Carbohydrates during high-intensity exercise

Is the intake of additional carbohydrates only recommended for long stamina competitions or should you resort to nutritional supplements even at shorter sporting events?

It has long been known that carbohydrate intake is beneficial for prolonged endurance competitions (over 2 hours). Recently, there is increasing evidence that carbohydrate intake can improve performance even at much shorter sports events of around 1 hour. This is probably due to an increase in the activity of the central nervous system. Scientists from Birmingham (England) now investigated whether these advantages can be transferred to even shorter competitions.

The study

Researchers examined the effect of carbohydrate intake during high-intensity exercise over a 25-minute period. The subjects were 12 endurance cyclists who simulated a 16-kilometer time trial in the lab on 3 separate days.

In one test, the cyclists were given a carbohydrate drink with a 6% KH electrolyte solution (a similar composition to many commercially available sports drinks). In the other two tests, they received an identical tasting placebo drink with electrolytes but no carbohydrates.

Both the carbohydrate drink and the two placebo drinks were consumed 5 minutes before each start (4 mls per kg of body weight). In addition, these drinks were administered when the athletes had passed 25, 50 and 75% of the time trial (each 1.4 mls per kg of body weight). The researchers then compared the times and power outputs of the different test arrangements.

The results

The recorded times among the 16-km time trialists were surprisingly similar - 25 min. 30 sec. And 25 min. 27 sec. For the two placebo tests versus 25 min. 38 sec. For the carbohydrate test. Also, the power output was almost the same for all 3 tests, namely 300, 301 and 299 watts. The same applies to the pacing strategies and the heart rate.


The researchers concluded that consuming carbohydrates at short intense loads of about 30 minutes at an intensity of 85-90% of VO2max causes no improvement in performance. In order to be able to say more precisely where the limit lies, ie from which point a carbohydrate intake brings advantages, further investigations are necessary. The results of the present study (and previous studies) suggest that this point is between 30 and 60 minutes.

Also read: Carbohydrate Protein Drinks

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