We're talking 8 miles round trip, but then again when I think of triathlon warriors (Brandon Frasier) I realize i'm being a woos complaining . . . but then again, damn some days are always more difficult than others.
I was over 300lbs doing an hour of cardio before I lifted...it never hurt me...if anything it kept my fat gain a bit in check. 4 miles won't do much of anything for you...good or bad. If 4 miles is difficult for you maybe thats a sign you need to get a bit more endurance...even as a power athlete.