Sports Nutrition

01What the measurements show

The Numbers Behind Athletic Fueling

Eight findings that place fueling inside the athlete as much as inside the meal.

02Carbohydrate and the brain

Carbohydrate Runs the Brain and the Muscle From One Store

Carbohydrate is the dominant fuel for both the working muscle and the central nervous system, and it is the first macronutrient an elite athlete should master. The body banks it as glycogen in muscle and liver. Pooled biopsy data from 181 studies of cycling and running put resting glycogen in the vastus lateralis at 462 plus or minus 132 mmol per kg dry mass Areta 2018. Those were men with normal carbohydrate availability.

That store is finite and the session spends it. Exercise intensity and the size of the store at the start are the two factors that decide the rate. Raise starting glycogen by 200 mmol per kg and an athlete uses 143 mmol per kg more of it by the point of fatigue.

What glycogen depletion costs the brain

When glycogen empties, the wall arrives. Athletes call it bonking, and it is as much a neurological event as a muscular one, because the brain itself is starved of its preferred fuel.

That is measurable, and the measurement is unusually direct. Eight endurance-trained men cycled for three hours with and without glucose. Without it, blood glucose fell from 4.5 to 3.0 mM. Force during a two minute maximal knee extension fell to 197 newtons, against 222 newtons with glucose and 248 newtons at baseline Nybo 2003.

The important half of that result is where the loss came from. Central activation, measured by twitch interpolation, dropped in the placebo trial and held in the glucose trial. The muscle was not the part that quit. Reaction time slows, decision making blurs, and coordination frays for the same reason: the system doing the deciding is the one short of fuel.

Carbohydrate also spares protein from being burned for energy, which protects the tissue the athlete is training to build. Which pathway spends which fuel at which intensity belongs to Exercise Physiology and Energy Systems.

03Carbohydrate in grams per kilogram

Carbohydrate Targets Are Written in Grams Per Kilogram of Body Mass

Endogenous glycogen stores are maximized on 8 to 12 g of carbohydrate per kg per day, and high volume exercise is what depletes them most Kerksick 2017. The percentage-of-calories figures that circulate in general nutrition advice do not survive contact with a training week.

During the work itself the numbers change again. Bouts beyond 60 minutes at above 70 percent of maximal oxygen uptake challenge both fuel supply and fluid regulation. The position stand's figure there is roughly 30 to 60 g of carbohydrate per hour, in a 6 to 8 percent carbohydrate electrolyte solution taken every 10 to 15 minutes Kerksick 2017. That guidance is aimed in particular at bouts spanning beyond 70 minutes.

Refeeding carbohydrate when two sessions sit close together

Recovery time decides the refeed. If less than four hours separate two sessions, the stated strategy is aggressive carbohydrate refeeding at 1.2 g per kg per hour from sources with a glycemic index above 70. The alternative pairs 0.8 g per kg per hour of carbohydrate with 0.2 to 0.4 g per kg per hour of protein Kerksick 2017.

The variable all of those numbers aim at is carbohydrate availability, and the pooled biopsy data show how much weight it carries. High availability raised resting glycogen by 102 mmol per kg dry mass and low availability cut it by 253 Areta 2018. Every 10 mL per kg per minute of maximal oxygen uptake was worth 67 mmol per kg.

Diet moved the store further than fitness did. An athlete cannot train their way past a week of underfueling, because the store is filled at the table.

04Protein and the daily total

Protein Rebuilds Tissue, and the Daily Total Decides More Than Any Other Variable

The daily figure is 1.4 to 2.0 g of protein per kg of body weight, which is sufficient for most exercising individuals to build and maintain muscle mass Jager 2017. Protein supplies the raw material of recovery, and everything else about it, including source and timing, sits downstream of that total.

The pooled trial evidence puts a ceiling on that. Across 49 randomized trials and 1863 participants, protein supplementation raised one-repetition maximum strength by 2.49 kg and fat-free mass by 0.30 kg Morton 2018. Beyond a total intake of 1.62 g per kg per day, no further fat-free mass gain appeared.

Protein builds the enzymes, antibodies, messengers and transport molecules that keep an athlete adapting rather than breaking down, and muscle is only its most visible product. The body assembles all of it from twenty amino acids, eleven it can synthesize and nine it cannot. Those nine are the essential aminos, and they must arrive in the diet every single day.

Leucine is the one that starts the process. Acute protein doses should carry 700 to 3000 mg of leucine alongside a balanced supply of the other essential amino acids Jager 2017.

