlete better than one large one. There is no evidence of kidney harm from higher intakes in healthy athletes.

Source: Sports nutrition position stands / general reference

Pre-sleep protein is a reasonable way to add to the daily total, but the daily total and the training remain what matter most.

Source: Sports nutrition position stands / general reference

Fast in-season loss generally reflects a large energy shortfall and costs lean tissue as well as fat. Higher protein helps but does not make a large deficit safe under heavy load.

Source: Sports nutrition position stands / general reference

A build phase asks for the most recovery, which is exactly what a large deficit removes, so fitness gained per session falls.

Source: Sports nutrition position stands / general reference

Protein and carbohydrate do different jobs, and no amount of protein replaces the fuel that intensity requires.

Source: Sports nutrition position stands / general reference

Variety and adequate total intake cover the amino acid profile over the day; the idea that foods must be paired at every single meal is outdated.

Source: Sports nutrition position stands / general reference

There is a point beyond which extra protein adds no further benefit for repair, and the surplus is simply metabolised.

Source: Sports nutrition position stands / general reference

Intentional energy restriction is a common trigger for low energy availability, so a body-composition goal belongs with a qualified professional rather than being self-managed.

Source: Sports nutrition position stands / general reference

Energy availability is what remains for everything other than exercise: immune function, hormones, bone and repair. It is usually expressed relative to fat-free mass.

Source: IOC consensus statements on RED-S / general reference

The body can defend weight while cutting back on functions you cannot see, so a stable number on the scales is not evidence that fuelling is adequate.

Source: IOC consensus statements on RED-S / general reference

RED-S is a broad framework covering effects on bone, hormones, immunity, metabolism and performance. Only a qualified clinician can assess it in an individual.

Source: IOC consensus statements on RED-S / general reference

Low energy availability can arise inadvertently when a training block outgrows eating habits, and it can also arise from disordered eating or an eating disorder. Both pathways need qualified assessment.

Source: IOC consensus statements on RED-S / general reference

A cluster of signs persisting over weeks or months is the signal, not any single ordinary training response. Assessment belongs with a clinician, not a self-check.

Source: IOC consensus statements on RED-S / general reference

When training burns a lot and appetite does not automatically keep pace, a shortfall can build quietly over weeks of a big block.

Source: IOC consensus statements on RED-S / general reference

Bone needs both loading and adequate energy and hormonal support; a prolonged shortfall undermines it and stress injuries are a common presenting sign.

Source: IOC consensus statements on RED-S / general reference

The body down-regulates reproductive and other hormonal functions when energy is persistently short. Any suspected hormonal change should be assessed medically.

Source: IOC consensus statements on RED-S / general reference

The underlying problem is an energy shortfall, which affects athletes of any sex. The absence of a clear early marker in men often delays recognition.

Source: IOC consensus statements on RED-S / general reference

This is a clinical matter, and recovery usually involves adjusting both intake and training load with qualified support. If eating itself feels difficult or controlling, an eating disorder service or your doctor is the right place to start.

Source: IOC consensus statements on RED-S / general reference

Muscle and liver glycogen typically cover somewhere around 90-120 minutes of sustained work, less at higher intensity, so a sprint is fuelled almost entirely from what is already stored. A full-distance race lasts many times longer than those stores.

Source: Sports nutrition position stands / general reference

Below about an hour, stored glycogen is generally sufficient. Benefits of in-race carbohydrate become consistent as efforts extend past roughly 60-90 minutes.

Source: Sports nutrition position stands / general reference

The recommendation is duration-dependent, not a single number. Intakes above 90 g/h are used by some long-course athletes but need a glucose-fructose mix and gradual gut habituation.

Source: Sports nutrition position stands / general reference

Glucose uses a sodium-dependent transporter that saturates, while fructose uses a separate one. Using both routes at once raises total delivery.

Source: Sports nutrition position stands / general reference

The long-established and best-evidenced blend is around 2:1 glucose (or maltodextrin) to fructose. Some newer high-intake products use ratios nearer 1:0.8, though evidence that this is superior is still limited.

Source: Sports nutrition position stands / general reference

Single-transportable carbohydrates saturate one intestinal transporter at roughly 1 g/min. Exceeding that adds gut load without adding usable fuel.

Source: Sports nutrition position stands / general reference

An hourly target multiplied by expected race hours gives a total in grams. That total determines what you pack and what you must collect on course.

Source: Sports nutrition position stands / general reference

An hour of racing sits inside the capacity of stored glycogen, so extra fuel adds little substrate. Small amounts, or a carbohydrate mouth rinse, may still give a small central benefit at this duration.

Source: Sports nutrition position stands / general reference

Carbohydrate mouth rinsing has repeatedly shown small benefits in efforts of roughly 30-60 minutes, via oral receptors rather than absorption.

