The foremost factor that determines the need for a maximally high or very low carb carb diet is the total time performing at very high rates of glycolysis.

The area to the right of the red line is marked ‘HIGH CARB’ because of the extremely high rates of glycolysis and acid production.

The problem with extreme acid production however, is that it severely limits the time exercising in the red zone, which means exercising at high intensity for very brief times do not necessitate eating a high carb diet.

Total time ‘how you live/what you do’ on either side of the red line is what really matters.

However, very small changes in intensity just above the circled spot begin to severely limit the time to do ‘stuff’ or exercise. It’s these small changes we want to understand, which cause big changes in both nutritional intake and how your body adapts to exercise.

The circled spot is technically called the ‘inflection point’ on the blue line of the graph.

• The inflection point is identified where the acid-lactate level starts rapidly increasing – but remains momentarily below a concentration 4mmol/L.

The red line drops down from the inflection point merely to identify the intensity and set the optimal speed for competing in a long distance race.

Once you see how optimal ‘max-speed’ is maintained then you can see how Maximal High Carb Intake is set and why it exists. So first we look at ‘How to Set Optimal Speed’ – next!

The key to maximizing a constant speed or intensity over time demands one thing: not working excessively hard – with the expressed purpose to limit acid production. This is where measuring acid-lactate levels during exercise becomes important, shown below.

Maximizing an optimal constant speed over distance is called race pace.

Race pace occurs when acid levels remain limited and steady – below 4mmol/L – the red line in this graph.

BREAK: See Visualizing Lactate Threshold in Workbook, Week 4

• The purpose of measuring lactate levels during exercise is to help an athlete develop a feel for ‘race pace’ – the optimal intensity to sustain maximal speed over time.

• Race pace is also called Threshold Pace.  More detail on this shown in Week 14, Section C5. (Advanced Strategies for Endurance Training)

• Knowing the feel of the body working at race pace is more important than trying to pinpoint an exact ‘perfect speed’ through a lactate test in a lab due to variation in a person’s lactate levels under variable training conditions, e.g. weather, surfaces, stress, hydration, etc. Developing such a feel is an art and science.

• Not coincidentally, the absolute maximum amount of fat burned during exercise occurs at speeds close to red line zone – graphed here .

For nutritional purposes, knowing the maximum intensity that can be sustained over time is the key for knowing how to ‘cut down on carbs’ –  for any sport, activity, or lifestyle. To start, we look at the two training methodologies and sports where athletes maximize glycolysis and high acid production over time, typically in a period from 2 to 3 hours – next section.

• Method 1: MAXIMAL STEADY STATE TRAINING
• Method 2: INTERVAL TRAINING

METHOD 1 – Maximal Steady State Training.

The red line in the graph below shows the maximum speed running where acid production stays constant – just below 4 mmol/L.

4.2 m/s is the maximum speed tolerated before the spike in lactate occurs. This maximum speed is called MLSS: Maximum Lactate Steady State.

This person’s MLSS occurs running 4.2 m/s and is sustained for 16,000 meters, which covers almost 10 miles running 9.4mph steadily. This is a very fast pace; it equates to running a 2:47 marathon.

• Any speed resulting in flat-lined acid levels allow anyone to sustain a certain pace, workload, or intensity ‘forever’.

• Steady State Training is a specific speed or intensity that keeps glycolysis and acid production steady over time.

MLSS Pace on a ‘regular acid graph’ below is estimated by ‘eyeball guessing’ what’s called the inflection point. Simply mark the spot where the acid-lactate level start increasing exponentially. Note the similarity with the spot I circled on the first graph at the very top of this page.

The black arrow points from the inflection point to the ‘race pace’ speed – a bit slower than 4.4 m/s – which of course coincides with the MLSS in the top graph.

METHOD 2 – Interval Training: Perform briefly at intensities where glucose utilization and acid production are very highly spiked.

Repetitive bursts of high intensity provide another way to deplete great amounts of glycogen. You must rest, do nothing, or perform very easy exercise between the bursts.

Intervals can be performed through totally seemingly different types of exercise.

For example, consider the similarity between running and weight training – specifically the 400m dash and performing Leg Presses in a gym.

1. 400m dash: Mostly legs power the motion up to 50seconds at the finish- failure to maintain power. The 400 m world record time is 43.03 seconds. Held by Wayde van Niekerk

2. Leg presses – from 15-20 reps: Takes up to 50 seconds to reach failure.

Both approaches rapidly deplete glycogen. Thus, the nutritional requirement for recovery – carbohydrate wise – is essentially identical.

Which athletes classically perform steady state or interval style?

Below are two prototypical athletes who train or perform above the red zone – although in two different ways. Both sports above require maximizing carb intake in order to replete glycogen stores.

• Steady State: Cross Country skiers. Perform sustained steady state motion. Likewise, any long distance runner, biker, or swimmer simply sets a pace anywhere near or slightly above lactate threshold – at intensities near  or in the red zone. Keep moving.

• Intervals: Hockey players: a) Perform intermittent sprints during play, often moving slowly otherwise between sprints. b) Sit on bench, then repeat part a = interval training.

