Girls as young as nine exercise to stay slim, while boys see sport as being just plain fun.
A study looking at the attitudes towards exercise of 74 girls and boys aged nine, conducted by Carol Burrows at Luton University, shows a significant gender divide.
While girls consider exercise to be a means to an end, citing fitness, slenderness and healthiness as their main motivations for exercising, boys rate the fun element of exercise, particularly sports, more highly than any other factor.
The gap between the sexes narrows when they explain their reasons for not exercising.
While five times as many girls as boys said they didn't exercise because it wasn't fun, there was general agreement that exercise caused tiredness and that staying in bed was preferable to jumping about.
Many more girls than boys claimed that, although they liked exercising, they didn't have enough time for it.
Enquiries to Carol Burrows, Faculty of Science, Technology and Design, Department of Sport and Exercise Science, University of Luton, Park Square, Luton, Bedforshire LU1 3JU (01582 489289)