Metric · CarbMax

CarbMax. Carbohydrate sparing ability.

CarbMax describes the power output or speed at which an athlete combusts 90 grams of carbohydrates per hour.

Instead of analyzing a carbohydrate combustion graph, CarbMax provides a simple measure of carbohydrate sparing ability: the higher the power or speed at CarbMax, the more performance an athlete can produce while consuming the same amount of carbohydrate.

This makes it easy to compare athletes or track how an individual athlete’s carbohydrate sparing ability changes following training.

In short: CarbMax tells you how much performance an athlete gets from a given amount of carbohydrate.

Fat & carbohydrate combustion

fatFatMax zonecarbohydratemax. carb. intake
5210015020025030033803006009001200150001002003001673.04399.77kcal/hg/h90 g/hCarbMax 214 W
Intensity - power/speed

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CarbMax - best predictor of long-distance performance

Carbohydrate availability is a major constraint in long-duration endurance events. CarbMax therefore provides a particularly relevant performance marker for events such as long-distance triathlon, where athletes need to maximize power or speed while conserving a limited carbohydrate supply.

Scientific studies have shown that CarbMax is a better predictor for long endurance events, such as long distance triathlon, than other traditional markers such as thresholds and maximal lactate steady state.

If the goal is to understand or improve long-distance performance, CarbMax shows how much power or speed an athlete can produce for a defined carbohydrate cost.

anaerobic thresholdCarbMaxrace performancemean ± SD
Mean ± SD. CarbMax closely matched observed long-distance race intensity in this cohort, whereas the anaerobic threshold did not.
Recreated from Ohr & Lindschulten (2023), Sport Performance & Science Reports.

What determines CarbMax?

CarbMax is directly linked to the athlete’s fat and carbohydrate combustion rates. Greater fat utilization allows more energy to be produced from fat while sparing the athlete’s limited carbohydrate stores, shifting CarbMax toward a higher power output or speed.

But substrate utilization is only part of the equation. Economy also influences CarbMax. A better economy, for example better running economy, means that less metabolic energy is required to produce a given speed. The athlete can therefore move faster for the same carbohydrate demand.

CarbMax combines substrate utilization and economy into one practical performance metric: how much power or speed can the athlete produce while consuming 90 grams of carbohydrate per hour?

Fat & carbohydrate combustion

fatcarbohydratemax. carb. intakebaseline
1.522.02.53.03.54.04.3803006009001200150001002003001673.04399.77kcal/hg/h90 g/hCarbMax 3.14 m/s
Speed (m/s)
CarbMax3.14m/sbaselineCarbohydrate at 3.14 m/s90g/hbaseline
The 90 g/h line remains fixed while the athlete’s metabolic and economy profile changes: less carbohydrate combustion, or better economy, shifts CarbMax to a higher power or speed.
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