sladerunner69
Member
Well it depends on how many calories are available for muscle growth. If there is a big surplus some extra cardio will not hamper muscle growth. But if there isn't a lot of extra calories available cardio will hamper muscle growth.
Then you also have to take into consideration what kind of cardio it is (cycling, jogging, etc.) and the duration, frequency and intensity. Longer duration, more frequent and more intense cardio will hamper hypertrophy and strength to a greater extent. Jogging also has the greatest interference effect while cycling the least.
I'm not sure why someone would want to do cardio when bulking though unless they just really like it.
Also take into account the fact that any form of cardio will increase cortisol significantly, which is an hormone whose primary role is to catabolize muscle for energy.