Toolbox: Rinse and Repeat?
Carbohydrates are known to be an important fuel for peak cycling performance. It’s the preferred fuel for the high-intensity efforts, and its availability is often seen as a limiter for performance. Carbohydrate drinks are therefore often used to deliver both fluids and energy during cycling, but can carbohydrates serve as a special ergogenic aid by tricking you into riding harder?
If you’ve been following my Toolbox articles for the past few years, you will know that many of them revolve around pacing strategy or else ergogenic aids in some form or another. I have a special interest in writing about these issues, as they relate very closely to my current research emphases on these topics. The other reason for writing about them, of course, is because they form some of the hottest current topics in exercise science and sports performance itself.
Pacing itself is so interesting because you can look at it as how you play the genetic and fitness cards that you’ve been dealt. How do you lay out the watts that you’ve trained yourself to produce? Do you go at a steady pace or power output throughout a time trial? What if there’s a headwind and tailwind? Does your strategy change? And how do you go about learning a pacing strategy? At the heart of such questions is really the over-riding big question of “how do you control or regulate your exercise intensity?”
The Sports Drink Industry
Certainly an easy case can be made for interest in ergogenic aids. Whether it’s a (legal) drug like caffeine, or more complex manipulations like hypoxic training or pre-cooling strategies, the opportunity to maximize what we have achieved through hard training is of course very tempting. While the coaching industry exists to “sell” us better fitness, there is a much bigger industry out there to sell us on the advantages of their particular system in improving our performance. Therefore, my aim has always been on providing objective, evidence-based information so that you can make informed decisions rather than relying on marketing hype.
One major component of the ergogenic aid spectrum is sports nutrition, and especially the sports drink industry. To say that companies like Gatorade and Powerade are big business is an exercise in epic understatement. Every day it seems there is a new drink on the marketplace and grocery store shelves too.
While sports drinks vary in their ingredients (protein, electrolytes, etc.), one general constant is not just the presence of carbohydrates, but their concentration in roughly similar concentrations of 6-8%. That’s because decades of science have demonstrated that this provides the optimal rate of carbohydrate absorption into your body. Research has also led to the general consensus that the target rate of carbohydrate consumption should be in the 30-60 grams per hour range. The goal is to spare muscle glycogen and avoid bonking from depleting this high-energy fuel.
When Do You Need a Sports Drink?
The other main message that you’ve likely heard is the general rule of thumb that you only really require sports drinks if your training ride or your race event exceeds about 90 min. Before then, it is generally believed that you can ride on water alone or even without water, as there is not enough time for the carbohydrates to get through your stomach, be absorbed through your small intestines, and make it to your muscles in meaningful amounts. It’s also believed that you cannot deplete your muscle glycogen stores to bonk-inducing levels unless exercise proceed much beyond 90 minutes.
In the past 5-7 years however, evidence began emerging that even short-term high intensity exercise may benefit from carbohydrate consumption. Carter et al. (2004) and Rollo et al. (2010) have investigated the role of carbohydrates on enhancing short-term, high-intensity performance, and have both suggested that, beyond any effects as a fuel for your muscles, carbohydrates (CHO) seems to have a direct effect on how hard we can voluntarily exercise.
Double the Data
As the two studies are very similar, I’ll try to present the data from both in the same article:
• Carter studied trained cyclists performing an ~1 h (completed 914 kJ as quickly as possible) time trial in the lab, while Rollo studied trained runners performing a 1 h treadmill run.
• Both studies used the interesting design of having subjects periodically rinse their mouth with ~25 mL of a CHO solution. The subjects essentially rinsed a bit of sports drink around their mouth similar to what we might do with mouthwash, then spat the solution out.
• Each study featured a placebo trial where subjects rinsed with a non-CHO solution matched for taste and colour (Rollo) or water (Carter).
