The objective of this study was to analyse sex stereotypes in Spanish high-school students. Three hundred boys and girls from 12 to 17 years old participated in this study by completing a 41-item survey about their preferences for different body types. The survey was applied using a set of visual triggers. Analysis of data showed that body stereotypes determined the way boys and girls perceived physical activities. These influences made boys manifest masculine stereotypes (cult of muscularity) and girls to follow traditional feminine stereotypes (cult of thinness). We conclude that teachers have to be alert for sports practices becoming a vehicle for reproducing stereotypes related to gender. (Contains 7 figures and 1 table.)