The above athletes require Max Carb Intake. From this ‘pinnacle’ we breakdown the method for cutting carbs progressively – from the maximum intake to the lowest levels – for optimal fitness and performance.

So how do we calculate Max Carb Intake in terms of grams of carbs needed to replete glycogen?

Cheat.

Learn How to Use the Cheat Sheet Method, next section.

Multiply body weight (in kg) by the gram counts of carbs (CHO, how much)

Who?	How Much?
Individuals who exercise regularly	4.5 – 6.0 CHO g/kg BW/day
Intermittent, power, strength or sprint sports	5 or more CHO g/kg BW/day
Endurance sports (aerobic training>90 minutes a day most days of the week)	8 – 10 CHO g/kg BW/day

Source: http://btc.montana.edu/olympics/nutrition/eat10.html  – MSU no longer provides this info.

EXAMPLE CALCULATION:

Maximal Carb (CHO) Intake

Consider a 70kg male (154lb) top endurance athlete:

• 70kg x 9g  = 630g.
• Convert grams to calories: 630g/day x 4cal/g = 2520 cals from carbs

However, even top endurance athletes must cut ‘maximum carb intake’ when they reduce time performing. Thus, we proceed by cutting carbs progressively from the maximum amount to cut carbs to the ‘correct’ amount for all other conditions.

Begin cutting carbs progressively from the Max Carb Intake: 630g

Who Needs the Max Carb Intake of 603g?

• Competitive cross country skiers, elite marathoners, or hockey players playing games consecutively day to day.  A sprinter, wide receiver, defensive back, soccer or basketball player who is training/practicing heavily and/or running sprints often may need to eat maximally. Time spent in glycolysis is the primary factor for eating maximum amounts.

• 9g/kg x 70kg person = 630 grams of carbs/day.

Cut #1:  From Max time in Glycolysis to Moderately High Intensity Steady State Training.

• Dependent on reduced time spent training (duration) – intake may be half of 9g/kg. This conforms with the cheating table, which lists 4.5-6g/kg for ‘regular exercisers’. I use 5g/kg for the calculation below.

• 70kg x 5g/kg = 350g carbs. (per day)
  

Cut #2: Down to Low Intensity Steady State Training (and Pure Strength Training).

• After cutting to low intensity – carb intake may need to be cut in half again. Pure strength training, although maximal in intensity is so short lived – little glycogen is depleted. Let’s be conservative and decrease the amount to 3g/kg, which is not quite a 50% reduction.

• 70kg x 3g/kg = 210g carbs. (per day)
  

Not low at all in the view of people who understand how the body works.

Cut # 3: Little or No Exercise – Lowest Amount of Carbs.

• Cut the 3g/kg in half to 1.5g/kg. Couch potatoes or anyone who performs hardly any low-intensity training (walking) and yet again… even pure strength athletes may eat dramatically less carbs at certain times.

• 70kg x 1.5 g/kg =105 g carbs.

Again, not low at all in the view of people who understand how the body works.

To begin, we look at a landmark study by David Costill that established Max Carb Intake in humans.

First, realize the classic Costill study of elite cyclists (graphed below) was a contrived and rare event, purposely designed to force extreme glycogen depletion.

This study required trained cyclists to repeat 2 hours of intense exercise 3 days in a row. Practically nobody performs repeated bouts of extreme red zone level activity unless:

1. You are an elite cyclist participating in a study designed to wipe out glycogen stores.
2. Racing in the Tour de France
3. Playing triple overtime in hockey followed by another game the next day.
4. Competing in the Quintuple Anvil Triathlon
   — five Ironman-length races in five days

The cyclists in the High CHO (carb) group ingested an average of 587 grams of carbs to fully replete glycogen within 24 hours.

Thus, a precedent for Max Carb Intake was established @ 587 grams.

• 587 grams of carbs = 2,348 calories per day from carbs.  (587g x 4cal/g)
• Imagine eating 117 grams of carbs per meal. (at 5 meals/day… 587g/5 = 117 grams)

Compare this way of obtaining Max Amount of 587 grams of carbs (or 2,348 calories) to the ‘Max Amount’ from the cheating table in the previous section.

We had calculated 630 grams of carbs, which = 2,520 calories.

• Each method resulted in a difference of 172 calories, which is insignificant. (2520-2348 =172)

Extreme performances which demand Max Carb Intakes are rare events for most humans.

Only certain competitive athletes from a few sports and a handful of obsessive endurance racers train and compete in extreme ways.

Cutting the Carbs Progressively According to Reduced Glycogen Depletion:

This time we do not cut carbs using the cheat sheet. Instead, we look at directly at how reducing intensity and time reduces glycogen depletion, which therefore decreases carbs needed for repletion.

Like the cheat sheet reductions, I list the cuts in carb intake in a progressively descending way from Max Carb Intake.

Trial 1 is the first cut. It cuts the ‘Max Amount’ of 587 grams of carbs obtained from the cyclists in the Costill study who fully repleted glycogen levels after 2 hours of very intense exercise.

