FItness and nutrition, Sports psychology

The physiological benefits of ingesting carbohydrate during prolonged exercise are well documented. But little is known about its effect on mood, which can be an equally important determinant of performance.

Now a group of UK researchers have carried out a groundbreaking study showing that carbohydrate enhances feelings of pleasure both during and after prolonged cycling.

Nine endurance-trained men cycled on ergometers for two hours at 70% VO2max on two occasions, one week apart. On one occasion, they consumed a 6.4% carbohydrate-electrolyte solution immediately before cycling and every 15 minutes during cycling. On the other occasion they followed exactly the same procedure with an identical-tasting water drink (placebo).

The cyclists’ feelings of pleasure/displeasure were rated on a special scale – the Feeling Scale – before cycling bouts, every 15 minutes during cycling, immediately after finishing and 5, 15 and 30 minutes afterwards.
Additionally, the RPE (rating of perceived exertion) scale, which measures how easy or hard the exercise feels, was administered every 15 minutes during the trial.

Overall, the cyclists’ ratings of pleasure were higher during the carbohydrate trial than during the placebo trial. Furthermore, pleasure ratings became more positive and were maintained throughout exercise in the carbohydrate trial, whereas they became less positive in the placebo trial.

Feelings of pleasure were significantly higher 15 minutes after exercise than before exercise in the carbohydrate trial, whereas in the placebo trial they were lower.

Interestingly, perceived exertion increased over time in both trials and was significantly lower in the carbohydrate trial only at 75 minutes into the cycling bout. This suggests that perceived exertion (what you feel) is not closely related to how you feel.

'Whether one feels good or bad during exercise is clearly an important factor,’ comment the researchers. Indeed, it could determine the outcome of a competitive event and also impact on task persistence.

‘It appears that nutritional intervention during prolonged exercise may be a key determinant of the exercise experience and should be considered in future studies.’

Med Sci Sports Exerc, vol 37, no 10, pp1768-1773