Based on the research, acute dosages of Cialis don’t have performance-enhancing effects, but a new study shows that Cialis increases testosterone. Researchers had participants perform three 30-second ‘all-out’ sprints to exhaustion and measured testosterone and cortisol responses to exercise. They discovered that only after Cialis and use did testosterone increase, however Cialis also increased cortisol levels. Cialis also lowered the DHEA to cortisol response. The study implies that Cialis enhances the ‘stress’ reaction to your body, but additionally has some testosterone-enhancing effects also.