49. HOW MANY CARBS DURING EXERCISE? MORE IS NOT (ALWAYS) BETTER

Photo by Oleg Kukharuk on Unsplash

In a previous KisW Research Note, we saw that ingesting 120 vs 90 g/h of carbs during exercise with a 0.8:1 glucose:fructose ratio do not make spare any additional endogenous carbs (glycogen) during a 3 hours ride in high zone 2 (~250 W for the amateur cyclists in that study). So, it is very likely that even performance will be not enhanced by 120 g/h vs 90 g/h in a similar scenario. However, it is always better to have a look at the data.

Does ingesting more than 90 g/h of carbs increase performance at the end of a long ride?

A study published by King and Colleagues from Leeds Beckett University (UK) on Physiological Reports in 2018 tried to answer this question. (1)

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WHAT DID THEY DO?

• They recruited ten trained males amateur cyclists.

• In a randomized order, on 5 different days and conditions, they rode for 2h at 77% VO2max (read high zone 2 or low zone 3 in a 5/7 zones model), followed by a 30‐min time‐trial (TT).

  The 5 conditions differed for the amounts and types of carbs ingested during the 2hrs ride:

  1. 0 g/h

  2. 60 g/h only glucose

  3. 75 g/h only glucose

  4. 90 g/h glucose+fructose (2:1 ratio, so 60g glucose and 30g fructose)

  5. 112.5 g/h glucose+fructose (2:1 ratio, so 75g glucose and 37.5g fructose)

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WHAT DID THEY FIND?