Wednesday 27 March 2013

Sugary mouthwash might make you faster

It is no secret that the key to success in endurance sports, from a nutritional standpoint, is carbs.  I have blogged about them in the past, and it is clear that you can really make or break your race with how many carbs you have taken in.

Now, a new line if research is showing it is not only important to ingest enough carbs, but that it can also be beneficial to trick your brain into THINKING carbs are being ingested.  

How do we do this?  We rinse with a sugary solution. 

Quick background

For any short duration activity (like a golf swing, or quick sprints), carbohydrates are not the primary source of fuel.  However, once you get to an activity duration of around 5 minutes at a decent intensity, you start to tap into glycogen- the chains of sugar stored in your muscles.

So whether you are running a few miles or running a marathon, glycogen is important.  We can top these glycogen stores up by making sure we consume sufficient amounts of carbohydrates in the days leading up an event- there is no mystery here.  

Unfortunately, these glycogen stores are not always enough.  Scientists have consistently shown that if the activity is long enough, that glycogen source will become depleted and performance will plummet   

So what do we do?  Eat carbs during an event.  

Interestingly, it is not the size of the person that dictates how much to consume.  Instead, we are limited by how quickly carbs can be absorbed in the intestines.  So whether you are 5'2 or 6'2, this number (for glucose) is about 1g per minute.  So really, the max glucose you are going to be able to take in during an event is 60g/hour (there are ways to ingest more, but that is for another day).  

However, for shorter events, 60g/hour is excessive, especially for events under an hour in duration.  If your body is constantly fed carbs in close proximity to the start of an event, insulin will spike.  This will result in a decreased ability to access the glycogen and fat already stored in your body, and once again, performance will suffer.

That does not mean there is nothing you can to do enhance your performance with carbs during events under an hour.  The answer: a sugary mouth wash.


This 2010 summary article does a great job of breaking down a new(er) line of carb research: the benefits of rinsing your mouth with sugar and spitting it out.

The basic idea is this: your brain controls your performance partially in anticipation of what is GOING to happen to the body.  For instance, studies like this one show that when the temperature goes up, we slow down BEFORE our body temperature goes up - in other words, our mind FIRST slows us down to try to prevent overheating, not in response to it.

The same concept applies to the sugary mouth wash.  The thought is that when sugar is sensed in the mouth, the reward system in the brain is activated; the brain thinks food is coming, and as a result our body gets the green light to hammer away.  We are able to go faster not because we are actually fed, but because we are anticipating we WILL be fed.  

And whether we fully understand the mechanism or not, the fact is, a sugary mouthwash seems to work.  Check out these results  from the study.  The first one shows a 2.9% improvement in a cycling time trial.  The third study shows a 1.7% increase in distance traveled during a 30 minute get the idea.  These results are pretty impressive because there is no actual impact on the body's physical ability to perform; just the mind is giving the body a message to push harder.

Some practical notes

The most important note about this line of research is that this strategy only works for activities at a particular duration.  The range for this is usually quoted to be for activities that are about 30-75 minutes in duration.  Once you get over this 75 minute mark (or even for events over 1 hour), carbs definitely need to be ingested to maximize performance.  Once your glycogen is low, you can rinse all you want with sugar, but without fuel you will be unable to continue!

So, if you are trying to break that 50 minute mark for the 10K for the first time, it may be a good idea to try this mouth-rinsing strategy.  The science suggests you will get the energy boost of carbs without actually having to swallow them and risk getting an upset stomach!  However, when running that half or full marathon, you're better off to actually swallow 30-60g of carbs/hour.