I have never heard that "omen." Improper wordage aside, the only thing that strength and conditioning on the same day is going to cut into is (1) your time and (2) your ability to put on mass. The real issue is that you are inviting overtraining. You should lift 4 days per week, max. Do some light conditioning on those days and leave your real running/agility for two of your off days. Save at least one rest day per week.