Source: Sports nutrition position stands / general reference

Absorption is usually capped below the rate carbohydrate is burned at race intensity, more so the harder the pace, so a long race generally runs a deficit that fuelling makes smaller and slower.

Source: Sports nutrition position stands / general reference

Repeated carbohydrate exposure during exercise upregulates intestinal transport, cutting malabsorption and gut discomfort substantially. Gastric emptying rate has not been shown to change.

Source: Gut-training systematic review (Martinez et al. 2023) / sports nutrition position stands

Adaptation comes from repeated, progressive exposure across many sessions. A single large dose or a rested gut produces no adaptation at all.

Source: Sports nutrition position stands / general reference

Gut training raises the absorption ceiling and reduces symptoms, but the ceiling still exists and no amount of training makes unlimited intake safe.

Source: Gut-training systematic review (Martinez et al. 2023) / sports nutrition position stands

Surveys of long-course and ultra-endurance fields consistently report gut symptoms in a large share of athletes, and they are a leading cause of slowdowns and DNFs.

Source: Sports nutrition position stands / general reference

Highly concentrated drinks are hypertonic: they slow gastric emptying and pull fluid into the intestinal lumen, a common trigger of bloating and diarrhoea.

Source: Sports nutrition position stands / general reference

Dehydration compounds the exercise-induced reduction in splanchnic blood flow, which is one reason gut symptoms often appear late in hot races.

Source: Sports nutrition position stands / general reference

Splanchnic blood flow drops steeply as intensity rises, impairing emptying and absorption. This is also why the run leg tends to produce more symptoms than the bike.

Source: Sports nutrition position stands / general reference

Fibre, fat and protein all delay emptying and leave more residue in the gut, so pre-race and in-race choices are usually kept low in all three.

Source: Sports nutrition position stands / general reference

Lowering intensity restores some blood flow to the gut and pausing concentrated carbohydrate lets the stomach clear. If nausea comes with headache, confusion or bloating, or you have been drinking heavily, stop drinking and seek medical help: these can signal low blood sodium.

Source: Sports nutrition position stands / general reference

NSAIDs reduce gut blood flow and increase intestinal permeability during exercise, and their use is repeatedly linked to more severe gastrointestinal symptoms.

Source: Sports nutrition position stands / general reference

Sweat is overwhelmingly water, and sodium chloride accounts for by far the largest share of the electrolytes it carries.

Source: Sports nutrition position stands / general reference

Sweat is hypotonic relative to plasma: the sweat gland reabsorbs much of the sodium before the fluid reaches the skin.

Source: Sports nutrition position stands / general reference

These minerals appear in sweat only in small quantities. Replacement strategies during events therefore centre on sodium and fluid.

Source: Sports nutrition position stands / general reference

Sweat rate tracks heat production and the environment's ability to take that heat away, so pace, air temperature and humidity dominate.

Source: Sports nutrition position stands / general reference

Body-mass change alone understates sweat loss if you drank during the session, so intake must be added back and urine subtracted.

Source: Sports nutrition position stands / general reference

Body fluid is close enough to the density of water that 1 kg of acute mass loss is treated as roughly 1 L. Fuel burned contributes almost nothing to short-term mass change.

Source: Sports nutrition position stands / general reference

Sodium supports fluid retention and plasma sodium concentration. It has no effect on how much you sweat, and typical drinks contain less sodium per litre than sweat does.

Source: Sports nutrition position stands / general reference

Sweat sodium concentration differs several-fold between people. Visible salt crusting is a rough practical indicator of the higher end of that range.

Source: Sports nutrition position stands / general reference

Sodium becomes relevant when both losses and fluid intake are large and sustained. Short or cool sessions produce losses easily covered by a normal diet.

Source: Sports nutrition position stands / general reference

It is a dilution problem caused by drinking beyond your losses, not a salt-loss or dehydration problem, which is why drinking to thirst rather than to a schedule is the main prevention. Early signs include nausea, headache and confusion, and they need medical help.

Source: Sports nutrition position stands / general reference

Position stands converge on roughly 3-6 mg/kg as the range where an ergogenic effect is reliably seen. Dosing is scaled to body mass rather than given as a fixed amount.

Source: Sports nutrition position stands / general reference

Caffeine is absorbed quickly but peaks in the blood around 45-60 minutes after ingestion, which is why a pre-exercise window of roughly an hour is the standard guidance.

Source: Sports nutrition position stands / general reference

Studies comparing moderate and high doses show no additional performance gain above roughly 6 mg/kg, but a clear rise in side effects. More is simply not better.

Source: Sports nutrition position stands / general reference

The dose-response curve flattens early: doses as low as 1-3 mg/kg have produced performance benefits in trials, making low doses a reasonable option for sensitive athletes.

