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In the never ending quest to go further, faster, harder, longer etc, scientists are forever looking at new methods of training, diet and supplementation. One particular model/theory that has gained a lot of momentum in recent years involves the periodic manipulation of carbohydrate intake coincidental with exercise. Such approaches involve a variation/combination of either:

  • Exercising in a fasted state
  • Restricting carbohydrate intake during exercise
  • Exercising with depleted glycogen stores

Whether they are used in combination or isolation, each of these strategies invariably results in reduced carbohydrate availability during exercise. Studies have shown that molecular responses at the level of the mitochondria are different when exercise is conducted with reduced carbohydrate availability compared to when glycogen stores are fuel. Such molecular responses entail changes in the expression pattern of proteins in mitochondria. These ultimately result in an increased ability to utilise fat as an energy source during exercise, which invariably leads to better performance during endurance type events. This approach to endurance training that incorporate by diet and exercise modification has been coined the Train Low-Compete High model. This article will describe the theory behind the Train Low-Compete High model and how to practically implement it into an endurance training program.

Glycogen Basics

To better understand how the Train Low-Compete High model works, one needs to understand the importance of muscle glycogen as a fuel source during exercise. Whenever exercising at an intensity above 65% of maximal oxygen uptake (VO2max), glycogen is the major fuel source. Or to put it another way, one’s ability to exercise for any length of time at a high intensity is dictated in large part by their muscle glycogen reserves. Consuming a carbohydrate rich diet that includes ample carbohydrate intake pre, during and post exercise is the principle means of maintaining high glycogen levels. The most obvious example of the value of high glycogen stores is the practice of carbohydrate loading, where athletes aim to consume somewhere between 10-12g of carbohydrate per kilogram bodyweight per day1.

Glycogen and Fuel Use During Exercise

It follows that when glycogen reserves are low; there is a significant shift in the body’s metabolism and fuel use during exercise. When exercising with low glycogen levels, there is an increased use of fat as fuel as well as an increased release of amino acids into the blood as muscle protein is broken down. An increase in the levels of the stress hormones cortisol and epinephrine can also occur1. With these changes, it’s no surprise that performance is negatively affected by low glycogen levels1. But recent studies suggest that training with low glycogen levels also triggers a cascade of events in muscle that mirrors the gradual molecular changes that occur in mitochondria as a result of increased endurance capacity2.

Endurance Training Adaptations and Glycogen Levels

The basic goal of all endurance training is to increase mitochondrial biogenesis; a fancy term that refers to the combined process of increased mitochondrial size, content, number, and activity3. Mitochondria are often referred to as the ‘powerhouse of cells’ in that they are responsible for producing most of the energy required during exercise. Making one’s mitochondria bigger and more efficient goes a long way to improving endurance exercise capacity3.

Regulation of Mitochondrial Energy Production

To understand how the Train Low-Compete High model works, one needs to understand a little about the way in which mitochondria produce energy. Energy production by mitochondria is dictated in large part by the types of proteins (i.e. metabolic machinery) that are expressed. The levels of these proteins in turn determine how much fat and carbohydrate the mitochondria can oxidize (i.e. burn).

Delving just a little deeper, sports scientists have discovered that there are master regulator molecules, which have a major bearing on the expression of the whole cascade of proteins involved in the regulation of fat and carbohydrate oxidation in mitochondria. One example worth mentioning is that of peroxisome proliferator-activated gamma receptor co-activator 1 alpha or PGC-1a. Apart from having one of the hardest names to memorise, PGC-1a is believed to be the ‘master’ regulator of mitochondrial biogenesis. So increasing PGC-1a by any means (i.e. exercise or nutrition intervention) should be the goal of any endurance training

Effect of Low Glycogen on Mitochondrial Biogenesis

The fascinating aspect of the recently coined Train Low-Compete High model is that it has been found to significantly alter levels of PGC-1a compared with conventional training where carbohydrate intake is not restricted and glycogen stores are normal. As an example, one recent study found that the protein levels of PGC-1a were enhanced 8.1 fold when exercise was performed with low glycogen compared with normal glycogen which only enhanced PGC-1a levels 2.5 fold2. Scientists have known for some time now that different types of exercise (i.e. long endurance/low intensity vs short high intensity) result in different molecular signals at the level of mitochondria. But it is only more recently that scientists have uncovered that exercise with differing nutritional status (i.e. low glycogen vs normal glycogen) can also result in dramatically different molecular signalling that mediates the muscle adaptive responses to endurance training.

