SPORTtheir endurance (the controlled use of morphine during training is
legal). When it came to the day of the real event, the researchers replaced
the morphine with salt solution without telling the athletes. The result?
Compared with a control group, the athletes showed enhanced endur-
ance just as if they’d been given a real dose of morphine that day.
In another Benedetti study, published in 2008, weightlifters in training
were tricked into thinking they’d been given a high dose of caffeine
prior to each lift. The participants subsequently worked their muscles
harder than if they hadn’t had the placebo, although their feelings of
muscle fatigue were unchanged. Next, to make the placebo even more
convincing, the researchers surreptitiously reduced the weight being
lifted, so that it felt lighter than usual, thus creating the illusion that the
effect of the placebo had kicked in. Afterwards the weight was returned
to normal and the placebo re-administered. This time the participants
worked their muscles harder and reported less muscle fatigue than if the
placebo hadn’t been given.