Coping with mental challenges is vital to everyday functioning. In accordance with prominent theories, the adaptive and flexible adjustment of the organism to daily demands is well expressed in task-related changes of cardiac vagal control. While many mental challenges are associated with increased effort and associated decreased task-related heart rate variability (HRV), some cognitive challenges go along with HRV increases. Especially creativity represents a cognitive process, which not only results from mental effort but also from spontaneous modes of thinking. Critically, creativity and HRV are associated with regular exercising and fitness. Furthermore, the cross-stressor adaptation theory suggests that changes in cardiac reactions to physical challenges may generalize to mental challenges. In line with this idea the amount of regular exercising was hypothesized to moderate the association between HRV changes and creativity. A sample of 97 participants was investigated. They reported the amount of regular exercise and their ECG was measured at baseline and during a creativity task. An association between task-related HRV changes and originality as a function of participants' amount of regular exercise was found. Participants reporting more regular exercising produced more original ideas when they had higher HRV increases during the task, while more sedentary participants showed the opposite association. Results suggest that individuals with a higher amount of regular exercise achieve higher originality probably via the engagement in more spontaneous modes of thinking, while more sedentary people may primarily benefit from increased mental effort. This supports the conclusion that higher creativity can be achieved by different strategies.