We all know that thinking about exercise isn't the same as doing it. But researchers from the University of New Hampshire have confirmed what may be the next best thing: just thinking about a past exercise experience can motivate us to actually do it.

Working on the premise that 'memories of past experiences guide current and future behaviours', psychologists Mathew J. Biondolillo and David B. Pillemer asked over 200 students to complete a questionnaire, ostensibly about college activity choices. Those not in the control group were asked to recall either a positive or a negative memory that they felt could motivate them to exercise. Both groups were then asked to report how much exercise they did over the following days.

As predicted, students who were asked to recall a positive memory about exercise reported 'significantly higher levels of subsequent exercise activity than students in the control group', even when controlling for other factors. Students who were asked to recall a negative memory also reported an increase in exercise, but to a lesser extent.

Students who recalled positive memories 'may have prompted positive feelings' related to exercise about themselves, which in turn increased both their intentions to exercise and subsequent exercise. But why should recalling negative memories also have a modest, but still positive, effect? Biondolillo and Pillemer explain that 'these memories may have activated general self-related feelings about the need to improve in the domain of exercise,' motivating the students in a different way.

Summing up their findings in the current issue of Memory, the pair writes: "These results provide the first experimental evidence that autobiographical memory activation can be an effective tool in motivating individuals to adopt healthier lifestyles."

Though limited in scope, this discovery has great potential, as it 'underscores the power of memory's directive influence in a new domain with practical applications: exercise behaviours.'

If remembering just one episode of exercise - especially a positive one - has a noticeable effect on reported rates of exercise, imagine the effects of 'exercise programmes that explicitly encourage or train participants to regularly activate emotional memories as a motivational tool'; more intensive interventions 'could result in greater and longer lasting increases in exercise activities', the authors write.

With more than one third of adults worldwide now overweight according to the WHO, Biondolillo and Pillemer's research is both fascinating and timely.

We certainly can't think ourselves thin, but we may be able to think ourselves to the gym.