Working the prowler is downright brutal for conditioning and VERY applicable for combative athletes.
Pushing against a weighted object makes perfect sense, especially when you can match similar times and intensity to a game / match situation.
We like to load our prowler (we actually rigged our prowler with an extra loading pole for kettlebells and wedging sandbags on) with kettlebells.
This way, we can drive or drag the prowler to a certain distance and then immediately follow up with a kettlebell or sandbag movement.
Below you see we followed up with double cleans.
Too many athletes are in crap shape and the prowler is a HUGE wake up call for what they can do physically when pushing against another weighted object!