Temporal Changes in Delay Discounting Before and After a Bout of Moderate－Intensity Aerobic Exercise－

Background: Exercise adherence often declines during the early adoption period.Decisions to continue exercise may reflect a trade-off between immediate costs, such as time constraints and fatigue, and delayed benefits, which can be indexed by monetary delay discounting.Although sustained exercise programs have been associated with lower discounting, shortterm temporal changes before and after moderate-intensity aerobic exercise remain unclear.Objective: This study examined temporal changes in monetary delay discounting before, immediately after, and one week after moderate-intensity aerobic exercise in young adults.Methods: Twenty-nine healthy young adults aged 18-29 years completed a single-group, within-subject, three-time-point protocol.Baseline delay discounting was assessed online using the Japanese version of the 27-item Monetary Choice Questionnaire (MCQ) .Seven days later, participants completed cycling exercise consisting of a 5-min warm-up, 20-min main exercise at moderate intensity (target 60% HRmax; RPE 11-13) , and 5-min cool-down.The MCQ was administered 5 min after exercise in the laboratory (Tx) .Seven days after Tx, the MCQ was re-administered online (Mx) .The primary outcome was the natural-log-transformed geometric mean discount rate (Ln Geomean k) ; secondary outcomes were k estimates for small, medium, and large reward magnitudes.Changes across baseline, Tx, and Mx were analyzed using repeated-measures ANOVA, with Friedman tests as a robustness check.Results: No statistically significant differences among time points were observed for the primary or magnitude-specific outcomes (ANOVA p = 0.274-0.863;partial η 2 = 0.004-0.045) .Friedman tests yielded consistent results (p = 0.279-0.881;Kendall's W = 0.004-0.044) .Conclusions: Under this single-group within-subject design, no clear short-term temporal changes in monetary delay discounting were observed before, immediately after, or one week after moderate-intensity aerobic exercise.Because no control condition was included, the findings should be interpreted as exploratory evidence, rather than causal evidence.