Evidence suggests that the same high volume of aerobic activity may also impede muscle hypertrophy, strength and power development. Studies show hypertrophy appears to drop off around three to four days of cardio per week, andadditional interference has been shown for cardio sessions lasting more than thirty minutes a day. But, again that will depend on the type and intensity of cardio, therefore it is equally crucial to address both the cardio part as well as the weight lifting and rest required.