Definitely circuit training. If you prefer to only run, it can still be done. An old standby training regimen for both HS and college wrestlers was to run "circuits" - example of which would be laps around the gym/arena where you run to stairwell in one corner, run up and down the stairs, run to the next corner of the gym/arena, run up then down the stairs there, repeat for the other two corners of the gym. That's one "circuit". We'd usually run 3 sets of 50 circuits each practice, in addition to all the other "torture" (3-3 1/2hrs.). Wrestlers are without doubt the fittest athletes around, only marathoners and cyclists compare.