Why 20 grams of whey is the per-meal ceiling

Per meal, the dose response flattens early. Forty-eight resistance-trained men were given 0, 10, 20 or 40 g of whey after unilateral leg press and leg extension. Myofibrillar protein synthesis rose 49 percent at 20 g and 56 percent at 40 g, while 10 g moved nothing Witard 2014.

The 40 g arm paid for the extra. Phenylalanine oxidation and urea production both rose, which means the surplus was disposed of rather than built with. General recommendations sit at 0.25 g of high-quality protein per kg of body weight, or an absolute dose of 20 to 40 g, spaced every 3 to 4 hours Jager 2017.

One qualification runs through all of it. Those are population figures, and the number a single athlete needs is set by their body mass, their training load and their goal.

05Fat and the nerve membrane

Fat Builds the Membranes the Nervous System Signals Across

Fat is the macronutrient the nervous system is physically made of, and the elite athlete treats it as performance infrastructure. At 9 kcal per gram it carries more than twice the energy density of carbohydrate or protein. Lipids supply membrane integrity, the substrate for hormone and vitamin production, and the material that makes nerve cell conduction possible.

The myelin that wraps a fast axon and the membrane of every neuron are built from lipid. That makes nerve conduction partly a question of which fats arrive, and fueling the brain and the peripheral nerves partly a question of lipid quality.

Quality is the operative word. Human beings evolved consuming roughly equal amounts of omega 6 and omega 3 essential fatty acids. Western diets now run a ratio of about 10:1 to 20:1 against a traditional range of 1:1 to 2:1 Simopoulos 2007.

A high omega 6 intake shifts the physiology toward a prothrombotic and proaggregatory state, with increased blood viscosity, vasospasm and vasoconstriction. The omega 3 fatty acids EPA and DHA carry anti-inflammatory, antithrombotic, antiarrhythmic, hypolipidemic and vasodilatory properties Simopoulos 2007. The general guideline offered for most athletes is 1 to 2 g per day of EPA and DHA at a 2:1 ratio.

Why lipid quality reaches the nervous system

The inflammatory state that follows hard training is a regulated program rather than an accident, and Inflammation and Tissue Healing carries that literature together with the trials that tested interfering with it. What the diet contributes is the signaling environment that program runs in, and the omega 6 to omega 3 ratio is the dial. Excess radical formation and trauma during high intensity exercise worsen that state, and EPA and DHA counteract it Simopoulos 2007. Lipid quality belongs to recovery and to the resolution of training stress.

That environment is also the one that governs autonomic readiness and the central integrative state, the baseline from which every adaptation is made. An athlete managing inflammation through the diet is working on the summed state a neuron holds before any single input arrives. In concentrated supplement form the question changes, and Supplements carries the evidence and the contamination record.

06The post-exercise window

The Anabolic Window Is Wider Than the Advice Built Around It

The post-exercise window for protein is measured in hours. Timing turns good nutrition into competitive nutrition, because the same macronutrients deliver different results depending on when they land. The post workout window is when carbohydrate replenishes the glycogen just spent and protein delivers the amino acids the muscle is primed to absorb.

Feeding with intent before and after training keeps the athlete out of the protein burning, glycogen depleted state where performance and the central nervous system both degrade. What the trials will not support is the half hour version of that advice, and several went looking for it.

A multi-level meta-regression of the timing trials covered 478 subjects and 96 effect sizes for strength, and 525 subjects and 132 effect sizes for hypertrophy Schoenfeld 2013.

A simple pooled analysis showed a small to moderate effect on hypertrophy and no significant effect on strength. In the full model controlling for all covariates, no significant difference remained between treatment and control for either outcome. Total daily protein intake was the strongest predictor of the hypertrophy effect size.

The authors state the conclusion without softening it. Their results refute the belief that timing protein around a training session is critical, and they place adequate total protein combined with resistance exercise as the factor that maximizes muscle protein accretion.

A controlled test followed four years later. Twenty-one resistance-trained men took 25 g of protein either immediately before or immediately after training, three sessions a week for ten weeks. Strength, hypertrophy and body composition changes were similar on every measure Schoenfeld 2017.

The authors put the usable interval at several hours or more, set partly by when the pre-workout meal was eaten. Two null results in a row on the same question are the answer.

How protein distribution across the day changes the result

Distribution across the day is where the feeding schedule earns its keep. Twenty-four trained men received 80 g of whey across 12 hours of recovery from resistance exercise, in three patterns Areta 2013.

Four doses of 20 g every 3 hours raised myofibrillar protein synthesis 31 to 48 percent above eight doses of 10 g every 1.5 hours or two doses of 40 g every 6 hours. One total, three schedules, three answers. That is a timing effect, and it operates across a day rather than inside a half hour after the last set.

