The Effect of Placebo-Induced Changes in Expectancies on Maximal Force Production in College Students

Abstract

This study used false information about a placebo (milk-sugar tablet) to induce expectancies regarding force production. Forty-two college students were assigned to a placebo/placebo (PP), placebo/no-placebo (PN), or control group, and underwent baseline testing and two trials assessing one-repetition maximum (1 RM) strength on a bench press and seated leg press. The PP and PN groups improved significantly compared to the control at Trial 1 for the bench press (p ≤ .01) and leg press (p ≤ .01). Disclosure of the true nature of the placebo resulted in force production declines in the PN group to levels approximating controls on the bench press (p > .05) and seated leg press (p > .05). The results suggest that placebo-associated expectancy effects played a significant part in the observed changes. Implications include information for coaches, teachers, and fitness enthusiasts about the importance of psychological factors in successful performance.

John Fitzpatrick is now with the Department of Sport Science and Physical Education, Idaho State University.

Notes

^a n = 14 for each group.