Virtual reality has emerged as a helpful tool in exercise facilitation and performance enhancement. As a highly immersive medium, it enables diversion of attention, embodiment of virtual avatars, and display of false performance feedback. These mechanisms can reduce strain, improve affective responses, and influence behaviour or performance. While the role of avatar design in these relations has been extensively studied, other areas of virtual reality require further investigation. Especially scene configurations bear the potential to enable realistic first-person scenarios of exercise, for instance, by showing action feedback such as visual flow during locomotion. The present study aims to investigate the impact of unmatching visual flow speed on heart rate and subjective effort during moderate intensity cycling in virtual reality. Both were expected to decrease with increasing visual flow speed. Eighty university sports students cycled at a self-chosen cadence for ten minutes, viewing a virtual cycling track at one of two velocities (0.5*actual speed or 1.5*actual speed). Each participant experienced both velocity conditions in counterbalanced order. Heart rate and perceived exertion were recorded continuously. Linear mixed model analyses revealed a significant main effect of visual flow speed on heart rate but not on perceived exertion. This suggests a dissociation between physiological and perceived effort, which calls for future research to identify the specific sources of effort ratings.