In recent years, high-carbohydrate – and increasingly ultra high-carbohydrate – fueling strategies have surged in popularity across long-course triathlon, particularly in 70.3 and Ironman racing. Professional athletes routinely share fueling protocols on social media that exceed 90-120 grams of carbohydrate per hour, often positioning these intakes as a decisive performance advantage.
The proposed rationale is that higher carbohydrate availability should preserve glycogen stored in the liver and muscles, delay fatigue, and sustain higher outputs deeper into races. But does the scientific evidence support this? And, perhaps most importantly, should age-group athletes attempt to replicate these strategies in their own training and competition?
What the Research Says
Dr. Dan Plews was recently involved in a meta-analysis of 31 placebo-controlled studies examining the effects of carbohydrate intake on muscle glycogen sparing, and the findings are perhaps surprising. As he recently shared on Instagram, while the ingestion of carbohydrates does certainly confer a performance benefit (which is of particular importance in long-duration, metabolically constrained events such as the Ironman), the relationship between carbohydrate intake and glycogen sparing is not as straightforward as commonly assumed.
As he points out, there is no consistent relationship between carbohydrate type, dose, duration, or timing and the magnitude of muscle glycogen sparing. Crucially, more carbohydrate does not translate to greater muscle glycogen preservation. As Plews notes, “In the context of muscle glycogen depletion, there seems to be no added benefit beyond ~45-50 g/hour.”
View this post on Instagram
This meta-analysis is just one example among several that complicates the prevailing narrative around carbohydrate intake.
Could There Be A Benefit of High and Ultra-High Carb Strategies Anyway?
While the current evidence – both from this recent meta-analysis as well as the body of literature more broadly – is insufficient to explain or justify ever-increasing carbohydrate intake on the basis of glycogen sparing, importantly, the absence of evidence does not equate to evidence of no benefit.
For professional athletes whose livelihoods depend on every percentage of performance, many have experimented extensively in training and racing, effectively running repeated n=1 trials. When perceived benefits emerge consistently at the individual level, the question shifts from whether the strategy works to why it might be working – and whether potential benefit is confined to a small subset of elite athletes (who have superior physiological capacity and derive more value from marginal gains) or whether it could meaningfully extend to the age-group population.
Notably, Plews and colleagues do not dismiss the possibility of benefit. Rather, they highlight the need to explore alternative mechanisms beyond glycogen sparing that could plausibly explain observed performance effects at very high carbohydrate intakes.
Footnotes:
1. The meta-analysis referenced here did not directly investigate ultra-high carbohydrate intakes. Rather, it examined the relationship between carbohydrate ingestion and muscle glycogen sparing across a range of intake levels. Accordingly, this article draws on both findings of that analysis and the larger body of evidence related to high-carbohydrate fueling strategies.
2. There are studies demonstrating that very high carbohydrate intakes can be absorbed, particularly under controlled laboratory conditions that use optimized carbohydrate formulations and minimize external stressors. However, demonstrating the capacity for absorption is not the same as demonstrating a meaningful performance benefit in real-world competition (nor does absorption alone explain a potential mechanism of benefit).
The post Do Ultra-High Carbohydrate Intakes Really Enhance Triathlon Performance? appeared first on Triathlon Magazine Canada.