This is also where fueling meets the broader physiology of energy systems, the phosphagen, glycolytic and oxidative pathways that draw on these very substrates. An athlete who knows which system powers a given effort can fuel it precisely, matching carbohydrate to high intensity work and fat to the long oxidative grind Exercise Physiology and Energy Systems.

Glycogen is the other place the clock matters, and it matters when the next session is close. Recovery is a feeding decision the athlete makes deliberately rather than a stretch of passive rest. The refeeding rates above are what that decision looks like when two sessions sit inside four hours of each other Kerksick 2017.

Why carbohydrate added to a protein feed changes nothing

Adding carbohydrate to a protein feed does not add to the rebuild. Nine men took 25 g of whey, or 25 g of whey plus 50 g of maltodextrin, after unilateral knee extension. The carbohydrate arm produced a five-fold larger insulin curve and a 17.5-fold larger glucose curve Staples 2011.

Neither muscle protein synthesis nor muscle protein breakdown differed, at rest or after exercise. Insulin was not a missing lever at a protein dose that already stimulates synthesis maximally. Carbohydrate earns its place on the plate by refilling glycogen and by feeding the brain, which is a different job from building tissue.

07Same feed, different athlete

Fed or Fasted Changes What the Same Carbohydrate Does

The cleanest demonstration in sports nutrition that food is an input meeting a state does not involve swallowing anything. Twelve competitive male cyclists completed 60 minute simulated time trials after rinsing with a 10 percent maltodextrin solution or a taste-matched placebo for 10 seconds, then spitting it out Lane 2013.

Two of each rider's four trials began two hours after a meal containing 2.5 g per kg of carbohydrate. The other two began after an overnight fast. The rinse raised mean power in both conditions, and it raised it unequally.

Fasted, power went from 273 to 282 W, a gain of 3.4 percent. Fed, it went from 281 to 286 W, a gain of 1.8 percent. The interaction between nutritional status and the rinse was significant. Nothing was absorbed, so the difference cannot be a difference in fuel delivered.

The carbohydrate mouth rinse and the brain regions it activates

The mechanism was imaged four years earlier. Eight endurance-trained cyclists completed a time trial faster while rinsing with 6.4 percent glucose than with a saccharin placebo, 60.4 against 61.6 minutes Chambers 2009. A second experiment in the same paper ran eight endurance-trained cyclists on a 6.4 percent maltodextrin rinse, and they finished in 62.6 minutes against 64.6 on placebo.

Functional MRI in the same study showed oral glucose activating reward-related regions including the anterior cingulate cortex and striatum, which did not respond to saccharin. Maltodextrin activated the insula and frontal operculum, orbitofrontal cortex and striatum. Maltodextrin is not sweet, and the authors point to a class of oral receptors that reads carbohydrate independently of the receptors for sweetness.

Carbohydrate reaches the nervous system before it reaches the muscle. How large the power gain is depends on what that nervous system already had.

State dependence in the long protein trials

State dependence is not confined to acute studies. In the pooled protein data, the effect of supplementation on fat-free mass fell as age rose, and it was larger in resistance-trained participants by 0.75 kg Morton 2018. One supplement, several starting states, several effect sizes.

The glycogen meta-analysis reports the same thing about work rather than about food. Baseline glycogen was one of the two factors determining how much glycogen a session used, while fitness had mainly trivial effects on utilization Areta 2018. The session did not decide alone. The state it met decided with it.

08Building the fueling plan

A Fueling Plan Is Built Around One Athlete and One Set of Demands

A sports nutrition plan is a deliberate construction of caloric needs, macronutrient ratios and timing tuned to a single athlete's goals. Determining caloric needs comes first. The diet then bends toward the objective, eating for performance, for weight gain or for weight loss, with the macronutrient split adjusted accordingly.

Sport demands, training phase, travel and body composition targets reshape it further, which is why no two elite athletes should eat the same way. The plan is not generic. It is built around the demands of the sport and the athlete in front of you. Body Composition carries what each measurement method actually resolves and the low energy availability literature a plan has to respect. Hydration and Electrolytes carries fluid and sodium.

The joint position stand of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine is explicit about who writes an individual plan. Athletes should be referred to a registered dietitian nutritionist, and in the United States and Canada the Certified Specialist in Sports Dietetics holds that credential Thomas 2016.

This practice reads nutrition the way it reads everything else, as an input to the nervous system that integrates fuel, recovery and readiness into one performance signal. It works alongside sports medicine, athletic trainers, strength staff and sports dietitians, and the written plan goes to the person credentialed to produce it.