Possibly Drawbacks with Train Low-Compete High Model

Although deliberately restricting carbohydrate intake periodically can potentiate the metabolic adaptations to aerobic exercise, it has also been shown to lead to an increase in the breakdown of muscle protein. Whenever glycogen stores are low, there is a larger reliance on muscle protein for energy provision. Therefore, researchers have proposed that consuming protein before and/or during exercise with low glycogen reserves is a good way to offset its negative effects on muscle protein loss. In fact, a recent study found that consumption of 20g before, 10g during and 20g after of a casein hydrolysate prevented the muscle protein breakdown normally associated with train low-compete high model, while still preserving the significant increase in PGC-1a levels normally associated with training with low muscle glycogen4.

Because glycogen serves as the principal fuel substrate during intense exercise, when training with low glycogen reserves, it’s inevitable that individuals reduce the intensity of their exercise session. The other inherent risk is the reduced central nervous and immune system function, which leads to a decrease in self selected intensity and an increased risk of infection, respectively. For this reason athletes are strongly advised to ease into it slowly as individual responses can be highly variable.

Caffeine Intake and Train Low-Compete High Model

While it is well documented that exercise intensity capacity is significantly reduced when exercising with low glycogen reserves, one recent study has found that supplementation with caffeine can help restore some of the lost intensity. The study in question found that a 3mg/kg dose of caffeine 60 minutes prior to exercise increased power output by 3.5% in cyclists when exercising with low glycogen stores5.

It would appear therefore that protein ingestion prior, during and after exercise combined with pre exercise ingestion of caffeine can help offset some of the negative effects of training with low glycogen reserves on muscle protein breakdown and exercise intensity respectively.

Variations of the Train Low-Compete High Model

Training with a reduced carbohydrate intake and/or glycogen stores can be achieved in a number of ways. The table below is taken from a hallmark publication on the Train Low-Compete High model and gives an overview of the different exercise-diet strategies that can be employed and their respective outcomes in terms of their impact on immune and nervous system function as well as recovery. These strategies can be used interchangeably based on an athlete’s tolerance to low carbohydrate training.

 

Exercise-Diet Strategy

Main Outcomes

Chronically low carbohydrate diet (carbohydrate intake less than fuel requirements for training)

Chronic reduction in muscle carbohydrate availability for all training sessions, depending on degree of fuel mismatch. Chronic whole-body effects of low carbohydrate availability including impairment of immune system and central nervous system function.

Twice a day training (low carbohydrate availability for the second session in a day achieved by limiting the duration and carbohydrate intake in recovery period after the first session).

Reduction in the body stores of carbohydrate as well as abstaining from carbohydrate consumption during the second training session. Results in an acute reduction of carbohydrate availability for immune and central nervous system depending on length of training session.

Training after an overnight fast

Restrict the provision of carbohydrate during the training session. Potential reduction in carbohydrate availability if there is inadequate glycogen restoration from previous day’s training.

Prolonged training with or without an overnight fast and/or withholding carbohydrate intake during the session

Reduction in carbohydrate supply for the muscle for the specific session. Magnitude of reduction in carbohydrate availability depends on length and intensity of session.

Withholding carbohydrate during the first hours of recovery

Could provide adequate fuel availability for the specific session but amplify post-exercise signalling due to the short but targeted time of low carbohydrate availability. This approach achieves both a “train hard” and “train smarter” effect. However, can interfere with re-fuelling for subsequent training sessions if total carbohydrate intake is reduced rather than just delayed. May reduce immune system function or accentuate the immune suppression that occurs after exercise.

