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Toolbox: Carbohydrate – Liquids, Gels, or Bars?
We know very well that it is important to fuel properly during a long or hard ride, especially with carbohydrate. Does it matter whether that carbohydrate comes in solid, gel, or liquid form?

Cycling: 10th Strade Bianche 2016 PUCCIO Salvatore (ITA)/  Siena - Siena (176km)/  Eroica/ (c) Tim De Waele

The Importance of Carbohydrates
An appropriate nutrition plan is essential in an endurance sport such as cycling, and this applies to both off-bike and on-bike fuelling. While fuel intake may not be necessary or essential for short-term exercise, the importance of maintaining adequate carbohydrate stores is hard to overstate. That is because you have only a very small (~1500 Kcal) supply of carbohydrates stored in the form of liver and muscle glycogen, compared to the essentially limitless supply of fat in even lean endurance athletes.

Besides the small amount available, metabolic use of glycogen for energy increases with higher intensity exercise, meeting to the dreaded bonk or “hitting the wall” when these stores become too low. Even at relatively low or moderate intensity cycling, carbohydrate stores are continually used to some extent.

Another important reason for maintaining carbohydrate stores is that the central nervous system (i.e., the brain) is only able to metabolize carbohydrates for energy. This helps to explain why bonking feels so terrible both physically and mentally/emotionally.

The current consensus for prolonged exercise suggests that carbohydrate intake should be at a rate of approximately 60 to 90 g per hour.

Nuits-Saint-Georges - France - wielrennen - cycling - cyclisme - radsport - illustration - sfeer - illustratie food banana Rigoberto URAN URAN (Columbia / Cannondale Drapac Professsional Cycling Team)  pictured during the 104th Tour de France 2017 - stage 7  from Troyes to Nuits-Saint-Georges, 213.50 km - foto  Miwa iijima/Cor Vos © 2017

What Form Carbohydrate?
Sports drinks have been around since the early 1970s. I well remember the very first bars coming out in the late 1980s, with the consistency of either melted or frozen, rockhard gruel depending on the weather. Fortunately, since then sports nutrition companies have developed wide ranges of products that generally taste a lot better. And about 15 to 20 years ago, sports gels came onto the market, somewhat of a mix between solid and liquid feeding.

These innovations made to a somewhat obvious but surprisingly little research question. Does carbohydrate intake as liquid, gel, solid, or a mix have any difference in performance or gastric sensation? For the large part, the studies that have tackled this question have tested only two forms (e.g. liquid versus solid), and there were issues with scientific controls such as differences in the amount of fluid that was consumed.

Sophia Antipolis - Frankrijk - wielrennen - cycling - radsport - cyclisme - Parijs - Nice - Paris - Nice - 7e etappe Brignoles > Sophia Antipolis: 215 km - sfeer illustratie Musette etenszakje ravitaillering bevoorrading - Rabobank - foto Cor Vos ©2011

Guillochon et al. 2017
The question I posed above was the research question in a study in the latest issue of the journal International Journal of Sport Nutrition & Exercise Metabolism by researchers at Massey University in New Zealand (Guillochon and Rowlands 2017). Here was the study design:

• 12 trained male competitive cyclists, 18-55 y, training >8h/week with VO2max = 67 mL/kg/min.

• Training and diet were standardized over the 4 week (1 experimental trial/week) study.

• Each test involved 140 min of indoor riding simulating a road race with varying power profiles. This was immediately followed by a performance test beginning at 50% of baseline max wattage, increasing by 1 W every three seconds until voluntary exhaustion.

• The four carbohydrate conditions were from the same company using a similar 2:1 maltodextrin: fructose ratio, and was ingested at a rate of 80.1 g per hour. Feeding occurred in equal doses at the start and every 20 minutes during the 1 40 minute simulated race, with no feeding occurring during the final performance test.

• The four carbohydrate conditions were: 1) liquid, 2) gel, 3) bar, and 4) mix (40% drink, 25% bar, 35% gel). During the 140 minute race simulation, fluid was provided at a standard rate of 235 mm every 20 minutes.

Cycling: BMC Racing Team 2016  Illustration Illustratie / Powerbar Ravitaillement Bevoorrading / ATAPUMA Darwin (COL)/  Equipe Ploeg /(c)Tim De Waele

Gut Instincts
Overall, the study was nicely designed to control for carbohydrate content and fluid intake. What were the key findings?

• In the final performance test, maximal power output was quite variable however the general condition at slightly higher values than the bar condition, while the drink in the mix conditions was similar and generally in between the gel and bar values.

• Subjective ratings of gastrointestinal comfort (stomach fullness, nausea, abdominal cramping) suggest that all conditions had impaired ratings as the 140 min race simulation progressed.

• In general, the trend was for bars to have higher/worse values for GI comfort compared to gels and drink, with the mix condition in the middle.

• Perceived exertion and muscle tiredness increased in all conditions over time. Again, in general, the bar condition scored higher/worse than the other conditions.

Eijsden - Nederland - wielrennen - cycling - radsport - cyclisme - Hel van het Mergelland  - sfeer illustratie - Steven Kruijswijk (Rabobank) - foto Wessel van Keuk/Cor Vos ©2010

Loading the Musette
I found this study quite interesting because the vast majority of existing carbohydrate research on athletes have been done using carbohydrate drinks, with little known about the relative efficacy of other commonly used carbohydrate form such as gels and solid foods.

Of course, the relatively hard 140 min race simulation may cause greater stress on your overall GI system than easier endurance rides, and it is possible that bars and solid food may not cause the same issues and performance decrease in those situations.

I would've liked to see the data for individual cyclists, to see whether the trend of bars being the worst was consistent across the majority of participants, or whether a few participants skewed the values.

However, the summary finding from this study suggests that simpler forms of carbohydrates intake, in the form of drinks or gels, may cause less gastrointestinal distress and may even be preferred from a performance standpoint compared to solid foods.

Have fun and ride fast!

Foligno - Italy - wielrennen - cycling - radsport - cyclisme - Tom Dumoulin (Netherlands / Team Giant - Alpecin) and the "Pizza" girl pictured during stage 7 of the 99th Giro d'Italia 2016 from Sulmona - Foligno 211 km - foto LB/RB/Cor Vos © 2016

Guillochon M, Rowlands DS (2017) Solid, Gel, and Liquid Carbohydrate Format Effects on Gut Comfort and Performance. Int J Sport Nutr Exerc Metab 27:247–254. doi: 10.1123/ijsnem.2016-0211

About Stephen:
Stephen Cheung is a Canada Research Chair at Brock University, and has published over 90 scientific articles and book chapters dealing with the effects of thermal and hypoxic stress on human physiology and performance. Stephen’s new book “Cycling Science” with Dr. Mikel Zabala from the Movistar Pro Cycling Team has just hit the bookshelves this summer, following up Cutting-Edge Cycling written with Hunter Allen.

Stephen can be reached for comments at [email protected] .


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