Whole food fueling and the anti-doping question

Whole-food fueling raises no anti-doping question. Concentrated products do, and both the ingredient evidence and the contamination record sit in Supplements. Any product used by an athlete under testing should be third-party batch tested and checked against the current prohibited list before it is opened.

An athlete who fuels with intent is not eating to feel full. They are feeding the nervous system that decides how fast they react, how cleanly they coordinate, and how quickly they recover. The edge is built in the nervous system, and the nervous system is fed.

09What we corrected

The Macronutrient Percentages and Three Untraceable Figures Are Gone

This page previously set macronutrient targets as shares of total calories: 45 to 65 percent carbohydrate, 20 to 30 percent protein, 20 to 25 percent fat. Those are general-population distribution ranges. Athlete guidelines are written per kilogram of body mass, so the percentages are gone and the per-kilogram figures above replace them Kerksick 2017.

Three further numbers could not be traced to a source and have been removed. One was a glycogen store of 500 to 2000 kcal. One was a trained athlete carrying 20 to 50 percent more stored glycogen than an untrained one. One was roughly ninety minutes of hard work before the tank runs low. The measured concentrations replace all three Areta 2018, and they put carbohydrate availability ahead of fitness.

The page also stated that carbohydrate eaten alongside protein aids protein digestion and absorption. The controlled test of that idea found no effect on muscle protein synthesis or breakdown Staples 2011. Carbohydrate is on the plate for glycogen and for the brain.

A quotation about fueling attributed to Dr. Jason Dulberg sat on the page and came from nothing he said or wrote. It is gone. Every claim here is sourced to the literature or named as the model's.

10The model's claim

Fueling Is One Input Meeting One State, and Both Halves Are Measurable

Two layers run through this page, and the sources carry only one of them. The glycogen concentrations, the protein dose response, the 1.62 g per kg plateau, the timing meta-regression and the two mouth-rinse trials belong to the investigators named beside them. Each of those results describes what happened when one defined feed met one defined group of athletes.

The second layer is what the Unified Model of Tone contributes, and it is a claim about the other half of that sentence. The model's input law holds that the effect of any event is determined by how that event interacts with the organism's existing tone. A meal is an event. The athlete is the organization it meets.

That reading predicts the scatter in the nutrient timing literature. A window that seems to close quickly in one trial and stay open for hours in another is one dose meeting two states. The fed and fasted rinse arms measured exactly that inside the same twelve cyclists, and the gap was 3.4 percent against 1.8 percent.

The prediction this page makes

Take one squad and one standardized feeding challenge, delivered twice in the same athletes: once after a high carbohydrate availability day, once after a low one. Record RMSSD for variability structure and stride-interval variability across a fixed submaximal run for coupling. Add reaction time variability on a choice task for reflex responsiveness. Add the time heart rate takes to return to its own baseline after a fixed step test for recovery time.

The model predicts the response to the identical feed scales with the state it meets rather than with the dose. It predicts those four readouts share one underlying factor within athlete across the two conditions rather than drifting independently. It predicts the spread between athletes on that factor is widest in the low availability condition, because a depleted system has less room to organize.

This is a claim about how fueling is organized rather than a claim about what any treatment does. It is also cheap to run, because every instrument in it already sits in a monitoring program.

If RMSSD, stride-interval variability, reaction time variability and time to return to baseline heart rate are shown to move together within the same athletes across the two feeding states, the unification claim is confirmed.

11The tone reading

Fueling as One Regulated State

Three signatures of tone carry this page, each in a figure a fueling plan already produces.

The rest of the library carries the same logic through its other foundations. Gain decides the size of the answer a feed produces, which is why 20 g of whey returned a 49 percent rise in synthesis and 10 g returned nothing. Set-point is the blood glucose value the body defends, and three hours of cycling without carbohydrate pulled it from 4.5 to 3.0 mM. Prediction covers the forward read the brain makes of carbohydrate in the mouth before a gram of it is absorbed. Constraint is why intake above 1.62 g per kg per day stops adding fat-free mass. Coupling names the relationship between the feeding rhythm and the training rhythm that a plan has to hold, and oscillation is the daily cycle underneath both. The whole framework is laid out in the Unified Model of Tone.

12Where this sits

How This Page Relates to the Rest of the Library

Seven places the sports nutrition argument continues, each with the claim that earns the link.

13Questions athletes ask

Questions Athletes Ask

14The sources

References

14 primary sources, each linked to its record. Figures quoted on this page were checked against the published abstract.