 

Practical Application of Train Low-Compete High

Because of the inherent risks associated with the Train Low-Compete High model, athletes need to exercise caution when starting to incorporate low carbohydrate availability sessions into their training. The table below was presented at the 2012 Nestle Sports Nutrition Conference in New York and provides an overview of a sample training plan for an advanced runner preparing for a marathon and looking to progressively incorporate low carbohydrate availability training. It’s important to remember that this table is just a rough outline of the principles, which ultimately need to be adapted and fitted to the individual. This program is not set in stone and flexibility is needed in any training or nutrition program. Also there are large individual responses, and some or all of these interventions may not work in all endurance athletes. Nonetheless, the table gives a good overview of how to go about incorporating low carbohydrate availability training.

 

# of Weeks Prior to Marathon

Training Phase

Type of Training Session

# of Sessions per Week

Length of longest session (min)

Quality of Session

Comments

9 to 16 weeks prior to marathon

General Prep Phase (Maximising training adaptation and recovery focus)

Fasted

1 to 3

45-120min

Steady easy to moderate

Slowly build out length of morning fasted running during this period – individualise as the athlete adapts

Low Glycogen

1 to 2

45-70min

Steady easy to moderate

Test out low-glycogen training, see how athlete responds. Perhaps only start with fasted training first

Long Run

1

>120min

Steady easy to moderate

Use and record fluid and CHO intakes into spreadsheet; probably do not need CHO intake in runs less than 120mins

5 to 8 weeks prior to marathon

Specific Prep Phase (Individualising sweat rates and optimising fluid and CHO intakes)

Fasted

2 to 3

90-120min

Steady easy to moderate

On one fasted run incorporate ~60-70min of tempo or some quality; other fasted runs could be only ~60-75min

Low Glycogen

1

50-70min

Steady easy to moderate

Could consider some tempo in second run if split workout or consider eliminating from program if not adapting favourably.

Individualise

1 to 2

>75min

Moderate to tempo to hard workout (with CHO and fluid)

On every run longer than ~75min record pre and post-body weight and temperature: one 1 to 2 sessions per week start to experiment with higher levels of fluid & CHO intake; record into spreadsheet.

Long Run

1

>120min

Steady easy to moderate

Use and record fluid and CHO intakes into spreadsheet.

Last 4 weeks prior to marathon

Final Preparation Phase (individualising CHO and fluid & Gut Adaptation)

Fasted

1 to 2

90-120min

 

 

Low Glycogen

 

 

 

Consider dropping all low glycogen training if undertaking

Individualise

2 to 3

>75min

Moderate to tempo to hard workout (with CHO and fluid)

On every run longer than ~75 min record pre and post-body weight and temperature; focus on a “key” practice

Long Run

1

>120min

Steady easy to moderate

Use and record fluid and CHO intakes into spreadsheet

Race

 

 

 

 

 

 

 

References

1. Burke LM. Fuelling strategies to optimize performance: training high or training low? Scand J Med Sci Sports. 2010:20(Suppl. 2):48–58.
2. Psilander N, et al. Exercise with low glycogen increases PGC-1a gene expression in human skeletal muscle. Eur J Appl Physiol. 2013;113:951–963.
3. Lee M. Margolis and Stefan M. Pasiakos. Optimizing intramuscular adaptations to aerobic exercise: effects of carbohydrate restriction and protein supplementation on mitochondrial biogenesis. Adv Nutr.2013; 4:657–664.
4. Taylor C, et al. Protein ingestion does not impair exercise-induced AMPK signalling when in a glycogen-depleted state: implications for train-low compete-high. Eur J Appl Physiol. 2013; 113:1457–1468.
5. Lane SC, et al. Caffeine ingestion and cycling power output in a low or normal muscle glycogen state. Med Sci Sports Exerc. 2013;45(8):1577-84.

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