Relevance: Despite the evidence supporting
the health benefits of physical activity, studies show that there is low
adherence level to exercise schemes (Dishman 1988). Activities that lead to
the individual feeling ‘good’ are more likely to facilitate future
participation (Parfitt et al., 2006). However, whether sedentary and active
individuals perceive exercise as rewarding as other established rewards is
not well investigated.
Purpose: This study aims to investigate the
reward value of exercise using a discounting paradigm and to compare the
discounting parameters of exercise with established rewards of food and money
(Rasmussen et al., 2010). Moreover, the exercise discounting decay rates (k),
as well as those of food and money, are compared between sedentary and active
people. Discounting parameters will be analysed in association with body
characteristics to find influencing factors of reward perception of exercise
as well as for food and money.
Methods/analysis: A cross sectional study
was performed for 21 healthy subjects (nine females and 12 males), with a
mean age of 31.26 (SD = ± 12.70). They
underwent three exercise trials on a treadmill to determine their optimal
self-selected exercise settings, then answered the delay discounting task for
exercise, money and food on a PC. A battery of psychological and health
questionnaires were also used to characterize individuals for data analysis,
correlation coefficient analysis and one-way ANOVA in SPSS were used.
Results: The results show that exercise is
discounted in a hyperbolic manner like established rewards, food and money.
The goodness of fit of the indifference points using a hyperbolic function
(R2) for money, exercise and food were 0.884, 0.857 and 0.91 respectively.
Exercise discounting was not significantly different to those of money and
food. Moreover, exercise k values were not different to other commodities,
food and money. This indicates that exercise is discounted in similar fashion
like money and food which are known to be perceived as rewarding. Using
correlation analysis, body fat percentage and the mean k values for money and
food were positively correlated, r = 0.451, P = 0.026 and r = 0.426, P =
0.027. In contrast, body fat percentage and mean k values for exercise were
negatively correlated, r = −0.396, P = 0.039.
Discussion and conclusions: Exercise is
discounted like established rewards of money and food with k values similar
to the other tested modalities. Subjects with higher body fat percentages
revealed higher discounting rates for money and food; on the other hand, they
shown lower discounting rates for exercise. These results could be
interpreted as indication that exercise can be perceived as a reward if
adjusted for pleasantness and that body characteristics influence the kinetic
of exercise discounting.
Impact and implications: This conclusion
might be crucial for understanding the reasons after low exercise adherence
rates and for improving exercise participation.
Funding acknowledgement: The Saudi Ministry
of Health has funded this project and related future projects.