A new review study shows that taking carbohydrates during shorter races is useless.
We have all been told that taking carbohydrates during an endurance race will boost our performance. Numerous scientific studies have indeed shown this effect but unfortunately the set-up of the experiments did not always correspond to what most of us do.
Many researchers asked elite athletes to exercise at a fixed intensity for as long as possible. They then compared how long it took the athletes to get exhausted with and without taking carbohydrates. These tests are called time-to-exhaustion tests. The problem is that they do not mimic a real event; in real life you typically try to cover a fixed distance as quickly as possible. A time trial would therefore be a better test.
Moreover, the athletes usually performed their test after an overnight fast. Scientifically this makes sense, because it is easier to compare two fasted individuals than two fed ones, as not everybody digests and absorbs food in exactly the same way. However, this is not a realistic situation as nobody would race without a pre-race meal.
In the last issue of Nutrition Journal Paolo Colombani and his colleagues reviewed studies that have tried to mimic real-time events by studying recreational athletes (as most of us are) performing time trials 4 to 2 hours after a meal. They concluded that taking carbohydrates does not lead to significant improvements during races shorter than 70 minutes. For longer races, the picture is a bit more complicated, as 10 of the 17 studies showed improvements up to 13%.
You can therefore gain some time by not having carbohydrates during shorter races (I always have to slow down when I am having a drink or a gel). Concerning the longer ones however, you will have to experiment to find out what is best for you.