Are Carbohydrates Maximising your Athletic Potential?
Now that we have touched on some of the effects of carbohydrate on general health, let’s progress into carbohydrate as a primary fuel source in athletic events. In this article we will have a look at the literature and discuss how you can optimise your performance through the fourth discipline of triathlon, aka “fuel and nutrition”.
Limited Storage Capacity
The leading limitation of carbohydrate (CHO) as a fuel is it’s storage capacity (500-600 grams) and the need for continually refueling to maintain these stores. The rate of CHO absorption can be minimally manipulated and may depend on your CHO sources used. Interestingly the maximal CHO absorption capacity that has been achieved is 1.8g of CHO / min (4,6). But CHO storage (500-600g) is dwarfed by fat storage (5+) kg even in a very lean individual). This is a phenomenal difference, this benefit alone should be enough to spike any endurance athletes attention. I say endurance athlete because any sport under 1-1.5 hr can store enough CHO to supply energy for their chosen activity, and in this case using fat as a fuel may not be the best strategy. But it is endurance athletes who regularly exceed this time threshold and who can really benefit from utilising fat as a fuel. However, this is only one benefit and there is a growing body of scientific evidence suggesting a wide range of other benefits that I will discuss and will benefit majority of athletes regardless of the sporting event.
Source of Carbohydrate: Is it important?
Many athletes fail to recognise or understand the difference between different types of CHO. CHO can be divided into two main divisions, the rapidly oxidized CHO (up to ~60 g/hr or 1 g/min; include: glucose, maltose, sucrose, maltodextrin and amylopectin starch) and slower oxidized CHO (up to ~30 g/hr or 0.5 g/min; include: fructose, galactose, isomaltulose, trehalose and amylose). The reason for different oxidation rates is due to the different CHO sources using different CHO transporters in the gut and increasing the amount going from the gut to the blood. Therefore, ingestion of multiple transportable (glucose + fructose) CHO vs. single transportable CHO enhances exogenous (external from body eg food, supplements etc) CHO oxidation and increases performance (9)
Gels & Long distance Triathlon
To the best of my knowledge Zügel, (2016) (15), is the only study that has specifically looked at the administration of gels in long distance triathlon. A number of studies have looked at other shorter disciplines comparing gels to a liquid source of CHO with varied results. (1,2,12) Long distance triathlon possess several unique conditions compared to these sports such as, the inability to consume fuel while in the swim and possibly the change in body position across the three disciplines over the day that may impair gastric emptying (nutrition moving from the stomach into the intestine to be absorbed) and increase GI distress(11). In a study of long distance triathletes (15) the results suggested that gels compared to liquid CHO caused no difference in performance. But the study did show that people that consumed gels had an increase GI distress.
As a CHO based athlete the need for continuous refueling is essential part of training and racing. But what we see is that sometimes these high and regular fuel intakes are closely related to Gastrointestinal (GI) distress. The ability to tap into endogenous fuel (produced internally in body) sources over exogenous fuel (external from body eg food, supplements etc) would be extremely advantageous in minimising/preventing GI distress.
When consuming exogenous CHO, multiple transporters have been shown to not only increases CHO absorption but also aid in reducing GI complaints. Therefore, it is advantageous to consume CHO from multiple transporters, from a performance standpoint along with minimising GI distress. O’Brien, & Rowlands (2011) (8) concluded that a 0.8 ratio (0.8 fructose + 1.0 maltodextrin) presented the least amount of GI distress. If you are someone who is particular sensitive, this is an important consideration when selecting you personal fueling strategy.
Higher absorption of CHO is associated with less residual CHO in the intestine and it could prevent GI distress, an obvious potential strategy would be to increase absorptive capacity of the gut through training the gut to tolerate higher levels of CHO (15). However, more research is required.
Carbohydrate Mouth Rinsing
In recent years there has been emerging research around the ergogenic (performance enhancing) action via the central nervous system. It has been demonstrated that CHO mouth rinsing presents performance enhancing benefits in events 60 min or less. There is limited research in endurance based events (60 min+). But this could offer athletes the ability to bypass or reduce GI distress associated with CHO refueling, making it especially useful in the run segment of triathlon due to increase in GI distress seen with high impact and jaring activity. However, as an emerging area of research more depth is required to identify the exact mechanisms at play and to provide guidance on best practice for a strategy like this.
When it comes to optimising you your fourth discipline “Nutrition”, you need to look at what your current training load, the duration of the event you are training for and what is the best practice nutrition that will allow you to achieve your goals. For longer events (training 12 + hours a week and events greater than 2 hours in duration) the best possible nutritional approach would be to seek and attain metabolic flexibility.
So what is Metabolic flexibility:
When I say metabolic flexibility I am referring to your ability to adapt your fuel utilisation to meet the energy demands of the exercise stress which you are putting yourself through. For long distance events, low-moderate exercise intensity your body will be most efficient when utilizing fat as a fuel. You want to be an efficient fat burning machine, this will allow you spare your limited muscle glycogen stores so that when you need to use them for that all out maximal sprint finish, your body can adapt and change fuel sources from fat to CHO to meet energy demands.
By not aiming to achieve metabolic flexibility you are limiting your performance potential by not maximising your ability to utilise alternative fuel sources. I would even go as far to argue metabolic flexibility is one of the most performance enhancing strategies you can train to promote overall health, weight maintenance, longevity and sporting performance.
As a metabolically flexible athlete having the ability to shift from CHO to Fat as a primary fuel source (almost exclusively, very minimal CHO) when they are resting, sleeping and moving slowly is highly beneficial. One of the most beneficial components is that you are reserving your limited CHO to be utilised in higher intensity activities like sprinting. Therefore a metabolically flexible athlete or fat adapted athlete has the ability to maximise their substrate utilization and ensure optimal efficiency for endurance events. It is like fueling your body with diesel (fat) & high octane fuel (CHO), giving you the efficiency and endurance of the diesel coupled with the ability to tap into your high octane fuel when you need surge or increase intensity. Compared to fueling with one or the other on its own, this approach would seemingly limit your capacity to shift between the two when required.
To achieve this you need to look beyond the limited CHO and train your body to utilise other limitless fuel sources like fat alongside CHO to truly maximise your potential. In our next post we will compare the metabolically flexible fat adapted athlete vs the traditional high CHO based athlete.
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