Researchers from Case Western Reserve University in the US analysed new gym member for six weeks.
They promised participants one of three modest rewards: a USD 30 Amazon gift card, a prize item, such as a blender, of equivalent value or a USD 60 Amazon gift card, for visiting the gym nine total times during the study (an average of 1.5 times per week).
The team noted that after the first week, 14 per cent did not visit the gym again. Participants given incentives showed a slight increase in gym visits in the sixth week - their last chance to make enough visits to earn their prize.
However, those given incentives made only 0.14 more visits per week than those promised no reward at all.
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"They wanted to exercise regularly, and yet their behaviour did not match their intent, even with a reward," said Mariana Carrera, an assistant professor at Case Western Reserve University.
Researchers noted that the group promised the USD 60 gift card also did not visit the gym more often than those given the USD 30 gift card or prize.
The rewards also had no lasting effect: gym visits stabilised after the modest incentives ended, they said.
Researchers also found that despite timing incentives to when people were already more motivated to exercise, the approach proved ineffective in initiating a healthy behaviour: only 21 per cent get a recommended amount of weekly exercise, according to the Centers for Disease Control in the US.
"Maybe the internal motivation that gets a person to start a gym membership is unrelated to what drives them to earn financial incentives. What is clear was there was no complementarity in lumping these two motivations together," she said.