TRIAL 1. Cut time by 50%.

This cuts the cyclists’ time performing from 2 hours to 1 hour, but maintains the same intensity.

Because time is halved we assume glycogen depletion is halved, thus we cut carbs in half.

• Carb intake halved = 587g/2 = 294g
• 294 grams of carbs per day = 1174 calories.  (294 x 4)

Compare the 294g of carbs to using the cheating table method: halving 9g/kg to 4.5g/kg – for a 70kg man.

• 70kg x 4.5g/kg = 315 grams carbs; is fairly close to 294 grams.

TRIAL 2. Cut intensity of Trial 1.

Perform again in a 1hr bout, but reduce intensity. The effective drop is shown by comparing the glycogen depletion in the middle bar to the right bar in the graph below. It is approximately 50% less.

Now, 294 grams/day is excessive.

So, 294g must be lowered. Let’s be conservative again and say the repletion amount is slightly more than half of trial one’s total of 294g – say 55%.

• 294 x .55 = 161.7 g carbs/day.
• 161.7 x 4 = 647 calories from carbs.

TRIAL 3: Little to no exercise.

Cut the trial 2 amount in half.

• 162 grams /2 = 81 grams of carbs per day.

COMPARE the 81g of carbs day to the previous section’s calculation for little to no exercise:

• 70kg x 1.5 g/kg =105 g. This is fairly close to 81g.

Six Takeaway Messages

1. Indisputably, low rates of glycolysis spare a person’s glycogen stores.

2. Sports that require exerting absolute maximum strength for very short periods of time overall – or athletes who are very mechanically efficient and never exhaust themselves – do not require max carb intakes and maximal glycogen levels in their muscles for performance.

3. It is not necessary to have full muscle glycogen stores to perform at full strength.

Consider thoughts of this martial artist who answers the question on why he purposely does not replete glycogen after workouts.

“I don’t actually top it off every workout. I try to maintain just enough to keep me going during each workout. If I have a really long session coming up (sometimes I’ll be doing stuff for hours and hours with my friends on weekends) I might shoot for supercompensation, but that’s mostly for giggles.”

4. There is no reason to eat a high carb diet to top off muscle glycogen ever –  especially if you don’t plan on performing lots of ‘reps-exhaustion’ exercise.

• Thus, powerlifters, martial artists, rock climbers, and other ‘power athletes’ do not require high carb diets to maximize strength and performance. Under a ‘low carb diet’ scenario – fat and protein must comprise a greater percentage of total calories. See pie charts in the Metabolism Wheel.

• Pure strength training does not require much carbs. Body builders perform reps-exhaustion schemes – but power lifters do not.
  

5. Many sports nutrition charts are geared to fully replete glycogen – which is necessary only for repeating extreme performances.

6. People who ‘exercise regularly’ may easily eat excessive  amounts of carbohydrates, since they may think the exercise they do requires it.

SUMMARY:

Ultimately, the only thing that determines the need for a high carb diet is total time performing at high or exponentially high rates of glycolysis. Simply adjust intake to your current regimen. You must not be afraid to increase fat and protein levels when carb intake should be low.

Costill and others laid down a holy grail for non-athletes competing in marathons and such to practice high carb recovery nutrition as if they trained like Tour de France riders – for example, by piggin’ out on pasta the night before an endurance race.

Legions jumped on the bandwagon, and many have remained on it since. Famous authors like Professor Tim Noakes (writer of the Lore of Running) taught legions of runners to maximize carb intake after running or after ‘aerobic exercise’. However, Noakes has since changed his mind as a result of developing ‘prediabetes’. Read on that here.

Forcing the body to ‘recover’ by fully restoring muscle and liver glycogen may stress the organs (pancreas and liver mainly) doing the work. Eating 800 to 1000 grams of carbs/sugar a day to force maximal glycogen repletion means the pancreas must secrete insulin constantly and often in high amounts. Now, if you’re an athlete who must repeat a performance, then yes, you must ‘overfeed’. But assuming you are not trying to repeat high intensity exercise in consecutive days, there definitely is no need to force full repletion.

It just may be healthier to avoid refilling glycogen levels as fast as possible and take a few days as opposed to making it happen in 24 hours.

Only people who train at Steady States near MLSS or Intermittently Above MLSS for appreciable amounts of time need to eat high carb diets.

[HR]

MLSS is the essential dividing line for improving fitness for the body to compete in endurance events and for determining the need to eat a low or high carb diet.

Indisputably, low rates of glycolysis spare a person’s glycogen stores. There is no reason to eat a high carb diet to top off muscle glycogen ever –  especially if you don’t plan on performing lots of ‘reps-exhaustion’ exercise.

• Sports that require exerting absolute maximum strength for short periods of time overall – or athletes who are very efficient and never exhaust themselves – do not require high glycogen levels in their muscles to perform.

• Thus, powerlifters, martial artists, rock climbers, and other ‘power athletes’ do not require high carb diets to maximize strength and performance. Under a ‘low carb diet’ scenario – fat and protein must comprise a greater percentage of total calories. See pie charts in the Metabolism Wheel.