Train Low, Compete High
Matt Durkin explains why athletes are now choosing to adopt a periodised approach to their nutrition, just like they do with their training.
Since the landmark study of Hansen and colleagues in 2005, it is well-known that the availability of carbohydrates in the body can influence how we adapt to exercise training.
These preliminary findings have not only stimulated many further investigations but have also shaped a training ideology known as "train low, compete high". Otherwise known as 'carbohydrate periodisation', or 'fuelling for the work required', this is, in essence, a way of inducing greater training adaptations by manipulating carb intake (train low). When competing, however, athletes should always perform with optimal carbohydrate stores and adhere to an appropriate fuelling strategy (compete high).
The totality of evidence suggests that performing specific training sessions with low carbohydrate stores drives adaptations to fat metabolism. This allows athletes to burn more fat at a given exercise intensity and therefore, fewer carbs. As carbs are being more efficiently used, they are preserved for use later in an event, such as during hill climbs or sprint finishes. This is something commonly known to sports scientists as 'metabolic flexibility'.
Many athletes are now choosing to adopt a periodised approach to their nutrition, just like they do with their training. One of the most publicised of these athletes is 4-time Tour de France winner Chris Froome, who believes this approach has helped his athletic development and weight-management.
Now we have touched on what train low, compete high is, let us have a quick look through some key research findings.
Back in 2005, researchers wanted to assess whether training twice every other day was more effective than training once every day. In a group of healthy, but untrained men, one leg was trained every day using the leg extension exercise, whilst the other leg was trained twice, every other day using the same exercise.
In the leg that trained twice every other day, there was a lack of carbohydrates in the recovery period. This meant that the second session of the day was performed with low carbohydrate availability.
After a 10-week training block, the leg that training twice every other day saw a greater resistance to fatigue, an increase in muscle glycogen stores, and an upregulation of key enzymes involved in fat metabolism. Despite some limitations in the study, such as using untrained individuals, these were fascinating findings that inspired further work.
For many years after, there were a collection of studies that looked at the benefits of twice per day training in both running and cycling, where again the second session of the day was with low carbohydrate availability. Interestingly, these studies agreed that this method of training led to impressive adaptations in the muscle, but this rarely translated to an improvement in performance.
These results seemed to come about because the participants in the studies were instructed to perform high-intensity interval training whilst deficient in carbohydrates. As this type of activity is almost exclusively fuelled by glucose, the performance drops in the training sessions were quite substantial. Despite this, none of the studies found that 'training low' worsened performance during a simulated time trial event.
A further study conducted at Liverpool John Moores University in 2014 found that training low led to 'time-efficient' training adaptations. This means that those training low saw as impressive training adaptations as those who always trained with high carbohydrate availability. This was realised despite those in the "train low" group performing a much lower training volume. Again though, there was no benefit to performance.
Learning from the pitfalls of previous investigations, more recent work has employed an approach that has been coined as 'sleep low'. This is where athletes complete an exercise session in the evening and restrict carbohydrate feeding after, thereby going to sleep with reduced carbohydrate availability. The following morning the athletes perform a low-intensity session in their fasted state.
Not only has this method been shown to induce favourable adaptations at a cellular level, but this has also translated into improved exercise performance. A study from 2016 showed that in as little as three weeks, 'sleeping low' led to a group of elite triathletes/cyclists improving cycling efficiency (3.1%), 20km cycling time trial performance (3.2%), and 10km running performance (2.9%) when compared to a traditional diet of chronic high carbohydrate availability. What is more is that these athletes managed to lose more body fat, thus also improving their power-to-mass ratio.
Hopefully, future investigations build upon these findings and uncover the best method of 'training low' for boosting exercise performance.
The Different Ways to Train Low
Now we have highlighted the merits of performing specific training sessions under conditions of low carb availability, some of you may be wondering how best this could be done. It is accepted that there are numerous ways to do it, each of which we will describe below.
Low Carbohydrate Diet
There are many types of low carbohydrate diets, but they all ultimately restrict carbohydrates and see an increase in fat and more often than not, protein. Despite much attention, a chronically low carbohydrate diet is not recommended for athletes who are required to train and perform at high intensities.
This is for numerous reasons. Firstly, a chronically high fat intake reduces the body's ability to use carbohydrates for fuel. This means that although glycogen may be spared on this diet, it cannot effectively be used.
Furthermore, fat is a less efficient fuel source than glucose/glycogen. This means that athletes on a low carbohydrate (and thus a high fat) diet uses more oxygen for a given intensity. Naturally, this decreases exercise economy, which is a key determinant of performance during endurance exercise.
Twice Per Day Training
This is the method that has been used mostly in this area of research. Although most studies have failed to see an increase in performance, this is because the second session of the day has been an interval-type session that has demanded high-intensity efforts. As we know, this has performance repercussions when completed with sub-optimal carbohydrate stores.
