Since running is cardio and heavy duty leg workout, consider doing Circuit Max with a difference.
Instead of doing the compound upper body moves as Cathe does, use those 2 minutes to pump out, alternatively, squats, plie squats, lunges, lunges onto and off step as in CTX Power Circuit, and step ups. This will totally fatigue the lower body, in fact, probably more than the 5 mile run to someone accustomed to running.
This is the only way I ever do Circuit Max and it's the cardio workout that gives me the most sense of accomplishment when I'm done, more so than the Imaxes.
Give it a whirl!
Clare