Source: Sports nutrition position stands / general reference

Habituation is one of the least settled areas in caffeine research, with trials pointing in different directions and no clear support for withdrawal protocols.

Source: Sports nutrition position stands / general reference

Caffeine acts mainly on the central nervous system as an adenosine antagonist, reducing perception of effort. The older glycogen-sparing explanation is no longer considered the primary mechanism.

Source: Sports nutrition position stands / general reference

The practical problems are gut distress and anxiety or jitters, and at higher doses an elevated heart rate that can make pacing by heart rate less reliable.

Source: ISSN position stand on caffeine (Guest et al. 2021) / caffeine and cycling meta-analysis

How fast caffeine clears differs widely between people, driven largely by genetics. Slow metabolisers are affected far longer, so an afternoon dose can still delay and shorten sleep that night.

Source: ISSN position stand on caffeine and exercise performance (Guest et al. 2021)

Caffeine was removed from the prohibited list in 2004 and placed on WADA's monitoring programme, so it is legal in sport while its use is still observed.

Source: WADA prohibited list and monitoring programme / general reference

Research on caffeine at typical performance doses shows no meaningful effect on hydration status during exercise, and exercise itself reduces urine production.

Source: Sports nutrition position stands / general reference

Recovery nutrition is about readiness for the next session, not soreness. Lactate clears within roughly an hour and is not what recovery eating addresses.

Source: Sports nutrition position stands / general reference

The three targets are fuel, repair material and fluid balance. Everything else in recovery eating is secondary to those.

Source: Sports nutrition position stands / general reference

Rapid glycogen resynthesis studies converge on about 1.0-1.2 g/kg/h for the first hours when recovery time is short. Larger intakes do not speed storage further.

Source: Sports nutrition position stands / general reference

Muscle protein synthesis responds strongly to roughly 0.3 g/kg per feeding. Larger single doses are not required to trigger that response, though recent work suggests very large doses can extend it.

Source: ACSM/AND/DC joint position statement (2016); Trommelen et al. 2023

Some of what is drunk is lost again as urine, so replacing 125-150% of the deficit with sodium present restores fluid balance more reliably than matching losses exactly.

Source: Sports nutrition position stands / general reference

With a long gap and a light session, ordinary meals across the day are enough. Structured recovery feeding earns its place when sessions are close together or very demanding.

Source: Sports nutrition position stands / general reference

The body responds to nutrients, not to packaging. Recovery products are useful when food is impractical to carry or prepare, not because they are physiologically superior.

Source: Sports nutrition position stands / general reference

Alcohol directly suppresses the muscle protein synthesis response to training and tends to crowd out the carbohydrate and fluid that recovery depends on.

Source: Sports nutrition position stands / general reference

A deficit that is barely noticeable on day one compounds over a block, which is why heavy days need matching intake rather than a single big meal at the end.

Source: Sports nutrition position stands / general reference

Hard or hot efforts blunt appetite temporarily, and drinkable options such as milk-based drinks, smoothies or soups are far easier to get down than a full meal.

Source: Sports nutrition position stands / general reference

The effect sizes are not comparable: consistent training and adequate fuelling move performance far more than any supplement, which is why food comes first.

Source: Sports nutrition position stands / general reference

Consensus reviews repeatedly identify the same short list of performance supplements with credible evidence; the others lack consistent support in trained athletes.

Source: IOC consensus statement on dietary supplements / general reference

The pattern is a single promising small trial that never replicates. Independent replication in relevant athletes is what separates the short list from the long one.

Source: Sports nutrition position stands / general reference

Batch testing narrows risk to a sampled batch and a defined screening panel; it says nothing about efficacy and offers no anti-doping guarantee.

Source: Anti-doping and supplement certification guidance / general reference

Surveys find undeclared substances in a minority of products rather than most of them, but the risk is real and clusters in specific product categories.

Source: Anti-doping and supplement surveillance literature / general reference

Strict liability places responsibility on the athlete. Evidence of contamination may reduce a sanction in some cases, but it does not remove responsibility.

Source: World Anti-Doping Code / general reference

Several prohibited stimulants and hormone-like compounds are plant-derived. 'Natural' is a marketing word, not a safety or anti-doping category.

Source: Anti-doping education materials / general reference

Iron status has to be measured, not guessed: fatigue has many causes, and unnecessary iron accumulates in the body and can cause harm.

Source: Sports medicine and sports nutrition guidance / general reference

Vitamin D status is measurable and varies widely with season, latitude and lifestyle, so testing risk groups beats blanket supplementation in either direction.

Source: Sports medicine and sports nutrition guidance / general reference

Supplements sit under a lighter regulatory regime than medicines, which is precisely why label accuracy and contamination are recurring problems.

Source: Supplement regulation overview / general reference