As an alternative, it is proposed that those wishing to embark on this method perform a high-intensity session in the morning under optimal carbohydrate availability, and then a lower intensity session later in the day following carbohydrate restriction.
Long Training Sessions Without Carbs
Current sports nutrition guidelines recommend consuming carbohydrates at a rate of 30-60g per hour during sessions that exceed 90 minutes. Up to 90g per hour is often recommended for training sessions that exceed 3 hours.
By restricting carbohydrate intake, muscle and liver glycogen stores will become depleted, which will increase the stimulus for training adaptations. However, this will also increase perceived exertion, as the athlete will have to dig deeper to maintain training intensity.
As discussed, this is a relatively new approach to training low and one that appears to have merit. Sleeping low is characterised by an evening exercise session designed to lower glycogen stores. The following morning and without the ingestion of carbs, a low-intensity session is performed. Due to the nature of the training sessions and the lack of carbohydrates, this seems to exaggerate training adaptations.
This is the least complicated method of training low, and athletes often consume black coffee before training. Interestingly, it seems that consuming a breakfast containing some protein and fat does not negate the benefits.
No Carbs During Recovery
Traditionally, it is recommended to consume a rich carbohydrate source at least once within two hours of exercise. This is because the body is primed to replace glycogen stores within this timeframe. However, it is thought that prolonging the time in a low carbohydrate state can accentuate the adaptations to training, whilst the trade-off being a slower recovery time.
The Downsides to Training Low
As well as understanding that not all studies have seen a performance improvement, it is important to mention that there are certain downsides to training low. As mentioned previously, carbohydrate is the primary fuel source for exercise. So, it should come as no surprise then that performance at high intensities is impaired.
Even when low-intensity sessions are performed, it is well accepted that the athletes perceive themselves as working significantly harder to maintain the required intensity and achieve the training volume.
Furthermore, it is well-known that high training volumes can impair immune function. As carbohydrates act as fuel for immune cells, providing the body with adequate carbohydrates can help keep illnesses at bay.
Although the only research study in this area has shown that training low does not lead to more illnesses than normal training, athletes who often suffer from illnesses may be wise to limit the amount of training low they complete.
Finally, regularly training without taking on carbohydrates can affect the ability of the gut to absorb and utilise this fuel source seamlessly. Research has shown that the gut can be 'trained', as it can become accustomed to taking on large boluses of carbohydrates whilst exercising at high intensities. Having the ability to fuel correctly during endurance events without suffering from stomach upsets is a crucial aspect of performance.
For the above reasons, it cannot be stressed enough that training low is not something that should be done too regularly. Instead, it should be incorporated into the mesocycle is a phase where optimal performance and fast recovery are not paramount.
Strategies to Negate Dips in Training Performance
Certain nutrition strategies can be employed to help maintain training intensity whilst training low. The first of these is caffeine, which is one of the most researched supplements in sports nutrition.
The research is almost unanimous in favour of caffeine's ability to improve endurance exercise performance. Aim for a dose of 3mg per kg of body weight. For most athletes, taking ~200mg 30-60 minutes before exercise will suffice.
Secondly, carbohydrate beverages do not even need to be consumed to elicit a performance benefit. Research has consistently shown that swilling a carbohydrate solution in the mouth for 5-10 seconds and then spitting it out increases performance as it positively influences the reward centre in the brain. A 2-3% performance benefit is often noted in the literature.
Interestingly, there is a scientific study to validate the use of these strategies, as trained cyclists were able to perform much better, using caffeine and carbohydrate mouth-rinsing whilst training low.
The role of carbohydrates in exercise performance is a topic that is still fascinating to exercise physiologists over 100 years since it was first investigated. Despite training, low being a relatively new topic in the field, and further investigations are of course warranted, there are some conclusions we can confidently come to:
Training under conditions of low carbohydrate availability increases exercise adaptations and, when performed correctly, can translate into improvements in exercise performance. Competitions should always be performed with optimal carbohydrate stores.
For best results, it seems 'fuelling for the work required' is the approach to adhere to. This ensures that the athlete can perform optimally during high-intensity sessions and then promote adaptations in low-intensity sessions when high carbohydrate availability is not paramount.
It is accepted that there are numerous different ways to train low, and each has similarities, differences, strengths, and weaknesses.
Training low should be used sparingly as a tool to induce adaptations when performance and recovery is not the main focus. This is because, among other limitations, it can worsen performance and delay recovery. Caffeine supplementation and carbohydrate mouth-rinsing can be utilised to negate performance decrements partially.
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About the Author
Matt Durkin MSc is a principal nutritionist at Simply Supplements. With extensive sports nutrition experience, Matt advises on new product formulations and provides tailored nutrition to clients.