• Mouth rinse occurred at periodic intervals over the course of both studies, at the completion of each 12.5% of the effort (Carter) or every 15 min (Rollo).
What the mouth rinse protocol was designed to do was to remove the metabolic benefits of the CHO, as the solution was spat out rather than swallowed. There might be some absorption of the CHO through the mouth, but it would be hard to argue that there would be more than a very tiny amount getting into the blood and muscles. Rollo also took blood samples to test for blood glucose and insulin values.
Another nice addition to Rollo’s study was that, in addition to the trained runners, he also had a group of 10 healthy and active males perform the CHO/placebo mouth rinse conditions over the course of 1h of rest. This helps to give more insight about whether the CHO rinse had any effect on the blood and potentially the muscles.
So now we have two very similar studies. Do they provide similar results?
• Carter found that time required to complete the set amount of work was significantly less with the CHO due to a higher power output (59.57 min, 259 W) than with water rinse (61.37 min, 252 W).
• No differences were found in heart rate or perceived exertion with Carter. This suggests that just the simple presence of CHO in the mouth somehow “tricked” the subjects into riding at a higher power output, and made that harder effort feel relatively the same as when they went at a slower power output with the water rinse.
Rollo closed some important loopholes from Carter’s study. First, they had a true control group of people who rested rather than exercised. This, coupled with their measuring blood glucose and insulin, enabled them to decisively test the metabolic effects of CHO rinse on CHO availability to the body. Further, rather than water, Rollo had a better control solution that looked and tasted the same as the CHO rinse, removing any placebo effects.
• Just like Carter, Rollo found that the runners went significantly further with the CHO rinse (14.298 km) compared to placebo (14.086 km). 8/10 runners improved their run distances, with one increasing by 600 and another by 800 m. Interestingly, these two subjects did not habitually use sports drinks during training or competitions. This sets up the question of whether they were less sensitized to CHO, and therefore it had a bigger effect on them. This is analogous of caffeine sensitization, where larger doses are needed with habitual users than people who rarely ingest caffeine. With the two runners who went less distance with CHO, one was less by 50 m and the other by 200 m.
• No changes were found in the blood glucose concentrations, with the running group having values well within normal values (~4.3 mmol/L) both before and after the runs. The same lack of difference was seen in the resting group in both glucose and insulin values.
Overall, the combined studies suggest that CHO has an ergogenic benefit beyond any mechanisms involving its role as a metabolic fuel. What these are remain unclear. One intriguing suggestion is that there might be direct glucose receptors within the mouth that feed directly to the brain. These sensors may tell the brain that there is a large pool of CHO within the body (whether that’s actually true or not), in that sense tricking the brain into thinking that it’s better armed for battle and able to permit the body to ride harder as a result.
In conclusion, it may well be worth experimenting with a small packet or bottle of sports drink even during a hard time trial of about an hour, even if it’s simply to rinse the mouth. Nothing beats experimenting on yourself, and there’s no better guinea pig than yourself. So try it out in training to see if it works for you, and let me know how you respond.
Have fun and ride safe!
Carter, J.M., A.E. Jeukendrup, and D.A. Jones. 2004. The effect of carbohydrate mouth rinse on 1-h cycle time trial performance. Medicine and Science in Sports and Exercise 36: 2107-11.
Rollo, I., M. Cole, R. Miller, and C. Williams. 2010. The influence of mouth-rinsing a carbohydrate solution on 1-hour running performance. Medicine and Science in Sports and Exercise 42: 798-804.
Stephen Cheung is a Canada Research Chair at Brock University, and has published over 50 scientific articles and book chapters dealing with the effects of thermal and hypoxic stress on human physiology and performance. He has just published the book Advanced Environmental Exercise Physiology dealing with environments ranging from heat and cold through to hydration, altitude training, air pollution, and chronobiology. Stephen’s currently writing “Cutting Edge Cycling,” a book on the science of cycling, and can be reached for comments at [email protected] .